15263807472

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

#include <sys/ioctl.h>
#include <threads.h>
#include <unistd.h>

#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "missing_fs.h"
#include "missing_magic.h"
#include "mountpoint-util.h"
#include "parse-util.h"
#include "pidfd-util.h"
#include "process-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"

static int have_pidfs = -1;

static int pidfd_check_pidfs(int pid_fd) {

        /* NB: the passed fd *must* be acquired via pidfd_open(), i.e. must be a true pidfd! */

        if (have_pidfs >= 0)
                return have_pidfs;

        return (have_pidfs = fd_is_fs_type(pid_fd, PID_FS_MAGIC));
}

int pidfd_get_namespace(int fd, unsigned long ns_type_cmd) {
        static bool cached_supported = true;

        /* Obtain the namespace fd from pidfd directly through ioctl(PIDFD_GET_*_NAMESPACE).
         *
         * Returns -EOPNOTSUPP if ioctl on pidfds are not supported, -ENOPKG if the requested namespace
         * is disabled in kernel. (The errno used are different from what kernel returns via ioctl(),
         * see below) */

        assert(fd >= 0);

        /* If we know ahead of time that pidfs is unavailable, shortcut things. But otherwise we don't
         * call pidfd_check_pidfs() here, which is kinda extraneous and our own cache is required
         * anyways (pidfs is introduced in kernel 6.9 while ioctl support there is added in 6.11). */
        if (have_pidfs == 0 || !cached_supported)
                return -EOPNOTSUPP;

        int nsfd = ioctl(fd, ns_type_cmd);
        if (nsfd < 0) {
                /* Kernel returns EOPNOTSUPP if the ns type in question is disabled. Hence we need to look
                 * at precise errno instead of generic ERRNO_IS_(IOCTL_)NOT_SUPPORTED. */
                if (IN_SET(errno, ENOTTY, EINVAL)) {
                        cached_supported = false;
                        return -EOPNOTSUPP;
                }
                if (errno == EOPNOTSUPP) /* Translate to something more recognizable */
                        return -ENOPKG;

                return -errno;
        }

        return nsfd;
}

static int pidfd_get_info(int fd, struct pidfd_info *info) {
        static bool cached_supported = true;

        assert(fd >= 0);
        assert(info);

        if (have_pidfs == 0 || !cached_supported)
                return -EOPNOTSUPP;

        if (ioctl(fd, PIDFD_GET_INFO, info) < 0) {
                if (ERRNO_IS_IOCTL_NOT_SUPPORTED(errno)) {
                        cached_supported = false;
                        return -EOPNOTSUPP;
                }

                return -errno;
        }

        return 0;
}

static int pidfd_get_pid_fdinfo(int fd, pid_t *ret) {
        char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
        _cleanup_free_ char *p = NULL;
        int r;

        assert(fd >= 0);

        xsprintf(path, "/proc/self/fdinfo/%i", fd);

        r = get_proc_field(path, "Pid", &p);
        if (r == -ENOENT)
                return -EBADF;
        if (r == -ENODATA) /* not a pidfd? */
                return -ENOTTY;
        if (r < 0)
                return r;

        if (streq(p, "0"))
                return -EREMOTE; /* PID is in foreign PID namespace? */
        if (streq(p, "-1"))
                return -ESRCH;   /* refers to reaped process? */

        return parse_pid(p, ret);
}

static int pidfd_get_pid_ioctl(int fd, pid_t *ret) {
        struct pidfd_info info = { .mask = PIDFD_INFO_PID };
        int r;

        assert(fd >= 0);

        r = pidfd_get_info(fd, &info);
        if (r < 0)
                return r;

        assert(FLAGS_SET(info.mask, PIDFD_INFO_PID));

        if (ret)
                *ret = info.pid;
        return 0;
}

int pidfd_get_pid(int fd, pid_t *ret) {
        int r;

