/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #if WANT_LINUX_FS_H #include #endif #include #include #include #include #include #include "alloc-util.h" #include "dirent-util.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "io-util.h" #include "macro.h" #include "missing_fcntl.h" #include "missing_fs.h" #include "missing_syscall.h" #include "mountpoint-util.h" #include "parse-util.h" #include "path-util.h" #include "process-util.h" #include "socket-util.h" #include "sort-util.h" #include "stat-util.h" #include "stdio-util.h" #include "tmpfile-util.h" /* The maximum number of iterations in the loop to close descriptors in the fallback case * when /proc/self/fd/ is inaccessible. */ #define MAX_FD_LOOP_LIMIT (1024*1024) int close_nointr(int fd) { assert(fd >= 0); if (close(fd) >= 0) return 0; /* * Just ignore EINTR; a retry loop is the wrong thing to do on * Linux. * * http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html * https://bugzilla.gnome.org/show_bug.cgi?id=682819 * http://utcc.utoronto.ca/~cks/space/blog/unix/CloseEINTR * https://sites.google.com/site/michaelsafyan/software-engineering/checkforeintrwheninvokingclosethinkagain */ if (errno == EINTR) return 0; return -errno; } int safe_close(int fd) { /* * Like close_nointr() but cannot fail. Guarantees errno is unchanged. Is a noop for negative fds, * and returns -EBADF, so that it can be used in this syntax: * * fd = safe_close(fd); */ if (fd >= 0) { PROTECT_ERRNO; /* The kernel might return pretty much any error code * via close(), but the fd will be closed anyway. The * only condition we want to check for here is whether * the fd was invalid at all... */ assert_se(close_nointr(fd) != -EBADF); } return -EBADF; } void safe_close_pair(int p[static 2]) { assert(p); if (p[0] == p[1]) { /* Special case pairs which use the same fd in both * directions... */ p[0] = p[1] = safe_close(p[0]); return; } p[0] = safe_close(p[0]); p[1] = safe_close(p[1]); } void close_many(const int fds[], size_t n_fds) { assert(fds || n_fds == 0); FOREACH_ARRAY(fd, fds, n_fds) safe_close(*fd); } void close_many_unset(int fds[], size_t n_fds) { assert(fds || n_fds == 0); FOREACH_ARRAY(fd, fds, n_fds) *fd = safe_close(*fd); } void close_many_and_free(int *fds, size_t n_fds) { assert(fds || n_fds == 0); close_many(fds, n_fds); free(fds); } int fclose_nointr(FILE *f) { assert(f); /* Same as close_nointr(), but for fclose() */ errno = 0; /* Extra safety: if the FILE* object is not encapsulating an fd, it might not set errno * correctly. Let's hence initialize it to zero first, so that we aren't confused by any * prior errno here */ if (fclose(f) == 0) return 0; if (errno == EINTR) return 0; return errno_or_else(EIO); } FILE* safe_fclose(FILE *f) { /* Same as safe_close(), but for fclose() */ if (f) { PROTECT_ERRNO; assert_se(fclose_nointr(f) != -EBADF); } return NULL; } DIR* safe_closedir(DIR *d) { if (d) { PROTECT_ERRNO; assert_se(closedir(d) >= 0 || errno != EBADF); } return NULL; } int fd_nonblock(int fd, bool nonblock) { int flags, nflags; assert(fd >= 0); flags = fcntl(fd, F_GETFL, 0); if (flags < 0) return -errno; nflags = UPDATE_FLAG(flags, O_NONBLOCK, nonblock); if (nflags == flags) return 0; return RET_NERRNO(fcntl(fd, F_SETFL, nflags)); } int fd_cloexec(int fd, bool cloexec) { int flags, nflags; assert(fd >= 0); flags = fcntl(fd, F_GETFD, 0); if (flags < 0) return -errno; nflags = UPDATE_FLAG(flags, FD_CLOEXEC, cloexec); if (nflags == flags) return 0; return RET_NERRNO(fcntl(fd, F_SETFD, nflags)); } int fd_cloexec_many(const int fds[], size_t n_fds, bool cloexec) { int r = 0; assert(fds || n_fds == 0); FOREACH_ARRAY(fd, fds, n_fds) { if (*fd < 0) /* Skip gracefully over already invalidated fds */ continue; RET_GATHER(r, fd_cloexec(*fd, cloexec)); if (r >= 0) r = 1; /* report if we did anything */ } return r; } static bool fd_in_set(int fd, const int fds[], size_t n_fds) { assert(fd >= 0); assert(fds || n_fds == 0); FOREACH_ARRAY(i, fds, n_fds) { if (*i < 0) continue; if (*i == fd) return true; } return