]>
git.ipfire.org Git - thirdparty/systemd.git/blob - src/basic/fd-util.c
59c243e70d13ee759d2165843037a7976a324a07
1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
8 #include <linux/magic.h>
10 #include <sys/resource.h>
14 #include "alloc-util.h"
15 #include "dirent-util.h"
21 #include "missing_fcntl.h"
22 #include "missing_fs.h"
23 #include "missing_syscall.h"
24 #include "mountpoint-util.h"
25 #include "parse-util.h"
26 #include "path-util.h"
27 #include "process-util.h"
28 #include "socket-util.h"
29 #include "sort-util.h"
30 #include "stat-util.h"
31 #include "stdio-util.h"
32 #include "tmpfile-util.h"
34 /* The maximum number of iterations in the loop to close descriptors in the fallback case
35 * when /proc/self/fd/ is inaccessible. */
36 #define MAX_FD_LOOP_LIMIT (1024*1024)
38 int close_nointr(int fd
) {
45 * Just ignore EINTR; a retry loop is the wrong thing to do on
48 * http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
49 * https://bugzilla.gnome.org/show_bug.cgi?id=682819
50 * http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR
51 * https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain
59 int safe_close(int fd
) {
61 * Like close_nointr() but cannot fail. Guarantees errno is unchanged. Is a noop for negative fds,
62 * and returns -EBADF, so that it can be used in this syntax:
64 * fd = safe_close(fd);
70 /* The kernel might return pretty much any error code
71 * via close(), but the fd will be closed anyway. The
72 * only condition we want to check for here is whether
73 * the fd was invalid at all... */
75 assert_se(close_nointr(fd
) != -EBADF
);
81 void safe_close_pair(int p
[static 2]) {
85 /* Special case pairs which use the same fd in both
87 p
[0] = p
[1] = safe_close(p
[0]);
91 p
[0] = safe_close(p
[0]);
92 p
[1] = safe_close(p
[1]);
95 void close_many(const int fds
[], size_t n_fd
) {
96 assert(fds
|| n_fd
<= 0);
98 for (size_t i
= 0; i
< n_fd
; i
++)
102 void close_many_unset(int fds
[], size_t n_fd
) {
103 assert(fds
|| n_fd
<= 0);
105 for (size_t i
= 0; i
< n_fd
; i
++)
106 fds
[i
] = safe_close(fds
[i
]);
109 void close_many_and_free(int *fds
, size_t n_fds
) {
110 assert(fds
|| n_fds
<= 0);
112 close_many(fds
, n_fds
);
116 int fclose_nointr(FILE *f
) {
119 /* Same as close_nointr(), but for fclose() */
121 errno
= 0; /* Extra safety: if the FILE* object is not encapsulating an fd, it might not set errno
122 * correctly. Let's hence initialize it to zero first, so that we aren't confused by any
123 * prior errno here */
130 return errno_or_else(EIO
);
133 FILE* safe_fclose(FILE *f
) {
135 /* Same as safe_close(), but for fclose() */
140 assert_se(fclose_nointr(f
) != -EBADF
);
146 DIR* safe_closedir(DIR *d
) {
151 assert_se(closedir(d
) >= 0 || errno
!= EBADF
);
157 int fd_nonblock(int fd
, bool nonblock
) {
162 flags
= fcntl(fd
, F_GETFL
, 0);
166 nflags
= UPDATE_FLAG(flags
, O_NONBLOCK
, nonblock
);
170 return RET_NERRNO(fcntl(fd
, F_SETFL
, nflags
));
173 int fd_cloexec(int fd
, bool cloexec
) {
178 flags
= fcntl(fd
, F_GETFD
, 0);
182 nflags
= UPDATE_FLAG(flags
, FD_CLOEXEC
, cloexec
);
186 return RET_NERRNO(fcntl(fd
, F_SETFD
, nflags
));
189 int fd_cloexec_many(const int fds
[], size_t n_fds
, bool cloexec
) {
192 assert(n_fds
== 0 || fds
);
194 for (size_t i
= 0; i
< n_fds
; i
++) {
195 if (fds
[i
] < 0) /* Skip gracefully over already invalidated fds */
198 r
= fd_cloexec(fds
[i
], cloexec
);
199 if (r
< 0 && ret
>= 0) /* Continue going, but return first error */
202 ret
= 1; /* report if we did anything */
208 static bool fd_in_set(int fd
, const int fdset
[], size_t n_fdset
) {
209 assert(n_fdset
== 0 || fdset
);
