13082854884

Committed 31 Jan 2025 09:05AM UTC coverage: 71.823% (+0.02%) from 71.804%

Build # 13082854884

Build Type

push

github

Committed by

poettering

Commit Message

uki: introduce support for a .efifw section

UKIs can be used to bundle uefi firmwares that can be measured and
used on a confidential computing environment. There can be more than one
firmware blob bundle, each one for a specific platform. Also firmware images
can themselves be containers like IGVM files that can in turn bundle the
actual firmware blob. This change is specifically for uefi firmwares, not
IGVM container files.

This change adds support to introduce a .efifw section in UKI that can be
used for firmware blobs/images. There can be multiple such sections and each
section can contain a single firmware image.

The matching .hwids entry for a specific platform can be used to select the
most appropriate firmware blob.

ukify tool has been also changed to support addition of a firmware image
in UKI.

Since firmware gets measured automatically, we do not need to measure it
separately as a part of the UKI.

Coverage Stats

292987 of 407930 relevant lines covered (71.82%)

711545.13 hits per line

Source File
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70.07

/src/core/exec-invoke.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <linux/sched.h>
#include <sys/eventfd.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/prctl.h>

#if HAVE_PAM
#include <security/pam_appl.h>
#include <security/pam_misc.h>
#endif

#if HAVE_APPARMOR
#include <sys/apparmor.h>
#endif

#include "sd-messages.h"

#if HAVE_APPARMOR
#include "apparmor-util.h"
#endif
#include "argv-util.h"
#include "ask-password-api.h"
#include "barrier.h"
#include "bitfield.h"
#include "bpf-dlopen.h"
#include "bpf-restrict-fs.h"
#include "btrfs-util.h"
#include "capability-util.h"
#include "cgroup-setup.h"
#include "chase.h"
#include "chattr-util.h"
#include "chown-recursive.h"
#include "copy.h"
#include "env-util.h"
#include "escape.h"
#include "exec-credential.h"
#include "exec-invoke.h"
#include "execute.h"
#include "exit-status.h"
#include "fd-util.h"
#include "hexdecoct.h"
#include "hostname-setup.h"
#include "io-util.h"
#include "iovec-util.h"
#include "journal-send.h"
#include "memfd-util.h"
#include "missing_ioprio.h"
#include "missing_prctl.h"
#include "missing_sched.h"
#include "missing_securebits.h"
#include "missing_syscall.h"
#include "mkdir-label.h"
#include "proc-cmdline.h"
#include "process-util.h"
#include "psi-util.h"
#include "rlimit-util.h"
#include "seccomp-util.h"
#include "selinux-util.h"
#include "signal-util.h"
#include "smack-util.h"
#include "socket-util.h"
#include "string-table.h"
#include "strv.h"
#include "terminal-util.h"
#include "utmp-wtmp.h"
#include "vpick.h"

#define IDLE_TIMEOUT_USEC (5*USEC_PER_SEC)
#define IDLE_TIMEOUT2_USEC (1*USEC_PER_SEC)

#define SNDBUF_SIZE (8*1024*1024)

static int flag_fds(
                const int fds[],
                size_t n_socket_fds,
                size_t n_fds,
                bool nonblock) {

        int r;

        assert(fds || n_fds == 0);

        /* Drops/Sets O_NONBLOCK and FD_CLOEXEC from the file flags.
         * O_NONBLOCK only applies to socket activation though. */

        for (size_t i = 0; i < n_fds; i++) {

                if (i < n_socket_fds) {
                        r = fd_nonblock(fds[i], nonblock);
                        if (r < 0)
                                return r;
                }

                /* We unconditionally drop FD_CLOEXEC from the fds,
                 * since after all we want to pass these fds to our
                 * children */

                r = fd_cloexec(fds[i], false);
                if (r < 0)
                        return r;
        }

        return 0;
}

static bool is_terminal_input(ExecInput i) {
        return IN_SET(i,
                      EXEC_INPUT_TTY,
                      EXEC_INPUT_TTY_FORCE,
                      EXEC_INPUT_TTY_FAIL);
}

static bool is_terminal_output(ExecOutput o) {
        return IN_SET(o,
                      EXEC_OUTPUT_TTY,
                      EXEC_OUTPUT_KMSG_AND_CONSOLE,
                      EXEC_OUTPUT_JOURNAL_AND_CONSOLE);
}

static bool is_kmsg_output(ExecOutput o) {
        return IN_SET(o,
                      EXEC_OUTPUT_KMSG,
                      EXEC_OUTPUT_KMSG_AND_CONSOLE);
}

static bool exec_context_needs_term(const ExecContext *c) {
        assert(c);

        /* Return true if the execution context suggests we should set $TERM to something useful. */

        if (is_terminal_input(c->std_input))
                return true;

        if (is_terminal_output(c->std_output))
                return true;

        if (is_terminal_output(c->std_error))
                return true;

        return !!c->tty_path;
}

static int open_null_as(int flags, int nfd) {
        int fd;

        assert(nfd >= 0);

        fd = open("/dev/null", flags|O_NOCTTY);
        if (fd < 0)
                return -errno;

        return move_fd(fd, nfd, false);
}

static int connect_journal_socket(
                int fd,
                const char *log_namespace,
                uid_t uid,
                gid_t gid) {

        uid_t olduid = UID_INVALID;
        gid_t oldgid = GID_INVALID;
        const char *j;
        int r;

        assert(fd >= 0);

        j = journal_stream_path(log_namespace);
        if (!j)
                return -EINVAL;

        if (gid_is_valid(gid)) {
                oldgid = getgid();

                if (setegid(gid) < 0)
                        return -errno;
        }

        if (uid_is_valid(uid)) {
                olduid = getuid();

                if (seteuid(uid) < 0) {
                        r = -errno;
                        goto restore_gid;
                }
        }

        r = connect_unix_path(fd, AT_FDCWD, j);

        /* If we fail to restore the uid or gid, things will likely fail later on. This should only happen if
           an LSM interferes. */

        if (uid_is_valid(uid))
                (void) seteuid(olduid);

 restore_gid:
        if (gid_is_valid(gid))
                (void) setegid(oldgid);

        return r;
}

static int connect_logger_as(
                const ExecContext *context,
                const ExecParameters *params,
                ExecOutput output,
                const char *ident,
                int nfd,
                uid_t uid,
                gid_t gid) {

        _cleanup_close_ int fd = -EBADF;
        int r;

        assert(context);
        assert(params);
        assert(output < _EXEC_OUTPUT_MAX);
        assert(ident);
        assert(nfd >= 0);

        fd = socket(AF_UNIX, SOCK_STREAM, 0);
        if (fd < 0)
                return -errno;

        r = connect_journal_socket(fd, context->log_namespace, uid, gid);
        if (r < 0)
                return r;

        if (shutdown(fd, SHUT_RD) < 0)
                return -errno;

        (void) fd_inc_sndbuf(fd, SNDBUF_SIZE);

        if (dprintf(fd,
                "%s\n"
                "%s\n"
                "%i\n"
                "%i\n"
                "%i\n"
                "%i\n"
                "%i\n",
                context->syslog_identifier ?: ident,
                params->flags & EXEC_PASS_LOG_UNIT ? params->unit_id : "",
                context->syslog_priority,
                !!context->syslog_level_prefix,
                false,
                is_kmsg_output(output),
                is_terminal_output(output)) < 0)
                return -errno;

        return move_fd(TAKE_FD(fd), nfd, false);
}

static int open_terminal_as(const char *path, int flags, int nfd) {
        int fd;

        assert(path);
        assert(nfd >= 0);

        fd = open_terminal(path, flags | O_NOCTTY);
        if (fd < 0)
                return fd;

        return move_fd(fd, nfd, false);
}

static int acquire_path(const char *path, int flags, mode_t mode) {
        _cleanup_close_ int fd = -EBADF;
        int r;

        assert(path);

        if (IN_SET(flags & O_ACCMODE, O_WRONLY, O_RDWR))
                flags |= O_CREAT;

        fd = open(path, flags|O_NOCTTY, mode);
        if (fd >= 0)
                return TAKE_FD(fd);

        if (errno != ENXIO) /* ENXIO is returned when we try to open() an AF_UNIX file system socket on Linux */
                return -errno;

        /* So, it appears the specified path could be an AF_UNIX socket. Let's see if we can connect to it. */

        fd = socket(AF_UNIX, SOCK_STREAM, 0);
        if (fd < 0)
                return -errno;

        r = connect_unix_path(fd, AT_FDCWD, path);
        if (IN_SET(r, -ENOTSOCK, -EINVAL))
                /* Propagate initial error if we get ENOTSOCK or EINVAL, i.e. we have indication that this
                 * wasn't an AF_UNIX socket after all */
                return -ENXIO;
        if (r < 0)
                return r;

        if ((flags & O_ACCMODE) == O_RDONLY)
                r = shutdown(fd, SHUT_WR);
        else if ((flags & O_ACCMODE) == O_WRONLY)
                r = shutdown(fd, SHUT_RD);
        else
                r = 0;
        if (r < 0)
                return -errno;

        return TAKE_FD(fd);
}

static int fixup_input(
                const ExecContext *context,
                int socket_fd,
                bool apply_tty_stdin) {

        ExecInput std_input;

        assert(context);

        std_input = context->std_input;

        if (is_terminal_input(std_input) && !apply_tty_stdin)
                return EXEC_INPUT_NULL;

        if (std_input == EXEC_INPUT_SOCKET && socket_fd < 0)
                return EXEC_INPUT_NULL;

        if (std_input == EXEC_INPUT_DATA && context->stdin_data_size == 0)
                return EXEC_INPUT_NULL;

        return std_input;
}

static int fixup_output(ExecOutput output, int socket_fd) {

        if (output == EXEC_OUTPUT_SOCKET && socket_fd < 0)
                return EXEC_OUTPUT_INHERIT;

        return output;
}

static int setup_input(
                const ExecContext *context,
                const ExecParameters *params,
                int socket_fd,
                const int named_iofds[static 3]) {

        ExecInput i;
        int r;

        assert(context);
        assert(params);
        assert(named_iofds);

        if (params->stdin_fd >= 0) {
                if (dup2(params->stdin_fd, STDIN_FILENO) < 0)
                        return -errno;

                /* Try to make this the controlling tty, if it is a tty */
                if (isatty_safe(STDIN_FILENO))
                        (void) ioctl(STDIN_FILENO, TIOCSCTTY, context->std_input == EXEC_INPUT_TTY_FORCE);

                return STDIN_FILENO;
        }

        i = fixup_input(context, socket_fd, params->flags & EXEC_APPLY_TTY_STDIN);

        switch (i) {

        case EXEC_INPUT_NULL:
                return open_null_as(O_RDONLY, STDIN_FILENO);

        case EXEC_INPUT_TTY:
        case EXEC_INPUT_TTY_FORCE:
        case EXEC_INPUT_TTY_FAIL: {
                _cleanup_close_ int tty_fd = -EBADF;
                const char *tty_path;

                tty_path = ASSERT_PTR(exec_context_tty_path(context));

                tty_fd = acquire_terminal(tty_path,
                                          i == EXEC_INPUT_TTY_FAIL  ? ACQUIRE_TERMINAL_TRY :
                                          i == EXEC_INPUT_TTY_FORCE ? ACQUIRE_TERMINAL_FORCE :
                                                                      ACQUIRE_TERMINAL_WAIT,
                                          USEC_INFINITY);
                if (tty_fd < 0)
                        return tty_fd;

                r = move_fd(tty_fd, STDIN_FILENO, /* cloexec= */ false);
                if (r < 0)
                        return r;

                TAKE_FD(tty_fd);
                return r;
        }

        case EXEC_INPUT_SOCKET:
                assert(socket_fd >= 0);

                return RET_NERRNO(dup2(socket_fd, STDIN_FILENO));

        case EXEC_INPUT_NAMED_FD:
                assert(named_iofds[STDIN_FILENO] >= 0);

                (void) fd_nonblock(named_iofds[STDIN_FILENO], false);
                return RET_NERRNO(dup2(named_iofds[STDIN_FILENO], STDIN_FILENO));

        case EXEC_INPUT_DATA: {
                int fd;

                fd = memfd_new_and_seal("exec-input", context->stdin_data, context->stdin_data_size);
                if (fd < 0)
                        return fd;

                return move_fd(fd, STDIN_FILENO, false);
        }

        case EXEC_INPUT_FILE: {
                bool rw;
                int fd;

                assert(context->stdio_file[STDIN_FILENO]);

                rw = (context->std_output == EXEC_OUTPUT_FILE && streq_ptr(context->stdio_file[STDIN_FILENO], context->stdio_file[STDOUT_FILENO])) ||
                        (context->std_error == EXEC_OUTPUT_FILE && streq_ptr(context->stdio_file[STDIN_FILENO], context->stdio_file[STDERR_FILENO]));

                fd = acquire_path(context->stdio_file[STDIN_FILENO], rw ? O_RDWR : O_RDONLY, 0666 & ~context->umask);
                if (fd < 0)
                        return fd;

                return move_fd(fd, STDIN_FILENO, false);
        }

        default:
                assert_not_reached();
        }
}

static bool can_inherit_stderr_from_stdout(
                const ExecContext *context,
                ExecOutput o,
                ExecOutput e) {

        assert(context);

        /* Returns true, if given the specified STDERR and STDOUT output we can directly dup() the stdout fd to the
         * stderr fd */

        if (e == EXEC_OUTPUT_INHERIT)
                return true;
        if (e != o)
                return false;

        if (e == EXEC_OUTPUT_NAMED_FD)
                return streq_ptr(context->stdio_fdname[STDOUT_FILENO], context->stdio_fdname[STDERR_FILENO]);

        if (IN_SET(e, EXEC_OUTPUT_FILE, EXEC_OUTPUT_FILE_APPEND, EXEC_OUTPUT_FILE_TRUNCATE))
                return streq_ptr(context->stdio_file[STDOUT_FILENO], context->stdio_file[STDERR_FILENO]);

        return true;
}

static int setup_output(
                const ExecContext *context,
                const ExecParameters *params,
                int fileno,
                int socket_fd,
                const int named_iofds[static 3],
                const char *ident,
                uid_t uid,
                gid_t gid,
                dev_t *journal_stream_dev,
                ino_t *journal_stream_ino) {

        ExecOutput o;
        ExecInput i;
        int r;

        assert(context);
        assert(params);
        assert(ident);
        assert(journal_stream_dev);
        assert(journal_stream_ino);

        if (fileno == STDOUT_FILENO && params->stdout_fd >= 0) {

                if (dup2(params->stdout_fd, STDOUT_FILENO) < 0)
                        return -errno;

                return STDOUT_FILENO;
        }

        if (fileno == STDERR_FILENO && params->stderr_fd >= 0) {
                if (dup2(params->stderr_fd, STDERR_FILENO) < 0)
                        return -errno;

                return STDERR_FILENO;
        }

        i = fixup_input(context, socket_fd, params->flags & EXEC_APPLY_TTY_STDIN);
        o = fixup_output(context->std_output, socket_fd);

        // FIXME: we probably should spend some time here to verify that if we inherit an fd from stdin
        // (possibly indirect via inheritance from stdout) it is actually opened for write!

        if (fileno == STDERR_FILENO) {
                ExecOutput e;
                e = fixup_output(context->std_error, socket_fd);

                /* This expects the input and output are already set up */

                /* Don't change the stderr file descriptor if we inherit all
                 * the way and are not on a tty */
                if (e == EXEC_OUTPUT_INHERIT &&
                    o == EXEC_OUTPUT_INHERIT &&
                    i == EXEC_INPUT_NULL &&
                    !is_terminal_input(context->std_input) &&
                    getppid() != 1)
                        return fileno;

                /* Duplicate from stdout if possible */
                if (can_inherit_stderr_from_stdout(context, o, e))
                        return RET_NERRNO(dup2(STDOUT_FILENO, fileno));

                o = e;

        } else if (o == EXEC_OUTPUT_INHERIT) {
                /* If input got downgraded, inherit the original value */
                if (i == EXEC_INPUT_NULL && is_terminal_input(context->std_input))
                        return open_terminal_as(exec_context_tty_path(context), O_WRONLY, fileno);

                /* If the input is connected to anything that's not a /dev/null or a data fd, inherit that... */
                if (!IN_SET(i, EXEC_INPUT_NULL, EXEC_INPUT_DATA))
                        return RET_NERRNO(dup2(STDIN_FILENO, fileno));

                /* If we are not started from PID 1 we just inherit STDOUT from our parent process. */
                if (getppid() != 1)
                        return fileno;

                /* We need to open /dev/null here anew, to get the right access mode. */
                return open_null_as(O_WRONLY, fileno);
        }

        switch (o) {

        case EXEC_OUTPUT_NULL:
                return open_null_as(O_WRONLY, fileno);

        case EXEC_OUTPUT_TTY:
                if (is_terminal_input(i))
                        return RET_NERRNO(dup2(STDIN_FILENO, fileno));

                return open_terminal_as(exec_context_tty_path(context), O_WRONLY, fileno);

        case EXEC_OUTPUT_KMSG:
        case EXEC_OUTPUT_KMSG_AND_CONSOLE:
        case EXEC_OUTPUT_JOURNAL:
        case EXEC_OUTPUT_JOURNAL_AND_CONSOLE:
                r = connect_logger_as(context, params, o, ident, fileno, uid, gid);
                if (r < 0) {
                        log_exec_warning_errno(context,
                                               params,
                                               r,
                                               "Failed to connect %s to the journal socket, ignoring: %m",
                                               fileno == STDOUT_FILENO ? "stdout" : "stderr");
                        r = open_null_as(O_WRONLY, fileno);
                } else {
                        struct stat st;

                        /* If we connected this fd to the journal via a stream, patch the device/inode into the passed
                         * parameters, but only then. This is useful so that we can set $JOURNAL_STREAM that permits
                         * services to detect whether they are connected to the journal or not.
                         *
                         * If both stdout and stderr are connected to a stream then let's make sure to store the data
                         * about STDERR as that's usually the best way to do logging. */

                        if (fstat(fileno, &st) >= 0 &&
                            (*journal_stream_ino == 0 || fileno == STDERR_FILENO)) {
                                *journal_stream_dev = st.st_dev;
                                *journal_stream_ino = st.st_ino;
                        }
                }
                return r;

        case EXEC_OUTPUT_SOCKET:
                assert(socket_fd >= 0);

                return RET_NERRNO(dup2(socket_fd, fileno));

        case EXEC_OUTPUT_NAMED_FD:
                assert(named_iofds[fileno] >= 0);

                (void) fd_nonblock(named_iofds[fileno], false);
                return RET_NERRNO(dup2(named_iofds[fileno], fileno));

        case EXEC_OUTPUT_FILE:
        case EXEC_OUTPUT_FILE_APPEND:
        case EXEC_OUTPUT_FILE_TRUNCATE: {
                bool rw;
                int fd, flags;

                assert(context->stdio_file[fileno]);

                rw = context->std_input == EXEC_INPUT_FILE &&
                        streq_ptr(context->stdio_file[fileno], context->stdio_file[STDIN_FILENO]);

                if (rw)
                        return RET_NERRNO(dup2(STDIN_FILENO, fileno));

                flags = O_WRONLY;
                if (o == EXEC_OUTPUT_FILE_APPEND)
                        flags |= O_APPEND;
                else if (o == EXEC_OUTPUT_FILE_TRUNCATE)
                        flags |= O_TRUNC;

                fd = acquire_path(context->stdio_file[fileno], flags, 0666 & ~context->umask);
                if (fd < 0)
                        return fd;

                return move_fd(fd, fileno, 0);
        }

        default:
                assert_not_reached();
        }
}

static int chown_terminal(int fd, uid_t uid) {
        int r;

        assert(fd >= 0);

        /* Before we chown/chmod the TTY, let's ensure this is actually a tty */
        if (!isatty_safe(fd))
                return 0;

        /* This might fail. What matters are the results. */
        r = fchmod_and_chown(fd, TTY_MODE, uid, GID_INVALID);
        if (r < 0)
                return r;

        return 1;
}

static int setup_confirm_stdio(
                const ExecContext *context,
                const char *vc,
                int *ret_saved_stdin,
                int *ret_saved_stdout) {

        _cleanup_close_ int fd = -EBADF, saved_stdin = -EBADF, saved_stdout = -EBADF;
        int r;

        assert(ret_saved_stdin);
        assert(ret_saved_stdout);

        saved_stdin = fcntl(STDIN_FILENO, F_DUPFD_CLOEXEC, 3);
        if (saved_stdin < 0)
                return -errno;

        saved_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
        if (saved_stdout < 0)
                return -errno;

        fd = acquire_terminal(vc, ACQUIRE_TERMINAL_WAIT, DEFAULT_CONFIRM_USEC);
        if (fd < 0)
                return fd;

        _cleanup_close_ int lock_fd = lock_dev_console();
        if (lock_fd < 0)
                log_debug_errno(lock_fd, "Failed to lock /dev/console, ignoring: %m");

        r = chown_terminal(fd, getuid());
        if (r < 0)
                return r;

        r = terminal_reset_defensive(fd, /* switch_to_text= */ true);
        if (r < 0)
                return r;

        r = exec_context_apply_tty_size(context, fd, fd, vc);
        if (r < 0)
                return r;

        r = rearrange_stdio(fd, fd, STDERR_FILENO); /* Invalidates 'fd' also on failure */
        TAKE_FD(fd);
        if (r < 0)
                return r;

        *ret_saved_stdin = TAKE_FD(saved_stdin);
        *ret_saved_stdout = TAKE_FD(saved_stdout);
        return 0;
}

static void write_confirm_error_fd(int err, int fd, const char *unit_id) {
        assert(err != 0);
        assert(fd >= 0);
        assert(unit_id);

        errno = abs(err);

        if (errno == ETIMEDOUT)
                dprintf(fd, "Confirmation question timed out for %s, assuming positive response.\n", unit_id);
        else
                dprintf(fd, "Couldn't ask confirmation for %s, assuming positive response: %m\n", unit_id);
}

static void write_confirm_error(int err, const char *vc, const char *unit_id) {
        _cleanup_close_ int fd = -EBADF;

        assert(vc);

        fd = open_terminal(vc, O_WRONLY|O_NOCTTY|O_CLOEXEC);
        if (fd < 0)
                return;

        write_confirm_error_fd(err, fd, unit_id);
}

static int restore_confirm_stdio(int *saved_stdin, int *saved_stdout) {
        int r = 0;

        assert(saved_stdin);
        assert(saved_stdout);

        release_terminal();

        if (*saved_stdin >= 0)
                if (dup2(*saved_stdin, STDIN_FILENO) < 0)
                        r = -errno;

        if (*saved_stdout >= 0)
                if (dup2(*saved_stdout, STDOUT_FILENO) < 0)
                        r = -errno;

        *saved_stdin = safe_close(*saved_stdin);
        *saved_stdout = safe_close(*saved_stdout);

        return r;
}

enum {
        CONFIRM_PRETEND_FAILURE = -1,
        CONFIRM_PRETEND_SUCCESS =  0,
        CONFIRM_EXECUTE = 1,
};

static bool confirm_spawn_disabled(void) {
        return access("/run/systemd/confirm_spawn_disabled", F_OK) >= 0;
}

static int ask_for_confirmation(const ExecContext *context, const ExecParameters *params, const char *cmdline) {
        int saved_stdout = -EBADF, saved_stdin = -EBADF, r;
        _cleanup_free_ char *e = NULL;
        char c;

        assert(context);
        assert(params);

        /* For any internal errors, assume a positive response. */
        r = setup_confirm_stdio(context, params->confirm_spawn, &saved_stdin, &saved_stdout);
        if (r < 0) {
                write_confirm_error(r, params->confirm_spawn, params->unit_id);
                return CONFIRM_EXECUTE;
        }

        /* confirm_spawn might have been disabled while we were sleeping. */
        if (!params->confirm_spawn || confirm_spawn_disabled()) {
                r = 1;
                goto restore_stdio;
        }

        e = ellipsize(cmdline, 60, 100);
        if (!e) {
                log_oom();
                r = CONFIRM_EXECUTE;
                goto restore_stdio;
        }

        for (;;) {
                r = ask_char(&c, "yfshiDjcn", "Execute %s? [y, f, s – h for help] ", e);
                if (r < 0) {
                        write_confirm_error_fd(r, STDOUT_FILENO, params->unit_id);
                        r = CONFIRM_EXECUTE;
                        goto restore_stdio;
                }

                switch (c) {
                case 'c':
                        printf("Resuming normal execution.\n");
                        manager_disable_confirm_spawn();
                        r = 1;
                        break;
                case 'D':
                        printf("  Unit: %s\n",
                               params->unit_id);
                        exec_context_dump(context, stdout, "  ");
                        exec_params_dump(params, stdout, "  ");
                        continue; /* ask again */
                case 'f':
                        printf("Failing execution.\n");
                        r = CONFIRM_PRETEND_FAILURE;
                        break;
                case 'h':
                        printf("  c - continue, proceed without asking anymore\n"
                               "  D - dump, show the state of the unit\n"
                               "  f - fail, don't execute the command and pretend it failed\n"
                               "  h - help\n"
                               "  i - info, show a short summary of the unit\n"
                               "  j - jobs, show jobs that are in progress\n"
                               "  s - skip, don't execute the command and pretend it succeeded\n"
                               "  y - yes, execute the command\n");
                        continue; /* ask again */
                case 'i':
                        printf("  Unit:        %s\n"
                               "  Command:     %s\n",
                               params->unit_id, cmdline);
                        continue; /* ask again */
                case 'j':
                        if (sigqueue(getppid(),
                                     SIGRTMIN+18,
                                     (const union sigval) { .sival_int = MANAGER_SIGNAL_COMMAND_DUMP_JOBS }) < 0)
                                return -errno;