false; } int get_max_fd(void) { struct rlimit rl; rlim_t m; /* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary * and INT_MAX as upper boundary. */ if (getrlimit(RLIMIT_NOFILE, &rl) < 0) return -errno; m = MAX(rl.rlim_cur, rl.rlim_max); if (m < FD_SETSIZE) /* Let's always cover at least 1024 fds */ return FD_SETSIZE-1; if (m == RLIM_INFINITY || m > INT_MAX) /* Saturate on overflow. After all fds are "int", hence can * never be above INT_MAX */ return INT_MAX; return (int) (m - 1); } static int close_all_fds_frugal(const int except[], size_t n_except) { int max_fd, r = 0; assert(except || n_except == 0); /* This is the inner fallback core of close_all_fds(). This never calls malloc() or opendir() or so * and hence is safe to be called in signal handler context. Most users should call close_all_fds(), * but when we assume we are called from signal handler context, then use this simpler call * instead. */ max_fd = get_max_fd(); if (max_fd < 0) return max_fd; /* Refuse to do the loop over more too many elements. It's better to fail immediately than to * spin the CPU for a long time. */ if (max_fd > MAX_FD_LOOP_LIMIT) return log_debug_errno(SYNTHETIC_ERRNO(EPERM), "Refusing to loop over %d potential fds.", max_fd); for (int fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -EBADF) { int q; if (fd_in_set(fd, except, n_except)) continue; q = close_nointr(fd); if (q != -EBADF) RET_GATHER(r, q); } return r; } static bool have_close_range = true; /* Assume we live in the future */ static int close_all_fds_special_case(const int except[], size_t n_except) { assert(n_except == 0 || except); /* Handles a few common special cases separately, since they are common and can be optimized really * nicely, since we won't need sorting for them. Returns > 0 if the special casing worked, 0 * otherwise. */ if (!have_close_range) return 0; if (n_except == 1 && except[0] < 0) /* Minor optimization: if we only got one fd, and it's invalid, * we got none */ n_except = 0; switch (n_except) { case 0: /* Close everything. Yay! */ if (close_range(3, INT_MAX, 0) >= 0) return 1; if (ERRNO_IS_NOT_SUPPORTED(errno) || ERRNO_IS_PRIVILEGE(errno)) { have_close_range = false; return 0; } return -errno; case 1: /* Close all but exactly one, then we don't need no sorting. This is a pretty common * case, hence let's handle it specially. */ if ((except[0] <= 3 || close_range(3, except[0]-1, 0) >= 0) && (except[0] >= INT_MAX || close_range(MAX(3, except[0]+1), -1, 0) >= 0)) return 1; if (ERRNO_IS_NOT_SUPPORTED(errno) || ERRNO_IS_PRIVILEGE(errno)) { have_close_range = false; return 0; } return -errno; default: return 0; } } int close_all_fds_without_malloc(const int except[], size_t n_except) { int r; assert(n_except == 0 || except); r = close_all_fds_special_case(except, n_except); if (r < 0) return r; if (r > 0) /* special case worked! */ return 0; return close_all_fds_frugal(except, n_except); } int close_all_fds(const int except[], size_t n_except) { _cleanup_closedir_ DIR *d = NULL; int r = 0; assert(n_except == 0 || except); r = close_all_fds_special_case(except, n_except); if (r < 0) return r; if (r > 0) /* special case worked! */ return 0; if (have_close_range) { _cleanup_free_ int *sorted_malloc = NULL; size_t n_sorted; int *sorted; /* In the best case we have close_range() to close all fds between a start and an end fd, * which we can use on the "inverted" exception array, i.e. all intervals between all * adjacent pairs from the sorted exception array. This changes loop complexity from O(n) * where n is number of open fds to O(m⋅log(m)) where m is the number of fds to keep * open. Given that we assume n ≫ m that's preferable to us. */ assert(n_except < SIZE_MAX); n_sorted = n_except + 1; if (n_sorted > 64) /* Use heap for large numbers of fds, stack otherwise */ sorted = sorted_malloc = new(int, n_sorted); else sorted = newa(int, n_sorted); if (sorted) { memcpy(sorted, except, n_except * sizeof(int)); /* Let's add fd 2 to the list of fds, to simplify the loop below, as this * allows us to