summaryrefslogtreecommitdiffstats
path: root/src/basic/fs-util.c
diff options
context:
space:
mode:
Diffstat (limited to '')
-rw-r--r--src/basic/fs-util.c1109
1 files changed, 1109 insertions, 0 deletions
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
new file mode 100644
index 0000000..6b757bd
--- /dev/null
+++ b/src/basic/fs-util.c
@@ -0,0 +1,1109 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <linux/falloc.h>
+#include <linux/magic.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "dirent-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "hostname-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"
+#include "util.h"
+
+int unlink_noerrno(const char *path) {
+ PROTECT_ERRNO;
+ return RET_NERRNO(unlink(path));
+}
+
+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 β€” 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(p);
+
+ for (;;) {
+ _cleanup_free_ char *c = NULL;
+ ssize_t n;
+
+ c = new(char, l+1);
+ if (!c)
+ return -ENOMEM;
+
+ n = readlinkat(fd, 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_malloc(const char *p, char **ret) {
+ return readlinkat_malloc(AT_FDCWD, p, ret);
+}
+
+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 **r) {
+ _cleanup_free_ char *target = NULL;
+ char *k;
+ int j;
+
+ assert(p);
+ assert(r);
+
+ j = readlink_malloc(p, &target);
+ if (j < 0)
+ return j;
+
+ k = file_in_same_dir(p, target);
+ if (!k)
+ return -ENOMEM;
+
+ *r = k;
+ return 0;
+}
+
+int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
+ _cleanup_close_ int fd = -1;
+
+ assert(path);
+
+ fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); /* Let's acquire an O_PATH fd, as precaution to change
+ * mode/owner on the same file */
+ if (fd < 0)
+ return -errno;
+
+ return fchmod_and_chown(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. Indeed fchmodat() doesn't have the AT_EMPTY_PATH flag like
+ * fchownat() does. */
+
+ if (chmod(FORMAT_PROC_FD_PATH(fd), m) < 0) {
+ if (errno != ENOENT)
+ return -errno;
+
+ if (proc_mounted() == 0)
+ return -ENOSYS; /* if we have no /proc/, the concept is not implementable */
+
+ return -ENOENT;
+ }
+
+ return 0;
+}
+
+int futimens_opath(int fd, const struct timespec ts[2]) {
+ /* Similar to fchmod_path() but for futimens() */
+
+ if (utimensat(AT_FDCWD, FORMAT_PROC_FD_PATH(fd), ts, 0) < 0) {
+ if (errno != ENOENT)
+ return -errno;
+
+ if (proc_mounted() == 0)
+ return -ENOSYS; /* if we have no /proc/, the concept is not implementable */
+
+ return -ENOENT;
+ }
+
+ 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_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) {
+ _cleanup_close_ int fd = -1;
+ int r, 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 β€” which is
+ * something fchown(), fchmod(), futimensat() don't allow. */
+ ret = fchmod_and_chown(fd, mode, uid, gid);
+
+ if (stamp != USEC_INFINITY) {
+ struct timespec ts[2];
+
+ timespec_store(&ts[0], stamp);
+ ts[1] = ts[0];
+ r = futimens_opath(fd, ts);
+ } else
+ r = futimens_opath(fd, NULL);
+ if (r < 0 && ret >= 0)
+ return r;
+
+ return ret;
+}
+
+int symlink_idempotent(const char *from, 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 (symlink(from, to) < 0) {
+ _cleanup_free_ char *p = NULL;
+
+ if (errno != EEXIST)
+ return -errno;
+
+ r = readlink_malloc(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, true);
+ if (k == 0)
+ k = -ENOTDIR;
+ if (k < 0)
+ return r < 0 ? r : k;
+
+ *ret = def;
+ return 0;
+}
+
+int var_tmp_dir(const char **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) {
+
+ /* 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) {
+ 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) {
+ /* Like access() but operates on an already open fd */
+
+ if (access(FORMAT_PROC_FD_PATH(fd), mode) < 0) {
+ if (errno != ENOENT)
+ return -errno;
+
+ /* 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 0;
+}
+
+void unlink_tempfilep(char (*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_noerrno(*p);
+}
+
+int unlinkat_deallocate(int fd, const char *name, UnlinkDeallocateFlags flags) {
+ _cleanup_close_ int truncate_fd = -1;
+ struct stat st;
+ off_t l, bs;
+
+ 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 (πŸ‘Š) 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 (πŸ”ͺ), as our goal of deallocating the data space trumps our goal of being nice to readers (πŸ’).