                        continue; /* ask again */
                case 'n':
                        /* 'n' was removed in favor of 'f'. */
                        printf("Didn't understand 'n', did you mean 'f'?\n");
                        continue; /* ask again */
                case 's':
                        printf("Skipping execution.\n");
                        r = CONFIRM_PRETEND_SUCCESS;
                        break;
                case 'y':
                        r = CONFIRM_EXECUTE;
                        break;
                default:
                        assert_not_reached();
                }
                break;
        }

restore_stdio:
        restore_confirm_stdio(&saved_stdin, &saved_stdout);
        return r;
}

static int get_fixed_user(
                const char *user_or_uid,
                const char **ret_username,
                uid_t *ret_uid,
                gid_t *ret_gid,
                const char **ret_home,
                const char **ret_shell) {

        int r;

        assert(user_or_uid);
        assert(ret_username);

        r = get_user_creds(&user_or_uid, ret_uid, ret_gid, ret_home, ret_shell, USER_CREDS_CLEAN);
        if (r < 0)
                return r;

        /* user_or_uid is normalized by get_user_creds to username */
        *ret_username = user_or_uid;

        return 0;
}

static int get_fixed_group(
                const char *group_or_gid,
                const char **ret_groupname,
                gid_t *ret_gid) {

        int r;

        assert(group_or_gid);
        assert(ret_groupname);

        r = get_group_creds(&group_or_gid, ret_gid, /* flags = */ 0);
        if (r < 0)
                return r;

        /* group_or_gid is normalized by get_group_creds to groupname */
        *ret_groupname = group_or_gid;

        return 0;
}

static int get_supplementary_groups(const ExecContext *c, const char *user,
                                    const char *group, gid_t gid,
                                    gid_t **supplementary_gids, int *ngids) {
        int r, k = 0;
        int ngroups_max;
        bool keep_groups = false;
        gid_t *groups = NULL;
        _cleanup_free_ gid_t *l_gids = NULL;

        assert(c);

        /*
         * If user is given, then lookup GID and supplementary groups list.
         * We avoid NSS lookups for gid=0. Also we have to initialize groups
         * here and as early as possible so we keep the list of supplementary
         * groups of the caller.
         */
        if (user && gid_is_valid(gid) && gid != 0) {
                /* First step, initialize groups from /etc/groups */
                if (initgroups(user, gid) < 0)
                        return -errno;

                keep_groups = true;
        }

        if (strv_isempty(c->supplementary_groups))
                return 0;

        /*
         * If SupplementaryGroups= was passed then NGROUPS_MAX has to
         * be positive, otherwise fail.
         */
        errno = 0;
        ngroups_max = (int) sysconf(_SC_NGROUPS_MAX);
        if (ngroups_max <= 0)
                return errno_or_else(EOPNOTSUPP);

        l_gids = new(gid_t, ngroups_max);
        if (!l_gids)
                return -ENOMEM;

        if (keep_groups) {
                /*
                 * Lookup the list of groups that the user belongs to, we
                 * avoid NSS lookups here too for gid=0.
                 */
                k = ngroups_max;
                if (getgrouplist(user, gid, l_gids, &k) < 0)
                        return -EINVAL;
        } else
                k = 0;

        STRV_FOREACH(i, c->supplementary_groups) {
                const char *g;

                if (k >= ngroups_max)
                        return -E2BIG;

                g = *i;
                r = get_group_creds(&g, l_gids+k, 0);
                if (r < 0)
                        return r;

                k++;
        }

        /*
         * Sets ngids to zero to drop all supplementary groups, happens
         * when we are under root and SupplementaryGroups= is empty.
         */
        if (k == 0) {
                *ngids = 0;
                return 0;
        }

        /* Otherwise get the final list of supplementary groups */
        groups = memdup(l_gids, sizeof(gid_t) * k);
        if (!groups)
                return -ENOMEM;

        *supplementary_gids = groups;
        *ngids = k;

        groups = NULL;

        return 0;
}

static int enforce_groups(gid_t gid, const gid_t *supplementary_gids, int ngids) {
        int r;

        /* Handle SupplementaryGroups= if it is not empty */
        if (ngids > 0) {
                r = maybe_setgroups(ngids, supplementary_gids);
                if (r < 0)
                        return r;
        }

        if (gid_is_valid(gid)) {
                /* Then set our gids */
                if (setresgid(gid, gid, gid) < 0)
                        return -errno;
        }

        return 0;
}

static int set_securebits(unsigned bits, unsigned mask) {
        unsigned applied;
        int current;

        current = prctl(PR_GET_SECUREBITS);
        if (current < 0)
                return -errno;

        /* Clear all securebits defined in mask and set bits */
        applied = ((unsigned) current & ~mask) | bits;
        if ((unsigned) current == applied)
                return 0;

        if (prctl(PR_SET_SECUREBITS, applied) < 0)
                return -errno;

        return 1;
}

static int enforce_user(
                const ExecContext *context,
                uid_t uid,
                uint64_t capability_ambient_set) {
        assert(context);
        int r;

        if (!uid_is_valid(uid))
                return 0;

        /* Sets (but doesn't look up) the UIS and makes sure we keep the capabilities while doing so. For
         * setting secure bits the capability CAP_SETPCAP is required, so we also need keep-caps in this
         * case. */

        if ((capability_ambient_set != 0 || context->secure_bits != 0) && uid != 0) {

                /* First step: If we need to keep capabilities but drop privileges we need to make sure we
                 * keep our caps, while we drop privileges. Add KEEP_CAPS to the securebits */
                r = set_securebits(1U << SECURE_KEEP_CAPS, 0);
                if (r < 0)
                        return r;
        }

        /* Second step: actually set the uids */
        if (setresuid(uid, uid, uid) < 0)
                return -errno;

        /* At this point we should have all necessary capabilities but are otherwise a normal user. However,
         * the caps might got corrupted due to the setresuid() so we need clean them up later. This is done
         * outside of this call. */
        return 0;
}

#if HAVE_PAM

static void pam_response_free_array(struct pam_response *responses, size_t n_responses) {
        assert(responses || n_responses == 0);

        FOREACH_ARRAY(resp, responses, n_responses)
                erase_and_free(resp->resp);

        free(responses);
}

typedef struct AskPasswordConvData {
        const ExecContext *context;
        const ExecParameters *params;
} AskPasswordConvData;

static int ask_password_conv(
                int num_msg,
                const struct pam_message *msg[],
                struct pam_response **ret,
                void *userdata) {

        AskPasswordConvData *data = ASSERT_PTR(userdata);
        bool set_credential_env_var = false;
        int r;

        assert(num_msg >= 0);
        assert(msg);
        assert(data->context);
        assert(data->params);

        size_t n = num_msg;
        struct pam_response *responses = new0(struct pam_response, n);
        if (!responses)
                return PAM_BUF_ERR;
        CLEANUP_ARRAY(responses, n, pam_response_free_array);

        for (size_t i = 0; i < n; i++) {
                const struct pam_message *mi = *msg + i;

                switch (mi->msg_style) {

                case PAM_PROMPT_ECHO_ON:
                case PAM_PROMPT_ECHO_OFF: {

                        /* Locally set the $CREDENTIALS_DIRECTORY to the credentials directory we just populated */
                        if (!set_credential_env_var) {
                                _cleanup_free_ char *creds_dir = NULL;
                                r = exec_context_get_credential_directory(data->context, data->params, data->params->unit_id, &creds_dir);
                                if (r < 0)
                                        return log_exec_error_errno(data->context, data->params, r, "Failed to determine credentials directory: %m");

                                if (creds_dir) {
                                        if (setenv("CREDENTIALS_DIRECTORY", creds_dir, /* overwrite= */ true) < 0)
                                                return log_exec_error_errno(data->context, data->params, r, "Failed to set $CREDENTIALS_DIRECTORY: %m");
                                } else
                                        (void) unsetenv("CREDENTIALS_DIRECTORY");

                                set_credential_env_var = true;
                        }

                        _cleanup_free_ char *credential_name = strjoin("pam.authtok.", data->context->pam_name);
                        if (!credential_name)
                                return log_oom();

                        AskPasswordRequest req = {
                                .message = mi->msg,
                                .credential = credential_name,
                                .tty_fd = -EBADF,
                                .hup_fd = -EBADF,
                                .until = usec_add(now(CLOCK_MONOTONIC), 15 * USEC_PER_SEC),
                        };

                        _cleanup_strv_free_erase_ char **acquired = NULL;
                        r = ask_password_auto(
                                        &req,
                                        ASK_PASSWORD_ACCEPT_CACHED|
                                        ASK_PASSWORD_NO_TTY|
                                        (mi->msg_style == PAM_PROMPT_ECHO_ON ? ASK_PASSWORD_ECHO : 0),
                                        &acquired);
                        if (r < 0) {
                                log_exec_error_errno(data->context, data->params, r, "Failed to query for password: %m");
                                return PAM_CONV_ERR;
                        }

                        responses[i].resp = strdup(ASSERT_PTR(acquired[0]));
                        if (!responses[i].resp) {
                                log_oom();
                                return PAM_BUF_ERR;
                        }
                        break;
                }

                case PAM_ERROR_MSG:
                        log_exec_error(data->context, data->params, "PAM: %s", mi->msg);
                        break;

                case PAM_TEXT_INFO:
                        log_exec_info(data->context, data->params, "PAM: %s", mi->msg);
                        break;

                default:
                        return PAM_CONV_ERR;
                }
        }

        *ret = TAKE_PTR(responses);
        n = 0;

        return PAM_SUCCESS;
}

static int pam_close_session_and_delete_credentials(pam_handle_t *handle, int flags) {
        int r, s;

        assert(handle);

        r = pam_close_session(handle, flags);
        if (r != PAM_SUCCESS)
                log_debug("pam_close_session() failed: %s", pam_strerror(handle, r));

        s = pam_setcred(handle, PAM_DELETE_CRED | flags);
        if (s != PAM_SUCCESS)
                log_debug("pam_setcred(PAM_DELETE_CRED) failed: %s", pam_strerror(handle, s));

        return r != PAM_SUCCESS ? r : s;
}
#endif

static int setup_pam(
                const ExecContext *context,
                ExecParameters *params,
                const char *user,
                uid_t uid,
                gid_t gid,
                char ***env, /* updated on success */
                const int fds[], size_t n_fds,
                int exec_fd) {

#if HAVE_PAM
        AskPasswordConvData conv_data = {
                .context = context,
                .params = params,
        };

        const struct pam_conv conv = {
                .conv = ask_password_conv,
                .appdata_ptr = &conv_data,
        };

        _cleanup_(barrier_destroy) Barrier barrier = BARRIER_NULL;
        _cleanup_strv_free_ char **e = NULL;
        pam_handle_t *handle = NULL;
        sigset_t old_ss;
        int pam_code = PAM_SUCCESS, r;
        bool close_session = false;
        pid_t parent_pid;
        int flags = 0;

        assert(context);
        assert(params);
        assert(user);
        assert(uid_is_valid(uid));
        assert(gid_is_valid(gid));
        assert(fds || n_fds == 0);
        assert(env);

        /* We set up PAM in the parent process, then fork. The child
         * will then stay around until killed via PR_GET_PDEATHSIG or
         * systemd via the cgroup logic. It will then remove the PAM
         * session again. The parent process will exec() the actual
         * daemon. We do things this way to ensure that the main PID
         * of the daemon is the one we initially fork()ed. */

        r = barrier_create(&barrier);
        if (r < 0)
                goto fail;

        if (log_get_max_level() < LOG_DEBUG)
                flags |= PAM_SILENT;

        pam_code = pam_start(context->pam_name, user, &conv, &handle);
        if (pam_code != PAM_SUCCESS) {
                handle = NULL;
                goto fail;
        }

        const char *tty = context->tty_path;
        if (!tty) {
                _cleanup_free_ char *q = NULL;

                /* Hmm, so no TTY was explicitly passed, but an fd passed to us directly might be a TTY. Let's figure
                 * out if that's the case, and read the TTY off it. */

                if (getttyname_malloc(STDIN_FILENO, &q) >= 0)
                        tty = strjoina("/dev/", q);
        }

        if (tty) {
                pam_code = pam_set_item(handle, PAM_TTY, tty);
                if (pam_code != PAM_SUCCESS)
                        goto fail;
        }

        STRV_FOREACH(nv, *env) {
                pam_code = pam_putenv(handle, *nv);
                if (pam_code != PAM_SUCCESS)
                        goto fail;
        }

        pam_code = pam_acct_mgmt(handle, flags);
        if (pam_code != PAM_SUCCESS)
                goto fail;

        pam_code = pam_setcred(handle, PAM_ESTABLISH_CRED | flags);
        if (pam_code != PAM_SUCCESS)
                log_debug("pam_setcred(PAM_ESTABLISH_CRED) failed, ignoring: %s", pam_strerror(handle, pam_code));

        pam_code = pam_open_session(handle, flags);
        if (pam_code != PAM_SUCCESS)
                goto fail;

        close_session = true;

        e = pam_getenvlist(handle);
        if (!e) {
                pam_code = PAM_BUF_ERR;
                goto fail;
        }

        /* Block SIGTERM, so that we know that it won't get lost in the child */

        assert_se(sigprocmask_many(SIG_BLOCK, &old_ss, SIGTERM) >= 0);

        parent_pid = getpid_cached();

        r = safe_fork("(sd-pam)", 0, NULL);
        if (r < 0)
                goto fail;
        if (r == 0) {
                int ret = EXIT_PAM;

                /* The child's job is to reset the PAM session on termination */
                barrier_set_role(&barrier, BARRIER_CHILD);

                /* Make sure we don't keep open the passed fds in this child. We assume that otherwise only
                 * those fds are open here that have been opened by PAM. */
                (void) close_many(fds, n_fds);

                /* Also close the 'exec_fd' in the child, since the service manager waits for the EOF induced
                 * by the execve() to wait for completion, and if we'd keep the fd open here in the child
                 * we'd never signal completion. */
                exec_fd = safe_close(exec_fd);

                /* Drop privileges - we don't need any to pam_close_session and this will make
                 * PR_SET_PDEATHSIG work in most cases.  If this fails, ignore the error - but expect sd-pam
                 * threads to fail to exit normally */

                r = fully_set_uid_gid(uid, gid, /* supplementary_gids= */ NULL, /* n_supplementary_gids= */ 0);
                if (r < 0)
                        log_warning_errno(r, "Failed to drop privileges in sd-pam: %m");

                (void) ignore_signals(SIGPIPE);

                /* Wait until our parent died. This will only work if the above setresuid() succeeds,
                 * otherwise the kernel will not allow unprivileged parents kill their privileged children
                 * this way. We rely on the control groups kill logic to do the rest for us. */
                if (prctl(PR_SET_PDEATHSIG, SIGTERM) < 0)
                        goto child_finish;

                /* Tell the parent that our setup is done. This is especially important regarding dropping
                 * privileges. Otherwise, unit setup might race against our setresuid(2) call.
                 *
                 * If the parent aborted, we'll detect this below, hence ignore return failure here. */
                (void) barrier_place(&barrier);

                /* Check if our parent process might already have died? */
                if (getppid() == parent_pid) {
                        sigset_t ss;
                        int sig;

                        assert_se(sigemptyset(&ss) >= 0);
                        assert_se(sigaddset(&ss, SIGTERM) >= 0);

                        assert_se(sigwait(&ss, &sig) == 0);
                        assert(sig == SIGTERM);
                }

                /* If our parent died we'll end the session */
                if (getppid() != parent_pid) {
                        pam_code = pam_close_session_and_delete_credentials(handle, flags);
                        if (pam_code != PAM_SUCCESS)
                                goto child_finish;
                }

                ret = 0;

        child_finish:
                /* NB: pam_end() when called in child processes should set PAM_DATA_SILENT to let the module
                 * know about this. See pam_end(3) */
                (void) pam_end(handle, pam_code | flags | PAM_DATA_SILENT);
                _exit(ret);
        }

        barrier_set_role(&barrier, BARRIER_PARENT);

        /* If the child was forked off successfully it will do all the cleanups, so forget about the handle
         * here. */
        handle = NULL;

        /* Unblock SIGTERM again in the parent */
        assert_se(sigprocmask(SIG_SETMASK, &old_ss, NULL) >= 0);

        /* We close the log explicitly here, since the PAM modules might have opened it, but we don't want
         * this fd around. */
        closelog();

        /* Synchronously wait for the child to initialize. We don't care for errors as we cannot
         * recover. However, warn loudly if it happens. */
        if (!barrier_place_and_sync(&barrier))
                log_error("PAM initialization failed");

        return strv_free_and_replace(*env, e);

fail:
        if (pam_code != PAM_SUCCESS) {
                log_error("PAM failed: %s", pam_strerror(handle, pam_code));
                r = -EPERM;  /* PAM errors do not map to errno */
        } else
                log_error_errno(r, "PAM failed: %m");

        if (handle) {
                if (close_session)
                        pam_code = pam_close_session_and_delete_credentials(handle, flags);

                (void) pam_end(handle, pam_code | flags);
        }

        closelog();
        return r;
#else
        return 0;
#endif
}

static void rename_process_from_path(const char *path) {
        _cleanup_free_ char *buf = NULL;
        const char *p;

        assert(path);

        /* This resulting string must fit in 10 chars (i.e. the length of "/sbin/init") to look pretty in
         * /bin/ps */

        if (path_extract_filename(path, &buf) < 0) {
                rename_process("(...)");
                return;
        }

        size_t l = strlen(buf);
        if (l > 8) {
                /* The end of the process name is usually more interesting, since the first bit might just be
                 * "systemd-" */
                p = buf + l - 8;
                l = 8;
        } else
                p = buf;

        char process_name[11];
        process_name[0] = '(';
        memcpy(process_name+1, p, l);
        process_name[1+l] = ')';
        process_name[1+l+1] = 0;

        (void) rename_process(process_name);
}

static bool context_has_address_families(const ExecContext *c) {
        assert(c);

        return c->address_families_allow_list ||
                !set_isempty(c->address_families);
}

static bool context_has_syscall_filters(const ExecContext *c) {
        assert(c);

        return c->syscall_allow_list ||
                !hashmap_isempty(c->syscall_filter);
}

static bool context_has_syscall_logs(const ExecContext *c) {
        assert(c);

        return c->syscall_log_allow_list ||
                !hashmap_isempty(c->syscall_log);
}

static bool context_has_seccomp(const ExecContext *c) {
        /* We need NNP if we have any form of seccomp and are unprivileged */
        return c->lock_personality ||
                c->memory_deny_write_execute ||
                c->private_devices ||
                c->protect_clock ||
                c->protect_hostname == PROTECT_HOSTNAME_YES ||
                c->protect_kernel_tunables ||
                c->protect_kernel_modules ||
                c->protect_kernel_logs ||
                context_has_address_families(c) ||
                exec_context_restrict_namespaces_set(c) ||
                c->restrict_realtime ||
                c->restrict_suid_sgid ||
                !set_isempty(c->syscall_archs) ||
                context_has_syscall_filters(c) ||
                context_has_syscall_logs(c);
}

static bool context_has_no_new_privileges(const ExecContext *c) {
        assert(c);

        if (c->no_new_privileges)
                return true;

        if (have_effective_cap(CAP_SYS_ADMIN) > 0) /* if we are privileged, we don't need NNP */
                return false;

        return context_has_seccomp(c);
}

#if HAVE_SECCOMP

static bool seccomp_allows_drop_privileges(const ExecContext *c) {
        void *id, *val;
        bool has_capget = false, has_capset = false, has_prctl = false;

        assert(c);

        /* No syscall filter, we are allowed to drop privileges */
        if (hashmap_isempty(c->syscall_filter))
                return true;

        HASHMAP_FOREACH_KEY(val, id, c->syscall_filter) {
                _cleanup_free_ char *name = NULL;

                name = seccomp_syscall_resolve_num_arch(SCMP_ARCH_NATIVE, PTR_TO_INT(id) - 1);

                if (streq(name, "capget"))
                        has_capget = true;
                else if (streq(name, "capset"))
                        has_capset = true;
                else if (streq(name, "prctl"))
                        has_prctl = true;
        }

        if (c->syscall_allow_list)
                return has_capget && has_capset && has_prctl;
        else
                return !(has_capget || has_capset || has_prctl);
}

static bool skip_seccomp_unavailable(const ExecContext *c, const ExecParameters *p, const char* msg) {

        if (is_seccomp_available())
                return false;

        log_exec_debug(c, p, "SECCOMP features not detected in the kernel, skipping %s", msg);
        return true;
}

static int apply_syscall_filter(const ExecContext *c, const ExecParameters *p) {
        uint32_t negative_action, default_action, action;
        int r;

        assert(c);
        assert(p);

        if (!context_has_syscall_filters(c))
                return 0;

        if (skip_seccomp_unavailable(c, p, "SystemCallFilter="))
                return 0;

        negative_action = c->syscall_errno == SECCOMP_ERROR_NUMBER_KILL ? scmp_act_kill_process() : SCMP_ACT_ERRNO(c->syscall_errno);

        if (c->syscall_allow_list) {
                default_action = negative_action;
                action = SCMP_ACT_ALLOW;
        } else {
                default_action = SCMP_ACT_ALLOW;
                action = negative_action;
        }

        /* Sending over exec_fd or handoff_timestamp_fd requires write() syscall. */
        if (p->exec_fd >= 0 || p->handoff_timestamp_fd >= 0) {
                r = seccomp_filter_set_add_by_name(c->syscall_filter, c->syscall_allow_list, "write");
                if (r < 0)
                        return r;
        }

        return seccomp_load_syscall_filter_set_raw(default_action, c->syscall_filter, action, false);
}

static int apply_syscall_log(const ExecContext *c, const ExecParameters *p) {
#ifdef SCMP_ACT_LOG
        uint32_t default_action, action;
#endif

        assert(c);
        assert(p);

        if (!context_has_syscall_logs(c))
                return 0;

#ifdef SCMP_ACT_LOG
        if (skip_seccomp_unavailable(c, p, "SystemCallLog="))
                return 0;

        if (c->syscall_log_allow_list) {
                /* Log nothing but the ones listed */
                default_action = SCMP_ACT_ALLOW;
                action = SCMP_ACT_LOG;
        } else {
                /* Log everything but the ones listed */
                default_action = SCMP_ACT_LOG;
                action = SCMP_ACT_ALLOW;
        }

        return seccomp_load_syscall_filter_set_raw(default_action, c->syscall_log, action, false);
#else
        /* old libseccomp */
        log_exec_debug(c, p, "SECCOMP feature SCMP_ACT_LOG not available, skipping SystemCallLog=");
        return 0;
#endif
}

static int apply_syscall_archs(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (set_isempty(c->syscall_archs))
                return 0;

        if (skip_seccomp_unavailable(c, p, "SystemCallArchitectures="))
                return 0;

        return seccomp_restrict_archs(c->syscall_archs);
}

static int apply_address_families(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!context_has_address_families(c))
                return 0;

        if (skip_seccomp_unavailable(c, p, "RestrictAddressFamilies="))
                return 0;

        return seccomp_restrict_address_families(c->address_families, c->address_families_allow_list);
}

static int apply_memory_deny_write_execute(const ExecContext *c, const ExecParameters *p) {
        int r;

        assert(c);
        assert(p);

        if (!c->memory_deny_write_execute)
                return 0;