211 for (size_t i
= 0; i
< n_fdset
; i
++) {
222 int get_max_fd(void) {
226 /* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary
227 * and INT_MAX as upper boundary. */
229 if (getrlimit(RLIMIT_NOFILE
, &rl
) < 0)
232 m
= MAX(rl
.rlim_cur
, rl
.rlim_max
);
233 if (m
< FD_SETSIZE
) /* Let's always cover at least 1024 fds */
236 if (m
== RLIM_INFINITY
|| m
> INT_MAX
) /* Saturate on overflow. After all fds are "int", hence can
237 * never be above INT_MAX */
240 return (int) (m
- 1);
243 static int close_all_fds_frugal(const int except
[], size_t n_except
) {
246 assert(n_except
== 0 || except
);
248 /* This is the inner fallback core of close_all_fds(). This never calls malloc() or opendir() or so
249 * and hence is safe to be called in signal handler context. Most users should call close_all_fds(),
250 * but when we assume we are called from signal handler context, then use this simpler call
253 max_fd
= get_max_fd();
257 /* Refuse to do the loop over more too many elements. It's better to fail immediately than to
258 * spin the CPU for a long time. */
259 if (max_fd
> MAX_FD_LOOP_LIMIT
)
260 return log_debug_errno(SYNTHETIC_ERRNO(EPERM
),
261 "Refusing to loop over %d potential fds.",
264 for (int fd
= 3; fd
>= 0; fd
= fd
< max_fd
? fd
+ 1 : -EBADF
) {
267 if (fd_in_set(fd
, except
, n_except
))
270 q
= close_nointr(fd
);
271 if (q
< 0 && q
!= -EBADF
&& r
>= 0)
278 static bool have_close_range
= true; /* Assume we live in the future */
280 static int close_all_fds_special_case(const int except
[], size_t n_except
) {
281 assert(n_except
== 0 || except
);
283 /* Handles a few common special cases separately, since they are common and can be optimized really
284 * nicely, since we won't need sorting for them. Returns > 0 if the special casing worked, 0
287 if (!have_close_range
)
290 if (n_except
== 1 && except
[0] < 0) /* Minor optimization: if we only got one fd, and it's invalid,
297 /* Close everything. Yay! */
299 if (close_range(3, -1, 0) >= 0)
302 if (ERRNO_IS_NOT_SUPPORTED(errno
) || ERRNO_IS_PRIVILEGE(errno
)) {
303 have_close_range
= false;
310 /* Close all but exactly one, then we don't need no sorting. This is a pretty common
311 * case, hence let's handle it specially. */
313 if ((except
[0] <= 3 || close_range(3, except
[0]-1, 0) >= 0) &&
314 (except
[0] >= INT_MAX
|| close_range(MAX(3, except
[0]+1), -1, 0) >= 0))
317 if (ERRNO_IS_NOT_SUPPORTED(errno
) || ERRNO_IS_PRIVILEGE(errno
)) {
318 have_close_range
= false;
329 int close_all_fds_without_malloc(const int except
[], size_t n_except
) {
332 assert(n_except
== 0 || except
);
334 r
= close_all_fds_special_case(except
, n_except
);
337 if (r
> 0) /* special case worked! */
340 return close_all_fds_frugal(except
, n_except
);
343 int close_all_fds(const int except
[], size_t n_except
) {
344 _cleanup_closedir_
DIR *d
= NULL
;
347 assert(n_except
== 0 || except
);
349 r
= close_all_fds_special_case(except
, n_except
);
352 if (r
> 0) /* special case worked! */
355 if (have_close_range
) {
356 _cleanup_free_
int *sorted_malloc
= NULL
;
360 /* In the best case we have close_range() to close all fds between a start and an end fd,
361 * which we can use on the "inverted" exception array, i.e. all intervals between all
362 * adjacent pairs from the sorted exception array. This changes loop complexity from O(n)
363 * where n is number of open fds to O(m⋅log(m)) where m is the number of fds to keep
364 * open. Given that we assume n ≫ m that's preferable to us. */
366 assert(n_except
< SIZE_MAX
);
367 n_sorted
= n_except
+ 1;
369 if (n_sorted
> 64) /* Use heap for large numbers of fds, stack otherwise */
370 sorted
= sorted_malloc
