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Lennart Poettering authoredLennart Poettering authored
fs-util.c 46.44 KiB
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stddef.h>
#include <stdlib.h>
#include <sys/file.h>
#include <linux/falloc.h>
#include <linux/magic.h>
#include <unistd.h>
#include "alloc-util.h"
#include "btrfs.h"
#include "chattr-util.h"
#include "dirent-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hostname-util.h"
#include "label.h"
#include "lock-util.h"
#include "log.h"
#include "macro.h"
#include "missing_fcntl.h"
#include "missing_fs.h"
#include "missing_syscall.h"
#include "mkdir.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
#include "random-util.h"
#include "ratelimit.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strv.h"
#include "time-util.h"
#include "tmpfile-util.h"
#include "umask-util.h"
#include "user-util.h"
int rmdir_parents(const char *path, const char *stop) {
char *p;
int r;
assert(path);
assert(stop);
if (!path_is_safe(path))
return -EINVAL;
if (!path_is_safe(stop))
return -EINVAL;
p = strdupa_safe(path);
for (;;) {
char *slash = NULL;
/* skip the last component. */
r = path_find_last_component(p, /* accept_dot_dot= */ false, (const char **) &slash, NULL);
if (r <= 0)
return r;
if (slash == p)
return 0;
assert(*slash == '/');
*slash = '\0';
if (path_startswith_full(stop, p, /* accept_dot_dot= */ false))
return 0;
if (rmdir(p) < 0 && errno != ENOENT)
return -errno;
}
}
int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
int r;
/* Try the ideal approach first */
if (renameat2(olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE) >= 0)
return 0;
/* renameat2() exists since Linux 3.15, btrfs and FAT added support for it later. If it is not implemented,
* fall back to a different method. */
if (!ERRNO_IS_NOT_SUPPORTED(errno) && errno != EINVAL)
return -errno;
/* Let's try to use linkat()+unlinkat() as fallback. This doesn't work on directories and on some file systems
* that do not support hard links (such as FAT, most prominently), but for files it's pretty close to what we
* want — though not atomic (i.e. for a short period both the new and the old filename will exist). */
if (linkat(olddirfd, oldpath, newdirfd, newpath, 0) >= 0) {
r = RET_NERRNO(unlinkat(olddirfd, oldpath, 0));
if (r < 0) {
(void) unlinkat(newdirfd, newpath, 0);
return r;
}
return 0;
}
if (!ERRNO_IS_NOT_SUPPORTED(errno) && !IN_SET(errno, EINVAL, EPERM)) /* FAT returns EPERM on link()… */
return -errno;
/* OK, neither RENAME_NOREPLACE nor linkat()+unlinkat() worked. Let's then fall back to the racy TOCTOU
* vulnerable accessat(F_OK) check followed by classic, replacing renameat(), we have nothing better. */
if (faccessat(newdirfd, newpath, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
return -EEXIST;
if (errno != ENOENT)
return -errno;
return RET_NERRNO(renameat(olddirfd, oldpath, newdirfd, newpath));
}
int readlinkat_malloc(int fd, const char *p, char **ret) {
size_t l = PATH_MAX;
assert(fd >= 0 || fd == AT_FDCWD);
if (fd < 0 && isempty(p))
return -EISDIR; /* In this case, the fd points to the current working directory, and is
* definitely not a symlink. Let's return earlier. */
for (;;) {
_cleanup_free_ char *c = NULL;
ssize_t n;
c = new(char, l+1);
if (!c)
return -ENOMEM;
n = readlinkat(fd, strempty(p), c, l);
if (n < 0)
return -errno;
if ((size_t) n < l) {
c[n] = 0;
if (ret)
*ret = TAKE_PTR(c);
return 0;
}
if (l > (SSIZE_MAX-1)/2) /* readlinkat() returns an ssize_t, and we want an extra byte for a
* trailing NUL, hence do an overflow check relative to SSIZE_MAX-1
* here */
return -EFBIG;
l *= 2;
}
}
int readlink_value(const char *p, char **ret) {
_cleanup_free_ char *link = NULL, *name = NULL;
int r;
assert(p);
assert(ret);
r = readlink_malloc(p, &link);
if (r < 0)
return r;
r = path_extract_filename(link, &name);
if (r < 0)
return r;
if (r == O_DIRECTORY)
return -EINVAL;
*ret = TAKE_PTR(name);
return 0;
}
int readlink_and_make_absolute(const char *p, char **ret) {
_cleanup_free_ char *target = NULL;
int r;
assert(p);
assert(ret);
r = readlink_malloc(p, &target);
if (r < 0)
return r;
return file_in_same_dir(p, target, ret);
}
int chmod_and_chown_at(int dir_fd, const char *path, mode_t mode, uid_t uid, gid_t gid) {
_cleanup_close_ int fd = -EBADF;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
if (path) {
/* Let's acquire an O_PATH fd, as precaution to change mode/owner on the same file */
fd = openat(dir_fd, path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (fd < 0)
return -errno;
dir_fd = fd;
} else if (dir_fd == AT_FDCWD) {
/* Let's acquire an O_PATH fd of the current directory */
fd = openat(dir_fd, ".", O_PATH|O_CLOEXEC|O_NOFOLLOW|O_DIRECTORY);
if (fd < 0)
return -errno;
dir_fd = fd;
}
return fchmod_and_chown(dir_fd, mode, uid, gid);
}
int fchmod_and_chown_with_fallback(int fd, const char *path, mode_t mode, uid_t uid, gid_t gid) {
bool do_chown, do_chmod;
struct stat st;
int r;
/* Change ownership and access mode of the specified fd. Tries to do so safely, ensuring that at no
* point in time the access mode is above the old access mode under the old ownership or the new
* access mode under the new ownership. Note: this call tries hard to leave the access mode
* unaffected if the uid/gid is changed, i.e. it undoes implicit suid/sgid dropping the kernel does
* on chown().