        /* Converts a pidfd into a pid. We try ioctl(PIDFD_GET_INFO) (kernel 6.13+) first,
         * /proc/self/fdinfo/ as fallback. Well known errors:
         *
         *    -EBADF   → fd invalid
         *    -ESRCH   → fd valid, but process is already reaped
         *
         * pidfd_get_pid_fdinfo() might additionally fail for other reasons:
         *
         *    -ENOSYS  → /proc/ not mounted
         *    -ENOTTY  → fd valid, but not a pidfd
         *    -EREMOTE → fd valid, but pid is in another namespace we cannot translate to the local one
         *               (when using PIDFD_GET_INFO this is indistinguishable from -ESRCH)
         */

        assert(fd >= 0);

        r = pidfd_get_pid_ioctl(fd, ret);
        if (r != -EOPNOTSUPP)
                return r;

        return pidfd_get_pid_fdinfo(fd, ret);
}

int pidfd_verify_pid(int pidfd, pid_t pid) {
        pid_t current_pid;
        int r;

        assert(pidfd >= 0);
        assert(pid > 0);

        r = pidfd_get_pid(pidfd, &current_pid);
        if (r < 0)
                return r;

        return current_pid != pid ? -ESRCH : 0;
}

int pidfd_get_ppid(int fd, pid_t *ret) {
        struct pidfd_info info = { .mask = PIDFD_INFO_PID };
        int r;

        assert(fd >= 0);

        r = pidfd_get_info(fd, &info);
        if (r < 0)
                return r;

        assert(FLAGS_SET(info.mask, PIDFD_INFO_PID));

        if (info.ppid == 0) /* See comments in pid_get_ppid() */
                return -EADDRNOTAVAIL;

        if (ret)
                *ret = info.ppid;
        return 0;
}

int pidfd_get_uid(int fd, uid_t *ret) {
        struct pidfd_info info = { .mask = PIDFD_INFO_CREDS };
        int r;

        assert(fd >= 0);

        r = pidfd_get_info(fd, &info);
        if (r < 0)
                return r;

        assert(FLAGS_SET(info.mask, PIDFD_INFO_CREDS));

        if (ret)
                *ret = info.ruid;
        return 0;
}

int pidfd_get_cgroupid(int fd, uint64_t *ret) {
        struct pidfd_info info = { .mask = PIDFD_INFO_CGROUPID };
        int r;

        assert(fd >= 0);

        r = pidfd_get_info(fd, &info);
        if (r < 0)
                return r;

        assert(FLAGS_SET(info.mask, PIDFD_INFO_CGROUPID));

        if (ret)
                *ret = info.cgroupid;
        return 0;
}

int pidfd_get_inode_id(int fd, uint64_t *ret) {
        static bool file_handle_supported = true;
        int r;

        assert(fd >= 0);

        r = pidfd_check_pidfs(fd);
        if (r < 0)
                return r;
        if (r == 0)
                return -EOPNOTSUPP;

        if (file_handle_supported) {
                union {
                        struct file_handle file_handle;
                        uint8_t space[offsetof(struct file_handle, f_handle) + sizeof(uint64_t)];
                } fh = {
                        .file_handle.handle_bytes = sizeof(uint64_t),
                        .file_handle.handle_type = FILEID_KERNFS,
                };
                int mnt_id;

                r = RET_NERRNO(name_to_handle_at(fd, "", &fh.file_handle, &mnt_id, AT_EMPTY_PATH));
                if (r >= 0) {
                        if (ret)
                                *ret = *CAST_ALIGN_PTR(uint64_t, fh.file_handle.f_handle);
                        return 0;
                }
                assert(r != -EOVERFLOW);
                if (is_name_to_handle_at_fatal_error(r))
                        return r;

                file_handle_supported = false;
        }

#if SIZEOF_INO_T == 8
        struct stat st;
        if (fstat(fd, &st) < 0)
                return -errno;

        if (ret)
                *ret = (uint64_t) st.st_ino;
        return 0;

#elif SIZEOF_INO_T == 4
        /* On 32-bit systems (where sizeof(ino_t) == 4), the inode id returned by fstat() cannot be used to
         * reliably identify the process, nor can we communicate the origin of the id with the clients.
         * Hence let's just refuse to acquire pidfdid through fstat() here. All clients shall also insist on
         * the 64-bit id from name_to_handle_at(). */
        return -EOPNOTSUPP;
#else
#  error Unsupported ino_t size
#endif
}

int pidfd_get_inode_id_self_cached(uint64_t *ret) {
        static thread_local uint64_t cached = 0;
        static thread_local pid_t initialized = 0; /* < 0: cached error; == 0: invalid; > 0: valid and pid that was current */
        int r;

        assert(ret);

        if (initialized == getpid_cached()) {
                *ret = cached;
                return 0;
        }
        if (initialized < 0)
                return initialized;

