diff options
Diffstat (limited to 'src/basic/fs-util.c')
| -rw-r--r-- | src/basic/fs-util.c | 1358 |
1 files changed, 1358 insertions, 0 deletions
diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c new file mode 100644 index 0000000..f25bf2c --- /dev/null +++ b/src/basic/fs-util.c @@ -0,0 +1,1358 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#include <errno.h> +#include <stddef.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> +#include <linux/magic.h> +#include <time.h> +#include <unistd.h> + +#include "alloc-util.h" +#include "dirent-util.h" +#include "fd-util.h" +#include "fs-util.h" +#include "locale-util.h" +#include "log.h" +#include "macro.h" +#include "missing.h" +#include "mkdir.h" +#include "parse-util.h" +#include "path-util.h" +#include "process-util.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 "user-util.h" +#include "util.h" + +int unlink_noerrno(const char *path) { + PROTECT_ERRNO; + int r; + + r = unlink(path); + if (r < 0) + return -errno; + + return 0; +} + +int rmdir_parents(const char *path, const char *stop) { + size_t l; + int r = 0; + + assert(path); + assert(stop); + + l = strlen(path); + + /* Skip trailing slashes */ + while (l > 0 && path[l-1] == '/') + l--; + + while (l > 0) { + char *t; + + /* Skip last component */ + while (l > 0 && path[l-1] != '/') + l--; + + /* Skip trailing slashes */ + while (l > 0 && path[l-1] == '/') + l--; + + if (l <= 0) + break; + + t = strndup(path, l); + if (!t) + return -ENOMEM; + + if (path_startswith(stop, t)) { + free(t); + return 0; + } + + r = rmdir(t); + free(t); + + if (r < 0) + if (errno != ENOENT) + return -errno; + } + + return 0; +} + +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 (!IN_SET(errno, EINVAL, ENOSYS, ENOTTY)) + 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 â 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) { + + if (unlinkat(olddirfd, oldpath, 0) < 0) { + r = -errno; /* Backup errno before the following unlinkat() alters it */ + (void) unlinkat(newdirfd, newpath, 0); + return r; + } + + return 0; + } + + if (!IN_SET(errno, EINVAL, ENOSYS, ENOTTY, EPERM)) /* FAT returns EPERM on link()âĻ */ + return -errno; + + /* OK, neither RENAME_NOREPLACE nor linkat()+unlinkat() worked. Let's then fallback 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; + + if (renameat(olddirfd, oldpath, newdirfd, newpath) < 0) + return -errno; + + return 0; +} + +int readlinkat_malloc(int fd, const char *p, char **ret) { + size_t l = FILENAME_MAX+1; + int r; + + assert(p); + assert(ret); + + for (;;) { + char *c; + ssize_t n; + + c = new(char, l); + if (!c) + return -ENOMEM; + + n = readlinkat(fd, p, c, l-1); + if (n < 0) { + r = -errno; + free(c); + return r; + } + + if ((size_t) n < l-1) { + c[n] = 0; + *ret = c; + return 0; + } + + free(c); + 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; + char *value; + int r; + + r = readlink_malloc(p, &link); + if (r < 0) + return r; + + value = basename(link); + if (!value) + return -ENOENT; + + value = strdup(value); + if (!value) + return -ENOMEM; + + *ret = value; + + 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) { + char fd_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; + _cleanup_close_ int fd = -1; + assert(path); + + /* Under the assumption that we are running privileged we first change the access mode and only then hand out + * ownership to avoid a window where access is too open. */ + + 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; + + xsprintf(fd_path, "/proc/self/fd/%i", fd); + + if (mode != MODE_INVALID) { + + if ((mode & S_IFMT) != 0) { + struct stat st; + + if (stat(fd_path, &st) < 0) + return -errno; + + if ((mode & S_IFMT) != (st.st_mode & S_IFMT)) + return -EINVAL; + } + + if (chmod(fd_path, mode & 07777) < 0) + return -errno; + } + + if (uid != UID_INVALID || gid != GID_INVALID) + if (chown(fd_path, uid, gid) < 0) + return -errno; + + return 0; +} + +int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) { + /* Under the assumption that we are running privileged we first change the access mode and only then hand out + * ownership to avoid a window where access is too open. */ + + if (mode != MODE_INVALID) { + + if ((mode & S_IFMT) != 0) { + struct stat st; + + if (fstat(fd, &st) < 0) + return -errno; + + if ((mode & S_IFMT) != (st.st_mode & S_IFMT)) + return -EINVAL; + } + + if (fchmod(fd, mode & 0777) < 0) + return -errno; + } + + if (uid != UID_INVALID || gid != GID_INVALID) + if (fchown(fd, uid, gid) < 0) + return -errno; + + return 0; +} + +int fchmod_umask(int fd, mode_t m) { + mode_t u; + int r; + + u = umask(0777); + r = fchmod(fd, m & (~u)) < 0 ? -errno : 0; + umask(u); + + return r; +} + +int fchmod_opath(int fd, mode_t m) { + char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; + + /* 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. */ + + xsprintf(procfs_path, "/proc/self/fd/%i", fd); + if (chmod(procfs_path, m) < 0) + return -errno; + + return 0; +} + +int fd_warn_permissions(const char *path, int fd) { + struct stat st; + + if (fstat(fd, &st) < 0) + return -errno; + + 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 touch_file(const char *path, bool parents, usec_t stamp, uid_t uid, gid_t gid, mode_t mode) { + char fdpath[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; + _cleanup_close_ int fd = -1; + int r, ret = 0; + + 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 â which is + * something fchown(), fchmod(), futimensat() don't allow. */ + xsprintf(fdpath, "/proc/self/fd/%i", fd); + + if (mode != MODE_INVALID) + if (chmod(fdpath, mode) < 0) + ret = -errno; + + if (uid_is_valid(uid) || gid_is_valid(gid)) + if (chown(fdpath, uid, gid) < 0 && ret >= 0) + ret = -errno; + + if (stamp != USEC_INFINITY) { + struct timespec ts[2]; + + timespec_store(&ts[0], stamp); + ts[1] = ts[0]; + r = utimensat(AT_FDCWD, fdpath, ts, 0); + } else + r = utimensat(AT_FDCWD, fdpath, NULL, 0); + if (r < 0 && ret >= 0) + return -errno; + + return ret; +} + +int touch(const char *path) { + return touch_file(path, false, USEC_INFINITY, UID_INVALID, GID_INVALID, MODE_INVALID); +} + +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) { + _cleanup_free_ char *parent = NULL; + + parent = dirname_malloc(to); + if (!parent) + return -ENOMEM; + + r = path_make_relative(parent, 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 symlink_atomic(const char *from, const char *to) { + _cleanup_free_ char *t = NULL; + int r; + + assert(from); + assert(to); + + r = tempfn_random(to, NULL, &t); + if (r < 0) + return r; + + if (symlink(from, t) < 0) + return -errno; + + if (rename(t, to) < 0) { + unlink_noerrno(t); + return -errno; + } + + return 0; +} + +int mknod_atomic(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 (mknod(t, mode, dev) < 0) + return -errno; + + if (rename(t, path) < 0) { + unlink_noerrno(t); + return -errno; + } + + return 0; +} + +int mkfifo_atomic(const char *path, mode_t mode) { + _cleanup_free_ char *t = NULL; + int r; + + assert(path); + + r = tempfn_random(path, NULL, &t); + if (r < 0) + return r; + + if (mkfifo(t, mode) < 0) + return -errno; + + if (rename(t, path) < 0) { + unlink_noerrno(t); + return -errno; + } + + return 0; +} + +int mkfifoat_atomic(int dirfd, const char *path, mode_t mode) { + _cleanup_free_ char *t = NULL; + int r; + + assert(path); + + if (path_is_absolute(path)) + return mkfifo_atomic(path, mode); + + /* We're only interested in the (random) filename. */ + r = tempfn_random_child("", NULL, &t); + if (r < 0) + return r; + + if (mkfifoat(dirfd, t, mode) < 0) + return -errno; + + if (renameat(dirfd, t, dirfd, path) < 0) { + unlink_noerrno(t); + return -errno; + } + + return 0; +} + +int get_files_in_directory(const char *path, char ***list) { + _cleanup_closedir_ DIR *d = NULL; + struct dirent *de; + size_t bufsize = 0, n = 0; + _cleanup_strv_free_ char **l = NULL; + + 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) { + dirent_ensure_type(d, de); + + if (!dirent_is_file(de)) + continue; + + if (list) { + /* one extra slot is needed for the terminating NULL */ + if (!GREEDY_REALLOC(l, bufsize, 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) { + const char *n; + 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 inotify_add_watch_fd(int fd, int what, uint32_t mask) { + char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1]; + int r; + + /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */ + xsprintf(path, "/proc/self/fd/%i", what); + + r = inotify_add_watch(fd, path, mask); + if (r < 0) + return -errno; + + return r; +} + +static bool unsafe_transition(const struct stat *a, const struct stat *b) { + /* Returns true if the transition from a to b is safe, i.e. that we never transition from unprivileged to + * privileged files or directories. Why bother? So that unprivileged code can't symlink to privileged files + * making us believe we read something safe even though it isn't safe in the specific context we open it in. */ + + if (a->st_uid == 0) /* Transitioning from privileged to unprivileged is always fine */ + return false; + + return a->st_uid != b->st_uid; /* Otherwise we need to stay within the same UID */ +} + +static int log_unsafe_transition(int a, int b, const char *path, unsigned flags) { + _cleanup_free_ char *n1 = NULL, *n2 = NULL; + + if (!FLAGS_SET(flags, CHASE_WARN)) + return -ENOLINK; + + (void) fd_get_path(a, &n1); + (void) fd_get_path(b, &n2); + + return log_warning_errno(SYNTHETIC_ERRNO(ENOLINK), + "Detected unsafe path transition %s %s %s during canonicalization of %s.", + n1, special_glyph(SPECIAL_GLYPH_ARROW), n2, path); +} + +static int log_autofs_mount_point(int fd, const char *path, unsigned flags) { + _cleanup_free_ char *n1 = NULL; + + if (!FLAGS_SET(flags, CHASE_WARN)) + return -EREMOTE; + + (void) fd_get_path(fd, &n1); + + return log_warning_errno(SYNTHETIC_ERRNO(EREMOTE), + "Detected autofs mount point %s during canonicalization of %s.", + n1, path); +} + +int chase_symlinks(const char *path, const char *original_root, unsigned flags, char **ret) { + _cleanup_free_ char *buffer = NULL, *done = NULL, *root = NULL; + _cleanup_close_ int fd = -1; + unsigned max_follow = CHASE_SYMLINKS_MAX; /* how many symlinks to follow before giving up and returning ELOOP */ + struct stat previous_stat; + bool exists = true; + char *todo; + int r; + + assert(path); + + /* Either the file may be missing, or we return an fd to the final object, but both make no sense */ + if (FLAGS_SET(flags, CHASE_NONEXISTENT | CHASE_OPEN)) + return -EINVAL; + + if (FLAGS_SET(flags, CHASE_STEP | CHASE_OPEN)) + return -EINVAL; + + if (isempty(path)) + return -EINVAL; + + /* This is a lot like canonicalize_file_name(), but takes an additional "root" parameter, that allows following + * symlinks relative to a root directory, instead of the root of the host. + * + * Note that "root" primarily matters if we encounter an absolute symlink. It is also used when following + * relative symlinks to ensure they cannot be used to "escape" the root directory. The path parameter passed is + * assumed to be already prefixed by it, except if the CHASE_PREFIX_ROOT flag is set, in which case it is first + * prefixed