cover the head of the array the same way as the body */ sorted[n_sorted-1] = 2; typesafe_qsort(sorted, n_sorted, cmp_int); for (size_t i = 0; i < n_sorted-1; i++) { int start, end; start = MAX(sorted[i], 2); /* The first three fds shall always remain open */ end = MAX(sorted[i+1], 2); assert(end >= start); if (end - start <= 1) continue; /* Close everything between the start and end fds (both of which shall stay open) */ if (close_range(start + 1, end - 1, 0) < 0) { if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) return -errno; have_close_range = false; break; } } if (have_close_range) { /* The loop succeeded. Let's now close everything beyond the end */ if (sorted[n_sorted-1] >= INT_MAX) /* Dont let the addition below overflow */ return 0; if (close_range(sorted[n_sorted-1] + 1, INT_MAX, 0) >= 0) return 0; if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) return -errno; have_close_range = false; } } /* Fallback on OOM or if close_range() is not supported */ } d = opendir("/proc/self/fd"); if (!d) return close_all_fds_frugal(except, n_except); /* ultimate fallback if /proc/ is not available */ FOREACH_DIRENT(de, d, return -errno) { int fd = -EBADF, q; if (!IN_SET(de->d_type, DT_LNK, DT_UNKNOWN)) continue; fd = parse_fd(de->d_name); if (fd < 0) /* Let's better ignore this, just in case */ continue; if (fd < 3) continue; if (fd == dirfd(d)) continue; if (fd_in_set(fd, except, n_except)) continue; q = close_nointr(fd); if (q < 0 && q != -EBADF && r >= 0) /* Valgrind has its own FD and doesn't want to have it closed */ r = q; } return r; } int same_fd(int a, int b) { struct stat sta, stb; pid_t pid; int r, fa, fb; assert(a >= 0); assert(b >= 0); /* Compares two file descriptors. Note that semantics are quite different depending on whether we * have kcmp() or we don't. If we have kcmp() this will only return true for dup()ed file * descriptors, but not otherwise. If we don't have kcmp() this will also return true for two fds of * the same file, created by separate open() calls. Since we use this call mostly for filtering out * duplicates in the fd store this difference hopefully doesn't matter too much. */ if (a == b) return true; /* Try to use kcmp() if we have it. */ pid = getpid_cached(); r = kcmp(pid, pid, KCMP_FILE, a, b); if (r == 0) return true; if (r > 0) return false; if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) return -errno; /* We don't have kcmp(), use fstat() instead. */ if (fstat(a, &sta) < 0) return -errno; if (fstat(b, &stb) < 0) return -errno; if (!stat_inode_same(&sta, &stb)) return false; /* We consider all device fds different, since two device fds might refer to quite different device * contexts even though they share the same inode and backing dev_t. */ if (S_ISCHR(sta.st_mode) || S_ISBLK(sta.st_mode)) return false; /* The fds refer to the same inode on disk, let's also check if they have the same fd flags. This is * useful to distinguish the read and write side of a pipe created with pipe(). */ fa = fcntl(a, F_GETFL); if (fa < 0) return -errno; fb = fcntl(b, F_GETFL); if (fb < 0) return -errno; return fa == fb; } void cmsg_close_all(struct msghdr *mh) { struct cmsghdr *cmsg; assert(mh); CMSG_FOREACH(cmsg, mh) if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) close_many(CMSG_TYPED_DATA(cmsg, int), (cmsg->cmsg_len - CMSG_LEN(0)) / sizeof(int)); } bool fdname_is_valid(const char *s) { const char *p; /* Validates a name for $LISTEN_FDNAMES. We basically allow * everything ASCII that's not a control character. Also, as * special exception the ":" character is not allowed, as we * use that as field separator in $LISTEN_FDNAMES. * * Note that the empty string is explicitly allowed * here. However, we limit the length of the names to 255 * characters. */ if (!s) return false; for (p = s; *p; p++) { if (*p < ' ') return false; if (*p >= 127) return false; if (*p == ':') return false; } return p - s <= FDNAME_MAX; } int fd_get_path(int fd, char **ret) { int r; assert(fd >= 0 || fd == AT_FDCWD); if (fd == AT_FDCWD) return