= new(int, n_sorted
);
372 sorted
= newa(int, n_sorted
);
375 memcpy(sorted
, except
, n_except
* sizeof(int));
377 /* Let's add fd 2 to the list of fds, to simplify the loop below, as this
378 * allows us to cover the head of the array the same way as the body */
379 sorted
[n_sorted
-1] = 2;
381 typesafe_qsort(sorted
, n_sorted
, cmp_int
);
383 for (size_t i
= 0; i
< n_sorted
-1; i
++) {
386 start
= MAX(sorted
[i
], 2); /* The first three fds shall always remain open */
387 end
= MAX(sorted
[i
+1], 2);
389 assert(end
>= start
);
391 if (end
- start
<= 1)
394 /* Close everything between the start and end fds (both of which shall stay open) */
395 if (close_range(start
+ 1, end
- 1, 0) < 0) {
396 if (!ERRNO_IS_NOT_SUPPORTED(errno
) && !ERRNO_IS_PRIVILEGE(errno
))
399 have_close_range
= false;
404 if (have_close_range
) {
405 /* The loop succeeded. Let's now close everything beyond the end */
407 if (sorted
[n_sorted
-1] >= INT_MAX
) /* Dont let the addition below overflow */
410 if (close_range(sorted
[n_sorted
-1] + 1, -1, 0) >= 0)
413 if (!ERRNO_IS_NOT_SUPPORTED(errno
) && !ERRNO_IS_PRIVILEGE(errno
))
416 have_close_range
= false;
420 /* Fallback on OOM or if close_range() is not supported */
423 d
= opendir("/proc/self/fd");
425 return close_all_fds_frugal(except
, n_except
); /* ultimate fallback if /proc/ is not available */
427 FOREACH_DIRENT(de
, d
, return -errno
) {
430 if (!IN_SET(de
->d_type
, DT_LNK
, DT_UNKNOWN
))
433 fd
= parse_fd(de
->d_name
);
435 /* Let's better ignore this, just in case */
444 if (fd_in_set(fd
, except
, n_except
))
447 q
= close_nointr(fd
);
448 if (q
< 0 && q
!= -EBADF
&& r
>= 0) /* Valgrind has its own FD and doesn't want to have it closed */
455 int same_fd(int a
, int b
) {
456 struct stat sta
, stb
;
463 /* Compares two file descriptors. Note that semantics are quite different depending on whether we
464 * have kcmp() or we don't. If we have kcmp() this will only return true for dup()ed file
465 * descriptors, but not otherwise. If we don't have kcmp() this will also return true for two fds of
466 * the same file, created by separate open() calls. Since we use this call mostly for filtering out
467 * duplicates in the fd store this difference hopefully doesn't matter too much. */
472 /* Try to use kcmp() if we have it. */
473 pid
= getpid_cached();
474 r
= kcmp(pid
, pid
, KCMP_FILE
, a
, b
);
479 if (!ERRNO_IS_NOT_SUPPORTED(errno
) && !ERRNO_IS_PRIVILEGE(errno
))
482 /* We don't have kcmp(), use fstat() instead. */
483 if (fstat(a
, &sta
) < 0)
486 if (fstat(b
, &stb
) < 0)
489 if (!stat_inode_same(&sta
, &stb
))
492 /* We consider all device fds different, since two device fds might refer to quite different device
493 * contexts even though they share the same inode and backing dev_t. */
495 if (S_ISCHR(sta
.st_mode
) || S_ISBLK(sta
.st_mode
))
498 /* The fds refer to the same inode on disk, let's also check if they have the same fd flags. This is
499 * useful to distinguish the read and write side of a pipe created with pipe(). */
500 fa
= fcntl(a
, F_GETFL
);
504 fb
= fcntl(b
, F_GETFL
);
511 void cmsg_close_all(struct msghdr
*mh
) {
512 struct cmsghdr
*cmsg
;
516 CMSG_FOREACH(cmsg
, mh
)
517 if (cmsg
->cmsg_level
== SOL_SOCKET
&& cmsg
->cmsg_type
== SCM_RIGHTS
)
518 close_many(CMSG_TYPED_DATA(cmsg
, int),
519 (cmsg
->cmsg_len
- CMSG_LEN(0)) / sizeof(int));
522 bool fdname_is_valid(const char *s
) {
525 /* Validates a name for $LISTEN_FDNAMES. We basically allow
526 * everything ASCII that's not a control character. Also, as
527 * special exception the ":" character is not allowed, as we
528 * use that as field separator in $LISTEN_FDNAMES.