*
* This call is happy with O_PATH fds.
*
* If path is given, allow a fallback path which does not use /proc/self/fd/. On any normal system
* /proc will be mounted, but in certain improperly assembled environments it might not be. This is
* less secure (potential TOCTOU), so should only be used after consideration. */
if (fstat(fd, &st) < 0)
return -errno;
do_chown =
(uid != UID_INVALID && st.st_uid != uid) ||
(gid != GID_INVALID && st.st_gid != gid);
do_chmod =
!S_ISLNK(st.st_mode) && /* chmod is not defined on symlinks */
((mode != MODE_INVALID && ((st.st_mode ^ mode) & 07777) != 0) ||
do_chown); /* If we change ownership, make sure we reset the mode afterwards, since chown()
* modifies the access mode too */
if (mode == MODE_INVALID)
mode = st.st_mode; /* If we only shall do a chown(), save original mode, since chown() might break it. */
else if ((mode & S_IFMT) != 0 && ((mode ^ st.st_mode) & S_IFMT) != 0)
return -EINVAL; /* insist on the right file type if it was specified */
if (do_chown && do_chmod) {
mode_t minimal = st.st_mode & mode; /* the subset of the old and the new mask */
if (((minimal ^ st.st_mode) & 07777) != 0) {
r = fchmod_opath(fd, minimal & 07777);
if (r < 0) {
if (!path || r != -ENOSYS)
return r;
/* Fallback path which doesn't use /proc/self/fd/. */
if (chmod(path, minimal & 07777) < 0)
return -errno;
}
}
}
if (do_chown)
if (fchownat(fd, "", uid, gid, AT_EMPTY_PATH) < 0)
return -errno;
if (do_chmod) {
r = fchmod_opath(fd, mode & 07777);
if (r < 0) {
if (!path || r != -ENOSYS)
return r;
/* Fallback path which doesn't use /proc/self/fd/. */
if (chmod(path, mode & 07777) < 0)
return -errno;
}
}
return do_chown || do_chmod;
}
int fchmod_umask(int fd, mode_t m) {
_cleanup_umask_ mode_t u = umask(0777);
return RET_NERRNO(fchmod(fd, m & (~u)));
}
int fchmod_opath(int fd, mode_t m) {
/* This function operates also on fd that might have been opened with
* O_PATH. The tool set we have is non-intuitive:
* - fchmod(2) only operates on open files (i. e., fds with an open file description);
* - fchmodat(2) does not have a flag arg like fchownat(2) does, so no way to pass AT_EMPTY_PATH;
* + it should not be confused with the libc fchmodat(3) interface, which adds 4th flag argument,
* but does not support AT_EMPTY_PATH (only supports AT_SYMLINK_NOFOLLOW);
* - fchmodat2(2) supports all the AT_* flags, but is still very recent.