+ *
+ * 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 = DIV_ROUND_UP(st.st_size, bs) * 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(const char *path, int flags, mode_t mode) {
+ _cleanup_free_ char *parent = NULL;
+ int r;
+
+ r = path_extract_directory(path, &parent);
+ 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(open(parent, flags, mode));
+}
+
+int conservative_renameat(
+ int olddirfd, const char *oldpath,
+ int newdirfd, const char *newpath) {
+
+ _cleanup_close_ int old_fd = -1, new_fd = -1;
+ struct stat old_stat, new_stat;
+
+ /* Renames the old path to thew new path, much like renameat() β€” 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 = (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 "\" β†’ 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(int dirfd, const char *path, int flags, mode_t mode) {
+ _cleanup_close_ int fd = -1, parent_fd = -1;
+ _cleanup_free_ char *fname = NULL;
+ bool made;
+ 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 (isempty(path))
+ return -EINVAL;
+
+ if (!filename_is_valid(path)) {
+ _cleanup_free_ char *parent = NULL;
+
+ /* 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)
+ return r;
+
+ 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;
+ }
+
+ r = RET_NERRNO(mkdirat(dirfd, path, mode));
+ if (r == -EEXIST) {
+ if (FLAGS_SET(flags, O_EXCL))
+ return -EEXIST;
+
+ made = false;
+ } else if (r < 0)
+ return r;
+ else
+ made = true;
+
+ fd = RET_NERRNO(openat(dirfd, path, (flags & ~O_EXCL)|O_DIRECTORY|O_NOFOLLOW));
+ if (fd < 0) {
+ if (fd == -ENOENT) /* We got ENOENT? then someone else immediately removed it after we
+ * created it. In that case let's return immediately without unlinking
+ * anything, because there simply isn't anything to unlink anymore. */
+ return -ENOENT;
+ if (fd == -ELOOP) /* is a symlink? exists already β†’ created by someone else, don't unlink */
+ return -EEXIST;
+ if (fd == -ENOTDIR) /* not a directory? exists already β†’ created by someone else, don't unlink */
+ return -EEXIST;
+
+ if (made)
+ (void) unlinkat(dirfd, path, AT_REMOVEDIR);
+
+ return fd;
+ }
+
+ return TAKE_FD(fd);
+}
+
+int openat_report_new(int dirfd, const char *pathname, int flags, mode_t mode, bool *ret_newly_created) {
+ unsigned attempts = 7;
+ 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 */
+
+ if (!ret_newly_created)
+ return RET_NERRNO(openat(dirfd, pathname, flags, mode));
+
+ if (!FLAGS_SET(flags, O_CREAT) || FLAGS_SET(flags, O_EXCL)) {
+ fd = openat(dirfd, pathname, flags, mode);
+ if (fd < 0)
+ return -errno;
+
+ *ret_newly_created = FLAGS_SET(flags, O_CREAT);
+ return fd;
+ }
+
+ for (;;) {
+ /* 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) {
+ *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. */
+ fd = openat(dirfd, pathname, flags | O_CREAT | O_EXCL, mode);
+ if (fd >= 0) {
+ *ret_newly_created = true;
+ return fd;
+ }
+ if (errno != EEXIST)
+ return -errno;
+
+ /* Hmm, so now we got EEXIST? So it apparently exists now? If so, let's try to open again
+ * without the two flags. But let's not spin forever, hence put a limit on things */
+
+ if (--attempts == 0) /* Give up eventually, somebody is playing with us */
+ return -EEXIST;
+ }
+}