530 * Note that the empty string is explicitly allowed
531 * here. However, we limit the length of the names to 255
537 for (p
= s
; *p
; p
++) {
546 return p
- s
<= FDNAME_MAX
;
549 int fd_get_path(int fd
, char **ret
) {
552 assert(fd
>= 0 || fd
== AT_FDCWD
);
555 return safe_getcwd(ret
);
557 r
= readlink_malloc(FORMAT_PROC_FD_PATH(fd
), ret
);
559 /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's make
560 * things debuggable and distinguish the two. */
562 if (proc_mounted() == 0)
563 return -ENOSYS
; /* /proc is not available or not set up properly, we're most likely in some chroot
565 return -EBADF
; /* The directory exists, hence it's the fd that doesn't. */
571 int move_fd(int from
, int to
, int cloexec
) {
574 /* Move fd 'from' to 'to', make sure FD_CLOEXEC remains equal if requested, and release the old fd. If
575 * 'cloexec' is passed as -1, the original FD_CLOEXEC is inherited for the new fd. If it is 0, it is turned
576 * off, if it is > 0 it is turned on. */
586 r
= fd_cloexec(to
, cloexec
);
597 fl
= fcntl(from
, F_GETFD
, 0);
601 cloexec
= !!(fl
& FD_CLOEXEC
);
604 r
= dup3(from
, to
, cloexec
? O_CLOEXEC
: 0);
615 int fd_move_above_stdio(int fd
) {
619 /* Moves the specified file descriptor if possible out of the range [0…2], i.e. the range of
620 * stdin/stdout/stderr. If it can't be moved outside of this range the original file descriptor is
621 * returned. This call is supposed to be used for long-lasting file descriptors we allocate in our code that
622 * might get loaded into foreign code, and where we want ensure our fds are unlikely used accidentally as
623 * stdin/stdout/stderr of unrelated code.
625 * Note that this doesn't fix any real bugs, it just makes it less likely that our code will be affected by
626 * buggy code from others that mindlessly invokes 'fprintf(stderr, …' or similar in places where stderr has
627 * been closed before.
629 * This function is written in a "best-effort" and "least-impact" style. This means whenever we encounter an
630 * error we simply return the original file descriptor, and we do not touch errno. */
632 if (fd
< 0 || fd
> 2)
635 flags
= fcntl(fd
, F_GETFD
, 0);
639 if (flags
& FD_CLOEXEC
)
640 copy
= fcntl(fd
, F_DUPFD_CLOEXEC
, 3);
642 copy
= fcntl(fd
, F_DUPFD
, 3);
652 int rearrange_stdio(int original_input_fd
, int original_output_fd
, int original_error_fd
) {
653 int fd
[3] = { original_input_fd
, /* Put together an array of fds we work on */
656 null_fd
= -EBADF
, /* If we open /dev/null, we store the fd to it here */
657 copy_fd
[3] = { -EBADF
, -EBADF
, -EBADF
}, /* This contains all fds we duplicate here
658 * temporarily, and hence need to close at the end. */
660 bool null_readable
, null_writable
;
662 /* Sets up stdin, stdout, stderr with the three file descriptors passed in. If any of the descriptors
663 * is specified as -EBADF it will be connected with /dev/null instead. If any of the file descriptors
664 * is passed as itself (e.g. stdin as STDIN_FILENO) it is left unmodified, but the O_CLOEXEC bit is
665 * turned off should it be on.
667 * Note that if any of the passed file descriptors are > 2 they will be closed — both on success and
668 * on failure! Thus, callers should assume that when this function returns the input fds are
671 * Note that when this function fails stdin/stdout/stderr might remain half set up!