        _cleanup_close_ int fd = pidfd_open(getpid_cached(), 0);
        if (fd < 0)
                return -errno;

        r = pidfd_get_inode_id(fd, &cached);
        if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
                return (initialized = -EOPNOTSUPP);
        if (r < 0)
                return r;

        *ret = cached;
        initialized = getpid_cached();
        return 0;
}

1	/* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3	#include <sys/ioctl.h>
4	#include <threads.h>
5	#include <unistd.h>
6
7	#include "errno-util.h"
8	#include "fd-util.h"
9	#include "fileio.h"
10	#include "missing_fs.h"
11	#include "missing_magic.h"
12	#include "mountpoint-util.h"
13	#include "parse-util.h"
14	#include "pidfd-util.h"
15	#include "process-util.h"
16	#include "stat-util.h"
17	#include "stdio-util.h"
18	#include "string-util.h"
19
20	static int have_pidfs = -1;
21
22	static int pidfd_check_pidfs(int pid_fd) {	40,028✔
23
24	/* NB: the passed fd must be acquired via pidfd_open(), i.e. must be a true pidfd! */
25
26	if (have_pidfs >= 0)	40,028✔
27	return have_pidfs;
28
29	return (have_pidfs = fd_is_fs_type(pid_fd, PID_FS_MAGIC));	18,797✔
30	}
31
32	int pidfd_get_namespace(int fd, unsigned long ns_type_cmd) {	8,279✔
33	static bool cached_supported = true;	8,279✔
34
35	/* Obtain the namespace fd from pidfd directly through ioctl(PIDFD_GET_*_NAMESPACE).
36	*
37	* Returns -EOPNOTSUPP if ioctl on pidfds are not supported, -ENOPKG if the requested namespace
38	* is disabled in kernel. (The errno used are different from what kernel returns via ioctl(),
39	* see below) */
40
41	assert(fd >= 0);	8,279✔
42
43	/* If we know ahead of time that pidfs is unavailable, shortcut things. But otherwise we don't
44	* call pidfd_check_pidfs() here, which is kinda extraneous and our own cache is required
45	* anyways (pidfs is introduced in kernel 6.9 while ioctl support there is added in 6.11). */
46	if (have_pidfs == 0 \|\| !cached_supported)	8,279✔
47	return -EOPNOTSUPP;
48
49	int nsfd = ioctl(fd, ns_type_cmd);	7,781✔
50	if (nsfd < 0) {	7,781✔
51	/* Kernel returns EOPNOTSUPP if the ns type in question is disabled. Hence we need to look
52	* at precise errno instead of generic ERRNO_IS_(IOCTL_)NOT_SUPPORTED. */
53	if (IN_SET(errno, ENOTTY, EINVAL)) {	48✔
54	cached_supported = false;	48✔
55	return -EOPNOTSUPP;	48✔
56	}
UNCOV 57	if (errno == EOPNOTSUPP) /* Translate to something more recognizable */	×
58	return -ENOPKG;
59
60	return -errno;	×
61	}
62
63	return nsfd;
64	}
65
66	static int pidfd_get_info(int fd, struct pidfd_info *info) {	52,347✔
67	static bool cached_supported = true;	52,347✔
68
69	assert(fd >= 0);	52,347✔
70	assert(info);	52,347✔
71
72	if (have_pidfs == 0 \|\| !cached_supported)	52,347✔
73	return -EOPNOTSUPP;
74
75	if (ioctl(fd, PIDFD_GET_INFO, info) < 0) {	37,615✔
76	if (ERRNO_IS_IOCTL_NOT_SUPPORTED(errno)) {	3,159✔
77	cached_supported = false;	2,593✔
78	return -EOPNOTSUPP;	2,593✔
79	}
80
81	return -errno;	566✔
82	}
83
84	return 0;
85	}
86
87	static int pidfd_get_pid_fdinfo(int fd, pid_t *ret) {	15,923✔
