/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include #if WANT_LINUX_FS_H #include #endif #include "alloc-util.h" #include "chase.h" #include "dissect-image.h" #include "exec-util.h" #include "extract-word.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "glyph-util.h" #include "hashmap.h" #include "initrd-util.h" #include "label-util.h" #include "libmount-util.h" #include "missing_mount.h" #include "missing_syscall.h" #include "mkdir-label.h" #include "mount-util.h" #include "mountpoint-util.h" #include "namespace-util.h" #include "parse-util.h" #include "path-util.h" #include "process-util.h" #include "set.h" #include "sort-util.h" #include "stat-util.h" #include "stdio-util.h" #include "string-table.h" #include "string-util.h" #include "strv.h" #include "tmpfile-util.h" #include "user-util.h" int umount_recursive_full(const char *prefix, int flags, char **keep) { _cleanup_fclose_ FILE *f = NULL; int n = 0, r; /* Try to umount everything recursively below a directory. Also, take care of stacked mounts, and * keep unmounting them until they are gone. */ f = fopen("/proc/self/mountinfo", "re"); /* Pin the file, in case we unmount /proc/ as part of the logic here */ if (!f) return log_debug_errno(errno, "Failed to open /proc/self/mountinfo: %m"); for (;;) { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; bool again = false; r = libmount_parse("/proc/self/mountinfo", f, &table, &iter); if (r < 0) return log_debug_errno(r, "Failed to parse /proc/self/mountinfo: %m"); for (;;) { bool shall_keep = false; 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 (prefix && !path_startswith(path, prefix)) { log_trace("Not unmounting %s, outside of prefix: %s", path, prefix); continue; } STRV_FOREACH(k, keep) /* Match against anything in the path to the dirs to keep, or below the dirs to keep */ if (path_startswith(path, *k) || path_startswith(*k, path)) { shall_keep = true; break; } if (shall_keep) { log_debug("Not unmounting %s, referenced by keep list.", path); continue; } if (umount2(path, flags | UMOUNT_NOFOLLOW) < 0) { log_debug_errno(errno, "Failed to umount %s, ignoring: %m", path); continue; } log_trace("Successfully unmounted %s", path); again = true; n++; break; } if (!again) break; rewind(f); } return n; } #define MS_CONVERTIBLE_FLAGS (MS_RDONLY|MS_NOSUID|MS_NODEV|MS_NOEXEC|MS_NOSYMFOLLOW) static uint64_t ms_flags_to_mount_attr(unsigned long a) { uint64_t f = 0; if (FLAGS_SET(a, MS_RDONLY)) f |= MOUNT_ATTR_RDONLY; if (FLAGS_SET(a, MS_NOSUID)) f |= MOUNT_ATTR_NOSUID; if (FLAGS_SET(a, MS_NODEV)) f |= MOUNT_ATTR_NODEV; if (FLAGS_SET(a, MS_NOEXEC)) f |= MOUNT_ATTR_NOEXEC; if (FLAGS_SET(a, MS_NOSYMFOLLOW)) f |= MOUNT_ATTR_NOSYMFOLLOW; return f; } static bool skip_mount_set_attr = false; /* 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_fclose_ FILE *proc_self_mountinfo_opened = NULL; _cleanup_set_free_ Set *done = NULL; unsigned n_tries = 0; int r; assert(prefix); if ((flags_mask & ~MS_CONVERTIBLE_FLAGS) == 0 && strv_isempty(deny_list) && !skip_mount_set_attr) { /* Let's take a shortcut for all the flags we know how to convert into mount_setattr() flags */ if (mount_setattr(AT_FDCWD, prefix, AT_SYMLINK_NOFOLLOW|AT_RECURSIVE, &(struct mount_attr) { .attr_set = ms_flags_to_mount_attr(new_flags & flags_mask), .attr_clr = ms_flags_to_mount_attr(~new_flags & flags_mask), }, MOUNT_ATTR_SIZE_VER0) < 0) { log_debug_errno(errno, "mount_setattr() failed, falling back to classic remounting: %m"); /* We fall through to classic behaviour if not supported (i.e. kernel < 5.12). We * also do this for all other kinds of errors since they are so many different, and * mount_setattr() has no graceful mode where it continues despite seeing errors one * some mounts, but we want that. Moreover mount_setattr() only works on the mount * point inode itself, not a non-mount point inode, and we want to support arbitrary * prefixes here. */ if (ERRNO_IS_NOT_SUPPORTED(errno)) /* if not supported, then don't bother at all anymore */ skip_mount_set_attr = true; } else return 0; /* Nice, this worked! */ } if (!proc_self_mountinfo) { r = fopen_unlocked("/proc/self/mountinfo", "re", &proc_self_mountinfo_opened); if (r < 0) return r; proc_self_mountinfo = proc_self_mountinfo_opened; } /* Recursively remount a directory (and all its submounts) with desired flags (MS_READONLY, * MS_NOSUID, MS_NOEXEC). 