accordingly. + * + * Algorithmically this operates on two path buffers: "done" are the components of the path we already + * processed and resolved symlinks, "." and ".." of. "todo" are the components of the path we still need to + * process. On each iteration, we move one component from "todo" to "done", processing it's special meaning + * each time. The "todo" path always starts with at least one slash, the "done" path always ends in no + * slash. We always keep an O_PATH fd to the component we are currently processing, thus keeping lookup races + * at a minimum. + * + * Suggested usage: whenever you want to canonicalize a path, use this function. Pass the absolute path you got + * as-is: fully qualified and relative to your host's root. Optionally, specify the root parameter to tell this + * function what to do when encountering a symlink with an absolute path as directory: prefix it by the + * specified path. + * + * There are three ways to invoke this function: + * + * 1. Without CHASE_STEP or CHASE_OPEN: in this case the path is resolved and the normalized path is returned + * in `ret`. The return value is < 0 on error. If CHASE_NONEXISTENT is also set 0 is returned if the file + * doesn't exist, > 0 otherwise. If CHASE_NONEXISTENT is not set >= 0 is returned if the destination was + * found, -ENOENT if it doesn't. + * + * 2. With CHASE_OPEN: in this case the destination is opened after chasing it as O_PATH and this file + * descriptor is returned as return value. This is useful to open files relative to some root + * directory. Note that the returned O_PATH file descriptors must be converted into a regular one (using + * fd_reopen() or such) before it can be used for reading/writing. CHASE_OPEN may not be combined with + * CHASE_NONEXISTENT. + * + * 3. With CHASE_STEP: in this case only a single step of the normalization is executed, i.e. only the first + * symlink or ".." component of the path is resolved, and the resulting path is returned. This is useful if + * a caller wants to trace the a path through the file system verbosely. Returns < 0 on error, > 0 if the + * path is fully normalized, and == 0 for each normalization step. This may be combined with + * CHASE_NONEXISTENT, in which case 1 is returned when a component is not found. + * + * 4. With CHASE_SAFE: in this case the path must not contain unsafe transitions, i.e. transitions from + * unprivileged to privileged files or directories. In such cases the return value is -ENOLINK. If + * CHASE_WARN is also set a warning describing the unsafe transition is emitted. + * + * 5. With CHASE_NO_AUTOFS: in this case if an autofs mount point is encountered, the path normalization is + * aborted and -EREMOTE is returned. If CHASE_WARN is also set a warning showing the path of the mount point + * is emitted. + * + * */ + + /* A root directory of "/" or "" is identical to none */ + if (empty_or_root(original_root)) + original_root = NULL; + + if (!original_root && !ret && (flags & (CHASE_NONEXISTENT|CHASE_NO_AUTOFS|CHASE_SAFE|CHASE_OPEN|CHASE_STEP)) == CHASE_OPEN) { + /* Shortcut the CHASE_OPEN case if the caller isn't interested in the actual path and has no root set + * and doesn't care about any of the other special features we provide either. */ + r = open(path, O_PATH|O_CLOEXEC|((flags & CHASE_NOFOLLOW) ? O_NOFOLLOW : 0)); + if (r < 0) + return -errno; + + return r; + } + + if (original_root) { + r = path_make_absolute_cwd(original_root, &root); + if (r < 0) + return r; + + if (flags & CHASE_PREFIX_ROOT) { + + /* We don't support relative paths in combination with a root directory */ + if (!path_is_absolute(path)) + return -EINVAL; + + path = prefix_roota(root, path); + } + } + + r = path_make_absolute_cwd(path, &buffer); + if (r < 0) + return r; + + fd = open("/", O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (fd < 0) + return -errno; + + if (flags & CHASE_SAFE) { + if (fstat(fd, &previous_stat) < 0) + return -errno; + } + + todo = buffer; + for (;;) { + _cleanup_free_ char *first = NULL; + _cleanup_close_ int child = -1; + struct stat st; + size_t n, m; + + /* Determine length of first component in the path */ + n = strspn(todo, "/"); /* The slashes */ + m = n + strcspn(todo + n, "/"); /* The entire length of the component */ + + /* Extract the first component. */ + first = strndup(todo, m); + if (!first) + return -ENOMEM; + + todo += m; + + /* Empty? Then we reached the end. */ + if (isempty(first)) + break; + + /* Just a single slash? Then we reached the end. */ + if (path_equal(first, "/")) { + /* Preserve the trailing slash */ + + if (flags & CHASE_TRAIL_SLASH) + if (!strextend(&done, "/", NULL)) + return -ENOMEM; + + break; + } + + /* Just a dot? Then let's eat this up. */ + if (path_equal(first, "/.")) + continue; + + /* Two dots? Then chop off the last bit of what we already found out. */ + if (path_equal(first, "/..")) { + _cleanup_free_ char *parent = NULL; + _cleanup_close_ int fd_parent = -1; + + /* If we already are at the top, then going up will not change anything. This is in-line with + * how the kernel handles this. */ + if (empty_or_root(done)) + continue; + + parent = dirname_malloc(done); + if (!parent) + return -ENOMEM; + + /* Don't allow this to leave the root dir. */ + if (root && + path_startswith(done, root) && + !path_startswith(parent, root)) + continue; + + free_and_replace(done, parent); + + if (flags & CHASE_STEP) + goto chased_one; + + fd_parent = openat(fd, "..", O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (fd_parent < 0) + return -errno; + + if (flags & CHASE_SAFE) { + if (fstat(fd_parent, &st) < 0) + return -errno; + + if (unsafe_transition(&previous_stat, &st)) + return log_unsafe_transition(fd, fd_parent, path, flags); + + previous_stat = st; + } + + safe_close(fd); + fd = TAKE_FD(fd_parent); + + continue; + } + + /* Otherwise let's see what this is. */ + child = openat(fd, first + n, O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (child < 0) { + + if (errno == ENOENT && + (flags & CHASE_NONEXISTENT) && + (isempty(todo) || path_is_normalized(todo))) { + + /* If CHASE_NONEXISTENT is set, and the path does not exist, then that's OK, return + * what we got so far. But don't allow this if the remaining path contains "../ or "./" + * or something else weird. */ + + /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */ + if (streq_ptr(done, "/")) + *done = '\0'; + + if (!strextend(&done, first, todo, NULL)) + return -ENOMEM; + + exists = false; + break; + } + + return -errno; + } + + if (fstat(child, &st) < 0) + return -errno; + if ((flags & CHASE_SAFE) && + unsafe_transition(&previous_stat, &st)) + return log_unsafe_transition(fd, child, path, flags); + + previous_stat = st; + + if ((flags & CHASE_NO_AUTOFS) && + fd_is_fs_type(child, AUTOFS_SUPER_MAGIC) > 0) + return log_autofs_mount_point(child, path, flags); + + if (S_ISLNK(st.st_mode) && !((flags & CHASE_NOFOLLOW) && isempty(todo))) { + char *joined; + + _cleanup_free_ char *destination = NULL; + + /* This is a symlink, in this case read the destination. But let's make sure we don't follow + * symlinks without bounds. */ + if (--max_follow <= 0) + return -ELOOP; + + r = readlinkat_malloc(fd, first + n, &destination); + if (r < 0) + return r; + if (isempty(destination)) + return -EINVAL; + + if (path_is_absolute(destination)) { + + /* An absolute destination. Start the loop from the beginning, but use the root + * directory as base. */ + + safe_close(fd); + fd = open(root ?: "/", O_CLOEXEC|O_NOFOLLOW|O_PATH); + if (fd < 0) + return -errno; + + if (flags & CHASE_SAFE) { + if (fstat(fd, &st) < 0) + return -errno; + + if (unsafe_transition(&previous_stat, &st)) + return log_unsafe_transition(child, fd, path, flags); + + previous_stat = st; + } + + free(done); + + /* Note that we do not revalidate the root, we take it as is. */ + if (isempty(root)) + done = NULL; + else { + done = strdup(root); + if (!done) + return -ENOMEM; + } + + /* Prefix what's left to do with what we just read, and start the loop again, but + * remain in the current directory. */ + joined = strjoin(destination, todo); + } else + joined = strjoin("/", destination, todo); + if (!joined) + return -ENOMEM; + + free(buffer); + todo = buffer = joined; + + if (flags & CHASE_STEP) + goto chased_one; + + continue; + } + + /* If this is not a symlink, then let's just add the name we read to what we already verified. */ + if (!done) + done = TAKE_PTR(first); + else { + /* If done is "/", as first also contains slash at the head, then remove this redundant slash. */ + if (streq(done, "/")) + *done = '\0'; + + if (!strextend(&done, first, NULL)) + return -ENOMEM; + } + + /* And iterate again, but go one directory further down. */ + safe_close(fd); + fd = TAKE_FD(child); + } + + if (!done) { + /* Special case, turn the empty string into "/", to indicate the root directory. */ + done = strdup("/"); + if (!done) + return -ENOMEM; + } + + if (ret) + *ret = TAKE_PTR(done); + + if (flags & CHASE_OPEN) { + /* Return the O_PATH fd we currently are looking to the caller. It can translate it to a proper fd by + * opening /proc/self/fd/xyz. */ + + assert(fd >= 0); + return TAKE_FD(fd); + } + + if (flags & CHASE_STEP) + return 1; + + return exists; + +chased_one: + if (ret) { + char *c; + + c = strjoin(strempty(done), todo); + if (!c) + return -ENOMEM; + + *ret = c; + } + + return 0; +} + +int chase_symlinks_and_open( + const char *path, + const char *root, + unsigned chase_flags, + int open_flags, + char **ret_path) { + + _cleanup_close_ int path_fd = -1; + _cleanup_free_ char *p = NULL; + int r; + + if (chase_flags & CHASE_NONEXISTENT) + return -EINVAL; + + if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { + /* Shortcut this call if none of the special features of this call are requested */ + r = open(path, open_flags); + if (r < 0) + return -errno; + + return r; + } + + path_fd = chase_symlinks(path, root, chase_flags|CHASE_OPEN, ret_path ? &p : NULL); + if (path_fd < 0) + return path_fd; + + r = fd_reopen(path_fd, open_flags); + if (r < 0) + return r; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + return r; +} + +int chase_symlinks_and_opendir( + const char *path, + const char *root, + unsigned chase_flags, + char **ret_path, + DIR **ret_dir) { + + char procfs_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; + _cleanup_close_ int path_fd = -1; + _cleanup_free_ char *p = NULL; + DIR *d; + + if (!ret_dir) + return -EINVAL; + if (chase_flags & CHASE_NONEXISTENT) + return -EINVAL; + + if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { + /* Shortcut this call if none of the special features of this call are requested */ + d = opendir(path); + if (!d) + return -errno; + + *ret_dir = d; + return 0; + } + + path_fd = chase_symlinks(path, root, chase_flags|CHASE_OPEN, ret_path ? &p : NULL); + if (path_fd < 0) + return path_fd; + + xsprintf(procfs_path, "/proc/self/fd/%i", path_fd); + d = opendir(procfs_path); + if (!d) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + *ret_dir = d; + return 0; +} + +int chase_symlinks_and_stat( + const char *path, + const char *root, + unsigned chase_flags, + char **ret_path, + struct stat *ret_stat) { + + _cleanup_close_ int