        /* use prctl() if kernel supports it (6.3) */
        r = prctl(PR_SET_MDWE, PR_MDWE_REFUSE_EXEC_GAIN, 0, 0, 0);
        if (r == 0) {
                log_exec_debug(c, p, "Enabled MemoryDenyWriteExecute= with PR_SET_MDWE");
                return 0;
        }
        if (r < 0 && errno != EINVAL)
                return log_exec_debug_errno(c,
                                            p,
                                            errno,
                                            "Failed to enable MemoryDenyWriteExecute= with PR_SET_MDWE: %m");
        /* else use seccomp */
        log_exec_debug(c, p, "Kernel doesn't support PR_SET_MDWE: falling back to seccomp");

        if (skip_seccomp_unavailable(c, p, "MemoryDenyWriteExecute="))
                return 0;

        return seccomp_memory_deny_write_execute();
}

static int apply_restrict_realtime(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!c->restrict_realtime)
                return 0;

        if (skip_seccomp_unavailable(c, p, "RestrictRealtime="))
                return 0;

        return seccomp_restrict_realtime();
}

static int apply_restrict_suid_sgid(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!c->restrict_suid_sgid)
                return 0;

        if (skip_seccomp_unavailable(c, p, "RestrictSUIDSGID="))
                return 0;

        return seccomp_restrict_suid_sgid();
}

static int apply_protect_sysctl(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        /* Turn off the legacy sysctl() system call. Many distributions turn this off while building the kernel, but
         * let's protect even those systems where this is left on in the kernel. */

        if (!c->protect_kernel_tunables)
                return 0;

        if (skip_seccomp_unavailable(c, p, "ProtectKernelTunables="))
                return 0;

        return seccomp_protect_sysctl();
}

static int apply_protect_kernel_modules(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        /* Turn off module syscalls on ProtectKernelModules=yes */

        if (!c->protect_kernel_modules)
                return 0;

        if (skip_seccomp_unavailable(c, p, "ProtectKernelModules="))
                return 0;

        return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_MODULE, SCMP_ACT_ERRNO(EPERM), false);
}

static int apply_protect_kernel_logs(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!c->protect_kernel_logs)
                return 0;

        if (skip_seccomp_unavailable(c, p, "ProtectKernelLogs="))
                return 0;

        return seccomp_protect_syslog();
}

static int apply_protect_clock(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!c->protect_clock)
                return 0;

        if (skip_seccomp_unavailable(c, p, "ProtectClock="))
                return 0;

        return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_CLOCK, SCMP_ACT_ERRNO(EPERM), false);
}

static int apply_private_devices(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        /* If PrivateDevices= is set, also turn off iopl and all @raw-io syscalls. */

        if (!c->private_devices)
                return 0;

        if (skip_seccomp_unavailable(c, p, "PrivateDevices="))
                return 0;

        return seccomp_load_syscall_filter_set(SCMP_ACT_ALLOW, syscall_filter_sets + SYSCALL_FILTER_SET_RAW_IO, SCMP_ACT_ERRNO(EPERM), false);
}

static int apply_restrict_namespaces(const ExecContext *c, const ExecParameters *p) {
        assert(c);
        assert(p);

        if (!exec_context_restrict_namespaces_set(c))
                return 0;

        if (skip_seccomp_unavailable(c, p, "RestrictNamespaces="))
                return 0;

        return seccomp_restrict_namespaces(c->restrict_namespaces);
}

static int apply_lock_personality(const ExecContext *c, const ExecParameters *p) {
        unsigned long personality;
        int r;

        assert(c);
        assert(p);

        if (!c->lock_personality)
                return 0;

        if (skip_seccomp_unavailable(c, p, "LockPersonality="))
                return 0;

        personality = c->personality;

        /* If personality is not specified, use either PER_LINUX or PER_LINUX32 depending on what is currently set. */
        if (personality == PERSONALITY_INVALID) {

                r = opinionated_personality(&personality);
                if (r < 0)
                        return r;
        }

        return seccomp_lock_personality(personality);
}

#endif

#if HAVE_LIBBPF
static int apply_restrict_filesystems(const ExecContext *c, const ExecParameters *p) {
        int r;

        assert(c);
        assert(p);

        if (!exec_context_restrict_filesystems_set(c))
                return 0;

        if (p->bpf_restrict_fs_map_fd < 0) {
                /* LSM BPF is unsupported or lsm_bpf_setup failed */
                log_exec_debug(c, p, "LSM BPF not supported, skipping RestrictFileSystems=");
                return 0;
        }

        /* We are in a new binary, so dl-open again */
        r = dlopen_bpf();
        if (r < 0)
                return r;

        return bpf_restrict_fs_update(c->restrict_filesystems, p->cgroup_id, p->bpf_restrict_fs_map_fd, c->restrict_filesystems_allow_list);
}
#endif

static int apply_protect_hostname(const ExecContext *c, const ExecParameters *p, int *ret_exit_status) {
        int r;

        assert(c);
        assert(p);

        if (c->protect_hostname == PROTECT_HOSTNAME_NO)
                return 0;

        if (ns_type_supported(NAMESPACE_UTS)) {
                if (unshare(CLONE_NEWUTS) < 0) {
                        if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) {
                                *ret_exit_status = EXIT_NAMESPACE;
                                return log_exec_error_errno(c, p, errno, "Failed to set up UTS namespacing: %m");
                        }

                        log_exec_warning(c, p,
                                         "ProtectHostname=%s is configured, but UTS namespace setup is prohibited (container manager?), ignoring namespace setup.",
                                         protect_hostname_to_string(c->protect_hostname));

                } else if (c->private_hostname) {
                        r = sethostname_idempotent(c->private_hostname);
                        if (r < 0) {
                                *ret_exit_status = EXIT_NAMESPACE;
                                return log_exec_error_errno(c, p, r, "Failed to set private hostname '%s': %m", c->private_hostname);
                        }
                }
        } else
                log_exec_warning(c, p,
                                 "ProtectHostname=%s is configured, but the kernel does not support UTS namespaces, ignoring namespace setup.",
                                 protect_hostname_to_string(c->protect_hostname));

#if HAVE_SECCOMP
        if (c->protect_hostname == PROTECT_HOSTNAME_YES) {
                if (skip_seccomp_unavailable(c, p, "ProtectHostname="))
                        return 0;

                r = seccomp_protect_hostname();
                if (r < 0) {
                        *ret_exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(c, p, r, "Failed to apply hostname restrictions: %m");
                }
        }
#endif

        return 0;
}

static void do_idle_pipe_dance(int idle_pipe[static 4]) {
        assert(idle_pipe);

        idle_pipe[1] = safe_close(idle_pipe[1]);
        idle_pipe[2] = safe_close(idle_pipe[2]);

        if (idle_pipe[0] >= 0) {
                int r;

                r = fd_wait_for_event(idle_pipe[0], POLLHUP, IDLE_TIMEOUT_USEC);

                if (idle_pipe[3] >= 0 && r == 0 /* timeout */) {
                        ssize_t n;

                        /* Signal systemd that we are bored and want to continue. */
                        n = write(idle_pipe[3], "x", 1);
                        if (n > 0)
                                /* Wait for systemd to react to the signal above. */
                                (void) fd_wait_for_event(idle_pipe[0], POLLHUP, IDLE_TIMEOUT2_USEC);
                }

                idle_pipe[0] = safe_close(idle_pipe[0]);

        }

        idle_pipe[3] = safe_close(idle_pipe[3]);
}

static const char *exec_directory_env_name_to_string(ExecDirectoryType t);

/* And this table also maps ExecDirectoryType, to the environment variable we pass the selected directory to
 * the service payload in. */
static const char* const exec_directory_env_name_table[_EXEC_DIRECTORY_TYPE_MAX] = {
        [EXEC_DIRECTORY_RUNTIME]       = "RUNTIME_DIRECTORY",
        [EXEC_DIRECTORY_STATE]         = "STATE_DIRECTORY",
        [EXEC_DIRECTORY_CACHE]         = "CACHE_DIRECTORY",
        [EXEC_DIRECTORY_LOGS]          = "LOGS_DIRECTORY",
        [EXEC_DIRECTORY_CONFIGURATION] = "CONFIGURATION_DIRECTORY",
};

DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(exec_directory_env_name, ExecDirectoryType);

static int build_environment(
                const ExecContext *c,
                const ExecParameters *p,
                const CGroupContext *cgroup_context,
                size_t n_fds,
                const char *home,
                const char *username,
                const char *shell,
                dev_t journal_stream_dev,
                ino_t journal_stream_ino,
                const char *memory_pressure_path,
                bool needs_sandboxing,
                char ***ret) {

        _cleanup_strv_free_ char **our_env = NULL;
        size_t n_env = 0;
        char *x;
        int r;

        assert(c);
        assert(p);
        assert(ret);

#define N_ENV_VARS 20
        our_env = new0(char*, N_ENV_VARS + _EXEC_DIRECTORY_TYPE_MAX);
        if (!our_env)
                return -ENOMEM;

        if (n_fds > 0) {
                _cleanup_free_ char *joined = NULL;

                if (asprintf(&x, "LISTEN_PID="PID_FMT, getpid_cached()) < 0)
                        return -ENOMEM;
                our_env[n_env++] = x;

                if (asprintf(&x, "LISTEN_FDS=%zu", n_fds) < 0)
                        return -ENOMEM;
                our_env[n_env++] = x;

                joined = strv_join(p->fd_names, ":");
                if (!joined)
                        return -ENOMEM;

                x = strjoin("LISTEN_FDNAMES=", joined);
                if (!x)
                        return -ENOMEM;
                our_env[n_env++] = x;
        }

        if ((p->flags & EXEC_SET_WATCHDOG) && p->watchdog_usec > 0) {
                if (asprintf(&x, "WATCHDOG_PID="PID_FMT, getpid_cached()) < 0)
                        return -ENOMEM;
                our_env[n_env++] = x;

                if (asprintf(&x, "WATCHDOG_USEC="USEC_FMT, p->watchdog_usec) < 0)
                        return -ENOMEM;
                our_env[n_env++] = x;
        }

        /* If this is D-Bus, tell the nss-systemd module, since it relies on being able to use blocking
         * Varlink calls back to us for look up dynamic users in PID 1. Break the deadlock between D-Bus and
         * PID 1 by disabling use of PID1' NSS interface for looking up dynamic users. */
        if (p->flags & EXEC_NSS_DYNAMIC_BYPASS) {
                x = strdup("SYSTEMD_NSS_DYNAMIC_BYPASS=1");
                if (!x)
                        return -ENOMEM;
                our_env[n_env++] = x;
        }

        /* We query "root" if this is a system unit and User= is not specified. $USER is always set. $HOME
         * could cause problem for e.g. getty, since login doesn't override $HOME, and $LOGNAME and $SHELL don't
         * really make much sense since we're not logged in. Hence we conditionalize the three based on
         * SetLoginEnvironment= switch. */
        if (!c->user && !c->dynamic_user && p->runtime_scope == RUNTIME_SCOPE_SYSTEM) {
                r = get_fixed_user("root", &username, NULL, NULL, &home, &shell);
                if (r < 0)
                        return log_exec_debug_errno(c,
                                                    p,
                                                    r,
                                                    "Failed to determine user credentials for root: %m");
        }

        bool set_user_login_env = exec_context_get_set_login_environment(c);

        if (username) {
                x = strjoin("USER=", username);
                if (!x)
                        return -ENOMEM;
                our_env[n_env++] = x;

                if (set_user_login_env) {
                        x = strjoin("LOGNAME=", username);
                        if (!x)
                                return -ENOMEM;
                        our_env[n_env++] = x;
                }
        }

        /* Note that we don't set $HOME or $SHELL if they are not particularly enlightening anyway
         * (i.e. are "/" or "/bin/nologin"). */

        if (home && set_user_login_env && !empty_or_root(home)) {
                x = strjoin("HOME=", home);
                if (!x)
                        return -ENOMEM;

                path_simplify(x + 5);
                our_env[n_env++] = x;
        }

        if (shell && set_user_login_env && !shell_is_placeholder(shell)) {
                x = strjoin("SHELL=", shell);
                if (!x)
                        return -ENOMEM;

                path_simplify(x + 6);
                our_env[n_env++] = x;
        }

        if (!sd_id128_is_null(p->invocation_id)) {
                assert(p->invocation_id_string);

                x = strjoin("INVOCATION_ID=", p->invocation_id_string);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        if (exec_context_needs_term(c)) {
                _cleanup_free_ char *cmdline = NULL;
                const char *tty_path, *term = NULL;

                tty_path = exec_context_tty_path(c);

                /* If we are forked off PID 1 and we are supposed to operate on /dev/console, then let's try
                 * to inherit the $TERM set for PID 1. This is useful for containers so that the $TERM the
                 * container manager passes to PID 1 ends up all the way in the console login shown. */

                if (path_equal(tty_path, "/dev/console") && getppid() == 1)
                        term = getenv("TERM");
                else if (tty_path && in_charset(skip_dev_prefix(tty_path), ALPHANUMERICAL)) {
                        _cleanup_free_ char *key = NULL;

                        key = strjoin("systemd.tty.term.", skip_dev_prefix(tty_path));
                        if (!key)
                                return -ENOMEM;

                        r = proc_cmdline_get_key(key, 0, &cmdline);
                        if (r < 0)
                                log_exec_debug_errno(c,
                                                     p,
                                                     r,
                                                     "Failed to read %s from kernel cmdline, ignoring: %m",
                                                     key);
                        else if (r > 0)
                                term = cmdline;
                }

                if (!term)
                        term = default_term_for_tty(tty_path);

                x = strjoin("TERM=", term);
                if (!x)
                        return -ENOMEM;
                our_env[n_env++] = x;
        }

        if (journal_stream_dev != 0 && journal_stream_ino != 0) {
                if (asprintf(&x, "JOURNAL_STREAM=" DEV_FMT ":" INO_FMT, journal_stream_dev, journal_stream_ino) < 0)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        if (c->log_namespace) {
                x = strjoin("LOG_NAMESPACE=", c->log_namespace);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
                _cleanup_free_ char *joined = NULL;
                const char *n;

                if (!p->prefix[t])
                        continue;

                if (c->directories[t].n_items == 0)
                        continue;

                n = exec_directory_env_name_to_string(t);
                if (!n)
                        continue;

                for (size_t i = 0; i < c->directories[t].n_items; i++) {
                        _cleanup_free_ char *prefixed = NULL;

                        prefixed = path_join(p->prefix[t], c->directories[t].items[i].path);
                        if (!prefixed)
                                return -ENOMEM;

                        if (!strextend_with_separator(&joined, ":", prefixed))
                                return -ENOMEM;
                }

                x = strjoin(n, "=", joined);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        _cleanup_free_ char *creds_dir = NULL;
        r = exec_context_get_credential_directory(c, p, p->unit_id, &creds_dir);
        if (r < 0)
                return r;
        if (r > 0) {
                x = strjoin("CREDENTIALS_DIRECTORY=", creds_dir);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        if (asprintf(&x, "SYSTEMD_EXEC_PID=" PID_FMT, getpid_cached()) < 0)
                return -ENOMEM;

        our_env[n_env++] = x;

        if (memory_pressure_path) {
                x = strjoin("MEMORY_PRESSURE_WATCH=", memory_pressure_path);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;

                if (cgroup_context && !path_equal(memory_pressure_path, "/dev/null")) {
                        _cleanup_free_ char *b = NULL, *e = NULL;

                        if (asprintf(&b, "%s " USEC_FMT " " USEC_FMT,
                                     MEMORY_PRESSURE_DEFAULT_TYPE,
                                     cgroup_context->memory_pressure_threshold_usec == USEC_INFINITY ? MEMORY_PRESSURE_DEFAULT_THRESHOLD_USEC :
                                     CLAMP(cgroup_context->memory_pressure_threshold_usec, 1U, MEMORY_PRESSURE_DEFAULT_WINDOW_USEC),
                                     MEMORY_PRESSURE_DEFAULT_WINDOW_USEC) < 0)
                                return -ENOMEM;

                        if (base64mem(b, strlen(b) + 1, &e) < 0)
                                return -ENOMEM;

                        x = strjoin("MEMORY_PRESSURE_WRITE=", e);
                        if (!x)
                                return -ENOMEM;

                        our_env[n_env++] = x;
                }
        }

        if (p->notify_socket) {
                x = strjoin("NOTIFY_SOCKET=", exec_get_private_notify_socket_path(c, p, needs_sandboxing) ?: p->notify_socket);
                if (!x)
                        return -ENOMEM;

                our_env[n_env++] = x;
        }

        assert(n_env < N_ENV_VARS + _EXEC_DIRECTORY_TYPE_MAX);
#undef N_ENV_VARS

        *ret = TAKE_PTR(our_env);

        return 0;
}

static int build_pass_environment(const ExecContext *c, char ***ret) {
        _cleanup_strv_free_ char **pass_env = NULL;
        size_t n_env = 0;

        STRV_FOREACH(i, c->pass_environment) {
                _cleanup_free_ char *x = NULL;
                char *v;

                v = getenv(*i);
                if (!v)
                        continue;
                x = strjoin(*i, "=", v);
                if (!x)
                        return -ENOMEM;

                if (!GREEDY_REALLOC(pass_env, n_env + 2))
                        return -ENOMEM;

                pass_env[n_env++] = TAKE_PTR(x);
                pass_env[n_env] = NULL;
        }

        *ret = TAKE_PTR(pass_env);

        return 0;
}

static int setup_private_users(PrivateUsers private_users, uid_t ouid, gid_t ogid, uid_t uid, gid_t gid, bool allow_setgroups) {
        _cleanup_free_ char *uid_map = NULL, *gid_map = NULL;
        _cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
        _cleanup_close_ int unshare_ready_fd = -EBADF;
        _cleanup_(sigkill_waitp) pid_t pid = 0;
        uint64_t c = 1;
        ssize_t n;
        int r;

        /* Set up a user namespace and map the original UID/GID (IDs from before any user or group changes, i.e.
         * the IDs from the user or system manager(s)) to itself, the selected UID/GID to itself, and everything else to
         * nobody. In order to be able to write this mapping we need CAP_SETUID in the original user namespace, which
         * we however lack after opening the user namespace. To work around this we fork() a temporary child process,
         * which waits for the parent to create the new user namespace while staying in the original namespace. The
         * child then writes the UID mapping, under full privileges. The parent waits for the child to finish and
         * continues execution normally.
         * For unprivileged users (i.e. without capabilities), the root to root mapping is excluded. As such, it
         * does not need CAP_SETUID to write the single line mapping to itself. */

        if (private_users == PRIVATE_USERS_NO)
                return 0;

        if (private_users == PRIVATE_USERS_IDENTITY) {
                uid_map = strdup("0 0 65536\n");
                if (!uid_map)
                        return -ENOMEM;
        } else if (private_users == PRIVATE_USERS_FULL) {
                /* Map all UID/GID from original to new user namespace. We can't use `0 0 UINT32_MAX` because
                 * this is the same UID/GID map as the init user namespace and systemd's running_in_userns()
                 * checks whether its in a user namespace by comparing uid_map/gid_map to `0 0 UINT32_MAX`.
                 * Thus, we still map all UIDs/GIDs but do it using two extents to differentiate the new user
                 * namespace from the init namespace:
                 *   0 0 1
                 *   1 1 UINT32_MAX - 1
                 *
                 * systemd will remove the heuristic in running_in_userns() and use namespace inodes in version 258
                 * (PR #35382). But some users may be running a container image with older systemd < 258 so we keep
                 * this uid_map/gid_map hack until version 259 for version N-1 compatibility.
                 *
                 * TODO: Switch to `0 0 UINT32_MAX` in systemd v259.
                 *
                 * Note the kernel defines the UID range between 0 and UINT32_MAX so we map all UIDs even though
                 * the UID range beyond INT32_MAX (e.g. i.e. the range above the signed 32-bit range) is
                 * icky. For example, setfsuid() returns the old UID as signed integer. But units can decide to
                 * use these UIDs/GIDs so we need to map them. */
                r = asprintf(&uid_map, "0 0 1\n"
                                       "1 1 " UID_FMT "\n", (uid_t) (UINT32_MAX - 1));
                if (r < 0)
                        return -ENOMEM;
        /* Can only set up multiple mappings with CAP_SETUID. */
        } else if (have_effective_cap(CAP_SETUID) > 0 && uid != ouid && uid_is_valid(uid)) {
                r = asprintf(&uid_map,
                             UID_FMT " " UID_FMT " 1\n"     /* Map $OUID → $OUID */
                             UID_FMT " " UID_FMT " 1\n",    /* Map $UID → $UID */
                             ouid, ouid, uid, uid);
                if (r < 0)
                        return -ENOMEM;
        } else {
                r = asprintf(&uid_map,
                             UID_FMT " " UID_FMT " 1\n",    /* Map $OUID → $OUID */
                             ouid, ouid);
                if (r < 0)
                        return -ENOMEM;
        }

        if (private_users == PRIVATE_USERS_IDENTITY) {
                gid_map = strdup("0 0 65536\n");
                if (!gid_map)
                        return -ENOMEM;
        } else if (private_users == PRIVATE_USERS_FULL) {
                r = asprintf(&gid_map, "0 0 1\n"
                                       "1 1 " GID_FMT "\n", (gid_t) (UINT32_MAX - 1));
                if (r < 0)
                        return -ENOMEM;
        /* Can only set up multiple mappings with CAP_SETGID. */
        } else if (have_effective_cap(CAP_SETGID) > 0 && gid != ogid && gid_is_valid(gid)) {
                r = asprintf(&gid_map,
                             GID_FMT " " GID_FMT " 1\n"     /* Map $OGID → $OGID */
                             GID_FMT " " GID_FMT " 1\n",    /* Map $GID → $GID */
                             ogid, ogid, gid, gid);
                if (r < 0)
                        return -ENOMEM;
        } else {
                r = asprintf(&gid_map,
                             GID_FMT " " GID_FMT " 1\n",    /* Map $OGID -> $OGID */
                             ogid, ogid);
                if (r < 0)
                        return -ENOMEM;
        }

        /* Create a communication channel so that the parent can tell the child when it finished creating the user
         * namespace. */
        unshare_ready_fd = eventfd(0, EFD_CLOEXEC);
        if (unshare_ready_fd < 0)
                return -errno;

        /* Create a communication channel so that the child can tell the parent a proper error code in case it
         * failed. */
        if (pipe2(errno_pipe, O_CLOEXEC) < 0)
                return -errno;

        r = safe_fork("(sd-userns)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL, &pid);
        if (r < 0)
                return r;
        if (r == 0) {
                _cleanup_close_ int fd = -EBADF;
                const char *a;
                pid_t ppid;

                /* Child process, running in the original user namespace. Let's update the parent's UID/GID map from
                 * here, after the parent opened its own user namespace. */

                ppid = getppid();
                errno_pipe[0] = safe_close(errno_pipe[0]);

                /* Wait until the parent unshared the user namespace */
                if (read(unshare_ready_fd, &c, sizeof(c)) < 0)
                        report_errno_and_exit(errno_pipe[1], -errno);

                /* Disable the setgroups() system call in the child user namespace, for good, unless PrivateUsers=full
                 * and using the system service manager. */
                a = procfs_file_alloca(ppid, "setgroups");
                fd = open(a, O_WRONLY|O_CLOEXEC);
                if (fd < 0) {
                        if (errno != ENOENT) {
                                r = log_debug_errno(errno, "Failed to open %s: %m", a);
                                report_errno_and_exit(errno_pipe[1], r);
                        }

                        /* If the file is missing the kernel is too old, let's continue anyway. */
                } else {
                        const char *setgroups = allow_setgroups ? "allow\n" : "deny\n";
                        if (write(fd, setgroups, strlen(setgroups)) < 0) {
                                r = log_debug_errno(errno, "Failed to write '%s' to %s: %m", setgroups, a);
                                report_errno_and_exit(errno_pipe[1], r);
                        }

                        fd = safe_close(fd);
                }

                /* First write the GID map */
                a = procfs_file_alloca(ppid, "gid_map");
                fd = open(a, O_WRONLY|O_CLOEXEC);
                if (fd < 0) {
                        r = log_debug_errno(errno, "Failed to open %s: %m", a);
                        report_errno_and_exit(errno_pipe[1], r);
                }

                if (write(fd, gid_map, strlen(gid_map)) < 0) {
                        r = log_debug_errno(errno, "Failed to write GID map to %s: %m", a);
                        report_errno_and_exit(errno_pipe[1], r);
                }

                fd = safe_close(fd);

                /* The write the UID map */
                a = procfs_file_alloca(ppid, "uid_map");
                fd = open(a, O_WRONLY|O_CLOEXEC);
                if (fd < 0) {
                        r = log_debug_errno(errno, "Failed to open %s: %m", a);
                        report_errno_and_exit(errno_pipe[1], r);
                }

                if (write(fd, uid_map, strlen(uid_map)) < 0) {
                        r = log_debug_errno(errno, "Failed to write UID map to %s: %m", a);
                        report_errno_and_exit(errno_pipe[1], r);
                }

                _exit(EXIT_SUCCESS);
        }

        errno_pipe[1] = safe_close(errno_pipe[1]);

        if (unshare(CLONE_NEWUSER) < 0)
                return log_debug_errno(errno, "Failed to unshare user namespace: %m");

        /* Let the child know that the namespace is ready now */
        if (write(unshare_ready_fd, &c, sizeof(c)) < 0)
                return -errno;

        /* Try to read an error code from the child */
        n = read(errno_pipe[0], &r, sizeof(r));
        if (n < 0)
                return -errno;
        if (n == sizeof(r)) { /* an error code was sent to us */
                if (r < 0)
                        return r;
                return -EIO;
        }
        if (n != 0) /* on success we should have read 0 bytes */
                return -EIO;

        r = wait_for_terminate_and_check("(sd-userns)", TAKE_PID(pid), 0);
        if (r < 0)
                return r;
        if (r != EXIT_SUCCESS) /* If something strange happened with the child, let's consider this fatal, too */
                return -EIO;

        return 1;
}

static int can_mount_proc(const ExecContext *c, ExecParameters *p) {
        _cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
        _cleanup_(sigkill_waitp) pid_t pid = 0;
        ssize_t n;
        int r;

        assert(c);
        assert(p);