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), ditto for other flags. If it * isn't we first make it one. Afterwards we apply (or remove) the flags 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 * etc. This includes future submounts that have been triggered via autofs. Also note that we can't * operate atomically here. Mounts established while we process the tree might or might not get * noticed and thus might or might not be covered. * * 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. */ for (;;) { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; _cleanup_hashmap_free_ Hashmap *todo = NULL; bool top_autofs = false; if (n_tries++ >= 32) /* Let's not retry this loop forever */ return -EBUSY; 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 (;;) { _cleanup_free_ char *d = NULL; const char *path, *type, *opts; unsigned long flags = 0; struct libmnt_fs *fs; r = mnt_table_next_fs(table, iter, &fs); if (r == 1) /* EOF */ 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; type = mnt_fs_get_fstype(fs); if (!type) 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, prefix); continue; } if (set_contains(done, path)) 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, prefix)) { bool deny_listed = false; STRV_FOREACH(i, deny_list) { if (path_equal(*i, prefix)) continue; if (!path_startswith(*i, prefix)) continue; if (path_startswith(path, *i)) { deny_listed = true; log_trace("Not remounting %s deny-listed by %s, called for %s", path, *i, prefix); break; } } if (deny_listed) continue; } opts = mnt_fs_get_vfs_options(fs); if (opts) { r = mnt_optstr_get_flags(opts, &flags, mnt_get_builtin_optmap(MNT_LINUX_MAP)); if (r < 0) log_debug_errno(r, "Could not get flags for '%s', ignoring: %m", path); } d = strdup(path); if (!d) return -ENOMEM; r = hashmap_ensure_put(&todo, &path_hash_ops_free, d, ULONG_TO_PTR(flags)); if (r == -EEXIST) /* If the same path was recorded, but with different mount flags, update it: * it means a mount point is overmounted, and libmount returns the "bottom" (or * older one) first, but we want to reapply the flags from the "top" (or newer * one). See: https://github.com/systemd/systemd/issues/20032 * Note that this shouldn't really fail, as we were just told that the key * exists, and it's an update so we want 'd' to be freed immediately. */ r = hashmap_update(todo, d, ULONG_TO_PTR(flags)); if (r < 0) return r; if (r > 0) TAKE_PTR(d); } /* Check if the top-level directory was among what we have seen so far. For that check both * 'done' and 'todo'. Also check 'top_autofs' because if the top-level dir is an autofs we'll * not include it in either set but will set this bool. */ if (!set_contains(done, prefix) && !(top_autofs || hashmap_contains(todo, prefix))) { /* The prefix directory itself is not yet a mount, make it one. */ r = mount_nofollow(prefix, prefix, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; /* Immediately rescan, so that we pick up the new mount's flags */ continue; } /* If we have no submounts to process anymore, we are done */ if (hashmap_isempty(todo)) return 0; for (;;) { unsigned long flags; char *x = NULL; /* Take the first mount from our list of mounts to still process */ flags = PTR_TO_ULONG(hashmap_steal_first_key_and_value(todo, (void**) &x)); if (!x) break; r = set_ensure_consume(&done, &path_hash_ops_free, x); if (IN_SET(r, 0, -EEXIST)) continue; /* Already done */ if (r < 0) return r; /* Now, remount this with the new flags set, but exclude MS_RELATIME from it. (It's * the default anyway, thus redundant, and in userns we'll get an error if we try to * explicitly enable it) */ r = mount_nofollow(NULL, x, NULL, ((flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags) & ~MS_RELATIME, NULL); if (r < 0) { int q; /* OK, so the remount of this entry failed. We'll ultimately ignore this in * almost all cases (there are simply so many reasons why this can fail, * think autofs, NFS, FUSE, …), but let's generate useful debug messages at * the very least. */ q = path_is_mount_point(x, NULL, 0); if (IN_SET(q, 0, -ENOENT)) { /* Hmm, whaaaa? The mount point is not actually a mount point? Then * it is either obstructed by a later mount or somebody has been * racing against us and removed it. Either way the mount point * doesn't matter to us, let's ignore it hence. */ log_debug_errno(r, "Mount point '%s' to remount is not a mount point anymore, ignoring remount failure: %m", x); continue; } if (q < 0) /* Any other error on this? Just log