safe_getcwd(ret); r = readlink_malloc(FORMAT_PROC_FD_PATH(fd), ret); if (r == -ENOENT) { /* ENOENT can mean two things: that the fd does not exist or that /proc is not mounted. Let's make * things debuggable and distinguish the two. */ if (proc_mounted() == 0) return -ENOSYS; /* /proc is not available or not set up properly, we're most likely in some chroot * environment. */ return -EBADF; /* The directory exists, hence it's the fd that doesn't. */ } return r; } int move_fd(int from, int to, int cloexec) { int r; /* Move fd 'from' to 'to', make sure FD_CLOEXEC remains equal if requested, and release the old fd. If * 'cloexec' is passed as -1, the original FD_CLOEXEC is inherited for the new fd. If it is 0, it is turned * off, if it is > 0 it is turned on. */ if (from < 0) return -EBADF; if (to < 0) return -EBADF; if (from == to) { if (cloexec >= 0) { r = fd_cloexec(to, cloexec); if (r < 0) return r; } return to; } if (cloexec < 0) { int fl; fl = fcntl(from, F_GETFD, 0); if (fl < 0) return -errno; cloexec = FLAGS_SET(fl, FD_CLOEXEC); } r = dup3(from, to, cloexec ? O_CLOEXEC : 0); if (r < 0) return -errno; assert(r == to); safe_close(from); return to; } int fd_move_above_stdio(int fd) { int flags, copy; PROTECT_ERRNO; /* Moves the specified file descriptor if possible out of the range [0…2], i.e. the range of * stdin/stdout/stderr. If it can't be moved outside of this range the original file descriptor is * returned. This call is supposed to be used for long-lasting file descriptors we allocate in our code that * might get loaded into foreign code, and where we want ensure our fds are unlikely used accidentally as * stdin/stdout/stderr of unrelated code. * * Note that this doesn't fix any real bugs, it just makes it less likely that our code will be affected by * buggy code from others that mindlessly invokes 'fprintf(stderr, …' or similar in places where stderr has * been closed before. * * This function is written in a "best-effort" and "least-impact" style. This means whenever we encounter an * error we simply return the original file descriptor, and we do not touch errno. */ if (fd < 0 || fd > 2) return fd; flags = fcntl(fd, F_GETFD, 0); if (flags < 0) return fd; if (flags & FD_CLOEXEC) copy = fcntl(fd, F_DUPFD_CLOEXEC, 3); else copy = fcntl(fd, F_DUPFD, 3); if (copy < 0) return fd; assert(copy > 2); (void) close(fd); return copy; } int rearrange_stdio(int original_input_fd, int original_output_fd, int original_error_fd) { int fd[3] = { original_input_fd, /* Put together an array of fds we work on */ original_output_fd, original_error_fd }, null_fd = -EBADF, /* If we open /dev/null, we store the fd to it here */ copy_fd[3] = EBADF_TRIPLET, /* This contains all fds we duplicate here * temporarily, and hence need to close at the end. */ r; bool null_readable, null_writable; /* Sets up stdin, stdout, stderr with the three file descriptors passed in. If any of the descriptors * is specified as -EBADF it will be connected with /dev/null instead. If any of the file descriptors * is passed as itself (e.g. stdin as STDIN_FILENO) it is left unmodified, but the O_CLOEXEC bit is * turned off should it be on. * * Note that if any of the passed file descriptors are > 2 they will be closed — both on success and * on failure! Thus, callers should assume that when this function returns the input fds are * invalidated. * * Note that when this function fails stdin/stdout/stderr might remain half set up! * * O_CLOEXEC is turned off for all three file descriptors (which is how it should be for * stdin/stdout/stderr). */ null_readable = original_input_fd < 0; null_writable = original_output_fd < 0 || original_error_fd < 0; /* First step, open /dev/null once, if we need it */ if (null_readable || null_writable) { /* Let's open this with O_CLOEXEC first, and convert it to non-O_CLOEXEC when we move the fd to the final position. */ null_fd = open("/dev/null", (null_readable && null_writable ? O_RDWR : null_readable ? O_RDONLY : O_WRONLY) | O_CLOEXEC); if (null_fd < 0) { r = -errno; goto finish; } /* If this fd is in the 0…2 range, let's move it out of it */ if (null_fd < 3) { int copy; copy = fcntl(null_fd, F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */ if (copy < 0) { r = -errno; goto finish; } close_and_replace(null_fd, copy); } } /* Let's assemble fd[] with the fds to install in place of stdin/stdout/stderr */ for (int i = 0; i < 3; i++) { if (fd[i] < 0) fd[i] = null_fd; /* A negative parameter means: connect this one to /dev/null */ else if (fd[i] != i && fd[i] < 3) { /* 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. */ copy_fd[i] = fcntl(fd[i], F_DUPFD_CLOEXEC, 3); /* Duplicate this with O_CLOEXEC set */ if (copy_fd[i] < 0) { r = -errno; goto finish; } fd[i] = copy_fd[i]; } } /* At this point we now have the fds to use in fd[], and they are all above the stdio range, so that * we have freedom to move them around. If the fds already were at the right places then the specific * fds are -EBADF. Let's now move them to the right places. This is the point of no return. */ for (int i = 0; i < 3; i++) { if (fd[i] == i) { /* fd is already in place, but let's make sure O_CLOEXEC is off */ r = fd_cloexec(i, false); if (r < 0) goto finish; } else { assert(fd[i] > 2); if (dup2(fd[i], i) < 0) { /* Turns off O_CLOEXEC on the new fd. */ r = -errno; goto finish; } } } r = 0; finish: /* Close the original fds, but only if they were outside of the stdio range. Also, properly check for the same * fd passed in multiple times. */ safe_close_above_stdio(original_input_fd); if (original_output_fd != original_input_fd) safe_close_above_stdio(original_output_fd); if (original_error_fd != original_input_fd && original_error_fd != original_output_fd) safe_close_above_stdio(original_error_fd); /* Close the copies we moved > 2 */ close_many(copy_fd, 3); /* Close our null fd, if it's > 2 */ safe_close_above_stdio(null_fd); return r; } int fd_reopen(int fd, int flags) { int r; assert(fd >= 0 || fd == AT_FDCWD); assert(!FLAGS_SET(flags, O_CREAT)); /* Reopens the specified fd with new flags. This is useful for convert an O_PATH fd into a regular one, or to * turn O_RDWR fds into O_RDONLY fds. * * This doesn't work on sockets (since they cannot be open()ed, ever). * * This implicitly resets the file read index to 0. * * If AT_FDCWD is specified as file descriptor gets an fd to the current cwd. * * If the specified file descriptor refers to a symlink via O_PATH, then this function cannot be used * to follow that symlink. Because we cannot have non-O_PATH fds to symlinks reopening it without * O_PATH will always result in -ELOOP. Or in other words: if you have an O_PATH fd to a symlink you * can reopen it only if you pass O_PATH again. */ if (FLAGS_SET(flags, O_NOFOLLOW)) /* O_NOFOLLOW is not allowed in fd_reopen(), because after all this is primarily implemented * via a symlink-based interface in /proc/self/fd. Let's refuse this here early. Note that * the kernel would generate ELOOP here too, hence this manual check is mostly redundant – * the only reason we add it here is so that the O_DIRECTORY special case (see below) behaves * the same way as the non-O_DIRECTORY case. */ return -ELOOP; if (FLAGS_SET(flags, O_DIRECTORY) || fd == AT_FDCWD) /* If we shall reopen the fd as directory we can just go via "." and thus bypass the whole * magic /proc/ directory, and make ourselves independent of that being mounted. */ return RET_NERRNO(openat(fd, ".", flags | O_DIRECTORY)); int new_fd = open(FORMAT_PROC_FD_PATH(fd), flags); if (new_fd < 0) { if (errno != ENOENT) return -errno; r = proc_mounted(); if (r == 0) return -ENOSYS; /* if we have no /proc/, the concept is not implementable */ return r > 0 ? -EBADF : -ENOENT; /* If /proc/ is definitely around then this means the fd is * not valid, otherwise let's propagate the original * error */ } return new_fd; } int fd_reopen_condition( int fd, int flags, int mask, int *ret_new_fd) { int r, new_fd; assert(fd >= 0); assert(!FLAGS_SET(flags, O_CREAT)); /* Invokes fd_reopen(fd, flags), but only if the existing