/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include "alloc-util.h" #include "extract-word.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "hashmap.h" #include "libmount-util.h" #include "mount-util.h" #include "mountpoint-util.h" #include "parse-util.h" #include "path-util.h" #include "set.h" #include "stat-util.h" #include "stdio-util.h" #include "string-util.h" #include "strv.h" int mount_fd(const char *source, int target_fd, const char *filesystemtype, unsigned long mountflags, const void *data) { char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)]; xsprintf(path, "/proc/self/fd/%i", target_fd); if (mount(source, path, filesystemtype, mountflags, data) < 0) { if (errno != ENOENT) return -errno; /* ENOENT can mean two things: either that the source is missing, or that /proc/ isn't * mounted. Check for the latter to generate better error messages. */ if (proc_mounted() == 0) return -ENOSYS; return -ENOENT; } return 0; } int mount_nofollow( const char *source, const char *target, const char *filesystemtype, unsigned long mountflags, const void *data) { _cleanup_close_ int fd = -1; /* In almost all cases we want to manipulate the mount table without following symlinks, hence * mount_nofollow() is usually the way to go. The only exceptions are environments where /proc/ is * not available yet, since we need /proc/self/fd/ for this logic to work. i.e. during the early * initialization of namespacing/container stuff where /proc is not yet mounted (and maybe even the * fs to mount) we can only use traditional mount() directly. * * Note that this disables following only for the final component of the target, i.e symlinks within * the path of the target are honoured, as are symlinks in the source path everywhere. */ fd = open(target, O_PATH|O_CLOEXEC|O_NOFOLLOW); if (fd < 0) return -errno; return mount_fd(source, fd, filesystemtype, mountflags, data); } int umount_recursive(const char *prefix, int flags) { int n = 0, r; bool again; /* Try to umount everything recursively below a * directory. Also, take care of stacked mounts, and keep * unmounting them until they are gone. */ do { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; again = false; r = libmount_parse("/proc/self/mountinfo", NULL, &table, &iter); if (r < 0) return log_debug_errno(r, "Failed to parse /proc/self/mountinfo: %m"); for (;;) { struct libmnt_fs *fs; const char *path; r = mnt_table_next_fs(table, iter, &fs); if (r == 1) break; if (r < 0) return log_debug_errno(r, "Failed to get next entry from /proc/self/mountinfo: %m"); path = mnt_fs_get_target(fs); if (!path) continue; if (!path_startswith(path, prefix)) continue; if (umount2(path, flags | UMOUNT_NOFOLLOW) < 0) { log_debug_errno(errno, "Failed to umount %s, ignoring: %m", path); continue; } log_debug("Successfully unmounted %s", path); again = true; n++; break; } } while (again); return n; } static int get_mount_flags( struct libmnt_table *table, const char *path, unsigned long *ret) { _cleanup_close_ int fd = -1; struct libmnt_fs *fs; struct statvfs buf; const char *opts; int r; /* Get the mount flags for the mountpoint at "path" from "table". We have a fallback using statvfs() * in place (which provides us with mostly the same info), but it's just a fallback, since using it * means triggering autofs or NFS mounts, which we'd rather avoid needlessly. * * This generally doesn't follow symlinks. */ fs = mnt_table_find_target(table, path, MNT_ITER_FORWARD); if (!fs) { log_debug("Could not find '%s' in mount table, ignoring.", path); goto fallback; } opts = mnt_fs_get_vfs_options(fs); if (!opts) { *ret = 0; return 0; } r = mnt_optstr_get_flags(opts, ret, mnt_get_builtin_optmap(MNT_LINUX_MAP)); if (r != 0) { log_debug_errno(r, "Could not get flags for '%s', ignoring: %m", path); goto fallback; } /* MS_RELATIME is default and trying to set it in an unprivileged container causes EPERM */ *ret &= ~MS_RELATIME; return 0; fallback: fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); if (fd < 0) return -errno; if (fstatvfs(fd, &buf) < 0) return -errno; /* The statvfs() flags and the mount flags mostly have the same values, but for some cases do * not. Hence map the flags manually. (Strictly speaking, ST_RELATIME/MS_RELATIME is the most * prominent one that doesn't match, but that's the one we mask away anyway, see above.) */ *ret = FLAGS_SET(buf.f_flag, ST_RDONLY) * MS_RDONLY | FLAGS_SET(buf.f_flag, ST_NODEV) * MS_NODEV | FLAGS_SET(buf.f_flag, ST_NOEXEC) * MS_NOEXEC | FLAGS_SET(buf.f_flag, ST_NOSUID) * MS_NOSUID | FLAGS_SET(buf.f_flag, ST_NOATIME) * MS_NOATIME | FLAGS_SET(buf.f_flag, ST_NODIRATIME) * MS_NODIRATIME; return 0; } /* Use this function only if you do not have direct access to /proc/self/mountinfo but the caller can open it * for you. This is the case when /proc is masked or not mounted. Otherwise, use bind_remount_recursive. */ int bind_remount_recursive_with_mountinfo( const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list, FILE *proc_self_mountinfo) { _cleanup_set_free_free_ Set *done = NULL; _cleanup_free_ char *simplified = NULL; int r; assert(prefix); assert(proc_self_mountinfo); /* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already * mounted, we reuse the mount and simply mark it MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write * operation). If it isn't we first make it one. Afterwards we apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to * all submounts we can access, too. When mounts are stacked on the same mount point we only care for each * individual "top-level" mount on each point, as we cannot influence/access the underlying mounts anyway. We * do not have any effect on future submounts that might get propagated, they might be writable. This includes * future submounts that have been triggered via autofs. * * If the "deny_list" parameter is specified it may contain a list of subtrees to exclude from the * remount operation. Note that we'll ignore the deny list for the top-level path. */ simplified = strdup(prefix); if (!simplified) return -ENOMEM; path_simplify(simplified, false); done = set_new(&path_hash_ops); if (!done) return -ENOMEM; for (;;) { _cleanup_set_free_free_ Set *todo = NULL; _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; bool top_autofs = false; char *x; unsigned long orig_flags; todo = set_new(&path_hash_ops); if (!todo) return -ENOMEM; rewind(proc_self_mountinfo); r = libmount_parse("/proc/self/mountinfo", proc_self_mountinfo, &table, &iter); if (r < 0) return log_debug_errno(r, "Failed to parse /proc/self/mountinfo: %m"); for (;;) { struct libmnt_fs *fs; const char *path, *type; r = mnt_table_next_fs(table, iter, &fs); if (r == 1) break; if (r < 0) return log_debug_errno(r, "Failed to get next entry from /proc/self/mountinfo: %m"); path = mnt_fs_get_target(fs); type = mnt_fs_get_fstype(fs); if (!path || !type) continue; if (!path_startswith(path, simplified)) continue; /* Ignore this mount if it is deny-listed, but only if it isn't the top-level mount * we shall operate on. */ if (!path_equal(path, simplified)) { bool deny_listed = false; char **i; STRV_FOREACH(i, deny_list) { if (path_equal(*i, simplified)) continue; if (!path_startswith(*i, simplified)) continue; if (path_startswith(path, *i)) { deny_listed = true; log_debug("Not remounting %s deny-listed by %s, called for %s", path, *i, simplified); break; } } if (deny_listed) continue; } /* Let's ignore autofs mounts. If they aren't * triggered yet, we want to avoid triggering * them, as we don't make any guarantees for * future submounts anyway. If they are * already triggered, then we will find * another entry for this. */ if (streq(type, "autofs")) { top_autofs = top_autofs || path_equal(path, simplified); continue; } if (!set_contains(done, path)) { r = set_put_strdup(&todo, path); if (r < 0) return r; } } /* If we have no submounts to process anymore and if * the root is either already done, or an autofs, we * are done */ if (set_isempty(todo) && (top_autofs || set_contains(done, simplified))) return 0; if (!set_contains(done, simplified) && !set_contains(todo, simplified)) { /* The prefix directory itself is not yet a mount, make it one. */ r = mount_nofollow(simplified, simplified, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; orig_flags = 0; (void) get_mount_flags(table, simplified, &orig_flags); r = mount_nofollow(NULL, simplified, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL); if (r < 0) return r; log_debug("Made top-level directory %s a mount point.", prefix); r = set_put_strdup(&done, simplified); if (r < 0) return r; } while ((x = set_steal_first(todo))) { r = set_consume(done, x); if (IN_SET(r, 0, -EEXIST)) continue; if (r < 0) return r; /* Deal with mount points that are obstructed by a later mount */ r = path_is_mount_point(x, NULL, 0); if (IN_SET(r, 0, -ENOENT)) continue; if (r < 0) { if (!ERRNO_IS_PRIVILEGE(r)) return r; /* Even if root user invoke this, submounts under private FUSE or NFS mount points * may not be acceessed. E.g., * * $ bindfs --no-allow-other ~/mnt/mnt ~/mnt/mnt * $ bindfs --no-allow-other ~/mnt ~/mnt * * Then, root user cannot access the mount point ~/mnt/mnt. * In such cases, the submounts are ignored, as we have no way to manage them. */ log_debug_errno(r, "Failed to determine '%s' is mount point or not, ignoring: %m", x); continue; } /* Try to reuse the original flag set */ orig_flags = 0; (void) get_mount_flags(table, x, &orig_flags); r = mount_nofollow(NULL, x, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL); if (r < 0) return r; log_debug("Remounted %s read-only.", x); } } } int bind_remount_recursive( const char *prefix, unsigned long new_flags, unsigned long flags_mask, char **deny_list) { _cleanup_fclose_ FILE *proc_self_mountinfo = NULL; int r; r = fopen_unlocked("/proc/self/mountinfo", "re", &proc_self_mountinfo); if (r < 0) return r; return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, deny_list, proc_self_mountinfo); } int bind_remount_one_with_mountinfo( const char *path, unsigned long new_flags, unsigned long flags_mask, FILE *proc_self_mountinfo) { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; unsigned long orig_flags = 0; int r; assert(path); assert(proc_self_mountinfo); rewind(proc_self_mountinfo); table = mnt_new_table(); if (!table) return -ENOMEM; r = mnt_table_parse_stream(table, proc_self_mountinfo, "/proc/self/mountinfo"); if (r < 0) return r; /* Try to reuse the original flag set */ (void) get_mount_flags(table, path, &orig_flags); r = mount_nofollow(NULL, path, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL); if (r < 0) return r; return 0; } int mount_move_root(const char *path) { assert(path); if (chdir(path) < 0) return -errno; if (mount(path, "/", NULL, MS_MOVE, NULL) < 0) return -errno; if (chroot(".") < 0) return -errno; if (chdir("/") < 0) return -errno; return 0; } int repeat_unmount(const char *path, int flags) { bool done = false; assert(path); /* If there are multiple mounts on a mount point, this * removes them all */ for (;;) { if (umount2(path, flags) < 0) { if (errno == EINVAL) return done; return -errno; } done = true; } } int mode_to_inaccessible_node( const char *runtime_dir, mode_t mode, char **ret) { /* This function maps a node type to a corresponding inaccessible file node. These nodes are created * during early boot by PID 1. In some cases we lacked the privs to create the character and block * devices (maybe because we run in an userns environment, or miss CAP_SYS_MKNOD, or run with a * devices policy that excludes device nodes with major and minor of 0), but that's fine, in that * case we use an AF_UNIX file node instead, which is not the same, but close enough for most * uses. And most importantly, the kernel allows bind mounts from socket nodes to any non-directory * file nodes, and that's the most important thing that matters. * * Note that the runtime directory argument shall be the top-level runtime directory, i.e. /run/ if * we operate in system context and $XDG_RUNTIME_DIR if we operate in user context. */ _cleanup_free_ char *d = NULL; const char *node = NULL; assert(ret); if (!runtime_dir) runtime_dir = "/run"; switch(mode & S_IFMT) { case S_IFREG: node = "/systemd/inaccessible/reg"; break; case S_IFDIR: node = "/systemd/inaccessible/dir"; break; case S_IFCHR: node = "/systemd/inaccessible/chr"; break; case S_IFBLK: node = "/systemd/inaccessible/blk"; break; case S_IFIFO: node = "/systemd/inaccessible/fifo"; break; case S_IFSOCK: node = "/systemd/inaccessible/sock"; break; } if (!node) return -EINVAL; d = path_join(runtime_dir, node); if (!d) return -ENOMEM; /* On new kernels unprivileged users are permitted to create 0:0 char device nodes (because they also * act as whiteout inode for overlayfs), but no other char or block device nodes. On old kernels no * device node whatsoever may be created by unprivileged processes. Hence, if the caller asks for the * inaccessible block device node let's see if the block device node actually exists, and if not, * fall back to the character device node. From there fall back to the socket device node. This means * in the best case we'll get the right device node type — but if not we'll hopefully at least get a * device node at all. */ if (S_ISBLK(mode) && access(d, F_OK) < 0 && errno == ENOENT) { free(d); d = path_join(runtime_dir, "/systemd/inaccessible/chr"); if (!d) return -ENOMEM; } if (IN_SET(mode & S_IFMT, S_IFBLK, S_IFCHR) && access(d, F_OK) < 0 && errno == ENOENT) { free(d); d = path_join(runtime_dir, "/systemd/inaccessible/sock"); if (!d) return -ENOMEM; } *ret = TAKE_PTR(d); return 0; } #define FLAG(name) (flags & name ? STRINGIFY(name) "|" : "") static char* mount_flags_to_string(long unsigned flags) { char *x; _cleanup_free_ char *y = NULL; long unsigned overflow; overflow = flags & ~(MS_RDONLY | MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_SYNCHRONOUS | MS_REMOUNT | MS_MANDLOCK | MS_DIRSYNC | MS_NOATIME | MS_NODIRATIME | MS_BIND | MS_MOVE | MS_REC | MS_SILENT | MS_POSIXACL | MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED | MS_RELATIME | MS_KERNMOUNT | MS_I_VERSION | MS_STRICTATIME | MS_LAZYTIME); if (flags == 0 || overflow != 0) if (asprintf(&y, "%lx", overflow) < 0) return NULL; x = strjoin(FLAG(MS_RDONLY), FLAG(MS_NOSUID), FLAG(MS_NODEV), FLAG(MS_NOEXEC), FLAG(MS_SYNCHRONOUS), FLAG(MS_REMOUNT), FLAG(MS_MANDLOCK), FLAG(MS_DIRSYNC), FLAG(MS_NOATIME), FLAG(MS_NODIRATIME), FLAG(MS_BIND), FLAG(MS_MOVE), FLAG(MS_REC), FLAG(MS_SILENT), FLAG(MS_POSIXACL), FLAG(MS_UNBINDABLE), FLAG(MS_PRIVATE), FLAG(MS_SLAVE), FLAG(MS_SHARED), FLAG(MS_RELATIME), FLAG(MS_KERNMOUNT), FLAG(MS_I_VERSION), FLAG(MS_STRICTATIME), FLAG(MS_LAZYTIME), y); if (!x) return NULL; if (!y) x[strlen(x) - 1] = '\0'; /* truncate the last | */ return x; } int mount_verbose_full( int error_log_level, const char *what, const char *where, const char *type, unsigned long flags, const char *options, bool follow_symlink) { _cleanup_free_ char *fl = NULL, *o = NULL; unsigned long f; int r; r = mount_option_mangle(options, flags, &f, &o); if (r < 0) return log_full_errno(error_log_level, r, "Failed to mangle mount options %s: %m", strempty(options)); fl = mount_flags_to_string(f); if ((f & MS_REMOUNT) && !what && !type) log_debug("Remounting %s (%s \"%s\")...", where, strnull(fl), strempty(o)); else if (!what && !type) log_debug("Mounting %s (%s \"%s\")...", where, strnull(fl), strempty(o)); else if ((f & MS_BIND) && !type) log_debug("Bind-mounting %s on %s (%s \"%s\")...", what, where, strnull(fl), strempty(o)); else if (f & MS_MOVE) log_debug("Moving mount %s → %s (%s \"%s\")...", what, where, strnull(fl), strempty(o)); else log_debug("Mounting %s (%s) on %s (%s \"%s\")...", strna(what), strna(type), where, strnull(fl), strempty(o)); if (follow_symlink) r = mount(what, where, type, f, o) < 0 ? -errno : 0; else r = mount_nofollow(what, where, type, f, o); if (r < 0) return log_full_errno(error_log_level, r, "Failed to mount %s (type %s) on %s (%s \"%s\"): %m", strna(what), strna(type), where, strnull(fl), strempty(o)); return 0; } int umount_verbose( int error_log_level, const char *what, int flags) { assert(what); log_debug("Umounting %s...", what); if (umount2(what, flags) < 0) return log_full_errno(error_log_level, errno, "Failed to unmount %s: %m", what); return 0; } int mount_option_mangle( const char *options, unsigned long mount_flags, unsigned long *ret_mount_flags, char **ret_remaining_options) { const struct libmnt_optmap *map; _cleanup_free_ char *ret = NULL; const char *p; int r; /* This extracts mount flags from the mount options, and store * non-mount-flag options to '*ret_remaining_options'. * E.g., * "rw,nosuid,nodev,relatime,size=1630748k,mode=700,uid=1000,gid=1000" * is split to MS_NOSUID|MS_NODEV|MS_RELATIME and * "size=1630748k,mode=700,uid=1000,gid=1000". * See more examples in test-mount-utils.c. * * Note that if 'options' does not contain any non-mount-flag options, * then '*ret_remaining_options' is set to NULL instead of empty string. * Note that this does not check validity of options stored in * '*ret_remaining_options'. * Note that if 'options' is NULL, then this just copies 'mount_flags' * to '*ret_mount_flags'. */ assert(ret_mount_flags); assert(ret_remaining_options); map = mnt_get_builtin_optmap(MNT_LINUX_MAP); if (!map) return -EINVAL; p = options; for (;;) { _cleanup_free_ char *word = NULL; const struct libmnt_optmap *ent; r = extract_first_word(&p, &word, ",", EXTRACT_UNQUOTE); if (r < 0) return r; if (r == 0) break; for (ent = map; ent->name; ent++) { /* All entries in MNT_LINUX_MAP do not take any argument. * Thus, ent->name does not contain "=" or "[=]". */ if (!streq(word, ent->name)) continue; if (!(ent->mask & MNT_INVERT)) mount_flags |= ent->id; else if (mount_flags & ent->id) mount_flags ^= ent->id; break; } /* If 'word' is not a mount flag, then store it in '*ret_remaining_options'. */ if (!ent->name && !strextend_with_separator(&ret, ",", word)) return -ENOMEM; } *ret_mount_flags = mount_flags; *ret_remaining_options = TAKE_PTR(ret); return 0; }