        /* If running via unprivileged user manager and /proc/ is masked (e.g. /proc/kmsg is over-mounted with tmpfs
         * like systemd-nspawn does), then mounting /proc/ will fail with EPERM. This is due to a kernel restriction
         * where unprivileged user namespaces cannot mount a less restrictive instance of /proc. */

        /* Create a communication channel so that the child can tell the parent a proper error code in case it
         * failed. */
        if (pipe2(errno_pipe, O_CLOEXEC) < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to create pipe for communicating with child process (sd-proc-check): %m");

        /* Fork a child process into its own mount and PID namespace. Note safe_fork() already remounts / as SLAVE
         * with FORK_MOUNTNS_SLAVE. */
        r = safe_fork("(sd-proc-check)",
                      FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL|FORK_NEW_MOUNTNS|FORK_MOUNTNS_SLAVE|FORK_NEW_PIDNS, &pid);
        if (r < 0)
                return log_exec_debug_errno(c, p, r, "Failed to fork child process (sd-proc-check): %m");
        if (r == 0) {
                errno_pipe[0] = safe_close(errno_pipe[0]);

                /* Try mounting /proc on /dev/shm/. No need to clean up the mount since the mount
                 * namespace will be cleaned up once the process exits. */
                r = mount_follow_verbose(LOG_DEBUG, "proc", "/dev/shm/", "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
                if (r < 0) {
                        (void) write(errno_pipe[1], &r, sizeof(r));
                        _exit(EXIT_FAILURE);
                }

                _exit(EXIT_SUCCESS);
        }

        errno_pipe[1] = safe_close(errno_pipe[1]);

        /* Try to read an error code from the child */
        n = read(errno_pipe[0], &r, sizeof(r));
        if (n < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to read errno from pipe with child process (sd-proc-check): %m");
        if (n == sizeof(r)) { /* an error code was sent to us */
                /* This is the expected case where proc cannot be mounted due to permissions. */
                if (ERRNO_IS_NEG_PRIVILEGE(r))
                        return 0;
                if (r < 0)
                        return r;

                return -EIO;
        }
        if (n != 0) /* on success we should have read 0 bytes */
                return -EIO;

        r = wait_for_terminate_and_check("(sd-proc-check)", TAKE_PID(pid), 0 /* flags= */);
        if (r < 0)
                return log_exec_debug_errno(c, p, r, "Failed to wait for (sd-proc-check) child process to terminate: %m");
        if (r != EXIT_SUCCESS) /* If something strange happened with the child, let's consider this fatal, too */
                return log_exec_debug_errno(c, p, SYNTHETIC_ERRNO(EIO), "Child process (sd-proc-check) exited with unexpected exit status '%d'.", r);

        return 1;
}

static int setup_private_pids(const ExecContext *c, ExecParameters *p) {
        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
        _cleanup_close_pair_ int errno_pipe[2] = EBADF_PAIR;
        ssize_t n;
        int r, q;

        assert(c);
        assert(p);
        assert(p->pidref_transport_fd >= 0);

        /* The first process created after unsharing a pid namespace becomes PID 1 in the pid namespace, so
         * we have to fork after unsharing the pid namespace to become PID 1. The parent sends the child
         * pidref to the manager and exits while the child process continues with the rest of exec_invoke()
         * and finally executes the actual payload. */

        /* Create a communication channel so that the parent can tell the child a proper error code in case it
         * failed to send child pidref to the manager. */
        if (pipe2(errno_pipe, O_CLOEXEC) < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to create pipe for communicating with parent process: %m");

        r = pidref_safe_fork("(sd-pidns-child)", FORK_NEW_PIDNS, &pidref);
        if (r < 0)
                return log_exec_debug_errno(c, p, r, "Failed to fork child into new pid namespace: %m");
        if (r > 0) {
                errno_pipe[0] = safe_close(errno_pipe[0]);

                /* In the parent process, we send the child pidref to the manager and exit.
                 * If PIDFD is not supported, only the child PID is sent. The server then
                 * uses the child PID to set the new exec main process. */
                q = send_one_fd_iov(
                                p->pidref_transport_fd,
                                pidref.fd,
                                &IOVEC_MAKE(&pidref.pid, sizeof(pidref.pid)),
                                /*iovlen=*/ 1,
                                /*flags=*/ 0);
                /* Send error code to child process. */
                (void) write(errno_pipe[1], &q, sizeof(q));
                /* Exit here so we only go through the destructors in exec_invoke only once - in the child - as
                 * some destructors have external effects. The main codepaths continue in the child process. */
                _exit(q < 0 ? EXIT_FAILURE : EXIT_SUCCESS);
        }

        errno_pipe[1] = safe_close(errno_pipe[1]);
        p->pidref_transport_fd = safe_close(p->pidref_transport_fd);

        /* Try to read an error code from the parent. Note a child process cannot wait for the parent so we always
         * receive an errno even on success. */
        n = read(errno_pipe[0], &r, sizeof(r));
        if (n < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to read errno from pipe with parent process: %m");
        if (n != sizeof(r))
                return log_exec_debug_errno(c, p, SYNTHETIC_ERRNO(EIO), "Failed to read enough bytes from pipe with parent process");
        if (r < 0)
                return log_exec_debug_errno(c, p, r, "Failed to send child pidref to manager: %m");

        /* NOTE! This function returns in the child process only. */
        return r;
}

static int create_many_symlinks(const char *root, const char *source, char **symlinks) {
        _cleanup_free_ char *src_abs = NULL;
        int r;

        assert(source);

        src_abs = path_join(root, source);
        if (!src_abs)
                return -ENOMEM;

        STRV_FOREACH(dst, symlinks) {
                _cleanup_free_ char *dst_abs = NULL;

                dst_abs = path_join(root, *dst);
                if (!dst_abs)
                        return -ENOMEM;

                r = mkdir_parents_label(dst_abs, 0755);
                if (r < 0)
                        return r;

                r = symlink_idempotent(src_abs, dst_abs, true);
                if (r < 0)
                        return r;
        }

        return 0;
}

static int setup_exec_directory(
                const ExecContext *context,
                const ExecParameters *params,
                uid_t uid,
                gid_t gid,
                ExecDirectoryType type,
                bool needs_mount_namespace,
                int *exit_status) {

        static const int exit_status_table[_EXEC_DIRECTORY_TYPE_MAX] = {
                [EXEC_DIRECTORY_RUNTIME]       = EXIT_RUNTIME_DIRECTORY,
                [EXEC_DIRECTORY_STATE]         = EXIT_STATE_DIRECTORY,
                [EXEC_DIRECTORY_CACHE]         = EXIT_CACHE_DIRECTORY,
                [EXEC_DIRECTORY_LOGS]          = EXIT_LOGS_DIRECTORY,
                [EXEC_DIRECTORY_CONFIGURATION] = EXIT_CONFIGURATION_DIRECTORY,
        };
        int r;

        assert(context);
        assert(params);
        assert(type >= 0 && type < _EXEC_DIRECTORY_TYPE_MAX);
        assert(exit_status);

        if (!params->prefix[type])
                return 0;

        if (params->flags & EXEC_CHOWN_DIRECTORIES) {
                if (!uid_is_valid(uid))
                        uid = 0;
                if (!gid_is_valid(gid))
                        gid = 0;
        }

        FOREACH_ARRAY(i, context->directories[type].items, context->directories[type].n_items) {
                _cleanup_free_ char *p = NULL, *pp = NULL;

                p = path_join(params->prefix[type], i->path);
                if (!p) {
                        r = -ENOMEM;
                        goto fail;
                }

                r = mkdir_parents_label(p, 0755);
                if (r < 0)
                        goto fail;

                if (IN_SET(type, EXEC_DIRECTORY_STATE, EXEC_DIRECTORY_LOGS) && params->runtime_scope == RUNTIME_SCOPE_USER) {

                        /* If we are in user mode, and a configuration directory exists but a state directory
                         * doesn't exist, then we likely are upgrading from an older systemd version that
                         * didn't know the more recent addition to the xdg-basedir spec: the $XDG_STATE_HOME
                         * directory. In older systemd versions EXEC_DIRECTORY_STATE was aliased to
                         * EXEC_DIRECTORY_CONFIGURATION, with the advent of $XDG_STATE_HOME it is now
                         * separated. If a service has both dirs configured but only the configuration dir
                         * exists and the state dir does not, we assume we are looking at an update
                         * situation. Hence, create a compatibility symlink, so that all expectations are
                         * met.
                         *
                         * (We also do something similar with the log directory, which still doesn't exist in
                         * the xdg basedir spec. We'll make it a subdir of the state dir.) */

                        /* this assumes the state dir is always created before the configuration dir */
                        assert_cc(EXEC_DIRECTORY_STATE < EXEC_DIRECTORY_LOGS);
                        assert_cc(EXEC_DIRECTORY_LOGS < EXEC_DIRECTORY_CONFIGURATION);

                        r = access_nofollow(p, F_OK);
                        if (r == -ENOENT) {
                                _cleanup_free_ char *q = NULL;

                                /* OK, we know that the state dir does not exist. Let's see if the dir exists
                                 * under the configuration hierarchy. */

                                if (type == EXEC_DIRECTORY_STATE)
                                        q = path_join(params->prefix[EXEC_DIRECTORY_CONFIGURATION], i->path);
                                else if (type == EXEC_DIRECTORY_LOGS)
                                        q = path_join(params->prefix[EXEC_DIRECTORY_CONFIGURATION], "log", i->path);
                                else
                                        assert_not_reached();
                                if (!q) {
                                        r = -ENOMEM;
                                        goto fail;
                                }

                                r = access_nofollow(q, F_OK);
                                if (r >= 0) {
                                        /* It does exist! This hence looks like an update. Symlink the
                                         * configuration directory into the state directory. */

                                        r = symlink_idempotent(q, p, /* make_relative= */ true);
                                        if (r < 0)
                                                goto fail;

                                        log_exec_notice(context, params, "Unit state directory %s missing but matching configuration directory %s exists, assuming update from systemd 253 or older, creating compatibility symlink.", p, q);
                                        continue;
                                } else if (r != -ENOENT)
                                        log_exec_warning_errno(context, params, r, "Unable to detect whether unit configuration directory '%s' exists, assuming not: %m", q);

                        } else if (r < 0)
                                log_exec_warning_errno(context, params, r, "Unable to detect whether unit state directory '%s' is missing, assuming it is: %m", p);
                }

                if (exec_directory_is_private(context, type)) {
                        /* So, here's one extra complication when dealing with DynamicUser=1 units. In that
                         * case we want to avoid leaving a directory around fully accessible that is owned by
                         * a dynamic user whose UID is later on reused. To lock this down we use the same
                         * trick used by container managers to prohibit host users to get access to files of
                         * the same UID in containers: we place everything inside a directory that has an
                         * access mode of 0700 and is owned root:root, so that it acts as security boundary
                         * for unprivileged host code. We then use fs namespacing to make this directory
                         * permeable for the service itself.
                         *
                         * Specifically: for a service which wants a special directory "foo/" we first create
                         * a directory "private/" with access mode 0700 owned by root:root. Then we place
                         * "foo" inside of that directory (i.e. "private/foo/"), and make "foo" a symlink to
                         * "private/foo". This way, privileged host users can access "foo/" as usual, but
                         * unprivileged host users can't look into it. Inside of the namespace of the unit
                         * "private/" is replaced by a more liberally accessible tmpfs, into which the host's
                         * "private/foo/" is mounted under the same name, thus disabling the access boundary
                         * for the service and making sure it only gets access to the dirs it needs but no
                         * others. Tricky? Yes, absolutely, but it works!
                         *
                         * Note that we don't do this for EXEC_DIRECTORY_CONFIGURATION as that's assumed not
                         * to be owned by the service itself.
                         *
                         * Also, note that we don't do this for EXEC_DIRECTORY_RUNTIME as that's often used
                         * for sharing files or sockets with other services. */

                        pp = path_join(params->prefix[type], "private");
                        if (!pp) {
                                r = -ENOMEM;
                                goto fail;
                        }

                        /* First set up private root if it doesn't exist yet, with access mode 0700 and owned by root:root */
                        r = mkdir_safe_label(pp, 0700, 0, 0, MKDIR_WARN_MODE);
                        if (r < 0)
                                goto fail;

                        if (!path_extend(&pp, i->path)) {
                                r = -ENOMEM;
                                goto fail;
                        }

                        /* Create all directories between the configured directory and this private root, and mark them 0755 */
                        r = mkdir_parents_label(pp, 0755);
                        if (r < 0)
                                goto fail;

                        if (is_dir(p, false) > 0 &&
                            (access_nofollow(pp, F_OK) == -ENOENT)) {

                                /* Hmm, the private directory doesn't exist yet, but the normal one exists? If so, move
                                 * it over. Most likely the service has been upgraded from one that didn't use
                                 * DynamicUser=1, to one that does. */

                                log_exec_info(context,
                                              params,
                                              "Found pre-existing public %s= directory %s, migrating to %s.\n"
                                              "Apparently, service previously had DynamicUser= turned off, and has now turned it on.",
                                              exec_directory_type_to_string(type), p, pp);

                                r = RET_NERRNO(rename(p, pp));
                                if (r < 0)
                                        goto fail;
                        } else {
                                /* Otherwise, create the actual directory for the service */

                                r = mkdir_label(pp, context->directories[type].mode);
                                if (r < 0 && r != -EEXIST)
                                        goto fail;
                        }

                        if (!FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE)) {
                                /* And link it up from the original place.
                                 * Notes
                                 * 1) If a mount namespace is going to be used, then this symlink remains on
                                 *    the host, and a new one for the child namespace will be created later.
                                 * 2) It is not necessary to create this symlink when one of its parent
                                 *    directories is specified and already created. E.g.
                                 *        StateDirectory=foo foo/bar
                                 *    In that case, the inode points to pp and p for "foo/bar" are the same:
                                 *        pp = "/var/lib/private/foo/bar"
                                 *        p = "/var/lib/foo/bar"
                                 *    and, /var/lib/foo is a symlink to /var/lib/private/foo. So, not only
                                 *    we do not need to create the symlink, but we cannot create the symlink.
                                 *    See issue #24783. */
                                r = symlink_idempotent(pp, p, true);
                                if (r < 0)
                                        goto fail;
                        }

                } else {
                        _cleanup_free_ char *target = NULL;

                        if (EXEC_DIRECTORY_TYPE_SHALL_CHOWN(type) &&
                            readlink_and_make_absolute(p, &target) >= 0) {
                                _cleanup_free_ char *q = NULL, *q_resolved = NULL, *target_resolved = NULL;

                                /* This already exists and is a symlink? Interesting. Maybe it's one created
                                 * by DynamicUser=1 (see above)?
                                 *
                                 * We do this for all directory types except for ConfigurationDirectory=,
                                 * since they all support the private/ symlink logic at least in some
                                 * configurations, see above. */

                                r = chase(target, NULL, 0, &target_resolved, NULL);
                                if (r < 0)
                                        goto fail;

                                q = path_join(params->prefix[type], "private", i->path);
                                if (!q) {
                                        r = -ENOMEM;
                                        goto fail;
                                }

                                /* /var/lib or friends may be symlinks. So, let's chase them also. */
                                r = chase(q, NULL, CHASE_NONEXISTENT, &q_resolved, NULL);
                                if (r < 0)
                                        goto fail;

                                if (path_equal(q_resolved, target_resolved)) {

                                        /* Hmm, apparently DynamicUser= was once turned on for this service,
                                         * but is no longer. Let's move the directory back up. */

                                        log_exec_info(context,
                                                      params,
                                                      "Found pre-existing private %s= directory %s, migrating to %s.\n"
                                                      "Apparently, service previously had DynamicUser= turned on, and has now turned it off.",
                                                      exec_directory_type_to_string(type), q, p);

                                        r = RET_NERRNO(unlink(p));
                                        if (r < 0)
                                                goto fail;

                                        r = RET_NERRNO(rename(q, p));
                                        if (r < 0)
                                                goto fail;
                                }
                        }

                        r = mkdir_label(p, context->directories[type].mode);
                        if (r < 0) {
                                if (r != -EEXIST)
                                        goto fail;

                                if (!EXEC_DIRECTORY_TYPE_SHALL_CHOWN(type)) {
                                        struct stat st;

                                        /* Don't change the owner/access mode of the configuration directory,
                                         * as in the common case it is not written to by a service, and shall
                                         * not be writable. */

                                        r = RET_NERRNO(stat(p, &st));
                                        if (r < 0)
                                                goto fail;

                                        /* Still complain if the access mode doesn't match */
                                        if (((st.st_mode ^ context->directories[type].mode) & 07777) != 0)
                                                log_exec_warning(context,
                                                                 params,
                                                                 "%s \'%s\' already exists but the mode is different. "
                                                                 "(File system: %o %sMode: %o)",
                                                                 exec_directory_type_to_string(type), i->path,
                                                                 st.st_mode & 07777, exec_directory_type_to_string(type), context->directories[type].mode & 07777);

                                        continue;
                                }
                        }
                }

                /* Lock down the access mode (we use chmod_and_chown() to make this idempotent. We don't
                 * specify UID/GID here, so that path_chown_recursive() can optimize things depending on the
                 * current UID/GID ownership.) */
                const char *target_dir = pp ?: p;
                r = chmod_and_chown(target_dir, context->directories[type].mode, UID_INVALID, GID_INVALID);
                if (r < 0)
                        goto fail;

                /* Skip the rest (which deals with ownership) in user mode, since ownership changes are not
                 * available to user code anyway */
                if (params->runtime_scope != RUNTIME_SCOPE_SYSTEM)
                        continue;

                int idmapping_supported = is_idmapping_supported(target_dir);
                if (idmapping_supported < 0) {
                        r = log_debug_errno(idmapping_supported, "Unable to determine if ID mapping is supported on mount '%s': %m", target_dir);
                        goto fail;
                }

                log_debug("ID-mapping is%ssupported for exec directory %s", idmapping_supported ? " " : " not ", target_dir);

                /* Change the ownership of the whole tree, if necessary. When dynamic users are used we
                 * drop the suid/sgid bits, since we really don't want SUID/SGID files for dynamic UID/GID
                 * assignments to exist. */
                uid_t chown_uid = uid;
                gid_t chown_gid = gid;
                bool do_chown = false;

                if (uid == 0 || gid == 0 || !idmapping_supported) {
                        do_chown = true;
                        i->idmapped = false;
                } else {
                        /* Use 'nobody' uid/gid for exec directories if ID-mapping is supported. For backward compatibility,
                         * continue doing chmod/chown if the directory was chmod/chowned before (if uid/gid is not 'nobody') */
                        struct stat st;
                        r = RET_NERRNO(stat(target_dir, &st));
                        if (r < 0)
                                goto fail;

                        if (st.st_uid == UID_NOBODY && st.st_gid == GID_NOBODY) {
                                do_chown = false;
                                i->idmapped = true;
                       } else if (exec_directory_is_private(context, type) && st.st_uid == 0 && st.st_gid == 0) {
                                chown_uid = UID_NOBODY;
                                chown_gid = GID_NOBODY;
                                do_chown = true;
                                i->idmapped = true;
                        } else {
                                do_chown = true;
                                i->idmapped = false;
                        }
                }

                if (do_chown) {
                        r = path_chown_recursive(target_dir, chown_uid, chown_gid, context->dynamic_user ? 01777 : 07777, AT_SYMLINK_FOLLOW);
                        if (r < 0)
                                goto fail;
                }
        }

        /* If we are not going to run in a namespace, set up the symlinks - otherwise
         * they are set up later, to allow configuring empty var/run/etc. */
        if (!needs_mount_namespace)
                FOREACH_ARRAY(i, context->directories[type].items, context->directories[type].n_items) {
                        r = create_many_symlinks(params->prefix[type], i->path, i->symlinks);
                        if (r < 0)
                                goto fail;
                }

        return 0;

fail:
        *exit_status = exit_status_table[type];
        return r;
}

#if ENABLE_SMACK
static int setup_smack(
                const ExecParameters *params,
                const ExecContext *context,
                int executable_fd) {
        int r;

        assert(params);
        assert(executable_fd >= 0);

        if (context->smack_process_label) {
                r = mac_smack_apply_pid(0, context->smack_process_label);
                if (r < 0)
                        return r;
        } else if (params->fallback_smack_process_label) {
                _cleanup_free_ char *exec_label = NULL;

                r = mac_smack_read_fd(executable_fd, SMACK_ATTR_EXEC, &exec_label);
                if (r < 0 && !ERRNO_IS_XATTR_ABSENT(r))
                        return r;

                r = mac_smack_apply_pid(0, exec_label ?: params->fallback_smack_process_label);
                if (r < 0)
                        return r;
        }

        return 0;
}
#endif

static int compile_bind_mounts(
                const ExecContext *context,
                const ExecParameters *params,
                uid_t exec_directory_uid, /* only used for id-mapped mounts Exec directories */
                gid_t exec_directory_gid, /* only used for id-mapped mounts Exec directories */
                BindMount **ret_bind_mounts,
                size_t *ret_n_bind_mounts,
                char ***ret_empty_directories) {

        _cleanup_strv_free_ char **empty_directories = NULL;
        BindMount *bind_mounts = NULL;
        size_t n, h = 0;
        int r;

        assert(context);
        assert(params);
        assert(ret_bind_mounts);
        assert(ret_n_bind_mounts);
        assert(ret_empty_directories);

        CLEANUP_ARRAY(bind_mounts, h, bind_mount_free_many);

        n = context->n_bind_mounts;
        for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
                if (!params->prefix[t])
                        continue;

                FOREACH_ARRAY(i, context->directories[t].items, context->directories[t].n_items)
                        n += !FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE) || FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY);
        }

        if (n <= 0) {
                *ret_bind_mounts = NULL;
                *ret_n_bind_mounts = 0;
                *ret_empty_directories = NULL;
                return 0;
        }

        bind_mounts = new(BindMount, n);
        if (!bind_mounts)
                return -ENOMEM;

        FOREACH_ARRAY(item, context->bind_mounts, context->n_bind_mounts) {
                r = bind_mount_add(&bind_mounts, &h, item);
                if (r < 0)
                        return r;
        }

        for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {
                if (!params->prefix[t])
                        continue;

                if (context->directories[t].n_items == 0)
                        continue;

                if (exec_directory_is_private(context, t) &&
                    !exec_context_with_rootfs(context)) {
                        char *private_root;

                        /* So this is for a dynamic user, and we need to make sure the process can access its own
                         * directory. For that we overmount the usually inaccessible "private" subdirectory with a
                         * tmpfs that makes it accessible and is empty except for the submounts we do this for. */

                        private_root = path_join(params->prefix[t], "private");
                        if (!private_root)
                                return -ENOMEM;

                        r = strv_consume(&empty_directories, private_root);
                        if (r < 0)
                                return r;
                }

                FOREACH_ARRAY(i, context->directories[t].items, context->directories[t].n_items) {
                        _cleanup_free_ char *s = NULL, *d = NULL;

                        /* When one of the parent directories is in the list, we cannot create the symlink
                         * for the child directory. See also the comments in setup_exec_directory().
                         * But if it needs to be read only, then we have to create a bind mount anyway to
                         * make it so. */
                        if (FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE) && !FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY))
                                continue;

                        if (exec_directory_is_private(context, t))
                                s = path_join(params->prefix[t], "private", i->path);
                        else
                                s = path_join(params->prefix[t], i->path);
                        if (!s)
                                return -ENOMEM;

                        if (exec_directory_is_private(context, t) &&
                            exec_context_with_rootfs(context))
                                /* When RootDirectory= or RootImage= are set, then the symbolic link to the private
                                 * directory is not created on the root directory. So, let's bind-mount the directory
                                 * on the 'non-private' place. */
                                d = path_join(params->prefix[t], i->path);
                        else
                                d = strdup(s);
                        if (!d)
                                return -ENOMEM;

                        bind_mounts[h++] = (BindMount) {
                                .source = TAKE_PTR(s),
                                .destination = TAKE_PTR(d),
                                .nosuid = context->dynamic_user, /* don't allow suid/sgid when DynamicUser= is on */
                                .recursive = true,
                                .read_only = FLAGS_SET(i->flags, EXEC_DIRECTORY_READ_ONLY),
                                .idmapped = i->idmapped,
                                .uid = exec_directory_uid,
                                .gid = exec_directory_gid,
                        };
                }
        }

        assert(h == n);

        *ret_bind_mounts = TAKE_PTR(bind_mounts);
        *ret_n_bind_mounts = n;
        *ret_empty_directories = TAKE_PTR(empty_directories);

        return (int) n;
}

/* ret_symlinks will contain a list of pairs src:dest that describes
 * the symlinks to create later on. For example, the symlinks needed
 * to safely give private directories to DynamicUser=1 users. */
static int compile_symlinks(
                const ExecContext *context,
                const ExecParameters *params,
                bool setup_os_release_symlink,
                char ***ret_symlinks) {