88	char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];	15,923✔
89	_cleanup_free_ char *p = NULL;	15,923✔
90	int r;	15,923✔
91
92	assert(fd >= 0);	15,923✔
93
94	xsprintf(path, "/proc/self/fdinfo/%i", fd);	15,923✔
95
96	r = get_proc_field(path, "Pid", &p);	15,923✔
97	if (r == -ENOENT)	15,923✔
98	return -EBADF;
99	if (r == -ENODATA) /* not a pidfd? */	15,923✔
100	return -ENOTTY;
101	if (r < 0)	15,923✔
102	return r;
103
104	if (streq(p, "0"))	15,923✔
105	return -EREMOTE; /* PID is in foreign PID namespace? */
106	if (streq(p, "-1"))	15,923✔
107	return -ESRCH; /* refers to reaped process? */
108
109	return parse_pid(p, ret);	14,409✔
110	}
111
112	static int pidfd_get_pid_ioctl(int fd, pid_t *ret) {	49,879✔
113	struct pidfd_info info = { .mask = PIDFD_INFO_PID };	49,879✔
114	int r;	49,879✔
115
116	assert(fd >= 0);	49,879✔
117
118	r = pidfd_get_info(fd, &info);	49,879✔
119	if (r < 0)	49,879✔
120	return r;	49,879✔
121
122	assert(FLAGS_SET(info.mask, PIDFD_INFO_PID));	33,390✔
123
124	if (ret)	33,390✔
125	*ret = info.pid;	33,390✔
126	return 0;
127	}
128
129	int pidfd_get_pid(int fd, pid_t *ret) {	49,879✔
130	int r;	49,879✔
131
132	/* Converts a pidfd into a pid. We try ioctl(PIDFD_GET_INFO) (kernel 6.13+) first,
133	* /proc/self/fdinfo/ as fallback. Well known errors:
134	*
135	* -EBADF → fd invalid
136	* -ESRCH → fd valid, but process is already reaped
137	*
138	* pidfd_get_pid_fdinfo() might additionally fail for other reasons:
139	*
140	* -ENOSYS → /proc/ not mounted
141	* -ENOTTY → fd valid, but not a pidfd
142	* -EREMOTE → fd valid, but pid is in another namespace we cannot translate to the local one
143	* (when using PIDFD_GET_INFO this is indistinguishable from -ESRCH)
144	*/
145
146	assert(fd >= 0);	49,879✔
147
148	r = pidfd_get_pid_ioctl(fd, ret);	49,879✔
149	if (r != -EOPNOTSUPP)	49,879✔
150	return r;
151
152	return pidfd_get_pid_fdinfo(fd, ret);	15,923✔
153	}
154
155	int pidfd_verify_pid(int pidfd, pid_t pid) {	32,993✔
156	pid_t current_pid;	32,993✔
157	int r;	32,993✔
158
159	assert(pidfd >= 0);	32,993✔
160	assert(pid > 0);	32,993✔
161
162	r = pidfd_get_pid(pidfd, &current_pid);	32,993✔
163	if (r < 0)	32,993✔
164	return r;	32,993✔
165
166	return current_pid != pid ? -ESRCH : 0;	30,913✔
167	}
168
169	int pidfd_get_ppid(int fd, pid_t *ret) {	2,414✔
170	struct pidfd_info info = { .mask = PIDFD_INFO_PID };	2,414✔
171	int r;	2,414✔
172
173	assert(fd >= 0);	2,414✔
174
175	r = pidfd_get_info(fd, &info);	2,414✔
176	if (r < 0)	2,414✔
177	return r;	2,414✔
178
179	assert(FLAGS_SET(info.mask, PIDFD_INFO_PID));	1,021✔
180
181	if (info.ppid == 0) /* See comments in pid_get_ppid() */	1,021✔
182	return -EADDRNOTAVAIL;
183
184	if (ret)	1,021✔
185	*ret = info.ppid;	1,021✔
186	return 0;
187	}
188
189	int pidfd_get_uid(int fd, uid_t *ret) {	54✔
190	struct pidfd_info info = { .mask = PIDFD_INFO_CREDS };	54✔
191	int r;	54✔
192
193	assert(fd >= 0);	54✔
194
195	r = pidfd_get_info(fd, &info);	54✔
196	if (r < 0)	54✔
197	return r;	54✔
198
199	assert(FLAGS_SET(info.mask, PIDFD_INFO_CREDS));	45✔
200
201	if (ret)	45✔
