summaryrefslogtreecommitdiffstats
path: root/src/basic/fd-util.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--src/basic/fd-util.c992
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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-03 19:52:55 +0000