        _cleanup_strv_free_ char **symlinks = NULL;
        int r;

        assert(context);
        assert(params);
        assert(ret_symlinks);

        for (ExecDirectoryType dt = 0; dt < _EXEC_DIRECTORY_TYPE_MAX; dt++)
                FOREACH_ARRAY(i, context->directories[dt].items, context->directories[dt].n_items) {
                        _cleanup_free_ char *private_path = NULL, *path = NULL;

                        STRV_FOREACH(symlink, i->symlinks) {
                                _cleanup_free_ char *src_abs = NULL, *dst_abs = NULL;

                                src_abs = path_join(params->prefix[dt], i->path);
                                dst_abs = path_join(params->prefix[dt], *symlink);
                                if (!src_abs || !dst_abs)
                                        return -ENOMEM;

                                r = strv_consume_pair(&symlinks, TAKE_PTR(src_abs), TAKE_PTR(dst_abs));
                                if (r < 0)
                                        return r;
                        }

                        if (!exec_directory_is_private(context, dt) ||
                            exec_context_with_rootfs(context) ||
                            FLAGS_SET(i->flags, EXEC_DIRECTORY_ONLY_CREATE))
                                continue;

                        private_path = path_join(params->prefix[dt], "private", i->path);
                        if (!private_path)
                                return -ENOMEM;

                        path = path_join(params->prefix[dt], i->path);
                        if (!path)
                                return -ENOMEM;

                        r = strv_consume_pair(&symlinks, TAKE_PTR(private_path), TAKE_PTR(path));
                        if (r < 0)
                                return r;
                }

        /* We make the host's os-release available via a symlink, so that we can copy it atomically
         * and readers will never get a half-written version. Note that, while the paths specified here are
         * absolute, when they are processed in namespace.c they will be made relative automatically, i.e.:
         * 'os-release -> .os-release-stage/os-release' is what will be created. */
        if (setup_os_release_symlink) {
                r = strv_extend_many(
                                &symlinks,
                                "/run/host/.os-release-stage/os-release",
                                "/run/host/os-release");
                if (r < 0)
                        return r;
        }

        *ret_symlinks = TAKE_PTR(symlinks);

        return 0;
}

static bool insist_on_sandboxing(
                const ExecContext *context,
                const char *root_dir,
                const char *root_image,
                const BindMount *bind_mounts,
                size_t n_bind_mounts) {

        assert(context);
        assert(n_bind_mounts == 0 || bind_mounts);

        /* Checks whether we need to insist on fs namespacing. i.e. whether we have settings configured that
         * would alter the view on the file system beyond making things read-only or invisible, i.e. would
         * rearrange stuff in a way we cannot ignore gracefully. */

        if (context->n_temporary_filesystems > 0)
                return true;

        if (root_dir || root_image)
                return true;

        if (context->n_mount_images > 0)
                return true;

        if (context->dynamic_user)
                return true;

        if (context->n_extension_images > 0 || !strv_isempty(context->extension_directories))
                return true;

        /* If there are any bind mounts set that don't map back onto themselves, fs namespacing becomes
         * essential. */
        FOREACH_ARRAY(i, bind_mounts, n_bind_mounts)
                if (!path_equal(i->source, i->destination))
                        return true;

        if (context->log_namespace)
                return true;

        return false;
}

static int setup_ephemeral(
                const ExecContext *context,
                ExecRuntime *runtime,
                char **root_image,            /* both input and output! modified if ephemeral logic enabled */
                char **root_directory,        /* ditto */
                char **reterr_path) {

        _cleanup_close_ int fd = -EBADF;
        _cleanup_free_ char *new_root = NULL;
        int r;

        assert(context);
        assert(root_image);
        assert(root_directory);

        if (!*root_image && !*root_directory)
                return 0;

        if (!runtime || !runtime->ephemeral_copy)
                return 0;

        assert(runtime->ephemeral_storage_socket[0] >= 0);
        assert(runtime->ephemeral_storage_socket[1] >= 0);

        new_root = strdup(runtime->ephemeral_copy);
        if (!new_root)
                return log_oom_debug();

        r = posix_lock(runtime->ephemeral_storage_socket[0], LOCK_EX);
        if (r < 0)
                return log_debug_errno(r, "Failed to lock ephemeral storage socket: %m");

        CLEANUP_POSIX_UNLOCK(runtime->ephemeral_storage_socket[0]);

        fd = receive_one_fd(runtime->ephemeral_storage_socket[0], MSG_PEEK|MSG_DONTWAIT);
        if (fd >= 0)
                /* We got an fd! That means ephemeral has already been set up, so nothing to do here. */
                return 0;
        if (fd != -EAGAIN)
                return log_debug_errno(fd, "Failed to receive file descriptor queued on ephemeral storage socket: %m");

        if (*root_image) {
                log_debug("Making ephemeral copy of %s to %s", *root_image, new_root);

                fd = copy_file(*root_image, new_root, O_EXCL, 0600,
                               COPY_LOCK_BSD|COPY_REFLINK|COPY_CRTIME|COPY_NOCOW_AFTER);
                if (fd < 0) {
                        *reterr_path = strdup(*root_image);
                        return log_debug_errno(fd, "Failed to copy image %s to %s: %m",
                                               *root_image, new_root);
                }
        } else {
                assert(*root_directory);

                log_debug("Making ephemeral snapshot of %s to %s", *root_directory, new_root);

                fd = btrfs_subvol_snapshot_at(
                                AT_FDCWD, *root_directory,
                                AT_FDCWD, new_root,
                                BTRFS_SNAPSHOT_FALLBACK_COPY |
                                BTRFS_SNAPSHOT_FALLBACK_DIRECTORY |
                                BTRFS_SNAPSHOT_RECURSIVE |
                                BTRFS_SNAPSHOT_LOCK_BSD);
                if (fd < 0) {
                        *reterr_path = strdup(*root_directory);
                        return log_debug_errno(fd, "Failed to snapshot directory %s to %s: %m",
                                               *root_directory, new_root);
                }
        }

        r = send_one_fd(runtime->ephemeral_storage_socket[1], fd, MSG_DONTWAIT);
        if (r < 0)
                return log_debug_errno(r, "Failed to queue file descriptor on ephemeral storage socket: %m");

        if (*root_image)
                free_and_replace(*root_image, new_root);
        else {
                assert(*root_directory);
                free_and_replace(*root_directory, new_root);
        }

        return 1;
}

static int verity_settings_prepare(
                VeritySettings *verity,
                const char *root_image,
                const void *root_hash,
                size_t root_hash_size,
                const char *root_hash_path,
                const void *root_hash_sig,
                size_t root_hash_sig_size,
                const char *root_hash_sig_path,
                const char *verity_data_path) {

        int r;

        assert(verity);

        if (root_hash) {
                void *d;

                d = memdup(root_hash, root_hash_size);
                if (!d)
                        return -ENOMEM;

                free_and_replace(verity->root_hash, d);
                verity->root_hash_size = root_hash_size;
                verity->designator = PARTITION_ROOT;
        }

        if (root_hash_sig) {
                void *d;

                d = memdup(root_hash_sig, root_hash_sig_size);
                if (!d)
                        return -ENOMEM;

                free_and_replace(verity->root_hash_sig, d);
                verity->root_hash_sig_size = root_hash_sig_size;
                verity->designator = PARTITION_ROOT;
        }

        if (verity_data_path) {
                r = free_and_strdup(&verity->data_path, verity_data_path);
                if (r < 0)
                        return r;
        }

        r = verity_settings_load(
                        verity,
                        root_image,
                        root_hash_path,
                        root_hash_sig_path);
        if (r < 0)
                return log_debug_errno(r, "Failed to load root hash: %m");

        return 0;
}

static int pick_versions(
                const ExecContext *context,
                const ExecParameters *params,
                char **ret_root_image,
                char **ret_root_directory,
                char **reterr_path) {

        int r;

        assert(context);
        assert(params);
        assert(ret_root_image);
        assert(ret_root_directory);

        if (context->root_image) {
                _cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL;

                r = path_pick(/* toplevel_path= */ NULL,
                              /* toplevel_fd= */ AT_FDCWD,
                              context->root_image,
                              &pick_filter_image_raw,
                              PICK_ARCHITECTURE|PICK_TRIES|PICK_RESOLVE,
                              &result);
                if (r < 0) {
                        *reterr_path = strdup(context->root_image);
                        return r;
                }

                if (!result.path) {
                        *reterr_path = strdup(context->root_image);
                        return log_exec_debug_errno(context, params, SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", context->root_image);
                }

                *ret_root_image = TAKE_PTR(result.path);
                *ret_root_directory = NULL;
                return r;
        }

        if (context->root_directory) {
                _cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL;

                r = path_pick(/* toplevel_path= */ NULL,
                              /* toplevel_fd= */ AT_FDCWD,
                              context->root_directory,
                              &pick_filter_image_dir,
                              PICK_ARCHITECTURE|PICK_TRIES|PICK_RESOLVE,
                              &result);
                if (r < 0) {
                        *reterr_path = strdup(context->root_directory);
                        return r;
                }

                if (!result.path) {
                        *reterr_path = strdup(context->root_directory);
                        return log_exec_debug_errno(context, params, SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", context->root_directory);
                }

                *ret_root_image = NULL;
                *ret_root_directory = TAKE_PTR(result.path);
                return r;
        }

        *ret_root_image = *ret_root_directory = NULL;
        return 0;
}

static int apply_mount_namespace(
                ExecCommandFlags command_flags,
                const ExecContext *context,
                const ExecParameters *params,
                ExecRuntime *runtime,
                const char *memory_pressure_path,
                bool needs_sandboxing,
                char **reterr_path,
                uid_t exec_directory_uid,
                gid_t exec_directory_gid) {

        _cleanup_(verity_settings_done) VeritySettings verity = VERITY_SETTINGS_DEFAULT;
        _cleanup_strv_free_ char **empty_directories = NULL, **symlinks = NULL,
                        **read_write_paths_cleanup = NULL;
        _cleanup_free_ char *creds_path = NULL, *incoming_dir = NULL, *propagate_dir = NULL,
                *private_namespace_dir = NULL, *host_os_release_stage = NULL, *root_image = NULL, *root_dir = NULL;
        const char *tmp_dir = NULL, *var_tmp_dir = NULL;
        char **read_write_paths;
        bool setup_os_release_symlink;
        BindMount *bind_mounts = NULL;
        size_t n_bind_mounts = 0;
        int r;

        assert(context);

        CLEANUP_ARRAY(bind_mounts, n_bind_mounts, bind_mount_free_many);

        if (params->flags & EXEC_APPLY_CHROOT) {
                r = pick_versions(
                                context,
                                params,
                                &root_image,
                                &root_dir,
                                reterr_path);
                if (r < 0)
                        return r;

                r = setup_ephemeral(
                                context,
                                runtime,
                                &root_image,
                                &root_dir,
                                reterr_path);
                if (r < 0)
                        return r;
        }

        r = compile_bind_mounts(context, params, exec_directory_uid, exec_directory_gid, &bind_mounts, &n_bind_mounts, &empty_directories);
        if (r < 0)
                return r;

        /* We need to make the pressure path writable even if /sys/fs/cgroups is made read-only, as the
         * service will need to write to it in order to start the notifications. */
        if (exec_is_cgroup_mount_read_only(context, params) && memory_pressure_path && !streq(memory_pressure_path, "/dev/null")) {
                read_write_paths_cleanup = strv_copy(context->read_write_paths);
                if (!read_write_paths_cleanup)
                        return -ENOMEM;

                r = strv_extend(&read_write_paths_cleanup, memory_pressure_path);
                if (r < 0)
                        return r;

                read_write_paths = read_write_paths_cleanup;
        } else
                read_write_paths = context->read_write_paths;

        if (needs_sandboxing) {
                /* The runtime struct only contains the parent of the private /tmp, which is non-accessible
                 * to world users. Inside of it there's a /tmp that is sticky, and that's the one we want to
                 * use here.  This does not apply when we are using /run/systemd/empty as fallback. */

                if (context->private_tmp == PRIVATE_TMP_CONNECTED && runtime && runtime->shared) {
                        if (streq_ptr(runtime->shared->tmp_dir, RUN_SYSTEMD_EMPTY))
                                tmp_dir = runtime->shared->tmp_dir;
                        else if (runtime->shared->tmp_dir)
                                tmp_dir = strjoina(runtime->shared->tmp_dir, "/tmp");

                        if (streq_ptr(runtime->shared->var_tmp_dir, RUN_SYSTEMD_EMPTY))
                                var_tmp_dir = runtime->shared->var_tmp_dir;
                        else if (runtime->shared->var_tmp_dir)
                                var_tmp_dir = strjoina(runtime->shared->var_tmp_dir, "/tmp");
                }
        }

        /* Symlinks (exec dirs, os-release) are set up after other mounts, before they are made read-only. */
        setup_os_release_symlink = needs_sandboxing && exec_context_get_effective_mount_apivfs(context) && (root_dir || root_image);
        r = compile_symlinks(context, params, setup_os_release_symlink, &symlinks);
        if (r < 0)
                return r;

        if (context->mount_propagation_flag == MS_SHARED)
                log_exec_debug(context,
                               params,
                               "shared mount propagation hidden by other fs namespacing unit settings: ignoring");

        r = exec_context_get_credential_directory(context, params, params->unit_id, &creds_path);
        if (r < 0)
                return r;

        if (params->runtime_scope == RUNTIME_SCOPE_SYSTEM) {
                propagate_dir = path_join("/run/systemd/propagate/", params->unit_id);
                if (!propagate_dir)
                        return -ENOMEM;

                incoming_dir = strdup("/run/systemd/incoming");
                if (!incoming_dir)
                        return -ENOMEM;

                private_namespace_dir = strdup("/run/systemd");
                if (!private_namespace_dir)
                        return -ENOMEM;

                /* If running under a different root filesystem, propagate the host's os-release. We make a
                 * copy rather than just bind mounting it, so that it can be updated on soft-reboot. */
                if (setup_os_release_symlink) {
                        host_os_release_stage = strdup("/run/systemd/propagate/.os-release-stage");
                        if (!host_os_release_stage)
                                return -ENOMEM;
                }
        } else {
                assert(params->runtime_scope == RUNTIME_SCOPE_USER);

                if (asprintf(&private_namespace_dir, "/run/user/" UID_FMT "/systemd", geteuid()) < 0)
                        return -ENOMEM;

                if (setup_os_release_symlink) {
                        if (asprintf(&host_os_release_stage,
                                     "/run/user/" UID_FMT "/systemd/propagate/.os-release-stage",
                                     geteuid()) < 0)
                                return -ENOMEM;
                }
        }

        if (root_image) {
                r = verity_settings_prepare(
                        &verity,
                        root_image,
                        context->root_hash, context->root_hash_size, context->root_hash_path,
                        context->root_hash_sig, context->root_hash_sig_size, context->root_hash_sig_path,
                        context->root_verity);
                if (r < 0)
                        return r;
        }

        NamespaceParameters parameters = {
                .runtime_scope = params->runtime_scope,

                .root_directory = root_dir,
                .root_image = root_image,
                .root_image_options = context->root_image_options,
                .root_image_policy = context->root_image_policy ?: &image_policy_service,

                .read_write_paths = read_write_paths,
                .read_only_paths = needs_sandboxing ? context->read_only_paths : NULL,
                .inaccessible_paths = needs_sandboxing ? context->inaccessible_paths : NULL,

                .exec_paths = needs_sandboxing ? context->exec_paths : NULL,
                .no_exec_paths = needs_sandboxing ? context->no_exec_paths : NULL,

                .empty_directories = empty_directories,
                .symlinks = symlinks,

                .bind_mounts = bind_mounts,
                .n_bind_mounts = n_bind_mounts,

                .temporary_filesystems = context->temporary_filesystems,
                .n_temporary_filesystems = context->n_temporary_filesystems,

                .mount_images = context->mount_images,
                .n_mount_images = context->n_mount_images,
                .mount_image_policy = context->mount_image_policy ?: &image_policy_service,

                .tmp_dir = tmp_dir,
                .var_tmp_dir = var_tmp_dir,

                .creds_path = creds_path,
                .log_namespace = context->log_namespace,
                .mount_propagation_flag = context->mount_propagation_flag,

                .verity = &verity,

                .extension_images = context->extension_images,
                .n_extension_images = context->n_extension_images,
                .extension_image_policy = context->extension_image_policy ?: &image_policy_sysext,
                .extension_directories = context->extension_directories,

                .propagate_dir = propagate_dir,
                .incoming_dir = incoming_dir,
                .private_namespace_dir = private_namespace_dir,
                .host_notify_socket = params->notify_socket,
                .notify_socket_path = exec_get_private_notify_socket_path(context, params, needs_sandboxing),
                .host_os_release_stage = host_os_release_stage,

                /* If DynamicUser=no and RootDirectory= is set then lets pass a relaxed sandbox info,
                 * otherwise enforce it, don't ignore protected paths and fail if we are enable to apply the
                 * sandbox inside the mount namespace. */
                .ignore_protect_paths = !needs_sandboxing && !context->dynamic_user && root_dir,

                .protect_control_groups = needs_sandboxing ? exec_get_protect_control_groups(context, params) : PROTECT_CONTROL_GROUPS_NO,
                .protect_kernel_tunables = needs_sandboxing && context->protect_kernel_tunables,
                .protect_kernel_modules = needs_sandboxing && context->protect_kernel_modules,
                .protect_kernel_logs = needs_sandboxing && context->protect_kernel_logs,

                .private_dev = needs_sandboxing && context->private_devices,
                .private_network = needs_sandboxing && exec_needs_network_namespace(context),
                .private_ipc = needs_sandboxing && exec_needs_ipc_namespace(context),
                .private_pids = needs_sandboxing && exec_needs_pid_namespace(context) ? context->private_pids : PRIVATE_PIDS_NO,
                .private_tmp = needs_sandboxing ? context->private_tmp : PRIVATE_TMP_NO,

                .mount_apivfs = needs_sandboxing && exec_context_get_effective_mount_apivfs(context),
                .bind_log_sockets = needs_sandboxing && exec_context_get_effective_bind_log_sockets(context),

                /* If NNP is on, we can turn on MS_NOSUID, since it won't have any effect anymore. */
                .mount_nosuid = needs_sandboxing && context->no_new_privileges && !mac_selinux_use(),

                .protect_home = needs_sandboxing ? context->protect_home : PROTECT_HOME_NO,
                .protect_hostname = needs_sandboxing ? context->protect_hostname : PROTECT_HOSTNAME_NO,
                .protect_system = needs_sandboxing ? context->protect_system : PROTECT_SYSTEM_NO,
                .protect_proc = needs_sandboxing ? context->protect_proc : PROTECT_PROC_DEFAULT,
                .proc_subset = needs_sandboxing ? context->proc_subset : PROC_SUBSET_ALL,
        };

        r = setup_namespace(&parameters, reterr_path);
        /* If we couldn't set up the namespace this is probably due to a missing capability. setup_namespace() reports
         * that with a special, recognizable error ENOANO. In this case, silently proceed, but only if exclusively
         * sandboxing options were used, i.e. nothing such as RootDirectory= or BindMount= that would result in a
         * completely different execution environment. */
        if (r == -ENOANO) {
                if (insist_on_sandboxing(
                                    context,
                                    root_dir, root_image,
                                    bind_mounts,
                                    n_bind_mounts))
                        return log_exec_debug_errno(context,
                                                    params,
                                                    SYNTHETIC_ERRNO(EOPNOTSUPP),
                                                    "Failed to set up namespace, and refusing to continue since "
                                                    "the selected namespacing options alter mount environment non-trivially.\n"
                                                    "Bind mounts: %zu, temporary filesystems: %zu, root directory: %s, root image: %s, dynamic user: %s",
                                                    n_bind_mounts,
                                                    context->n_temporary_filesystems,
                                                    yes_no(root_dir),
                                                    yes_no(root_image),
                                                    yes_no(context->dynamic_user));

                log_exec_debug(context, params, "Failed to set up namespace, assuming containerized execution and ignoring.");
                return 0;
        }

        return r;
}

static int apply_working_directory(
                const ExecContext *context,
                const ExecParameters *params,
                ExecRuntime *runtime,
                const char *home) {

        const char *wd;
        int r;

        assert(context);

        if (context->working_directory_home) {
                if (!home)
                        return -ENXIO;

                wd = home;
        } else
                wd = empty_to_root(context->working_directory);

        if (params->flags & EXEC_APPLY_CHROOT)
                r = RET_NERRNO(chdir(wd));
        else {
                _cleanup_close_ int dfd = -EBADF;

                r = chase(wd,
                          (runtime ? runtime->ephemeral_copy : NULL) ?: context->root_directory,
                          CHASE_PREFIX_ROOT|CHASE_AT_RESOLVE_IN_ROOT,
                          /* ret_path= */ NULL,
                          &dfd);
                if (r >= 0)
                        r = RET_NERRNO(fchdir(dfd));
        }
        return context->working_directory_missing_ok ? 0 : r;
}

static int apply_root_directory(
                const ExecContext *context,
                const ExecParameters *params,
                ExecRuntime *runtime,
                const bool needs_mount_ns,
                int *exit_status) {

        assert(context);
        assert(exit_status);

        if (params->flags & EXEC_APPLY_CHROOT)
                if (!needs_mount_ns && context->root_directory)
                        if (chroot((runtime ? runtime->ephemeral_copy : NULL) ?: context->root_directory) < 0) {
                                *exit_status = EXIT_CHROOT;
                                return -errno;
                        }

        return 0;
}

static int setup_keyring(
                const ExecContext *context,
                const ExecParameters *p,
                uid_t uid, gid_t gid) {

        key_serial_t keyring;
        int r = 0;
        uid_t saved_uid;
        gid_t saved_gid;

        assert(context);
        assert(p);

        /* Let's set up a new per-service "session" kernel keyring for each system service. This has the benefit that
         * each service runs with its own keyring shared among all processes of the service, but with no hook-up beyond
         * that scope, and in particular no link to the per-UID keyring. If we don't do this the keyring will be
         * automatically created on-demand and then linked to the per-UID keyring, by the kernel. The kernel's built-in
         * on-demand behaviour is very appropriate for login users, but probably not so much for system services, where
         * UIDs are not necessarily specific to a service but reused (at least in the case of UID 0). */

        if (context->keyring_mode == EXEC_KEYRING_INHERIT)
                return 0;

        /* Acquiring a reference to the user keyring is nasty. We briefly change identity in order to get things set up
         * properly by the kernel. If we don't do that then we can't create it atomically, and that sucks for parallel
         * execution. This mimics what pam_keyinit does, too. Setting up session keyring, to be owned by the right user
         * & group is just as nasty as acquiring a reference to the user keyring. */

        saved_uid = getuid();
        saved_gid = getgid();

        if (gid_is_valid(gid) && gid != saved_gid) {
                if (setregid(gid, -1) < 0)
                        return log_exec_error_errno(context,
                                                    p,
                                                    errno,
                                                    "Failed to change GID for user keyring: %m");
        }

        if (uid_is_valid(uid) && uid != saved_uid) {
                if (setreuid(uid, -1) < 0) {
                        r = log_exec_error_errno(context,
                                                 p,
                                                 errno,
                                                 "Failed to change UID for user keyring: %m");
                        goto out;
                }
        }

        keyring = keyctl(KEYCTL_JOIN_SESSION_KEYRING, 0, 0, 0, 0);
        if (keyring == -1) {
                if (errno == ENOSYS)
                        log_exec_debug_errno(context,
                                             p,
                                             errno,
                                             "Kernel keyring not supported, ignoring.");
                else if (ERRNO_IS_PRIVILEGE(errno))
                        log_exec_debug_errno(context,
                                             p,
                                             errno,
                                             "Kernel keyring access prohibited, ignoring.");
                else if (errno == EDQUOT)
                        log_exec_debug_errno(context,
                                             p,
                                             errno,
                                             "Out of kernel keyrings to allocate, ignoring.");
                else
                        r = log_exec_error_errno(context,
                                                 p,
                                                 errno,
                                                 "Setting up kernel keyring failed: %m");

                goto out;
        }

        /* When requested link the user keyring into the session keyring. */
        if (context->keyring_mode == EXEC_KEYRING_SHARED) {

                if (keyctl(KEYCTL_LINK,
                           KEY_SPEC_USER_KEYRING,
                           KEY_SPEC_SESSION_KEYRING, 0, 0) < 0) {
                        r = log_exec_error_errno(context,
                                                 p,
                                                 errno,
                                                 "Failed to link user keyring into session keyring: %m");
                        goto out;
                }
        }

        /* Restore uid/gid back */
        if (uid_is_valid(uid) && uid != saved_uid) {
                if (setreuid(saved_uid, -1) < 0) {
                        r = log_exec_error_errno(context,
                                                 p,
                                                 errno,
                                                 "Failed to change UID back for user keyring: %m");
                        goto out;
                }
        }

        if (gid_is_valid(gid) && gid != saved_gid) {
                if (setregid(saved_gid, -1) < 0)
                        return log_exec_error_errno(context,
                                                    p,
                                                    errno,
                                                    "Failed to change GID back for user keyring: %m");
        }