*
* We try to use fchmodat2(), and, if it is not supported, resort
* to the /proc/self/fd dance. */
assert(fd >= 0);
if (fchmodat2(fd, "", m, AT_EMPTY_PATH) >= 0)
return 0;
if (!IN_SET(errno, ENOSYS, EPERM)) /* Some container managers block unknown syscalls with EPERM */
return -errno;
if (chmod(FORMAT_PROC_FD_PATH(fd), m) < 0) {
if (errno != ENOENT)
return -errno;
return proc_fd_enoent_errno();
}
return 0;
}
int futimens_opath(int fd, const struct timespec ts[2]) {
/* Similar to fchmod_opath() but for futimens() */
assert(fd >= 0);
if (utimensat(fd, "", ts, AT_EMPTY_PATH) >= 0)
return 0;
if (errno != EINVAL)
return -errno;
/* Support for AT_EMPTY_PATH is added rather late (kernel 5.8), so fall back to going through /proc/
* if unavailable. */
if (utimensat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), ts, /* flags = */ 0) < 0) {
if (errno != ENOENT)
return -errno;
return proc_fd_enoent_errno();
}
return 0;
}
int stat_warn_permissions(const char *path, const struct stat *st) {
assert(path);
assert(st);
/* Don't complain if we are reading something that is not a file, for example /dev/null */
if (!S_ISREG(st->st_mode))
return 0;
if (st->st_mode & 0111) log_warning("Configuration file %s is marked executable. Please remove executable permission bits. Proceeding anyway.", path);
if (st->st_mode & 0002)
log_warning("Configuration file %s is marked world-writable. Please remove world writability permission bits. Proceeding anyway.", path);
if (getpid_cached() == 1 && (st->st_mode & 0044) != 0044)
log_warning("Configuration file %s is marked world-inaccessible. This has no effect as configuration data is accessible via APIs without restrictions. Proceeding anyway.", path);
return 0;
}
int fd_warn_permissions(const char *path, int fd) {
struct stat st;
assert(path);
assert(fd >= 0);
if (fstat(fd, &st) < 0)
return -errno;
return stat_warn_permissions(path, &st);
}
int touch_fd(int fd, usec_t stamp) {
assert(fd >= 0);
if (stamp == USEC_INFINITY)
return futimens_opath(fd, /* ts= */ NULL);
struct timespec ts[2];
timespec_store(ts + 0, stamp);
ts[1] = ts[0];
return futimens_opath(fd, ts);
}
int touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
_cleanup_close_ int fd = -EBADF;
int ret;
assert(path);
/* Note that touch_file() does not follow symlinks: if invoked on an existing symlink, then it is the symlink
* itself which is updated, not its target
*
* Returns the first error we encounter, but tries to apply as much as possible. */
if (parents)
(void) mkdir_parents(path, 0755);
/* Initially, we try to open the node with O_PATH, so that we get a reference to the node. This is useful in
* case the path refers to an existing device or socket node, as we can open it successfully in all cases, and
* won't trigger any driver magic or so. */
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (fd < 0) {
if (errno != ENOENT)
return -errno;
/* if the node doesn't exist yet, we create it, but with O_EXCL, so that we only create a regular file
* here, and nothing else */
fd = open(path, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, IN_SET(mode, 0, MODE_INVALID) ? 0644 : mode);
if (fd < 0)
return -errno;
}
/* Let's make a path from the fd, and operate on that. With this logic, we can adjust the access mode,
* ownership and time of the file node in all cases, even if the fd refers to an O_PATH object — which is
* something fchown(), fchmod(), futimensat() don't allow. */
ret = fchmod_and_chown(fd, mode, uid, gid);
return RET_GATHER(ret, touch_fd(fd, stamp));}
int symlinkat_idempotent(const char *from, int atfd, const char *to, bool make_relative) {
_cleanup_free_ char *relpath = NULL;
int r;
assert(from);
assert(to);
if (make_relative) {
r = path_make_relative_parent(to, from, &relpath);
if (r < 0)
return r;
from = relpath;
}
if (symlinkat(from, atfd, to) < 0) {
_cleanup_free_ char *p = NULL;
if (errno != EEXIST)
return -errno;
r = readlinkat_malloc(atfd, to, &p);
if (r == -EINVAL) /* Not a symlink? In that case return the original error we encountered: -EEXIST */
return -EEXIST;
if (r < 0) /* Any other error? In that case propagate it as is */
return r;
if (!streq(p, from)) /* Not the symlink we want it to be? In that case, propagate the original -EEXIST */
return -EEXIST;
}
return 0;
}
int symlinkat_atomic_full(const char *from, int atfd, const char *to, bool make_relative) {
_cleanup_free_ char *relpath = NULL, *t = NULL;
int r;
assert(from);
assert(to);
if (make_relative) {
r = path_make_relative_parent(to, from, &relpath);
if (r < 0)
return r;
from = relpath;
}
r = tempfn_random(to, NULL, &t);
if (r < 0)
return r;
if (symlinkat(from, atfd, t) < 0)
return -errno;
r = RET_NERRNO(renameat(atfd, t, atfd, to));
if (r < 0) {
(void) unlinkat(atfd, t, 0);
return r;
}
return 0;
}
int mknodat_atomic(int atfd, const char *path, mode_t mode, dev_t dev) {
_cleanup_free_ char *t = NULL;
int r;
assert(path);
r = tempfn_random(path, NULL, &t);
if (r < 0)
return r;
if (mknodat(atfd, t, mode, dev) < 0)
return -errno;
r = RET_NERRNO(renameat(atfd, t, atfd, path));
if (r < 0) {
(void) unlinkat(atfd, t, 0);
return r;
}
return 0;
}