673 * O_CLOEXEC is turned off for all three file descriptors (which is how it should be for
674 * stdin/stdout/stderr). */
676 null_readable
= original_input_fd
< 0;
677 null_writable
= original_output_fd
< 0 || original_error_fd
< 0;
679 /* First step, open /dev/null once, if we need it */
680 if (null_readable
|| null_writable
) {
682 /* Let's open this with O_CLOEXEC first, and convert it to non-O_CLOEXEC when we move the fd to the final position. */
683 null_fd
= open("/dev/null", (null_readable
&& null_writable
? O_RDWR
:
684 null_readable
? O_RDONLY
: O_WRONLY
) | O_CLOEXEC
);
690 /* If this fd is in the 0…2 range, let's move it out of it */
694 copy
= fcntl(null_fd
, F_DUPFD_CLOEXEC
, 3); /* Duplicate this with O_CLOEXEC set */
700 close_and_replace(null_fd
, copy
);
704 /* Let's assemble fd[] with the fds to install in place of stdin/stdout/stderr */
705 for (int i
= 0; i
< 3; i
++) {
708 fd
[i
] = null_fd
; /* A negative parameter means: connect this one to /dev/null */
709 else if (fd
[i
] != i
&& fd
[i
] < 3) {
710 /* This fd is in the 0…2 territory, but not at its intended place, move it out of there, so that we can work there. */
711 copy_fd
[i
] = fcntl(fd
[i
], F_DUPFD_CLOEXEC
, 3); /* Duplicate this with O_CLOEXEC set */
712 if (copy_fd
[i
] < 0) {
721 /* At this point we now have the fds to use in fd[], and they are all above the stdio range, so that
722 * we have freedom to move them around. If the fds already were at the right places then the specific
723 * fds are -EBADF. Let's now move them to the right places. This is the point of no return. */
724 for (int i
= 0; i
< 3; i
++) {
728 /* fd is already in place, but let's make sure O_CLOEXEC is off */
729 r
= fd_cloexec(i
, false);
736 if (dup2(fd
[i
], i
) < 0) { /* Turns off O_CLOEXEC on the new fd. */
746 /* Close the original fds, but only if they were outside of the stdio range. Also, properly check for the same
747 * fd passed in multiple times. */
748 safe_close_above_stdio(original_input_fd
);
749 if (original_output_fd
!= original_input_fd
)
750 safe_close_above_stdio(original_output_fd
);
751 if (original_error_fd
!= original_input_fd
&& original_error_fd
!= original_output_fd
)
752 safe_close_above_stdio(original_error_fd
);
754 /* Close the copies we moved > 2 */
755 close_many(copy_fd
, 3);
757 /* Close our null fd, if it's > 2 */
758 safe_close_above_stdio(null_fd
);
763 int fd_reopen(int fd
, int flags
) {
766 assert(fd
>= 0 || fd
== AT_FDCWD
);
768 /* Reopens the specified fd with new flags. This is useful for convert an O_PATH fd into a regular one, or to
769 * turn O_RDWR fds into O_RDONLY fds.
771 * This doesn't work on sockets (since they cannot be open()ed, ever).
773 * This implicitly resets the file read index to 0.
775 * If AT_FDCWD is specified as file descriptor gets an fd to the current cwd.
777 * If the specified file descriptor refers to a symlink via O_PATH, then this function cannot be used
778 * to follow that symlink. Because we cannot have non-O_PATH fds to symlinks reopening it without
779 * O_PATH will always result in -ELOOP. Or in other words: if you have an O_PATH fd to a symlink you
780 * can reopen it only if you pass O_PATH again. */
782 if (FLAGS_SET(flags
, O_NOFOLLOW
))
783 /* O_NOFOLLOW is not allowed in fd_reopen(), because after all this is primarily implemented
784 * via a symlink-based interface in /proc/self/fd. Let's refuse this here early. Note that
785 * the kernel would generate ELOOP here too, hence this manual check is mostly redundant –
786 * the only reason we add it here is so that the O_DIRECTORY special case (see below) behaves
787 * the same way as the non-O_DIRECTORY case. */
790 if (FLAGS_SET(flags
, O_DIRECTORY
) || fd
== AT_FDCWD
) {
791 /* If we shall reopen the fd as directory we can just go via "." and thus bypass the whole
792 * magic /proc/ directory, and make ourselves independent of that being mounted. */