        /* Populate they keyring with the invocation ID by default, as original saved_uid. */
        if (!sd_id128_is_null(p->invocation_id)) {
                key_serial_t key;

                key = add_key("user",
                              "invocation_id",
                              &p->invocation_id,
                              sizeof(p->invocation_id),
                              KEY_SPEC_SESSION_KEYRING);
                if (key == -1)
                        log_exec_debug_errno(context,
                                             p,
                                             errno,
                                             "Failed to add invocation ID to keyring, ignoring: %m");
                else {
                        if (keyctl(KEYCTL_SETPERM, key,
                                   KEY_POS_VIEW|KEY_POS_READ|KEY_POS_SEARCH|
                                   KEY_USR_VIEW|KEY_USR_READ|KEY_USR_SEARCH, 0, 0) < 0)
                                r = log_exec_error_errno(context,
                                                         p,
                                                         errno,
                                                         "Failed to restrict invocation ID permission: %m");
                }
        }

out:
        /* Revert back uid & gid for the last time, and exit */
        /* no extra logging, as only the first already reported error matters */
        if (getuid() != saved_uid)
                (void) setreuid(saved_uid, -1);

        if (getgid() != saved_gid)
                (void) setregid(saved_gid, -1);

        return r;
}

static void append_socket_pair(int *array, size_t *n, const int pair[static 2]) {
        assert(array);
        assert(n);
        assert(pair);

        if (pair[0] >= 0)
                array[(*n)++] = pair[0];
        if (pair[1] >= 0)
                array[(*n)++] = pair[1];
}

static int close_remaining_fds(
                const ExecParameters *params,
                const ExecRuntime *runtime,
                int socket_fd,
                const int *fds, size_t n_fds) {

        size_t n_dont_close = 0;
        int dont_close[n_fds + 17];

        assert(params);

        if (params->stdin_fd >= 0)
                dont_close[n_dont_close++] = params->stdin_fd;
        if (params->stdout_fd >= 0)
                dont_close[n_dont_close++] = params->stdout_fd;
        if (params->stderr_fd >= 0)
                dont_close[n_dont_close++] = params->stderr_fd;

        if (socket_fd >= 0)
                dont_close[n_dont_close++] = socket_fd;
        if (n_fds > 0) {
                memcpy(dont_close + n_dont_close, fds, sizeof(int) * n_fds);
                n_dont_close += n_fds;
        }

        if (runtime)
                append_socket_pair(dont_close, &n_dont_close, runtime->ephemeral_storage_socket);

        if (runtime && runtime->shared) {
                append_socket_pair(dont_close, &n_dont_close, runtime->shared->netns_storage_socket);
                append_socket_pair(dont_close, &n_dont_close, runtime->shared->ipcns_storage_socket);
        }

        if (runtime && runtime->dynamic_creds) {
                if (runtime->dynamic_creds->user)
                        append_socket_pair(dont_close, &n_dont_close, runtime->dynamic_creds->user->storage_socket);
                if (runtime->dynamic_creds->group)
                        append_socket_pair(dont_close, &n_dont_close, runtime->dynamic_creds->group->storage_socket);
        }

        if (params->user_lookup_fd >= 0)
                dont_close[n_dont_close++] = params->user_lookup_fd;

        if (params->handoff_timestamp_fd >= 0)
                dont_close[n_dont_close++] = params->handoff_timestamp_fd;

        if (params->pidref_transport_fd >= 0)
                dont_close[n_dont_close++] = params->pidref_transport_fd;

        assert(n_dont_close <= ELEMENTSOF(dont_close));

        return close_all_fds(dont_close, n_dont_close);
}

static int send_user_lookup(
                const char *unit_id,
                int user_lookup_fd,
                uid_t uid,
                gid_t gid) {

        assert(unit_id);

        /* Send the resolved UID/GID to PID 1 after we learnt it. We send a single datagram, containing the UID/GID
         * data as well as the unit name. Note that we suppress sending this if no user/group to resolve was
         * specified. */

        if (user_lookup_fd < 0)
                return 0;

        if (!uid_is_valid(uid) && !gid_is_valid(gid))
                return 0;

        if (writev(user_lookup_fd,
               (struct iovec[]) {
                           IOVEC_MAKE(&uid, sizeof(uid)),
                           IOVEC_MAKE(&gid, sizeof(gid)),
                           IOVEC_MAKE_STRING(unit_id) }, 3) < 0)
                return -errno;

        return 0;
}

static int acquire_home(const ExecContext *c, const char **home, char **ret_buf) {
        int r;

        assert(c);
        assert(home);
        assert(ret_buf);

        /* If WorkingDirectory=~ is set, try to acquire a usable home directory. */

        if (*home) /* Already acquired from get_fixed_user()? */
                return 0;

        if (!c->working_directory_home)
                return 0;

        if (c->dynamic_user || (c->user && is_this_me(c->user) <= 0))
                return -EADDRNOTAVAIL;

        r = get_home_dir(ret_buf);
        if (r < 0)
                return r;

        *home = *ret_buf;
        return 1;
}

static int compile_suggested_paths(const ExecContext *c, const ExecParameters *p, char ***ret) {
        _cleanup_strv_free_ char ** list = NULL;
        int r;

        assert(c);
        assert(p);
        assert(ret);

        assert(c->dynamic_user);

        /* Compile a list of paths that it might make sense to read the owning UID from to use as initial candidate for
         * dynamic UID allocation, in order to save us from doing costly recursive chown()s of the special
         * directories. */

        for (ExecDirectoryType t = 0; t < _EXEC_DIRECTORY_TYPE_MAX; t++) {

                if (!EXEC_DIRECTORY_TYPE_SHALL_CHOWN(t))
                        continue;

                if (!p->prefix[t])
                        continue;

                for (size_t i = 0; i < c->directories[t].n_items; i++) {
                        char *e;

                        if (exec_directory_is_private(c, t))
                                e = path_join(p->prefix[t], "private", c->directories[t].items[i].path);
                        else
                                e = path_join(p->prefix[t], c->directories[t].items[i].path);
                        if (!e)
                                return -ENOMEM;

                        r = strv_consume(&list, e);
                        if (r < 0)
                                return r;
                }
        }

        *ret = TAKE_PTR(list);

        return 0;
}

static int exec_context_cpu_affinity_from_numa(const ExecContext *c, CPUSet *ret) {
        _cleanup_(cpu_set_reset) CPUSet s = {};
        int r;

        assert(c);
        assert(ret);

        if (!c->numa_policy.nodes.set) {
                log_debug("Can't derive CPU affinity mask from NUMA mask because NUMA mask is not set, ignoring");
                return 0;
        }

        r = numa_to_cpu_set(&c->numa_policy, &s);
        if (r < 0)
                return r;

        cpu_set_reset(ret);

        return cpu_set_add_all(ret, &s);
}

static int add_shifted_fd(int *fds, size_t fds_size, size_t *n_fds, int *fd) {
        int r;

        assert(fds);
        assert(n_fds);
        assert(*n_fds < fds_size);
        assert(fd);

        if (*fd < 0)
               return 0;

        if (*fd < 3 + (int) *n_fds) {
                /* Let's move the fd up, so that it's outside of the fd range we will use to store
                 * the fds we pass to the process (or which are closed only during execve). */

                r = fcntl(*fd, F_DUPFD_CLOEXEC, 3 + (int) *n_fds);
                if (r < 0)
                        return -errno;

                close_and_replace(*fd, r);
        }

        fds[(*n_fds)++] = *fd;
        return 1;
}

static int connect_unix_harder(const ExecContext *c, const ExecParameters *p, const OpenFile *of, int ofd) {
        static const int socket_types[] = { SOCK_DGRAM, SOCK_STREAM, SOCK_SEQPACKET };

        union sockaddr_union addr = {
                .un.sun_family = AF_UNIX,
        };
        socklen_t sa_len;
        int r;

        assert(c);
        assert(p);
        assert(of);
        assert(ofd >= 0);

        r = sockaddr_un_set_path(&addr.un, FORMAT_PROC_FD_PATH(ofd));
        if (r < 0)
                return log_exec_debug_errno(c, p, r, "Failed to set sockaddr for '%s': %m", of->path);
        sa_len = r;

        FOREACH_ELEMENT(i, socket_types) {
                _cleanup_close_ int fd = -EBADF;

                fd = socket(AF_UNIX, *i|SOCK_CLOEXEC, 0);
                if (fd < 0)
                        return log_exec_debug_errno(c, p,
                                                    errno, "Failed to create socket for '%s': %m",
                                                    of->path);

                r = RET_NERRNO(connect(fd, &addr.sa, sa_len));
                if (r >= 0)
                        return TAKE_FD(fd);
                if (r != -EPROTOTYPE)
                        return log_exec_debug_errno(c, p,
                                                    r, "Failed to connect to socket for '%s': %m",
                                                    of->path);
        }

        return log_exec_debug_errno(c, p,
                                    SYNTHETIC_ERRNO(EPROTOTYPE), "No suitable socket type to connect to socket '%s'.",
                                    of->path);
}

static int get_open_file_fd(const ExecContext *c, const ExecParameters *p, const OpenFile *of) {
        _cleanup_close_ int fd = -EBADF, ofd = -EBADF;
        struct stat st;

        assert(c);
        assert(p);
        assert(of);

        ofd = open(of->path, O_PATH | O_CLOEXEC);
        if (ofd < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to open '%s' as O_PATH: %m", of->path);

        if (fstat(ofd, &st) < 0)
                return log_exec_debug_errno(c, p, errno, "Failed to stat '%s': %m", of->path);

        if (S_ISSOCK(st.st_mode)) {
                fd = connect_unix_harder(c, p, of, ofd);
                if (fd < 0)
                        return fd;

                if (FLAGS_SET(of->flags, OPENFILE_READ_ONLY) && shutdown(fd, SHUT_WR) < 0)
                        return log_exec_debug_errno(c, p,
                                                    errno, "Failed to shutdown send for socket '%s': %m",
                                                    of->path);

                log_exec_debug(c, p, "Opened socket '%s' as fd %d.", of->path, fd);
        } else {
                int flags = FLAGS_SET(of->flags, OPENFILE_READ_ONLY) ? O_RDONLY : O_RDWR;
                if (FLAGS_SET(of->flags, OPENFILE_APPEND))
                        flags |= O_APPEND;
                else if (FLAGS_SET(of->flags, OPENFILE_TRUNCATE))
                        flags |= O_TRUNC;

                fd = fd_reopen(ofd, flags|O_NOCTTY|O_CLOEXEC);
                if (fd < 0)
                        return log_exec_debug_errno(c, p, fd, "Failed to reopen file '%s': %m", of->path);

                log_exec_debug(c, p, "Opened file '%s' as fd %d.", of->path, fd);
        }

        return TAKE_FD(fd);
}

static int collect_open_file_fds(const ExecContext *c, ExecParameters *p, size_t *n_fds) {
        assert(c);
        assert(p);
        assert(n_fds);

        LIST_FOREACH(open_files, of, p->open_files) {
                _cleanup_close_ int fd = -EBADF;

                fd = get_open_file_fd(c, p, of);
                if (fd < 0) {
                        if (FLAGS_SET(of->flags, OPENFILE_GRACEFUL)) {
                                log_exec_full_errno(c, p,
                                                    fd == -ENOENT || ERRNO_IS_NEG_PRIVILEGE(fd) ? LOG_DEBUG : LOG_WARNING,
                                                    fd,
                                                    "Failed to get OpenFile= file descriptor for '%s', ignoring: %m",
                                                    of->path);
                                continue;
                        }

                        return log_exec_error_errno(c, p, fd,
                                                    "Failed to get OpenFile= file descriptor for '%s': %m",
                                                    of->path);
                }

                if (!GREEDY_REALLOC(p->fds, *n_fds + 1))
                        return log_oom();

                if (strv_extend(&p->fd_names, of->fdname) < 0)
                        return log_oom();

                p->fds[(*n_fds)++] = TAKE_FD(fd);
        }

        return 0;
}

static void log_command_line(
                const ExecContext *context,
                const ExecParameters *params,
                const char *msg,
                const char *executable,
                char **argv) {

        assert(context);
        assert(params);
        assert(msg);
        assert(executable);

        if (!DEBUG_LOGGING)
                return;

        _cleanup_free_ char *cmdline = quote_command_line(argv, SHELL_ESCAPE_EMPTY);

        log_exec_struct(context, params, LOG_DEBUG,
                        "EXECUTABLE=%s", executable,
                        LOG_EXEC_MESSAGE(params, "%s: %s", msg, strnull(cmdline)),
                        LOG_EXEC_INVOCATION_ID(params));
}

static bool exec_context_need_unprivileged_private_users(
                const ExecContext *context,
                const ExecParameters *params) {

        assert(context);
        assert(params);

        /* These options require PrivateUsers= when used in user units, as we need to be in a user namespace
         * to have permission to enable them when not running as root. If we have effective CAP_SYS_ADMIN
         * (system manager) then we have privileges and don't need this. */
        if (params->runtime_scope != RUNTIME_SCOPE_USER)
                return false;

        return context->private_users != PRIVATE_USERS_NO ||
               context->private_tmp != PRIVATE_TMP_NO ||
               context->private_devices ||
               context->private_network ||
               context->network_namespace_path ||
               context->private_ipc ||
               context->ipc_namespace_path ||
               context->private_mounts > 0 ||
               context->mount_apivfs > 0 ||
               context->bind_log_sockets > 0 ||
               context->n_bind_mounts > 0 ||
               context->n_temporary_filesystems > 0 ||
               context->root_directory ||
               !strv_isempty(context->extension_directories) ||
               context->protect_system != PROTECT_SYSTEM_NO ||
               context->protect_home != PROTECT_HOME_NO ||
               exec_needs_pid_namespace(context) ||
               context->protect_kernel_tunables ||
               context->protect_kernel_modules ||
               context->protect_kernel_logs ||
               exec_needs_cgroup_mount(context, params) ||
               context->protect_clock ||
               context->protect_hostname != PROTECT_HOSTNAME_NO ||
               !strv_isempty(context->read_write_paths) ||
               !strv_isempty(context->read_only_paths) ||
               !strv_isempty(context->inaccessible_paths) ||
               !strv_isempty(context->exec_paths) ||
               !strv_isempty(context->no_exec_paths);
}

static bool exec_context_shall_confirm_spawn(const ExecContext *context) {
        assert(context);

        if (confirm_spawn_disabled())
                return false;

        /* For some reasons units remaining in the same process group
         * as PID 1 fail to acquire the console even if it's not used
         * by any process. So skip the confirmation question for them. */
        return !context->same_pgrp;
}

static int exec_context_named_iofds(
                const ExecContext *c,
                const ExecParameters *p,
                int named_iofds[static 3]) {

        size_t targets;
        const char* stdio_fdname[3];
        size_t n_fds;

        assert(c);
        assert(p);
        assert(named_iofds);

        targets = (c->std_input == EXEC_INPUT_NAMED_FD) +
                  (c->std_output == EXEC_OUTPUT_NAMED_FD) +
                  (c->std_error == EXEC_OUTPUT_NAMED_FD);

        for (size_t i = 0; i < 3; i++)
                stdio_fdname[i] = exec_context_fdname(c, i);

        n_fds = p->n_storage_fds + p->n_socket_fds + p->n_extra_fds;

        for (size_t i = 0; i < n_fds  && targets > 0; i++)
                if (named_iofds[STDIN_FILENO] < 0 &&
                    c->std_input == EXEC_INPUT_NAMED_FD &&
                    stdio_fdname[STDIN_FILENO] &&
                    streq(p->fd_names[i], stdio_fdname[STDIN_FILENO])) {

                        named_iofds[STDIN_FILENO] = p->fds[i];
                        targets--;

                } else if (named_iofds[STDOUT_FILENO] < 0 &&
                           c->std_output == EXEC_OUTPUT_NAMED_FD &&
                           stdio_fdname[STDOUT_FILENO] &&
                           streq(p->fd_names[i], stdio_fdname[STDOUT_FILENO])) {

                        named_iofds[STDOUT_FILENO] = p->fds[i];
                        targets--;

                } else if (named_iofds[STDERR_FILENO] < 0 &&
                           c->std_error == EXEC_OUTPUT_NAMED_FD &&
                           stdio_fdname[STDERR_FILENO] &&
                           streq(p->fd_names[i], stdio_fdname[STDERR_FILENO])) {

                        named_iofds[STDERR_FILENO] = p->fds[i];
                        targets--;
                }

        return targets == 0 ? 0 : -ENOENT;
}

static void exec_shared_runtime_close(ExecSharedRuntime *shared) {
        if (!shared)
                return;

        safe_close_pair(shared->netns_storage_socket);
        safe_close_pair(shared->ipcns_storage_socket);
}

static void exec_runtime_close(ExecRuntime *rt) {
        if (!rt)
                return;

        safe_close_pair(rt->ephemeral_storage_socket);

        exec_shared_runtime_close(rt->shared);
        dynamic_creds_close(rt->dynamic_creds);
}

static void exec_params_close(ExecParameters *p) {
        if (!p)
                return;

        p->stdin_fd = safe_close(p->stdin_fd);
        p->stdout_fd = safe_close(p->stdout_fd);
        p->stderr_fd = safe_close(p->stderr_fd);
}

static int exec_fd_mark_hot(
                const ExecContext *c,
                ExecParameters *p,
                bool hot,
                int *reterr_exit_status) {

        assert(c);
        assert(p);

        if (p->exec_fd < 0)
                return 0;

        uint8_t x = hot;

        if (write(p->exec_fd, &x, sizeof(x)) < 0) {
                if (reterr_exit_status)
                        *reterr_exit_status = EXIT_EXEC;
                return log_exec_error_errno(c, p, errno, "Failed to mark exec_fd as %s: %m", hot ? "hot" : "cold");
        }

        return 1;
}

static int send_handoff_timestamp(
                const ExecContext *c,
                ExecParameters *p,
                int *reterr_exit_status) {

        assert(c);
        assert(p);

        if (p->handoff_timestamp_fd < 0)
                return 0;

        dual_timestamp dt;
        dual_timestamp_now(&dt);

        if (write(p->handoff_timestamp_fd, (const usec_t[2]) { dt.realtime, dt.monotonic }, sizeof(usec_t) * 2) < 0) {
                if (reterr_exit_status)
                        *reterr_exit_status = EXIT_EXEC;
                return log_exec_error_errno(c, p, errno, "Failed to send handoff timestamp: %m");
        }

        return 1;
}

static void prepare_terminal(
                const ExecContext *context,
                ExecParameters *p) {

        _cleanup_close_ int lock_fd = -EBADF;

        /* This is the "constructive" reset, i.e. is about preparing things for our invocation rather than
         * cleaning up things from older invocations. */

        assert(context);
        assert(p);

        /* We only try to reset things if we there's the chance our stdout points to a TTY */
        if (!(is_terminal_output(context->std_output) ||
              (context->std_output == EXEC_OUTPUT_INHERIT && is_terminal_input(context->std_input)) ||
              context->std_output == EXEC_OUTPUT_NAMED_FD ||
              p->stdout_fd >= 0))
                return;

        if (context->tty_reset) {
                /* When we are resetting the TTY, then let's create a lock first, to synchronize access. This
                 * in particular matters as concurrent resets and the TTY size ANSI DSR logic done by the
                 * exec_context_apply_tty_size() below might interfere */
                lock_fd = lock_dev_console();
                if (lock_fd < 0)
                        log_exec_debug_errno(context, p, lock_fd, "Failed to lock /dev/console, ignoring: %m");

                (void) terminal_reset_defensive(STDOUT_FILENO, /* switch_to_text= */ false);
        }

        (void) exec_context_apply_tty_size(context, STDIN_FILENO, STDOUT_FILENO, /* tty_path= */ NULL);
}

int exec_invoke(
                const ExecCommand *command,
                const ExecContext *context,
                ExecParameters *params,
                ExecRuntime *runtime,
                const CGroupContext *cgroup_context,
                int *exit_status) {

        _cleanup_strv_free_ char **our_env = NULL, **pass_env = NULL, **joined_exec_search_path = NULL, **accum_env = NULL, **replaced_argv = NULL;
        int r, ngids = 0;
        _cleanup_free_ gid_t *supplementary_gids = NULL;
        const char *username = NULL, *groupname = NULL;
        _cleanup_free_ char *home_buffer = NULL, *memory_pressure_path = NULL, *own_user = NULL;
        const char *home = NULL, *shell = NULL;
        char **final_argv = NULL;
        dev_t journal_stream_dev = 0;
        ino_t journal_stream_ino = 0;
        bool userns_set_up = false;
        bool needs_sandboxing,          /* Do we need to set up full sandboxing? (i.e. all namespacing, all MAC stuff, caps, yadda yadda */
                needs_setuid,           /* Do we need to do the actual setresuid()/setresgid() calls? */
                needs_mount_namespace;  /* Do we need to set up a mount namespace for this kernel? */
        bool keep_seccomp_privileges = false;
        bool has_cap_sys_admin = false;
#if HAVE_SELINUX
        _cleanup_free_ char *mac_selinux_context_net = NULL;
        bool use_selinux = false;
#endif
#if ENABLE_SMACK
        bool use_smack = false;
#endif
#if HAVE_APPARMOR
        bool use_apparmor = false;
#endif
#if HAVE_SECCOMP
        uint64_t saved_bset = 0;
#endif
        uid_t saved_uid = getuid();
        gid_t saved_gid = getgid();
        uid_t uid = UID_INVALID;
        gid_t gid = GID_INVALID;
        size_t n_fds, /* fds to pass to the child */
               n_keep_fds; /* total number of fds not to close */
        int secure_bits;
        _cleanup_free_ gid_t *gids_after_pam = NULL;
        int ngids_after_pam = 0;

        int socket_fd = -EBADF, named_iofds[3] = EBADF_TRIPLET;
        size_t n_storage_fds, n_socket_fds, n_extra_fds;

        assert(command);
        assert(context);
        assert(params);
        assert(exit_status);

        /* This should be mostly redundant, as the log level is also passed as an argument of the executor,
         * and is already applied earlier. Just for safety. */
        if (params->debug_invocation)
                log_set_max_level(LOG_PRI(LOG_DEBUG));
        else if (context->log_level_max >= 0)
                log_set_max_level(context->log_level_max);

        /* Explicitly test for CVE-2021-4034 inspired invocations */
        if (!command->path || strv_isempty(command->argv)) {
                *exit_status = EXIT_EXEC;
                return log_exec_error_errno(
                                context,
                                params,
                                SYNTHETIC_ERRNO(EINVAL),
                                "Invalid command line arguments.");
        }

        LOG_CONTEXT_PUSH_EXEC(context, params);

        if (context->std_input == EXEC_INPUT_SOCKET ||
            context->std_output == EXEC_OUTPUT_SOCKET ||
            context->std_error == EXEC_OUTPUT_SOCKET) {

                if (params->n_socket_fds > 1)
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EINVAL), "Got more than one socket.");

                if (params->n_socket_fds == 0)
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EINVAL), "Got no socket.");

                socket_fd = params->fds[0];
                n_storage_fds = n_socket_fds = n_extra_fds = 0;
        } else {
                n_socket_fds = params->n_socket_fds;
                n_storage_fds = params->n_storage_fds;
                n_extra_fds = params->n_extra_fds;
        }
        n_fds = n_socket_fds + n_storage_fds + n_extra_fds;

        r = exec_context_named_iofds(context, params, named_iofds);
        if (r < 0)
                return log_exec_error_errno(context, params, r, "Failed to load a named file descriptor: %m");

        rename_process_from_path(command->path);

        /* We reset exactly these signals, since they are the only ones we set to SIG_IGN in the main
         * daemon. All others we leave untouched because we set them to SIG_DFL or a valid handler initially,
         * both of which will be demoted to SIG_DFL. */
        (void) default_signals(SIGNALS_CRASH_HANDLER,
                               SIGNALS_IGNORE);

        if (context->ignore_sigpipe)
                (void) ignore_signals(SIGPIPE);

        r = reset_signal_mask();
        if (r < 0) {
                *exit_status = EXIT_SIGNAL_MASK;
                return log_exec_error_errno(context, params, r, "Failed to set process signal mask: %m");
        }

        if (params->idle_pipe)
                do_idle_pipe_dance(params->idle_pipe);

        /* Close fds we don't need very early to make sure we don't block init reexecution because it cannot bind its
         * sockets. Among the fds we close are the logging fds, and we want to keep them closed, so that we don't have
         * any fds open we don't really want open during the transition. In order to make logging work, we switch the
         * log subsystem into open_when_needed mode, so that it reopens the logs on every single log call. */

        log_forget_fds();
        log_set_open_when_needed(true);
        log_settle_target();

        /* In case anything used libc syslog(), close this here, too */
        closelog();

        r = collect_open_file_fds(context, params, &n_fds);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to get OpenFile= file descriptors: %m");
        }

        int keep_fds[n_fds + 4];
        memcpy_safe(keep_fds, params->fds, n_fds * sizeof(int));
        n_keep_fds = n_fds;

        r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->exec_fd);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to collect shifted fd: %m");
        }

        r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->handoff_timestamp_fd);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to collect shifted fd: %m");
        }