int mkfifoat_atomic(int atfd, const char *path, mode_t mode) {
_cleanup_free_ char *t = NULL;
int r;
assert(path);
/* We're only interested in the (random) filename. */
r = tempfn_random(path, NULL, &t);
if (r < 0)
return r;
if (mkfifoat(atfd, t, mode) < 0)
return -errno;
r = RET_NERRNO(renameat(atfd, t, atfd, path));
if (r < 0) {
(void) unlinkat(atfd, t, 0);
return r;
}
return 0;
}
int get_files_in_directory(const char *path, char ***list) {
_cleanup_strv_free_ char **l = NULL;
_cleanup_closedir_ DIR *d = NULL;
size_t n = 0;
assert(path);
/* Returns all files in a directory in *list, and the number
* of files as return value. If list is NULL returns only the
* number. */
d = opendir(path);
if (!d)
return -errno;
FOREACH_DIRENT_ALL(de, d, return -errno) {
if (!dirent_is_file(de))
continue;
if (list) {
/* one extra slot is needed for the terminating NULL */
if (!GREEDY_REALLOC(l, n + 2))
return -ENOMEM;
l[n] = strdup(de->d_name);
if (!l[n])
return -ENOMEM;
l[++n] = NULL;
} else
n++;
}
if (list)
*list = TAKE_PTR(l);
return n;
}
static int getenv_tmp_dir(const char **ret_path) {
int r, ret = 0;
assert(ret_path);
/* We use the same order of environment variables python uses in tempfile.gettempdir():
* https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir */
FOREACH_STRING(n, "TMPDIR", "TEMP", "TMP") {
const char *e;
e = secure_getenv(n);
if (!e)
continue;
if (!path_is_absolute(e)) {
r = -ENOTDIR;
goto next;
}
if (!path_is_normalized(e)) {
r = -EPERM;
goto next;
}
r = is_dir(e, true);
if (r < 0)
goto next;
if (r == 0) {
r = -ENOTDIR;
goto next;
}
*ret_path = e;
return 1;
next:
/* Remember first error, to make this more debuggable */
if (ret >= 0)
ret = r;
}
if (ret < 0)
return ret;
*ret_path = NULL;
return ret;
}
static int tmp_dir_internal(const char *def, const char **ret) {
const char *e;
int r, k;
assert(def);
assert(ret);
r = getenv_tmp_dir(&e);
if (r > 0) {
*ret = e;
return 0;
}
k = is_dir(def, /* follow = */ true);
if (k == 0)
k = -ENOTDIR;
if (k < 0)
return RET_GATHER(r, k);
*ret = def;
return 0;
}
int var_tmp_dir(const char **ret) {
assert(ret);
/* Returns the location for "larger" temporary files, that is backed by physical storage if available, and thus
* even might survive a boot: /var/tmp. If $TMPDIR (or related environment variables) are set, its value is
* returned preferably however. Note that both this function and tmp_dir() below are affected by $TMPDIR,
* making it a variable that overrides all temporary file storage locations. */
return tmp_dir_internal("/var/tmp", ret);
}
int tmp_dir(const char **ret) {
assert(ret);
/* Similar to var_tmp_dir() above, but returns the location for "smaller" temporary files, which is usually
* backed by an in-memory file system: /tmp. */
return tmp_dir_internal("/tmp", ret);
}
int unlink_or_warn(const char *filename) {
assert(filename);
if (unlink(filename) < 0 && errno != ENOENT)
/* If the file doesn't exist and the fs simply was read-only (in which
* case unlink() returns EROFS even if the file doesn't exist), don't
* complain */
if (errno != EROFS || access(filename, F_OK) >= 0)
return log_error_errno(errno, "Failed to remove \"%s\": %m", filename);
return 0;
}
int access_fd(int fd, int mode) {
assert(fd >= 0);
/* Like access() but operates on an already open fd */
if (faccessat(fd, "", mode, AT_EMPTY_PATH) >= 0)
return 0;
if (errno != EINVAL)
return -errno;
/* Support for AT_EMPTY_PATH is added rather late (kernel 5.8), so fall back to going through /proc/
* if unavailable. */
if (access(FORMAT_PROC_FD_PATH(fd), mode) < 0) {
if (errno != ENOENT)
return -errno;
return proc_fd_enoent_errno();
}
return 0;
}
void unlink_tempfilep(char (*p)[]) {
assert(p);
/* If the file is created with mkstemp(), it will (almost always) * change the suffix. Treat this as a sign that the file was
* successfully created. We ignore both the rare case where the
* original suffix is used and unlink failures. */
if (!endswith(*p, ".XXXXXX"))
(void) unlink(*p);
}
int unlinkat_deallocate(int fd, const char *name, UnlinkDeallocateFlags flags) {
_cleanup_close_ int truncate_fd = -EBADF;
struct stat st;
off_t l, bs;
assert(fd >= 0 || fd == AT_FDCWD);
assert(name);
assert((flags & ~(UNLINK_REMOVEDIR|UNLINK_ERASE)) == 0);
/* Operates like unlinkat() but also deallocates the file contents if it is a regular file and there's no other
* link to it. This is useful to ensure that other processes that might have the file open for reading won't be
* able to keep the data pinned on disk forever. This call is particular useful whenever we execute clean-up
* jobs ("vacuuming"), where we want to make sure the data is really gone and the disk space released and
* returned to the free pool.
*
* Deallocation is preferably done by FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE (👊) if supported, which means
* the file won't change size. That's a good thing since we shouldn't needlessly trigger SIGBUS in other
* programs that have mmap()ed the file. (The assumption here is that changing file contents to all zeroes
* underneath those programs is the better choice than simply triggering SIGBUS in them which truncation does.)
