diff options
Diffstat (limited to 'src/basic/fd-util.c')
| -rw-r--r-- | src/basic/fd-util.c | 992 |
1 files changed, 992 insertions, 0 deletions
diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c new file mode 100644 index 0000000..542acca --- /dev/null +++ b/src/basic/fd-util.c @@ -0,0 +1,992 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <errno.h> +#include <fcntl.h> +#if WANT_LINUX_FS_H +#include <linux/fs.h> +#endif +#include <linux/magic.h> +#include <sys/ioctl.h> +#include <sys/resource.h> +#include <sys/stat.h> +#include <unistd.h> + +#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; +} |