#if HAVE_LIBBPF
        r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &params->bpf_restrict_fs_map_fd);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to collect shifted fd: %m");
        }
#endif

        r = close_remaining_fds(params, runtime, socket_fd, keep_fds, n_keep_fds);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to close unwanted file descriptors: %m");
        }

        if (!context->same_pgrp &&
            setsid() < 0) {
                *exit_status = EXIT_SETSID;
                return log_exec_error_errno(context, params, errno, "Failed to create new process session: %m");
        }

        /* Now, reset the TTY associated to this service "destructively" (i.e. possibly even hang up or
         * disallocate the VT), to get rid of any prior uses of the device. Note that we do not keep any fd
         * open here, hence some of the settings made here might vanish again, depending on the TTY driver
         * used. A 2nd ("constructive") initialization after we opened the input/output fds we actually want
         * will fix this. */
        exec_context_tty_reset(context, params);

        if (params->shall_confirm_spawn && exec_context_shall_confirm_spawn(context)) {
                _cleanup_free_ char *cmdline = NULL;

                cmdline = quote_command_line(command->argv, SHELL_ESCAPE_EMPTY);
                if (!cmdline) {
                        *exit_status = EXIT_MEMORY;
                        return log_oom();
                }

                r = ask_for_confirmation(context, params, cmdline);
                if (r != CONFIRM_EXECUTE) {
                        if (r == CONFIRM_PRETEND_SUCCESS) {
                                *exit_status = EXIT_SUCCESS;
                                return 0;
                        }

                        *exit_status = EXIT_CONFIRM;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(ECANCELED),
                                                    "Execution cancelled by the user.");
                }
        }

        /* We are about to invoke NSS and PAM modules. Let's tell them what we are doing here, maybe they care. This is
         * used by nss-resolve to disable itself when we are about to start systemd-resolved, to avoid deadlocks. Note
         * that these env vars do not survive the execve(), which means they really only apply to the PAM and NSS
         * invocations themselves. Also note that while we'll only invoke NSS modules involved in user management they
         * might internally call into other NSS modules that are involved in hostname resolution, we never know. */
        if (setenv("SYSTEMD_ACTIVATION_UNIT", params->unit_id, true) != 0 ||
            setenv("SYSTEMD_ACTIVATION_SCOPE", runtime_scope_to_string(params->runtime_scope), true) != 0) {
                *exit_status = EXIT_MEMORY;
                return log_exec_error_errno(context, params, errno, "Failed to update environment: %m");
        }

        if (context->dynamic_user && runtime && runtime->dynamic_creds) {
                _cleanup_strv_free_ char **suggested_paths = NULL;

                /* On top of that, make sure we bypass our own NSS module nss-systemd comprehensively for any NSS
                 * checks, if DynamicUser=1 is used, as we shouldn't create a feedback loop with ourselves here. */
                if (putenv((char*) "SYSTEMD_NSS_DYNAMIC_BYPASS=1") != 0) {
                        *exit_status = EXIT_USER;
                        return log_exec_error_errno(context, params, errno, "Failed to update environment: %m");
                }

                r = compile_suggested_paths(context, params, &suggested_paths);
                if (r < 0) {
                        *exit_status = EXIT_MEMORY;
                        return log_oom();
                }

                r = dynamic_creds_realize(runtime->dynamic_creds, suggested_paths, &uid, &gid);
                if (r < 0) {
                        *exit_status = EXIT_USER;
                        if (r == -EILSEQ)
                                return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                                            "Failed to update dynamic user credentials: User or group with specified name already exists.");
                        return log_exec_error_errno(context, params, r, "Failed to update dynamic user credentials: %m");
                }

                if (!uid_is_valid(uid)) {
                        *exit_status = EXIT_USER;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(ESRCH), "UID validation failed for \""UID_FMT"\".", uid);
                }

                if (!gid_is_valid(gid)) {
                        *exit_status = EXIT_USER;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(ESRCH), "GID validation failed for \""GID_FMT"\".", gid);
                }

                if (runtime->dynamic_creds->user)
                        username = runtime->dynamic_creds->user->name;

        } else {
                const char *u;

                if (context->user)
                        u = context->user;
                else if (context->pam_name) {
                        /* If PAM is enabled but no user name is explicitly selected, then use our own one. */
                        own_user = getusername_malloc();
                        if (!own_user) {
                                *exit_status = EXIT_USER;
                                return log_exec_error_errno(context, params, r, "Failed to determine my own user ID: %m");
                        }
                        u = own_user;
                } else
                        u = NULL;

                if (u) {
                        r = get_fixed_user(u, &username, &uid, &gid, &home, &shell);
                        if (r < 0) {
                                *exit_status = EXIT_USER;
                                return log_exec_error_errno(context, params, r, "Failed to determine user credentials: %m");
                        }
                }

                if (context->group) {
                        r = get_fixed_group(context->group, &groupname, &gid);
                        if (r < 0) {
                                *exit_status = EXIT_GROUP;
                                return log_exec_error_errno(context, params, r, "Failed to determine group credentials: %m");
                        }
                }
        }

        /* Initialize user supplementary groups and get SupplementaryGroups= ones */
        r = get_supplementary_groups(context, username, groupname, gid,
                                     &supplementary_gids, &ngids);
        if (r < 0) {
                *exit_status = EXIT_GROUP;
                return log_exec_error_errno(context, params, r, "Failed to determine supplementary groups: %m");
        }

        r = send_user_lookup(params->unit_id, params->user_lookup_fd, uid, gid);
        if (r < 0) {
                *exit_status = EXIT_USER;
                return log_exec_error_errno(context, params, r, "Failed to send user credentials to PID1: %m");
        }

        params->user_lookup_fd = safe_close(params->user_lookup_fd);

        r = acquire_home(context, &home, &home_buffer);
        if (r < 0) {
                *exit_status = EXIT_CHDIR;
                return log_exec_error_errno(context, params, r, "Failed to determine $HOME for the invoking user: %m");
        }

        /* If a socket is connected to STDIN/STDOUT/STDERR, we must drop O_NONBLOCK */
        if (socket_fd >= 0)
                (void) fd_nonblock(socket_fd, false);

        /* Journald will try to look-up our cgroup in order to populate _SYSTEMD_CGROUP and _SYSTEMD_UNIT fields.
         * Hence we need to migrate to the target cgroup from init.scope before connecting to journald */
        if (params->cgroup_path) {
                _cleanup_free_ char *p = NULL;

                r = exec_params_get_cgroup_path(params, cgroup_context, &p);
                if (r < 0) {
                        *exit_status = EXIT_CGROUP;
                        return log_exec_error_errno(context, params, r, "Failed to acquire cgroup path: %m");
                }

                r = cg_attach_everywhere(params->cgroup_supported, p, 0);
                if (r == -EUCLEAN) {
                        *exit_status = EXIT_CGROUP;
                        return log_exec_error_errno(context, params, r,
                                                    "Failed to attach process to cgroup '%s', "
                                                    "because the cgroup or one of its parents or "
                                                    "siblings is in the threaded mode.", p);
                }
                if (r < 0) {
                        *exit_status = EXIT_CGROUP;
                        return log_exec_error_errno(context, params, r, "Failed to attach to cgroup %s: %m", p);
                }
        }

        if (context->network_namespace_path && runtime && runtime->shared && runtime->shared->netns_storage_socket[0] >= 0) {
                r = open_shareable_ns_path(runtime->shared->netns_storage_socket, context->network_namespace_path, CLONE_NEWNET);
                if (r < 0) {
                        *exit_status = EXIT_NETWORK;
                        return log_exec_error_errno(context, params, r, "Failed to open network namespace path %s: %m", context->network_namespace_path);
                }
        }

        if (context->ipc_namespace_path && runtime && runtime->shared && runtime->shared->ipcns_storage_socket[0] >= 0) {
                r = open_shareable_ns_path(runtime->shared->ipcns_storage_socket, context->ipc_namespace_path, CLONE_NEWIPC);
                if (r < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "Failed to open IPC namespace path %s: %m", context->ipc_namespace_path);
                }
        }

        r = setup_input(context, params, socket_fd, named_iofds);
        if (r < 0) {
                *exit_status = EXIT_STDIN;
                return log_exec_error_errno(context, params, r, "Failed to set up standard input: %m");
        }

        _cleanup_free_ char *fname = NULL;
        r = path_extract_filename(command->path, &fname);
        if (r < 0) {
                *exit_status = EXIT_STDOUT;
                return log_exec_error_errno(context, params, r, "Failed to extract filename from path %s: %m", command->path);
        }

        r = setup_output(context, params, STDOUT_FILENO, socket_fd, named_iofds, fname, uid, gid, &journal_stream_dev, &journal_stream_ino);
        if (r < 0) {
                *exit_status = EXIT_STDOUT;
                return log_exec_error_errno(context, params, r, "Failed to set up standard output: %m");
        }

        r = setup_output(context, params, STDERR_FILENO, socket_fd, named_iofds, fname, uid, gid, &journal_stream_dev, &journal_stream_ino);
        if (r < 0) {
                *exit_status = EXIT_STDERR;
                return log_exec_error_errno(context, params, r, "Failed to set up standard error output: %m");
        }

        /* Now that stdin/stdout are definiely opened, properly initialize it with our desired
         * settings. Note: this is a "constructive" reset, it prepares things for us to use. This is
         * different from the "destructive" TTY reset further up. Also note: we apply this on stdin/stdout in
         * case this is a tty, regardless if we opened it ourselves or got it passed in pre-opened. */
        prepare_terminal(context, params);

        if (context->oom_score_adjust_set) {
                /* When we can't make this change due to EPERM, then let's silently skip over it. User
                 * namespaces prohibit write access to this file, and we shouldn't trip up over that. */
                r = set_oom_score_adjust(context->oom_score_adjust);
                if (ERRNO_IS_NEG_PRIVILEGE(r))
                        log_exec_debug_errno(context, params, r,
                                             "Failed to adjust OOM setting, assuming containerized execution, ignoring: %m");
                else if (r < 0) {
                        *exit_status = EXIT_OOM_ADJUST;
                        return log_exec_error_errno(context, params, r, "Failed to adjust OOM setting: %m");
                }
        }

        if (context->coredump_filter_set) {
                r = set_coredump_filter(context->coredump_filter);
                if (ERRNO_IS_NEG_PRIVILEGE(r))
                        log_exec_debug_errno(context, params, r, "Failed to adjust coredump_filter, ignoring: %m");
                else if (r < 0) {
                        *exit_status = EXIT_LIMITS;
                        return log_exec_error_errno(context, params, r, "Failed to adjust coredump_filter: %m");
                }
        }

        if (context->cpu_sched_set) {
                struct sched_attr attr = {
                        .size = sizeof(attr),
                        .sched_policy = context->cpu_sched_policy,
                        .sched_priority = context->cpu_sched_priority,
                        .sched_flags = context->cpu_sched_reset_on_fork ? SCHED_FLAG_RESET_ON_FORK : 0,
                };

                r = sched_setattr(/* pid= */ 0, &attr, /* flags= */ 0);
                if (r < 0) {
                        *exit_status = EXIT_SETSCHEDULER;
                        return log_exec_error_errno(context, params, errno, "Failed to set up CPU scheduling: %m");
                }
        }

        /*
         * Set nice value _after_ the call to sched_setattr() because struct sched_attr includes sched_nice
         * which we do not set, thus it will clobber any previously set nice value. Scheduling policy might
         * be reasonably set together with nice value e.g. in case of SCHED_BATCH (see sched(7)).
         * It would be ideal to set both with the same call, but we cannot easily do so because of all the
         * extra logic in setpriority_closest().
         */
        if (context->nice_set) {
                r = setpriority_closest(context->nice);
                if (r < 0) {
                        *exit_status = EXIT_NICE;
                        return log_exec_error_errno(context, params, r, "Failed to set up process scheduling priority (nice level): %m");
                }
        }

        if (context->cpu_affinity_from_numa || context->cpu_set.set) {
                _cleanup_(cpu_set_reset) CPUSet converted_cpu_set = {};
                const CPUSet *cpu_set;

                if (context->cpu_affinity_from_numa) {
                        r = exec_context_cpu_affinity_from_numa(context, &converted_cpu_set);
                        if (r < 0) {
                                *exit_status = EXIT_CPUAFFINITY;
                                return log_exec_error_errno(context, params, r, "Failed to derive CPU affinity mask from NUMA mask: %m");
                        }

                        cpu_set = &converted_cpu_set;
                } else
                        cpu_set = &context->cpu_set;

                if (sched_setaffinity(0, cpu_set->allocated, cpu_set->set) < 0) {
                        *exit_status = EXIT_CPUAFFINITY;
                        return log_exec_error_errno(context, params, errno, "Failed to set up CPU affinity: %m");
                }
        }

        if (mpol_is_valid(numa_policy_get_type(&context->numa_policy))) {
                r = apply_numa_policy(&context->numa_policy);
                if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
                        log_exec_debug_errno(context, params, r, "NUMA support not available, ignoring.");
                else if (r < 0) {
                        *exit_status = EXIT_NUMA_POLICY;
                        return log_exec_error_errno(context, params, r, "Failed to set NUMA memory policy: %m");
                }
        }

        if (context->ioprio_set)
                if (ioprio_set(IOPRIO_WHO_PROCESS, 0, context->ioprio) < 0) {
                        *exit_status = EXIT_IOPRIO;
                        return log_exec_error_errno(context, params, errno, "Failed to set up IO scheduling priority: %m");
                }

        if (context->timer_slack_nsec != NSEC_INFINITY)
                if (prctl(PR_SET_TIMERSLACK, context->timer_slack_nsec) < 0) {
                        *exit_status = EXIT_TIMERSLACK;
                        return log_exec_error_errno(context, params, errno, "Failed to set up timer slack: %m");
                }

        if (context->personality != PERSONALITY_INVALID) {
                r = safe_personality(context->personality);
                if (r < 0) {
                        *exit_status = EXIT_PERSONALITY;
                        return log_exec_error_errno(context, params, r, "Failed to set up execution domain (personality): %m");
                }
        }

#if ENABLE_UTMP
        if (context->utmp_id) {
                _cleanup_free_ char *username_alloc = NULL;

                if (!username && context->utmp_mode == EXEC_UTMP_USER) {
                        username_alloc = uid_to_name(uid_is_valid(uid) ? uid : saved_uid);
                        if (!username_alloc) {
                                *exit_status = EXIT_USER;
                                return log_oom();
                        }
                }

                const char *line = context->tty_path ?
                        (path_startswith(context->tty_path, "/dev/") ?: context->tty_path) :
                        NULL;
                utmp_put_init_process(context->utmp_id, getpid_cached(), getsid(0),
                                      line,
                                      context->utmp_mode == EXEC_UTMP_INIT  ? INIT_PROCESS :
                                      context->utmp_mode == EXEC_UTMP_LOGIN ? LOGIN_PROCESS :
                                      USER_PROCESS,
                                      username ?: username_alloc);
        }
#endif

        if (uid_is_valid(uid)) {
                r = chown_terminal(STDIN_FILENO, uid);
                if (r < 0) {
                        *exit_status = EXIT_STDIN;
                        return log_exec_error_errno(context, params, r, "Failed to change ownership of terminal: %m");
                }
        }

        /* We need sandboxing if the caller asked us to apply it and the command isn't explicitly excepted
         * from it. */
        needs_sandboxing = (params->flags & EXEC_APPLY_SANDBOXING) && !(command->flags & EXEC_COMMAND_FULLY_PRIVILEGED);

        if (params->cgroup_path) {
                /* If delegation is enabled we'll pass ownership of the cgroup to the user of the new process. On cgroup v1
                 * this is only about systemd's own hierarchy, i.e. not the controller hierarchies, simply because that's not
                 * safe. On cgroup v2 there's only one hierarchy anyway, and delegation is safe there, hence in that case only
                 * touch a single hierarchy too. */

                if (params->flags & EXEC_CGROUP_DELEGATE) {
                        _cleanup_free_ char *p = NULL;

                        r = cg_set_access(SYSTEMD_CGROUP_CONTROLLER, params->cgroup_path, uid, gid);
                        if (r < 0) {
                                *exit_status = EXIT_CGROUP;
                                return log_exec_error_errno(context, params, r, "Failed to adjust control group access: %m");
                        }

                        r = exec_params_get_cgroup_path(params, cgroup_context, &p);
                        if (r < 0) {
                                *exit_status = EXIT_CGROUP;
                                return log_exec_error_errno(context, params, r, "Failed to acquire cgroup path: %m");
                        }
                        if (r > 0) {
                                r = cg_set_access_recursive(SYSTEMD_CGROUP_CONTROLLER, p, uid, gid);
                                if (r < 0) {
                                        *exit_status = EXIT_CGROUP;
                                        return log_exec_error_errno(context, params, r, "Failed to adjust control subgroup access: %m");
                                }
                        }
                }

                if (cgroup_context && cg_unified() > 0 && is_pressure_supported() > 0) {
                        if (cgroup_context_want_memory_pressure(cgroup_context)) {
                                r = cg_get_path("memory", params->cgroup_path, "memory.pressure", &memory_pressure_path);
                                if (r < 0) {
                                        *exit_status = EXIT_MEMORY;
                                        return log_oom();
                                }

                                r = chmod_and_chown(memory_pressure_path, 0644, uid, gid);
                                if (r < 0) {
                                        log_exec_full_errno(context, params, r == -ENOENT || ERRNO_IS_PRIVILEGE(r) ? LOG_DEBUG : LOG_WARNING, r,
                                                            "Failed to adjust ownership of '%s', ignoring: %m", memory_pressure_path);
                                        memory_pressure_path = mfree(memory_pressure_path);
                                }
                                /* First we use the current cgroup path to chmod and chown the memory pressure path, then pass the path relative
                                 * to the cgroup namespace to environment variables and mounts. If chown/chmod fails, we should not pass memory
                                 * pressure path environment variable or read-write mount to the unit. This is why we check if
                                 * memory_pressure_path != NULL in the conditional below. */
                                if (memory_pressure_path && needs_sandboxing && exec_needs_cgroup_namespace(context, params)) {
                                        memory_pressure_path = mfree(memory_pressure_path);
                                        r = cg_get_path("memory", "", "memory.pressure", &memory_pressure_path);
                                        if (r < 0) {
                                                *exit_status = EXIT_MEMORY;
                                                return log_oom();
                                        }
                                }
                        } else if (cgroup_context->memory_pressure_watch == CGROUP_PRESSURE_WATCH_NO) {
                                memory_pressure_path = strdup("/dev/null"); /* /dev/null is explicit indicator for turning of memory pressure watch */
                                if (!memory_pressure_path) {
                                        *exit_status = EXIT_MEMORY;
                                        return log_oom();
                                }
                        }
                }
        }

        needs_mount_namespace = exec_needs_mount_namespace(context, params, runtime);

        for (ExecDirectoryType dt = 0; dt < _EXEC_DIRECTORY_TYPE_MAX; dt++) {
                r = setup_exec_directory(context, params, uid, gid, dt, needs_mount_namespace, exit_status);
                if (r < 0)
                        return log_exec_error_errno(context, params, r, "Failed to set up special execution directory in %s: %m", params->prefix[dt]);
        }

        r = exec_setup_credentials(context, params, params->unit_id, uid, gid);
        if (r < 0) {
                *exit_status = EXIT_CREDENTIALS;
                return log_exec_error_errno(context, params, r, "Failed to set up credentials: %m");
        }

        r = build_environment(
                        context,
                        params,
                        cgroup_context,
                        n_fds,
                        home,
                        username,
                        shell,
                        journal_stream_dev,
                        journal_stream_ino,
                        memory_pressure_path,
                        needs_sandboxing,
                        &our_env);
        if (r < 0) {
                *exit_status = EXIT_MEMORY;
                return log_oom();
        }

        r = build_pass_environment(context, &pass_env);
        if (r < 0) {
                *exit_status = EXIT_MEMORY;
                return log_oom();
        }

        /* The $PATH variable is set to the default path in params->environment. However, this is overridden
         * if user-specified fields have $PATH set. The intention is to also override $PATH if the unit does
         * not specify PATH but the unit has ExecSearchPath. */
        if (!strv_isempty(context->exec_search_path)) {
                _cleanup_free_ char *joined = NULL;

                joined = strv_join(context->exec_search_path, ":");
                if (!joined) {
                        *exit_status = EXIT_MEMORY;
                        return log_oom();
                }

                r = strv_env_assign(&joined_exec_search_path, "PATH", joined);
                if (r < 0) {
                        *exit_status = EXIT_MEMORY;
                        return log_oom();
                }
        }

        accum_env = strv_env_merge(params->environment,
                                   our_env,
                                   joined_exec_search_path,
                                   pass_env,
                                   context->environment,
                                   params->files_env);
        if (!accum_env) {
                *exit_status = EXIT_MEMORY;
                return log_oom();
        }
        accum_env = strv_env_clean(accum_env);

        (void) umask(context->umask);

        r = setup_keyring(context, params, uid, gid);
        if (r < 0) {
                *exit_status = EXIT_KEYRING;
                return log_exec_error_errno(context, params, r, "Failed to set up kernel keyring: %m");
        }

        /* We need setresuid() if the caller asked us to apply sandboxing and the command isn't explicitly
         * excepted from either whole sandboxing or just setresuid() itself. */
        needs_setuid = (params->flags & EXEC_APPLY_SANDBOXING) && !(command->flags & (EXEC_COMMAND_FULLY_PRIVILEGED|EXEC_COMMAND_NO_SETUID));

        uint64_t capability_ambient_set = context->capability_ambient_set;

        /* Check CAP_SYS_ADMIN before we enter user namespace to see if we can mount /proc even though its masked. */
        has_cap_sys_admin = have_effective_cap(CAP_SYS_ADMIN) > 0;

        if (needs_sandboxing) {
                /* MAC enablement checks need to be done before a new mount ns is created, as they rely on
                 * /sys being present. The actual MAC context application will happen later, as late as
                 * possible, to avoid impacting our own code paths. */

#if HAVE_SELINUX
                use_selinux = mac_selinux_use();
#endif
#if ENABLE_SMACK
                use_smack = mac_smack_use();
#endif
#if HAVE_APPARMOR
                use_apparmor = mac_apparmor_use();
#endif
        }

        if (needs_sandboxing) {
                int which_failed;

                /* Let's set the resource limits before we call into PAM, so that pam_limits wins over what
                 * is set here. (See below.) */

                r = setrlimit_closest_all((const struct rlimit* const *) context->rlimit, &which_failed);
                if (r < 0) {
                        *exit_status = EXIT_LIMITS;
                        return log_exec_error_errno(context, params, r, "Failed to adjust resource limit RLIMIT_%s: %m", rlimit_to_string(which_failed));
                }
        }

        if (needs_setuid && context->pam_name && username) {
                /* Let's call into PAM after we set up our own idea of resource limits so that pam_limits
                 * wins here. (See above.) */

                /* All fds passed in the fds array will be closed in the pam child process. */
                r = setup_pam(context, params, username, uid, gid, &accum_env, params->fds, n_fds, params->exec_fd);
                if (r < 0) {
                        *exit_status = EXIT_PAM;
                        return log_exec_error_errno(context, params, r, "Failed to set up PAM session: %m");
                }

                /* PAM modules might have set some ambient caps. Query them here and merge them into
                 * the caps we want to set in the end, so that we don't end up unsetting them. */
                uint64_t ambient_after_pam;
                r = capability_get_ambient(&ambient_after_pam);
                if (r < 0) {
                        *exit_status = EXIT_CAPABILITIES;
                        return log_exec_error_errno(context, params, r, "Failed to query ambient caps: %m");
                }

                capability_ambient_set |= ambient_after_pam;

                ngids_after_pam = getgroups_alloc(&gids_after_pam);
                if (ngids_after_pam < 0) {
                        *exit_status = EXIT_GROUP;
                        return log_exec_error_errno(context, params, ngids_after_pam, "Failed to obtain groups after setting up PAM: %m");
                }
        }

        if (needs_sandboxing && exec_context_need_unprivileged_private_users(context, params)) {
                /* If we're unprivileged, set up the user namespace first to enable use of the other namespaces.
                 * Users with CAP_SYS_ADMIN can set up user namespaces last because they will be able to
                 * set up all of the other namespaces (i.e. network, mount, UTS) without a user namespace. */
                PrivateUsers pu = context->private_users;
                if (pu == PRIVATE_USERS_NO)
                        pu = PRIVATE_USERS_SELF;

                /* The kernel requires /proc/pid/setgroups be set to "deny" prior to writing /proc/pid/gid_map in
                 * unprivileged user namespaces. */
                r = setup_private_users(pu, saved_uid, saved_gid, uid, gid, /* allow_setgroups= */ false);
                /* If it was requested explicitly and we can't set it up, fail early. Otherwise, continue and let
                 * the actual requested operations fail (or silently continue). */
                if (r < 0 && context->private_users != PRIVATE_USERS_NO) {
                        *exit_status = EXIT_USER;
                        return log_exec_error_errno(context, params, r, "Failed to set up user namespacing for unprivileged user: %m");
                }
                if (r < 0)
                        log_exec_info_errno(context, params, r, "Failed to set up user namespacing for unprivileged user, ignoring: %m");
                else {
                        assert(r > 0);
                        userns_set_up = true;
                }
        }

        if (exec_needs_network_namespace(context) && runtime && runtime->shared && runtime->shared->netns_storage_socket[0] >= 0) {