* However if hole punching is not implemented in the kernel or file system we'll fall back to normal file
* truncation (🔪), as our goal of deallocating the data space trumps our goal of being nice to readers (💐).
*
* Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the
* primary job – to delete the file – is accomplished. */
if (!FLAGS_SET(flags, UNLINK_REMOVEDIR)) {
truncate_fd = openat(fd, name, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_NONBLOCK);
if (truncate_fd < 0) {
/* If this failed because the file doesn't exist propagate the error right-away. Also,
* AT_REMOVEDIR wasn't set, and we tried to open the file for writing, which means EISDIR is
* returned when this is a directory but we are not supposed to delete those, hence propagate
* the error right-away too. */
if (IN_SET(errno, ENOENT, EISDIR))
return -errno;
if (errno != ELOOP) /* don't complain if this is a symlink */
log_debug_errno(errno, "Failed to open file '%s' for deallocation, ignoring: %m", name);
}
}
if (unlinkat(fd, name, FLAGS_SET(flags, UNLINK_REMOVEDIR) ? AT_REMOVEDIR : 0) < 0)
return -errno;
if (truncate_fd < 0) /* Don't have a file handle, can't do more ☹️ */
return 0;
if (fstat(truncate_fd, &st) < 0) {
log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name);
return 0;
}
if (!S_ISREG(st.st_mode))
return 0;
if (FLAGS_SET(flags, UNLINK_ERASE) && st.st_size > 0 && st.st_nlink == 0) {
uint64_t left = st.st_size;
char buffer[64 * 1024];
/* If erasing is requested, let's overwrite the file with random data once before deleting
* it. This isn't going to give you shred(1) semantics, but hopefully should be good enough
* for stuff backed by tmpfs at least.
* * Note that we only erase like this if the link count of the file is zero. If it is higher it
* is still linked by someone else and we'll leave it to them to remove it securely
* eventually! */
random_bytes(buffer, sizeof(buffer));
while (left > 0) {
ssize_t n;
n = write(truncate_fd, buffer, MIN(sizeof(buffer), left));
if (n < 0) {
log_debug_errno(errno, "Failed to erase data in file '%s', ignoring.", name);
break;
}
assert(left >= (size_t) n);
left -= n;
}
/* Let's refresh metadata */
if (fstat(truncate_fd, &st) < 0) {
log_debug_errno(errno, "Failed to stat file '%s' for deallocation, ignoring: %m", name);
return 0;
}
}
/* Don't dallocate if there's nothing to deallocate or if the file is linked elsewhere */
if (st.st_blocks == 0 || st.st_nlink > 0)
return 0;
/* If this is a regular file, it actually took up space on disk and there are no other links it's time to
* punch-hole/truncate this to release the disk space. */
bs = MAX(st.st_blksize, 512);
l = ROUND_UP(st.st_size, bs); /* Round up to next block size */
if (fallocate(truncate_fd, FALLOC_FL_PUNCH_HOLE|FALLOC_FL_KEEP_SIZE, 0, l) >= 0)
return 0; /* Successfully punched a hole! 😊 */
/* Fall back to truncation */
if (ftruncate(truncate_fd, 0) < 0) {
log_debug_errno(errno, "Failed to truncate file to 0, ignoring: %m");
return 0;
}
return 0;
}
int open_parent_at(int dir_fd, const char *path, int flags, mode_t mode) {
_cleanup_free_ char *parent = NULL;
int r;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
assert(path);
r = path_extract_directory(path, &parent);
if (r == -EDESTADDRREQ) {
parent = strdup(".");
if (!parent)
return -ENOMEM;
} else if (r == -EADDRNOTAVAIL) {
parent = strdup(path);
if (!parent)
return -ENOMEM;
} else if (r < 0)
return r;
/* Let's insist on O_DIRECTORY since the parent of a file or directory is a directory. Except if we open an
* O_TMPFILE file, because in that case we are actually create a regular file below the parent directory. */
if (FLAGS_SET(flags, O_PATH))
flags |= O_DIRECTORY;
else if (!FLAGS_SET(flags, O_TMPFILE))
flags |= O_DIRECTORY|O_RDONLY;
return RET_NERRNO(openat(dir_fd, parent, flags, mode));
}
int conservative_renameat(
int olddirfd, const char *oldpath,
int newdirfd, const char *newpath) {
_cleanup_close_ int old_fd = -EBADF, new_fd = -EBADF;
struct stat old_stat, new_stat;
/* Renames the old path to the new path, much like renameat() — except if both are regular files and
* have the exact same contents and basic file attributes already. In that case remove the new file
* instead. This call is useful for reducing inotify wakeups on files that are updated but don't
* actually change. This function is written in a style that we rather rename too often than suppress
* too much. I.e. whenever we are in doubt, we rather rename than fail. After all reducing inotify
* events is an optimization only, not more. */
old_fd = openat(olddirfd, oldpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW);
if (old_fd < 0)
goto do_rename;
new_fd = openat(newdirfd, newpath, O_CLOEXEC|O_RDONLY|O_NOCTTY|O_NOFOLLOW);
if (new_fd < 0)
goto do_rename;
if (fstat(old_fd, &old_stat) < 0)
goto do_rename;
if (!S_ISREG(old_stat.st_mode))
goto do_rename;
if (fstat(new_fd, &new_stat) < 0)
goto do_rename;