F_GETFL flags don't match the specified * flags (masked by the specified mask). This is useful for converting O_PATH fds into real fds if * needed, but only then. */ r = fcntl(fd, F_GETFL); if (r < 0) return -errno; if ((r & mask) == (flags & mask)) { *ret_new_fd = -EBADF; return fd; } new_fd = fd_reopen(fd, flags); if (new_fd < 0) return new_fd; *ret_new_fd = new_fd; return new_fd; } int fd_is_opath(int fd) { int r; assert(fd >= 0); r = fcntl(fd, F_GETFL); if (r < 0) return -errno; return FLAGS_SET(r, O_PATH); } int read_nr_open(void) { _cleanup_free_ char *nr_open = NULL; int r; /* Returns the kernel's current fd limit, either by reading it of /proc/sys if that works, or using the * hard-coded default compiled-in value of current kernels (1M) if not. This call will never fail. */ r = read_one_line_file("/proc/sys/fs/nr_open", &nr_open); if (r < 0) log_debug_errno(r, "Failed to read /proc/sys/fs/nr_open, ignoring: %m"); else { int v; r = safe_atoi(nr_open, &v); if (r < 0) log_debug_errno(r, "Failed to parse /proc/sys/fs/nr_open value '%s', ignoring: %m", nr_open); else return v; } /* If we fail, fall back to the hard-coded kernel limit of 1024 * 1024. */ return 1024 * 1024; } int fd_get_diskseq(int fd, uint64_t *ret) { uint64_t diskseq; assert(fd >= 0); assert(ret); if (ioctl(fd, BLKGETDISKSEQ, &diskseq) < 0) { /* Note that the kernel is weird: non-existing ioctls currently return EINVAL * rather than ENOTTY on loopback block devices. They should fix that in the kernel, * but in the meantime we accept both here. */ if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL) return -errno; return -EOPNOTSUPP; } *ret = diskseq; return 0; } int path_is_root_at(int dir_fd, const char *path) { STRUCT_NEW_STATX_DEFINE(st); STRUCT_NEW_STATX_DEFINE(pst); _cleanup_close_ int fd = -EBADF; int r; assert(dir_fd >= 0 || dir_fd == AT_FDCWD); if (!isempty(path)) { fd = openat(dir_fd, path, O_PATH|O_DIRECTORY|O_CLOEXEC); if (fd < 0) return errno == ENOTDIR ? false : -errno; dir_fd = fd; } r = statx_fallback(dir_fd, ".", 0, STATX_TYPE|STATX_INO|STATX_MNT_ID, &st.sx); if (r == -ENOTDIR) return false; if (r < 0) return r; r = statx_fallback(dir_fd, "..", 0, STATX_TYPE|STATX_INO|STATX_MNT_ID, &pst.sx); if (r < 0) return r; /* First, compare inode. If these are different, the fd does not point to the root directory "/". */ if (!statx_inode_same(&st.sx, &pst.sx)) return false; /* Even if the parent directory has the same inode, the fd may not point to the root directory "/", * and we also need to check that the mount ids are the same. Otherwise, a construct like the * following could be used to trick us: * * $ mkdir /tmp/x /tmp/x/y * $ mount --bind /tmp/x /tmp/x/y * * Note, statx() does not provide the mount ID and path_get_mnt_id_at() does not work when an old * kernel is used. In that case, let's assume that we do not have such spurious mount points in an * early boot stage, and silently skip the following check. */ if (!FLAGS_SET(st.nsx.stx_mask, STATX_MNT_ID)) { int mntid; r = path_get_mnt_id_at_fallback(dir_fd, "", &mntid); if (ERRNO_IS_NEG_NOT_SUPPORTED(r)) return true; /* skip the mount ID check */ if (r < 0) return r; assert(mntid >= 0); st.nsx.stx_mnt_id = mntid; st.nsx.stx_mask |= STATX_MNT_ID; } if (!FLAGS_SET(pst.nsx.stx_mask, STATX_MNT_ID)) { int mntid; r = path_get_mnt_id_at_fallback(dir_fd, "..", &mntid); if (ERRNO_IS_NEG_NOT_SUPPORTED(r)) return true; /* skip the mount ID check */ if (r < 0) return r; assert(mntid >= 0); pst.nsx.stx_mnt_id = mntid; pst.nsx.stx_mask |= STATX_MNT_ID; } return statx_mount_same(&st.nsx, &pst.nsx); } const char *accmode_to_string(int flags) { switch (flags & O_ACCMODE) { case O_RDONLY: return "ro"; case O_WRONLY: return "wo"; case O_RDWR: return "rw"; default: return NULL; } } char *format_proc_pid_fd_path(char buf[static PROC_PID_FD_PATH_MAX], pid_t pid, int fd) { assert(buf); assert(fd >= 0); assert(pid >= 0); assert_se(snprintf_ok(buf, PROC_PID_FD_PATH_MAX, "/proc/" PID_FMT "/fd/%i", pid == 0 ? getpid_cached() : pid, fd)); return buf; }