                /* Try to enable network namespacing if network namespacing is available and we have
                 * CAP_NET_ADMIN. We need CAP_NET_ADMIN to be able to configure the loopback device in the
                 * new network namespace. And if we don't have that, then we could only create a network
                 * namespace without the ability to set up "lo". Hence gracefully skip things then. */
                if (ns_type_supported(NAMESPACE_NET) && have_effective_cap(CAP_NET_ADMIN) > 0) {
                        r = setup_shareable_ns(runtime->shared->netns_storage_socket, CLONE_NEWNET);
                        if (ERRNO_IS_NEG_PRIVILEGE(r))
                                log_exec_notice_errno(context, params, r,
                                                      "PrivateNetwork=yes is configured, but network namespace setup not permitted, proceeding without: %m");
                        else if (r < 0) {
                                *exit_status = EXIT_NETWORK;
                                return log_exec_error_errno(context, params, r, "Failed to set up network namespacing: %m");
                        }
                } else if (context->network_namespace_path) {
                        *exit_status = EXIT_NETWORK;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                                    "NetworkNamespacePath= is not supported, refusing.");
                } else
                        log_exec_notice(context, params, "PrivateNetwork=yes is configured, but the kernel does not support or we lack privileges for network namespace, proceeding without.");
        }

        if (exec_needs_ipc_namespace(context) && runtime && runtime->shared && runtime->shared->ipcns_storage_socket[0] >= 0) {

                if (ns_type_supported(NAMESPACE_IPC)) {
                        r = setup_shareable_ns(runtime->shared->ipcns_storage_socket, CLONE_NEWIPC);
                        if (ERRNO_IS_NEG_PRIVILEGE(r))
                                log_exec_warning_errno(context, params, r,
                                                       "PrivateIPC=yes is configured, but IPC namespace setup failed, ignoring: %m");
                        else if (r < 0) {
                                *exit_status = EXIT_NAMESPACE;
                                return log_exec_error_errno(context, params, r, "Failed to set up IPC namespacing: %m");
                        }
                } else if (context->ipc_namespace_path) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EOPNOTSUPP),
                                                    "IPCNamespacePath= is not supported, refusing.");
                } else
                        log_exec_warning(context, params, "PrivateIPC=yes is configured, but the kernel does not support IPC namespaces, ignoring.");
        }

        if (needs_sandboxing && exec_needs_cgroup_namespace(context, params)) {
                r = unshare(CLONE_NEWCGROUP);
                if (r < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "Failed to set up cgroup namespacing: %m");
                }
        }

        /* Unshare a new PID namespace before setting up mounts to ensure /proc/ is mounted with only processes in PID namespace visible.
         * Note PrivatePIDs=yes implies MountAPIVFS=yes so we'll always ensure procfs is remounted. */
        if (needs_sandboxing && exec_needs_pid_namespace(context)) {
                if (params->pidref_transport_fd < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "PidRef socket is not set up: %m");
                }

                /* If we had CAP_SYS_ADMIN prior to joining the user namespace, then we are privileged and don't need
                 * to check if we can mount /proc/.
                 *
                 * We need to check prior to entering the user namespace because if we're running unprivileged or in a
                 * system without CAP_SYS_ADMIN, then we can have CAP_SYS_ADMIN in the current user namespace but not
                 * once we unshare a mount namespace. */
                r = has_cap_sys_admin ? 1 : can_mount_proc(context, params);
                if (r < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "Failed to detect if /proc/ can be remounted: %m");
                }
                if (r == 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, SYNTHETIC_ERRNO(EPERM),
                                                    "PrivatePIDs=yes is configured, but /proc/ cannot be re-mounted due to lack of privileges, refusing.");
                }

                r = setup_private_pids(context, params);
                if (r < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "Failed to set up pid namespace: %m");
                }
        }

        /* If PrivatePIDs= yes is configured, we're now running as pid 1 in a pid namespace! */

        if (needs_mount_namespace) {
                _cleanup_free_ char *error_path = NULL;

                r = apply_mount_namespace(command->flags,
                                          context,
                                          params,
                                          runtime,
                                          memory_pressure_path,
                                          needs_sandboxing,
                                          &error_path,
                                          uid,
                                          gid);
                if (r < 0) {
                        *exit_status = EXIT_NAMESPACE;
                        return log_exec_error_errno(context, params, r, "Failed to set up mount namespacing%s%s: %m",
                                                    error_path ? ": " : "", strempty(error_path));
                }
        }

        if (needs_sandboxing) {
                r = apply_protect_hostname(context, params, exit_status);
                if (r < 0)
                        return r;
        }

        if (context->memory_ksm >= 0)
                if (prctl(PR_SET_MEMORY_MERGE, context->memory_ksm, 0, 0, 0) < 0) {
                        if (ERRNO_IS_NOT_SUPPORTED(errno))
                                log_exec_debug_errno(context,
                                                     params,
                                                     errno,
                                                     "KSM support not available, ignoring.");
                        else {
                                *exit_status = EXIT_KSM;
                                return log_exec_error_errno(context, params, errno, "Failed to set KSM: %m");
                        }
                }

        /* Drop groups as early as possible.
         * This needs to be done after PrivateDevices=yes setup as device nodes should be owned by the host's root.
         * For non-root in a userns, devices will be owned by the user/group before the group change, and nobody. */
        if (needs_setuid) {
                _cleanup_free_ gid_t *gids_to_enforce = NULL;
                int ngids_to_enforce = 0;

                ngids_to_enforce = merge_gid_lists(supplementary_gids,
                                                   ngids,
                                                   gids_after_pam,
                                                   ngids_after_pam,
                                                   &gids_to_enforce);
                if (ngids_to_enforce < 0) {
                        *exit_status = EXIT_GROUP;
                        return log_exec_error_errno(context, params,
                                                    ngids_to_enforce,
                                                    "Failed to merge group lists. Group membership might be incorrect: %m");
                }

                r = enforce_groups(gid, gids_to_enforce, ngids_to_enforce);
                if (r < 0) {
                        *exit_status = EXIT_GROUP;
                        return log_exec_error_errno(context, params, r, "Changing group credentials failed: %m");
                }
        }

        /* If the user namespace was not set up above, try to do it now.
         * It's preferred to set up the user namespace later (after all other namespaces) so as not to be
         * restricted by rules pertaining to combining user namespaces with other namespaces (e.g. in the
         * case of mount namespaces being less privileged when the mount point list is copied from a
         * different user namespace). */

        if (needs_sandboxing && !userns_set_up) {
                r = setup_private_users(context->private_users, saved_uid, saved_gid, uid, gid,
                                        /* allow_setgroups= */ context->private_users == PRIVATE_USERS_FULL);
                if (r < 0) {
                        *exit_status = EXIT_USER;
                        return log_exec_error_errno(context, params, r, "Failed to set up user namespacing: %m");
                }
        }

        /* Now that the mount namespace has been set up and privileges adjusted, let's look for the thing we
         * shall execute. */

        _cleanup_free_ char *executable = NULL;
        _cleanup_close_ int executable_fd = -EBADF;
        r = find_executable_full(command->path, /* root= */ NULL, context->exec_search_path, false, &executable, &executable_fd);
        if (r < 0) {
                *exit_status = EXIT_EXEC;
                log_exec_struct_errno(context, params, LOG_NOTICE, r,
                                      "MESSAGE_ID=" SD_MESSAGE_SPAWN_FAILED_STR,
                                      LOG_EXEC_MESSAGE(params,
                                                       "Unable to locate executable '%s': %m",
                                                       command->path),
                                      "EXECUTABLE=%s", command->path);
                /* If the error will be ignored by manager, tune down the log level here. Missing executable
                 * is very much expected in this case. */
                return r != -ENOMEM && FLAGS_SET(command->flags, EXEC_COMMAND_IGNORE_FAILURE) ? 1 : r;
        }

        r = add_shifted_fd(keep_fds, ELEMENTSOF(keep_fds), &n_keep_fds, &executable_fd);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to collect shifted fd: %m");
        }

#if HAVE_SELINUX
        if (needs_sandboxing && use_selinux && params->selinux_context_net) {
                int fd = -EBADF;

                if (socket_fd >= 0)
                        fd = socket_fd;
                else if (params->n_socket_fds == 1)
                        /* If stdin is not connected to a socket but we are triggered by exactly one socket unit then we
                         * use context from that fd to compute the label. */
                        fd = params->fds[0];

                if (fd >= 0) {
                        r = mac_selinux_get_child_mls_label(fd, executable, context->selinux_context, &mac_selinux_context_net);
                        if (r < 0) {
                                if (!context->selinux_context_ignore) {
                                        *exit_status = EXIT_SELINUX_CONTEXT;
                                        return log_exec_error_errno(context,
                                                                    params,
                                                                    r,
                                                                    "Failed to determine SELinux context: %m");
                                }
                                log_exec_debug_errno(context,
                                                     params,
                                                     r,
                                                     "Failed to determine SELinux context, ignoring: %m");
                        }
                }
        }
#endif

        /* We repeat the fd closing here, to make sure that nothing is leaked from the PAM modules. Note that
         * we are more aggressive this time, since we don't need socket_fd and the netns and ipcns fds any
         * more. We do keep exec_fd and handoff_timestamp_fd however, if we have it, since we need to keep
         * them open until the final execve(). But first, close the remaining sockets in the context
         * objects. */

        exec_runtime_close(runtime);
        exec_params_close(params);

        r = close_all_fds(keep_fds, n_keep_fds);
        if (r >= 0)
                r = pack_fds(params->fds, n_fds);
        if (r >= 0)
                r = flag_fds(params->fds, n_socket_fds, n_fds, context->non_blocking);
        if (r < 0) {
                *exit_status = EXIT_FDS;
                return log_exec_error_errno(context, params, r, "Failed to adjust passed file descriptors: %m");
        }

        /* At this point, the fds we want to pass to the program are all ready and set up, with O_CLOEXEC turned off
         * and at the right fd numbers. The are no other fds open, with one exception: the exec_fd if it is defined,
         * and it has O_CLOEXEC set, after all we want it to be closed by the execve(), so that our parent knows we
         * came this far. */

        secure_bits = context->secure_bits;

        if (needs_sandboxing) {
                uint64_t bset;

                /* Set the RTPRIO resource limit to 0, but only if nothing else was explicitly requested.
                 * (Note this is placed after the general resource limit initialization, see above, in order
                 * to take precedence.) */
                if (context->restrict_realtime && !context->rlimit[RLIMIT_RTPRIO]) {
                        if (setrlimit(RLIMIT_RTPRIO, &RLIMIT_MAKE_CONST(0)) < 0) {
                                *exit_status = EXIT_LIMITS;
                                return log_exec_error_errno(context, params, errno, "Failed to adjust RLIMIT_RTPRIO resource limit: %m");
                        }
                }

#if ENABLE_SMACK
                /* LSM Smack needs the capability CAP_MAC_ADMIN to change the current execution security context of the
                 * process. This is the latest place before dropping capabilities. Other MAC context are set later. */
                if (use_smack) {
                        r = setup_smack(params, context, executable_fd);
                        if (r < 0 && !context->smack_process_label_ignore) {
                                *exit_status = EXIT_SMACK_PROCESS_LABEL;
                                return log_exec_error_errno(context, params, r, "Failed to set SMACK process label: %m");
                        }
                }
#endif

                bset = context->capability_bounding_set;

#if HAVE_SECCOMP
                /* If the service has any form of a seccomp filter and it allows dropping privileges, we'll
                 * keep the needed privileges to apply it even if we're not root. */
                if (needs_setuid &&
                    uid_is_valid(uid) &&
                    context_has_seccomp(context) &&
                    seccomp_allows_drop_privileges(context)) {
                        keep_seccomp_privileges = true;

                        if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
                                *exit_status = EXIT_USER;
                                return log_exec_error_errno(context, params, errno, "Failed to enable keep capabilities flag: %m");
                        }

                        /* Save the current bounding set so we can restore it after applying the seccomp
                         * filter */
                        saved_bset = bset;
                        bset |= (UINT64_C(1) << CAP_SYS_ADMIN) |
                                (UINT64_C(1) << CAP_SETPCAP);
                }
#endif

                if (!cap_test_all(bset)) {
                        r = capability_bounding_set_drop(bset, /* right_now= */ false);
                        if (r < 0) {
                                *exit_status = EXIT_CAPABILITIES;
                                return log_exec_error_errno(context, params, r, "Failed to drop capabilities: %m");
                        }
                }

                /* Ambient capabilities are cleared during setresuid() (in enforce_user()) even with
                 * keep-caps set.
                 *
                 * To be able to raise the ambient capabilities after setresuid() they have to be added to
                 * the inherited set and keep caps has to be set (done in enforce_user()).  After setresuid()
                 * the ambient capabilities can be raised as they are present in the permitted and
                 * inhertiable set. However it is possible that someone wants to set ambient capabilities
                 * without changing the user, so we also set the ambient capabilities here.
                 *
                 * The requested ambient capabilities are raised in the inheritable set if the second
                 * argument is true. */
                if (capability_ambient_set != 0) {
                        r = capability_ambient_set_apply(capability_ambient_set, /* also_inherit= */ true);
                        if (r < 0) {
                                *exit_status = EXIT_CAPABILITIES;
                                return log_exec_error_errno(context, params, r, "Failed to apply ambient capabilities (before UID change): %m");
                        }
                }
        }

        /* chroot to root directory first, before we lose the ability to chroot */
        r = apply_root_directory(context, params, runtime, needs_mount_namespace, exit_status);
        if (r < 0)
                return log_exec_error_errno(context, params, r, "Chrooting to the requested root directory failed: %m");

        if (needs_setuid) {
                if (uid_is_valid(uid)) {
                        r = enforce_user(context, uid, capability_ambient_set);
                        if (r < 0) {
                                *exit_status = EXIT_USER;
                                return log_exec_error_errno(context, params, r, "Failed to change UID to " UID_FMT ": %m", uid);
                        }

                        if (keep_seccomp_privileges) {
                                if (!BIT_SET(capability_ambient_set, CAP_SETUID)) {
                                        r = drop_capability(CAP_SETUID);
                                        if (r < 0) {
                                                *exit_status = EXIT_USER;
                                                return log_exec_error_errno(context, params, r, "Failed to drop CAP_SETUID: %m");
                                        }
                                }

                                r = keep_capability(CAP_SYS_ADMIN);
                                if (r < 0) {
                                        *exit_status = EXIT_USER;
                                        return log_exec_error_errno(context, params, r, "Failed to keep CAP_SYS_ADMIN: %m");
                                }

                                r = keep_capability(CAP_SETPCAP);
                                if (r < 0) {
                                        *exit_status = EXIT_USER;
                                        return log_exec_error_errno(context, params, r, "Failed to keep CAP_SETPCAP: %m");
                                }
                        }

                        if (capability_ambient_set != 0) {

                                /* Raise the ambient capabilities after user change. */
                                r = capability_ambient_set_apply(capability_ambient_set, /* also_inherit= */ false);
                                if (r < 0) {
                                        *exit_status = EXIT_CAPABILITIES;
                                        return log_exec_error_errno(context, params, r, "Failed to apply ambient capabilities (after UID change): %m");
                                }
                        }
                }
        }

        /* Apply working directory here, because the working directory might be on NFS and only the user
         * running this service might have the correct privilege to change to the working directory. Also, it
         * is absolutely 💣 crucial 💣 we applied all mount namespacing rearrangements before this, so that
         * the cwd cannot be used to pin directories outside of the sandbox. */
        r = apply_working_directory(context, params, runtime, home);
        if (r < 0) {
                *exit_status = EXIT_CHDIR;
                return log_exec_error_errno(context, params, r, "Changing to the requested working directory failed: %m");
        }

        if (needs_sandboxing) {
                /* Apply other MAC contexts late, but before seccomp syscall filtering, as those should really be last to
                 * influence our own codepaths as little as possible. Moreover, applying MAC contexts usually requires
                 * syscalls that are subject to seccomp filtering, hence should probably be applied before the syscalls
                 * are restricted. */

#if HAVE_SELINUX
                if (use_selinux) {
                        char *exec_context = mac_selinux_context_net ?: context->selinux_context;

                        if (exec_context) {
                                r = setexeccon(exec_context);
                                if (r < 0) {
                                        if (!context->selinux_context_ignore) {
                                                *exit_status = EXIT_SELINUX_CONTEXT;
                                                return log_exec_error_errno(context, params, r, "Failed to change SELinux context to %s: %m", exec_context);
                                        }
                                        log_exec_debug_errno(context,
                                                             params,
                                                             r,
                                                             "Failed to change SELinux context to %s, ignoring: %m",
                                                             exec_context);
                                }
                        }
                }
#endif

#if HAVE_APPARMOR
                if (use_apparmor && context->apparmor_profile) {
                        r = aa_change_onexec(context->apparmor_profile);
                        if (r < 0 && !context->apparmor_profile_ignore) {
                                *exit_status = EXIT_APPARMOR_PROFILE;
                                return log_exec_error_errno(context,
                                                            params,
                                                            errno,
                                                            "Failed to prepare AppArmor profile change to %s: %m",
                                                            context->apparmor_profile);
                        }
                }
#endif

                /* PR_GET_SECUREBITS is not privileged, while PR_SET_SECUREBITS is. So to suppress potential
                 * EPERMs we'll try not to call PR_SET_SECUREBITS unless necessary. Setting securebits
                 * requires CAP_SETPCAP. */
                if (prctl(PR_GET_SECUREBITS) != secure_bits) {
                        /* CAP_SETPCAP is required to set securebits. This capability is raised into the
                         * effective set here.
                         *
                         * The effective set is overwritten during execve() with the following values:
                         *
                         * - ambient set (for non-root processes)
                         *
                         * - (inheritable | bounding) set for root processes)
                         *
                         * Hence there is no security impact to raise it in the effective set before execve
                         */
                        r = capability_gain_cap_setpcap(/* ret_before_caps = */ NULL);
                        if (r < 0) {
                                *exit_status = EXIT_CAPABILITIES;
                                return log_exec_error_errno(context, params, r, "Failed to gain CAP_SETPCAP for setting secure bits");
                        }
                        if (prctl(PR_SET_SECUREBITS, secure_bits) < 0) {
                                *exit_status = EXIT_SECUREBITS;
                                return log_exec_error_errno(context, params, errno, "Failed to set process secure bits: %m");
                        }
                }

                if (context_has_no_new_privileges(context))
                        if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
                                *exit_status = EXIT_NO_NEW_PRIVILEGES;
                                return log_exec_error_errno(context, params, errno, "Failed to disable new privileges: %m");
                        }

#if HAVE_SECCOMP
                r = apply_address_families(context, params);
                if (r < 0) {
                        *exit_status = EXIT_ADDRESS_FAMILIES;
                        return log_exec_error_errno(context, params, r, "Failed to restrict address families: %m");
                }

                r = apply_memory_deny_write_execute(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to disable writing to executable memory: %m");
                }

                r = apply_restrict_realtime(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply realtime restrictions: %m");
                }

                r = apply_restrict_suid_sgid(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply SUID/SGID restrictions: %m");
                }

                r = apply_restrict_namespaces(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply namespace restrictions: %m");
                }

                r = apply_protect_sysctl(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply sysctl restrictions: %m");
                }

                r = apply_protect_kernel_modules(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply module loading restrictions: %m");
                }

                r = apply_protect_kernel_logs(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply kernel log restrictions: %m");
                }

                r = apply_protect_clock(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply clock restrictions: %m");
                }

                r = apply_private_devices(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to set up private devices: %m");
                }

                r = apply_syscall_archs(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply syscall architecture restrictions: %m");
                }

                r = apply_lock_personality(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to lock personalities: %m");
                }

                r = apply_syscall_log(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply system call log filters: %m");
                }
#endif

#if HAVE_LIBBPF
                r = apply_restrict_filesystems(context, params);
                if (r < 0) {
                        *exit_status = EXIT_BPF;
                        return log_exec_error_errno(context, params, r, "Failed to restrict filesystems: %m");
                }
#endif

#if HAVE_SECCOMP
                /* This really should remain as close to the execve() as possible, to make sure our own code is affected
                 * by the filter as little as possible. */
                r = apply_syscall_filter(context, params);
                if (r < 0) {
                        *exit_status = EXIT_SECCOMP;
                        return log_exec_error_errno(context, params, r, "Failed to apply system call filters: %m");
                }

                if (keep_seccomp_privileges) {
                        /* Restore the capability bounding set with what's expected from the service + the
                         * ambient capabilities hack */
                        if (!cap_test_all(saved_bset)) {
                                r = capability_bounding_set_drop(saved_bset, /* right_now= */ false);
                                if (r < 0) {
                                        *exit_status = EXIT_CAPABILITIES;
                                        return log_exec_error_errno(context, params, r, "Failed to drop bset capabilities: %m");
                                }
                        }

                        /* Only drop CAP_SYS_ADMIN if it's not in the bounding set, otherwise we'll break
                         * applications that use it. */
                        if (!BIT_SET(saved_bset, CAP_SYS_ADMIN)) {
                                r = drop_capability(CAP_SYS_ADMIN);
                                if (r < 0) {
                                        *exit_status = EXIT_USER;
                                        return log_exec_error_errno(context, params, r, "Failed to drop CAP_SYS_ADMIN: %m");
                                }
                        }

                        /* Only drop CAP_SETPCAP if it's not in the bounding set, otherwise we'll break
                         * applications that use it. */
                        if (!BIT_SET(saved_bset, CAP_SETPCAP)) {
                                r = drop_capability(CAP_SETPCAP);
                                if (r < 0) {
                                        *exit_status = EXIT_USER;
                                        return log_exec_error_errno(context, params, r, "Failed to drop CAP_SETPCAP: %m");
                                }
                        }

                        if (prctl(PR_SET_KEEPCAPS, 0) < 0) {
                                *exit_status = EXIT_USER;
                                return log_exec_error_errno(context, params, errno, "Failed to drop keep capabilities flag: %m");
                        }
                }
#endif

        }

        if (!strv_isempty(context->unset_environment)) {
                char **ee = NULL;

                ee = strv_env_delete(accum_env, 1, context->unset_environment);
                if (!ee) {
                        *exit_status = EXIT_MEMORY;
                        return log_oom();
                }

                strv_free_and_replace(accum_env, ee);
        }

        if (!FLAGS_SET(command->flags, EXEC_COMMAND_NO_ENV_EXPAND)) {
                _cleanup_strv_free_ char **unset_variables = NULL, **bad_variables = NULL;

                r = replace_env_argv(command->argv, accum_env, &replaced_argv, &unset_variables, &bad_variables);
                if (r < 0) {
                        *exit_status = EXIT_MEMORY;
                        return log_exec_error_errno(context,
                                                    params,
                                                    r,
                                                    "Failed to replace environment variables: %m");
                }
                final_argv = replaced_argv;

                if (!strv_isempty(unset_variables)) {
                        _cleanup_free_ char *ju = strv_join(unset_variables, ", ");
                        log_exec_warning(context,
                                         params,
                                         "Referenced but unset environment variable evaluates to an empty string: %s",
                                         strna(ju));
                }

                if (!strv_isempty(bad_variables)) {
                        _cleanup_free_ char *jb = strv_join(bad_variables, ", ");
                        log_exec_warning(context,
                                         params,
                                         "Invalid environment variable name evaluates to an empty string: %s",
                                         strna(jb));
                }
        } else
                final_argv = command->argv;

        log_command_line(context, params, "Executing", executable, final_argv);

        /* We have finished with all our initializations. Let's now let the manager know that. From this
         * point on, if the manager sees POLLHUP on the exec_fd, then execve() was successful. */

        r = exec_fd_mark_hot(context, params, /* hot= */ true, exit_status);
        if (r < 0)
                return r;

        /* As last thing before the execve(), let's send the handoff timestamp */
        r = send_handoff_timestamp(context, params, exit_status);
        if (r < 0) {
                /* If this handoff timestamp failed, let's undo the marking as hot */
                (void) exec_fd_mark_hot(context, params, /* hot= */ false, /* reterr_exit_status= */ NULL);
                return r;
        }

        /* NB: we leave executable_fd, exec_fd, handoff_timestamp_fd open here. This is safe, because they
         * have O_CLOEXEC set, and the execve() below will thus automatically close them. In fact, for
         * exec_fd this is pretty much the whole raison d'etre. */

        r = fexecve_or_execve(executable_fd, executable, final_argv, accum_env);

        /* The execve() failed, let's undo the marking as hot */
        (void) exec_fd_mark_hot(context, params, /* hot= */ false, /* reterr_exit_status= */ NULL);

        *exit_status = EXIT_EXEC;
        return log_exec_error_errno(context, params, r, "Failed to execute %s: %m", executable);
}

systemd / systemd / 13082854884

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