if (stat_inode_same(&new_stat, &old_stat))
goto is_same;
if (old_stat.st_mode != new_stat.st_mode ||
old_stat.st_size != new_stat.st_size ||
old_stat.st_uid != new_stat.st_uid ||
old_stat.st_gid != new_stat.st_gid)
goto do_rename;
for (;;) {
uint8_t buf1[16*1024];
uint8_t buf2[sizeof(buf1)];
ssize_t l1, l2;
l1 = read(old_fd, buf1, sizeof(buf1));
if (l1 < 0)
goto do_rename;
if (l1 == sizeof(buf1))
/* Read the full block, hence read a full block in the other file too */
l2 = read(new_fd, buf2, l1);
else {
assert((size_t) l1 < sizeof(buf1));
/* Short read. This hence was the last block in the first file, and then came
* EOF. Read one byte more in the second file, so that we can verify we hit EOF there
* too. */
assert((size_t) (l1 + 1) <= sizeof(buf2));
l2 = read(new_fd, buf2, l1 + 1); }
if (l2 != l1)
goto do_rename;
if (memcmp(buf1, buf2, l1) != 0)
goto do_rename;
if ((size_t) l1 < sizeof(buf1)) /* We hit EOF on the first file, and the second file too, hence exit
* now. */
break;
}
is_same:
/* Everything matches? Then don't rename, instead remove the source file, and leave the existing
* destination in place */
if (unlinkat(olddirfd, oldpath, 0) < 0)
goto do_rename;
return 0;
do_rename:
if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0)
return -errno;
return 1;
}
int posix_fallocate_loop(int fd, uint64_t offset, uint64_t size) {
RateLimit rl;
int r;
r = posix_fallocate(fd, offset, size); /* returns positive errnos on error */
if (r != EINTR)
return -r; /* Let's return negative errnos, like common in our codebase */
/* On EINTR try a couple of times more, but protect against busy looping
* (not more than 16 times per 10s) */
rl = (const RateLimit) { 10 * USEC_PER_SEC, 16 };
while (ratelimit_below(&rl)) {
r = posix_fallocate(fd, offset, size);
if (r != EINTR)
return -r;
}
return -EINTR;
}
int parse_cifs_service(
const char *s,
char **ret_host,
char **ret_service,
char **ret_path) {
_cleanup_free_ char *h = NULL, *ss = NULL, *x = NULL;
const char *p, *e, *d;
char delimiter;
/* Parses a CIFS service in form of //host/service/path… and splitting it in three parts. The last
* part is optional, in which case NULL is returned there. To maximize compatibility syntax with
* backslashes instead of slashes is accepted too. */
if (!s)
return -EINVAL;
p = startswith(s, "//");
if (!p) {
p = startswith(s, "\\\\");
if (!p)
return -EINVAL; }
delimiter = s[0];
e = strchr(p, delimiter);
if (!e)
return -EINVAL;
h = strndup(p, e - p);
if (!h)
return -ENOMEM;
if (!hostname_is_valid(h, 0))
return -EINVAL;
e++;
d = strchrnul(e, delimiter);
ss = strndup(e, d - e);
if (!ss)
return -ENOMEM;
if (!filename_is_valid(ss))
return -EINVAL;
if (!isempty(d)) {
x = strdup(skip_leading_chars(d, CHAR_TO_STR(delimiter)));
if (!x)
return -EINVAL;
/* Make sure to convert Windows-style "\" → Unix-style / */
for (char *i = x; *i; i++)
if (*i == delimiter)
*i = '/';
if (!path_is_valid(x))
return -EINVAL;
path_simplify(x);
if (!path_is_normalized(x))
return -EINVAL;
}
if (ret_host)
*ret_host = TAKE_PTR(h);
if (ret_service)
*ret_service = TAKE_PTR(ss);
if (ret_path)
*ret_path = TAKE_PTR(x);
return 0;
}
int open_mkdir_at_full(int dirfd, const char *path, int flags, XOpenFlags xopen_flags, mode_t mode) {
_cleanup_close_ int fd = -EBADF, parent_fd = -EBADF;
_cleanup_free_ char *fname = NULL, *parent = NULL;
int r;
/* Creates a directory with mkdirat() and then opens it, in the "most atomic" fashion we can
* do. Guarantees that the returned fd refers to a directory. If O_EXCL is specified will fail if the
* dir already exists. Otherwise will open an existing dir, but only if it is one. */
if (flags & ~(O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_EXCL|O_NOATIME|O_NOFOLLOW|O_PATH))
return -EINVAL;
if ((flags & O_ACCMODE) != O_RDONLY)
return -EINVAL;
/* Note that O_DIRECTORY|O_NOFOLLOW is implied, but we allow specifying it anyway. The following
* flags actually make sense to specify: O_CLOEXEC, O_EXCL, O_NOATIME, O_PATH */
/* If this is not a valid filename, it's a path. Let's open the parent directory then, so
* that we can pin it, and operate below it. */
r = path_extract_directory(path, &parent);
if (r < 0) {
if (!IN_SET(r, -EDESTADDRREQ, -EADDRNOTAVAIL))
return r;
} else {
r = path_extract_filename(path, &fname);
if (r < 0)
return r;
parent_fd = openat(dirfd, parent, O_PATH|O_DIRECTORY|O_CLOEXEC);
if (parent_fd < 0)
return -errno;
dirfd = parent_fd;
path = fname;
}
fd = xopenat_full(dirfd, path, flags|O_CREAT|O_DIRECTORY|O_NOFOLLOW, xopen_flags, mode);
if (IN_SET(fd, -ELOOP, -ENOTDIR))
return -EEXIST;
if (fd < 0)
return fd;
return TAKE_FD(fd);
}
int openat_report_new(int dirfd, const char *pathname, int flags, mode_t mode, bool *ret_newly_created) {
int fd;
/* Just like openat(), but adds one thing: optionally returns whether we created the file anew or if
* it already existed before. This is only relevant if O_CREAT is set without O_EXCL, and thus will
* shortcut to openat() otherwise.