path_fd = -1; + _cleanup_free_ char *p = NULL; + + assert(path); + assert(ret_stat); + + if (chase_flags & CHASE_NONEXISTENT) + return -EINVAL; + + if (empty_or_root(root) && !ret_path && (chase_flags & (CHASE_NO_AUTOFS|CHASE_SAFE)) == 0) { + /* Shortcut this call if none of the special features of this call are requested */ + if (stat(path, ret_stat) < 0) + return -errno; + + return 1; + } + + path_fd = chase_symlinks(path, root, chase_flags|CHASE_OPEN, ret_path ? &p : NULL); + if (path_fd < 0) + return path_fd; + + if (fstat(path_fd, ret_stat) < 0) + return -errno; + + if (ret_path) + *ret_path = TAKE_PTR(p); + + if (chase_flags & CHASE_OPEN) + return TAKE_FD(path_fd); + + return 1; +} + +int access_fd(int fd, int mode) { + char p[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1]; + int r; + + /* Like access() but operates on an already open fd */ + + xsprintf(p, "/proc/self/fd/%i", fd); + r = access(p, mode); + if (r < 0) + return -errno; + + return r; +} + +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, int flags) { + _cleanup_close_ int truncate_fd = -1; + struct stat st; + off_t l, bs; + + /* 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 (đ) 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 (đĒ), as our goal of deallocating the data space trumps our goal of being nice to readers (đ). + * + * Note that we attempt deallocation, but failure to succeed with that is not considered fatal, as long as the + * primary job â to delete the file â is accomplished. */ + + if ((flags & AT_REMOVEDIR) == 0) { + 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) < 0) + return -errno; + + if (truncate_fd < 0) /* Don't have a file handle, can't do more âšī¸ */ + 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) || 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! đ */ + + /* 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 fsync_directory_of_file(int fd) { + _cleanup_free_ char *path = NULL; + _cleanup_close_ int dfd = -1; + int r; + + r = fd_verify_regular(fd); + if (r < 0) + return r; + + r = fd_get_path(fd, &path); + if (r < 0) { + log_debug_errno(r, "Failed to query /proc/self/fd/%d%s: %m", + fd, + r == -EOPNOTSUPP ? ", ignoring" : ""); + + if (r == -EOPNOTSUPP) + /* If /proc is not available, we're most likely running in some + * chroot environment, and syncing the directory is not very + * important in that case. Let's just silently do nothing. */ + return 0; + + return r; + } + + if (!path_is_absolute(path)) + return -EINVAL; + + dfd = open_parent(path, O_CLOEXEC, 0); + if (dfd < 0) + return dfd; + + if (fsync(dfd) < 0) + return -errno; + + return 0; +} + +int fsync_path_at(int at_fd, const char *path) { + _cleanup_close_ int opened_fd = -1; + int fd; + + if (isempty(path)) { + if (at_fd == AT_FDCWD) { + opened_fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC); + if (opened_fd < 0) + return -errno; + + fd = opened_fd; + } else + fd = at_fd; + } else { + + opened_fd = openat(at_fd, path, O_RDONLY|O_CLOEXEC); + if (opened_fd < 0) + return -errno; + + fd = opened_fd; + } + + if (fsync(fd) < 0) + return -errno; + + return 0; +} + +int open_parent(const char *path, int flags, mode_t mode) { + _cleanup_free_ char *parent = NULL; + int fd; + + if (isempty(path)) + return -EINVAL; + if (path_equal(path, "/")) /* requesting the parent of the root dir is fishy, let's prohibit that */ + return -EINVAL; + + parent = dirname_malloc(path); + if (!parent) + return -ENOMEM; + + /* 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 & O_PATH) == O_PATH) + flags |= O_DIRECTORY; + else if ((flags & O_TMPFILE) != O_TMPFILE) + flags |= O_DIRECTORY|O_RDONLY; + + fd = open(parent, flags, mode); + if (fd < 0) + return -errno; + + return fd; +} |