793 new_fd
= openat(fd
, ".", flags
| O_DIRECTORY
);
802 new_fd
= open(FORMAT_PROC_FD_PATH(fd
), flags
);
809 return -ENOSYS
; /* if we have no /proc/, the concept is not implementable */
811 return r
> 0 ? -EBADF
: -ENOENT
; /* If /proc/ is definitely around then this means the fd is
812 * not valid, otherwise let's propagate the original
819 int fd_reopen_condition(
829 /* Invokes fd_reopen(fd, flags), but only if the existing F_GETFL flags don't match the specified
830 * flags (masked by the specified mask). This is useful for converting O_PATH fds into real fds if
831 * needed, but only then. */
833 r
= fcntl(fd
, F_GETFL
);
837 if ((r
& mask
) == (flags
& mask
)) {
838 *ret_new_fd
= -EBADF
;
842 new_fd
= fd_reopen(fd
, flags
);
846 *ret_new_fd
= new_fd
;
850 int fd_is_opath(int fd
) {
855 r
= fcntl(fd
, F_GETFL
);
859 return FLAGS_SET(r
, O_PATH
);
862 int read_nr_open(void) {
863 _cleanup_free_
char *nr_open
= NULL
;
866 /* Returns the kernel's current fd limit, either by reading it of /proc/sys if that works, or using the
867 * hard-coded default compiled-in value of current kernels (1M) if not. This call will never fail. */
869 r
= read_one_line_file("/proc/sys/fs/nr_open", &nr_open
);
871 log_debug_errno(r
, "Failed to read /proc/sys/fs/nr_open, ignoring: %m");
875 r
= safe_atoi(nr_open
, &v
);
877 log_debug_errno(r
, "Failed to parse /proc/sys/fs/nr_open value '%s', ignoring: %m", nr_open
);
882 /* If we fail, fall back to the hard-coded kernel limit of 1024 * 1024. */
886 int fd_get_diskseq(int fd
, uint64_t *ret
) {
892 if (ioctl(fd
, BLKGETDISKSEQ
, &diskseq
) < 0) {
893 /* Note that the kernel is weird: non-existing ioctls currently return EINVAL
894 * rather than ENOTTY on loopback block devices. They should fix that in the kernel,
895 * but in the meantime we accept both here. */
896 if (!ERRNO_IS_NOT_SUPPORTED(errno
) && errno
!= EINVAL
)
907 int path_is_root_at(int dir_fd
, const char *path
) {
908 STRUCT_NEW_STATX_DEFINE(st
);
909 STRUCT_NEW_STATX_DEFINE(pst
);
910 _cleanup_close_
int fd
= -EBADF
;
913 assert(dir_fd
>= 0 || dir_fd
== AT_FDCWD
);
915 if (!isempty(path
)) {
916 fd
= openat(dir_fd
, path
, O_PATH
|O_DIRECTORY
|O_CLOEXEC
);
918 return errno
== ENOTDIR
? false : -errno
;
923 r
= statx_fallback(dir_fd
, ".", 0, STATX_TYPE
|STATX_INO
|STATX_MNT_ID
, &st
.sx
);
929 r
= statx_fallback(dir_fd
, "..", 0, STATX_TYPE
|STATX_INO
|STATX_MNT_ID
, &pst
.sx
);
933 /* First, compare inode. If these are different, the fd does not point to the root directory "/". */
934 if (!statx_inode_same(&st
.sx
, &pst
.sx
))
937 /* Even if the parent directory has the same inode, the fd may not point to the root directory "/",
938 * and we also need to check that the mount ids are the same. Otherwise, a construct like the
939 * following could be used to trick us:
941 * $ mkdir /tmp/x /tmp/x/y
942 * $ mount --bind /tmp/x /tmp/x/y
944 * Note, statx() does not provide the mount ID and path_get_mnt_id_at() does not work when an old
945 * kernel is used. In that case, let's assume that we do not have such spurious mount points in an
946 * early boot stage, and silently skip the following check. */
948 if (!FLAGS_SET(st
.nsx
.stx_mask
, STATX_MNT_ID
)) {
951 r
= path_get_mnt_id_at_fallback(dir_fd
, "", &mntid
);
952 if (ERRNO_IS_NEG_NOT_SUPPORTED(r
))
953 return true; /* skip the mount ID check */
958 st
.nsx
.stx_mnt_id
= mntid
;
959 st
.nsx
.stx_mask
|= STATX_MNT_ID
;
962 if (!FLAGS_SET(pst
.nsx
.stx_mask
, STATX_MNT_ID
)) {
965 r
= path_get_mnt_id_at_fallback(dir_fd
, "..", &mntid
);
966 if (ERRNO_IS_NEG_NOT_SUPPORTED(r
))
967 return true; /* skip the mount ID check */
972 pst
.nsx
.stx_mnt_id
= mntid
;
973 pst
.nsx
.stx_mask
|= STATX_MNT_ID
;
976 return statx_mount_same(&st
.nsx
, &pst
.nsx
);
979 const char *accmode_to_string(int flags
) {
980 switch (flags
& O_ACCMODE
) {