*
* Note that this routine is a bit more strict with symlinks than regular openat() is. If O_NOFOLLOW
* is not specified, then we'll follow the symlink when opening an existing file but we will *not*
* follow it when creating a new one (because that's a terrible UNIX misfeature and generally a
* security hole). */
if (!FLAGS_SET(flags, O_CREAT) || FLAGS_SET(flags, O_EXCL)) {
fd = openat(dirfd, pathname, flags, mode);
if (fd < 0)
return -errno;
if (ret_newly_created)
*ret_newly_created = FLAGS_SET(flags, O_CREAT);
return fd;
}
for (unsigned attempts = 7;;) {
/* First, attempt to open without O_CREAT/O_EXCL, i.e. open existing file */
fd = openat(dirfd, pathname, flags & ~(O_CREAT | O_EXCL), mode);
if (fd >= 0) {
if (ret_newly_created)
*ret_newly_created = false;
return fd;
}
if (errno != ENOENT)
return -errno;
/* So the file didn't exist yet, hence create it with O_CREAT/O_EXCL/O_NOFOLLOW. */
fd = openat(dirfd, pathname, flags | O_CREAT | O_EXCL | O_NOFOLLOW, mode);
if (fd >= 0) {
if (ret_newly_created)
*ret_newly_created = true;
return fd;
}
if (errno != EEXIST)
return -errno;
/* Hmm, so now we got EEXIST? Then someone might have created the file between the first and
* second call to openat(). Let's try again but with a limit so we don't spin forever. */
if (--attempts == 0) /* Give up eventually, somebody is playing with us */
return -EEXIST;
}
}
int xopenat_full(int dir_fd, const char *path, int open_flags, XOpenFlags xopen_flags, mode_t mode) {
_cleanup_close_ int fd = -EBADF;
bool made_dir = false, made_file = false;
int r;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
/* This is like openat(), but has a few tricks up its sleeves, extending behaviour:
*
* • O_DIRECTORY|O_CREAT is supported, which causes a directory to be created, and immediately
* opened. When used with the XO_SUBVOLUME flag this will even create a btrfs subvolume.
*
* • If O_CREAT is used with XO_LABEL, any created file will be immediately relabelled.
*
* • If the path is specified NULL or empty, behaves like fd_reopen().
*/
if (isempty(path)) {
assert(!FLAGS_SET(open_flags, O_CREAT|O_EXCL));
return fd_reopen(dir_fd, open_flags & ~O_NOFOLLOW);
}
bool call_label_ops_post = false;
if (FLAGS_SET(open_flags, O_CREAT) && FLAGS_SET(xopen_flags, XO_LABEL)) {
r = label_ops_pre(dir_fd, path, FLAGS_SET(open_flags, O_DIRECTORY) ? S_IFDIR : S_IFREG);
if (r < 0)
return r;
call_label_ops_post = true;
}
if (FLAGS_SET(open_flags, O_DIRECTORY|O_CREAT)) {
if (FLAGS_SET(xopen_flags, XO_SUBVOLUME))
r = btrfs_subvol_make_fallback(dir_fd, path, mode);
else
r = RET_NERRNO(mkdirat(dir_fd, path, mode));
if (r == -EEXIST) {
if (FLAGS_SET(open_flags, O_EXCL))
return -EEXIST;
} else if (r < 0)
return r;
else
made_dir = true;
open_flags &= ~(O_EXCL|O_CREAT);
}
fd = openat_report_new(dir_fd, path, open_flags, mode, &made_file);
if (fd < 0) {
r = fd;
goto error;
}
if (call_label_ops_post) {
call_label_ops_post = false;
r = label_ops_post(fd, /* path= */ NULL, made_file || made_dir);
if (r < 0)
goto error;
}
if (FLAGS_SET(xopen_flags, XO_NOCOW)) {
r = chattr_fd(fd, FS_NOCOW_FL, FS_NOCOW_FL, NULL);
if (r < 0 && !ERRNO_IS_NOT_SUPPORTED(r))
goto error;
}
return TAKE_FD(fd);
error:
if (call_label_ops_post)
(void) label_ops_post(fd >= 0 ? fd : dir_fd, fd >= 0 ? NULL : path, made_dir || made_file);
if (made_dir || made_file)
(void) unlinkat(dir_fd, path, made_dir ? AT_REMOVEDIR : 0);
return r;
}
int xopenat_lock_full(
int dir_fd,
const char *path,
int open_flags,
XOpenFlags xopen_flags,
mode_t mode,
LockType locktype,
int operation) {