202	*ret = info.ruid;	45✔
203	return 0;
204	}
205
UNCOV 206	int pidfd_get_cgroupid(int fd, uint64_t *ret) {	×
UNCOV 207	struct pidfd_info info = { .mask = PIDFD_INFO_CGROUPID };	×
UNCOV 208	int r;	×
209
210	assert(fd >= 0);	×
211
UNCOV 212	r = pidfd_get_info(fd, &info);	×
213	if (r < 0)	×
UNCOV 214	return r;	×
215
216	assert(FLAGS_SET(info.mask, PIDFD_INFO_CGROUPID));	×
217
UNCOV 218	if (ret)	×
219	*ret = info.cgroupid;	×
220	return 0;
221	}
222
223	int pidfd_get_inode_id(int fd, uint64_t *ret) {	40,028✔
224	static bool file_handle_supported = true;	40,028✔
225	int r;	40,028✔
226
227	assert(fd >= 0);	40,028✔
228
229	r = pidfd_check_pidfs(fd);	40,028✔
230	if (r < 0)	40,028✔
231	return r;	40,028✔
232	if (r == 0)	40,028✔
233	return -EOPNOTSUPP;
234
235	if (file_handle_supported) {	40,028✔
236	union {	37,936✔
237	struct file_handle file_handle;
238	uint8_t space[offsetof(struct file_handle, f_handle) + sizeof(uint64_t)];
239	} fh = {	37,936✔
240	.file_handle.handle_bytes = sizeof(uint64_t),
241	.file_handle.handle_type = FILEID_KERNFS,
242	};
243	int mnt_id;	37,936✔
244
245	r = RET_NERRNO(name_to_handle_at(fd, "", &fh.file_handle, &mnt_id, AT_EMPTY_PATH));	37,936✔
246	if (r >= 0) {	3,663✔
247	if (ret)	34,273✔
248	ret = CAST_ALIGN_PTR(uint64_t, fh.file_handle.f_handle);	34,273✔
249	return 0;	34,273✔
250	}
251	assert(r != -EOVERFLOW);	3,663✔
252	if (is_name_to_handle_at_fatal_error(r))	3,663✔
253	return r;
254
255	file_handle_supported = false;	3,663✔
256	}
257
258	#if SIZEOF_INO_T == 8
259	struct stat st;	5,755✔
260	if (fstat(fd, &st) < 0)	5,755✔
UNCOV 261	return -errno;	×
262
263	if (ret)	5,755✔
264	*ret = (uint64_t) st.st_ino;	5,755✔
265	return 0;
266
267	#elif SIZEOF_INO_T == 4
268	/* On 32-bit systems (where sizeof(ino_t) == 4), the inode id returned by fstat() cannot be used to
269	* reliably identify the process, nor can we communicate the origin of the id with the clients.
270	* Hence let's just refuse to acquire pidfdid through fstat() here. All clients shall also insist on
271	* the 64-bit id from name_to_handle_at(). */
272	return -EOPNOTSUPP;
273	#else
274	# error Unsupported ino_t size
275	#endif
276	}
277
278	int pidfd_get_inode_id_self_cached(uint64_t *ret) {	39,416✔
279	static thread_local uint64_t cached = 0;	39,416✔
280	static thread_local pid_t initialized = 0; /* < 0: cached error; == 0: invalid; > 0: valid and pid that was current */	39,416✔
281	int r;	39,416✔
282
283	assert(ret);	39,416✔
284
285	if (initialized == getpid_cached()) {	39,416✔
286	*ret = cached;	4,614✔
287	return 0;	4,614✔
288	}
289	if (initialized < 0)	34,802✔
290	return initialized;
291
292	_cleanup_close_ int fd = pidfd_open(getpid_cached(), 0);	74,218✔
293	if (fd < 0)	34,802✔
UNCOV 294	return -errno;	×
295
296	r = pidfd_get_inode_id(fd, &cached);	34,802✔
297	if (ERRNO_IS_NEG_NOT_SUPPORTED(r))	34,802✔
UNCOV 298	return (initialized = -EOPNOTSUPP);	×
299	if (r < 0)	34,802✔
300	return r;
301
302	*ret = cached;	34,802✔
303	initialized = getpid_cached();	34,802✔
304	return 0;	34,802✔
305	}

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