_cleanup_close_ int fd = -EBADF;
int r;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
assert(IN_SET(operation & ~LOCK_NB, LOCK_EX, LOCK_SH));
/* POSIX/UNPOSIX locks don't work on directories (errno is set to -EBADF so let's return early with
* the same error here). */
if (FLAGS_SET(open_flags, O_DIRECTORY) && !IN_SET(locktype, LOCK_BSD, LOCK_NONE))
return -EBADF;
for (;;) {
struct stat st;
fd = xopenat_full(dir_fd, path, open_flags, xopen_flags, mode);
if (fd < 0)
return fd;
r = lock_generic(fd, locktype, operation);
if (r < 0)
return r;
/* If we acquired the lock, let's check if the file/directory still exists in the file
* system. If not, then the previous exclusive owner removed it and then closed it. In such a
* case our acquired lock is worthless, hence try again. */
if (fstat(fd, &st) < 0)
return -errno;
if (st.st_nlink > 0)
break;
fd = safe_close(fd);
}
return TAKE_FD(fd);
}
int link_fd(int fd, int newdirfd, const char *newpath) {
int r, k;
assert(fd >= 0);
assert(newdirfd >= 0 || newdirfd == AT_FDCWD); assert(newpath);
/* Try linking via /proc/self/fd/ first. */
r = RET_NERRNO(linkat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), newdirfd, newpath, AT_SYMLINK_FOLLOW));
if (r != -ENOENT)
return r;
/* Fall back to symlinking via AT_EMPTY_PATH as fallback (this requires CAP_DAC_READ_SEARCH and a
* more recent kernel, but does not require /proc/ mounted) */
k = proc_mounted();
if (k < 0)
return r;
if (k > 0)
return -EBADF;
return RET_NERRNO(linkat(fd, "", newdirfd, newpath, AT_EMPTY_PATH));
}
int linkat_replace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath) {
_cleanup_close_ int old_fd = -EBADF;
int r;
assert(olddirfd >= 0 || olddirfd == AT_FDCWD);
assert(newdirfd >= 0 || newdirfd == AT_FDCWD);
assert(!isempty(newpath)); /* source path is optional, but the target path is not */
/* Like linkat() but replaces the target if needed. Is a NOP if source and target already share the
* same inode. */
if (olddirfd == AT_FDCWD && isempty(oldpath)) /* Refuse operating on the cwd (which is a dir, and dirs can't be hardlinked) */
return -EISDIR;
if (path_implies_directory(oldpath)) /* Refuse these definite directories early */
return -EISDIR;
if (path_implies_directory(newpath))
return -EISDIR;
/* First, try to link this directly */
if (oldpath)
r = RET_NERRNO(linkat(olddirfd, oldpath, newdirfd, newpath, 0));
else
r = link_fd(olddirfd, newdirfd, newpath);
if (r >= 0)
return 0;
if (r != -EEXIST)
return r;
old_fd = xopenat(olddirfd, oldpath, O_PATH|O_CLOEXEC);
if (old_fd < 0)
return old_fd;
struct stat old_st;
if (fstat(old_fd, &old_st) < 0)
return -errno;
if (S_ISDIR(old_st.st_mode)) /* Don't bother if we are operating on a directory */
return -EISDIR;
struct stat new_st;
if (fstatat(newdirfd, newpath, &new_st, AT_SYMLINK_NOFOLLOW) < 0)
return -errno;
if (S_ISDIR(new_st.st_mode)) /* Refuse replacing directories */
return -EEXIST;
if (stat_inode_same(&old_st, &new_st)) /* Already the same inode? Then shortcut this */
return 0;
_cleanup_free_ char *tmp_path = NULL; r = tempfn_random(newpath, /* extra= */ NULL, &tmp_path);
if (r < 0)
return r;
r = link_fd(old_fd, newdirfd, tmp_path);
if (r < 0) {
if (!ERRNO_IS_PRIVILEGE(r))
return r;
/* If that didn't work due to permissions then go via the path of the dentry */
r = RET_NERRNO(linkat(olddirfd, oldpath, newdirfd, tmp_path, 0));
if (r < 0)
return r;
}
r = RET_NERRNO(renameat(newdirfd, tmp_path, newdirfd, newpath));
if (r < 0) {
(void) unlinkat(newdirfd, tmp_path, /* flags= */ 0);
return r;
}
return 0;
}