and continue */ log_debug_errno(q, "Failed to determine whether '%s' is a mount point or not, ignoring: %m", x); if (((flags ^ new_flags) & flags_mask & ~MS_RELATIME) == 0) { /* ignore MS_RELATIME while comparing */ log_debug_errno(r, "Couldn't remount '%s', but the flags already match what we want, hence ignoring: %m", x); continue; } /* Make this fatal if this is the top-level mount */ if (path_equal(x, prefix)) return r; /* If this is not the top-level mount, then handle this gracefully: log but * otherwise ignore. With NFS, FUSE, autofs there are just too many reasons * this might fail without a chance for us to do anything about it, let's * hence be strict on the top-level mount and lenient on the inner ones. */ log_debug_errno(r, "Couldn't remount submount '%s' for unexpected reason, ignoring: %m", x); continue; } log_trace("Remounted %s.", x); } } } 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 flags = 0; struct libmnt_fs *fs; const char *opts; int r; assert(path); assert(proc_self_mountinfo); if ((flags_mask & ~MS_CONVERTIBLE_FLAGS) == 0 && !skip_mount_set_attr) { /* Let's take a shortcut for all the flags we know how to convert into mount_setattr() flags */ if (mount_setattr(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW, &(struct mount_attr) { .attr_set = ms_flags_to_mount_attr(new_flags & flags_mask), .attr_clr = ms_flags_to_mount_attr(~new_flags & flags_mask), }, MOUNT_ATTR_SIZE_VER0) < 0) { log_debug_errno(errno, "mount_setattr() didn't work, falling back to classic remounting: %m"); if (ERRNO_IS_NOT_SUPPORTED(errno)) /* if not supported, then don't bother at all anymore */ skip_mount_set_attr = true; } else return 0; /* Nice, this worked! */ } 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; fs = mnt_table_find_target(table, path, MNT_ITER_FORWARD); if (!fs) { r = laccess(path, F_OK); /* Hmm, it's not in the mount table, but does it exist at all? */ if (r < 0) return r; return -EINVAL; /* Not a mount point we recognize */ } opts = mnt_fs_get_vfs_options(fs); if (opts) { r = mnt_optstr_get_flags(opts, &flags, mnt_get_builtin_optmap(MNT_LINUX_MAP)); if (r < 0) log_debug_errno(r, "Could not get flags for '%s', ignoring: %m", path); } r = mount_nofollow(NULL, path, NULL, ((flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags) & ~MS_RELATIME, NULL); if (r < 0) { if (((flags ^ new_flags) & flags_mask & ~MS_RELATIME) != 0) /* Ignore MS_RELATIME again, * since kernel adds it in * everywhere, because it's the * default. */ return r; /* Let's handle redundant remounts gracefully */ log_debug_errno(r, "Failed to remount '%s' but flags already match what we want, ignoring: %m", path); } return 0; } static int mount_switch_root_pivot(int fd_newroot, const char *path) { assert(fd_newroot >= 0); assert(path); /* Change into the new rootfs. */ if (fchdir(fd_newroot) < 0) return log_debug_errno(errno, "Failed to chdir into new rootfs '%s': %m", path); /* Let the kernel tuck the new root under the old one. */ if (pivot_root(".", ".") < 0) return log_debug_errno(errno, "Failed to pivot root to new rootfs '%s': %m", path); /* Get rid of the old root and reveal our brand new root. (This will always operate on the top-most * mount on our cwd, regardless what our current directory actually points to.) */ if (umount2(".", MNT_DETACH) < 0) return log_debug_errno(errno, "Failed to unmount old rootfs: %m"); return 0; } static int mount_switch_root_move(int fd_newroot, const char *path) { assert(fd_newroot >= 0); assert(path); /* Change into the new rootfs. */ if (fchdir(fd_newroot) < 0) return log_debug_errno(errno, "Failed to chdir into new rootfs '%s': %m", path); /* Move the new root fs */ if (mount(".", "/", NULL, MS_MOVE, NULL) < 0) return log_debug_errno(errno, "Failed to move new rootfs '%s': %m", path); /* Also change root dir */ if (chroot(".") < 0) return log_debug_errno(errno, "Failed to chroot to new rootfs '%s': %m", path); return 0; } int mount_switch_root_full(const char *path, unsigned long mount_propagation_flag, bool force_ms_move) { _cleanup_close_ int fd_newroot = -EBADF; int r; assert(path); assert(mount_propagation_flag_is_valid(mount_propagation_flag)); fd_newroot = open(path, O_PATH|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW); if (fd_newroot < 0) return log_debug_errno(errno, "Failed to open new rootfs '%s': %m", path); if (!force_ms_move) { r = mount_switch_root_pivot(fd_newroot, path); if (r < 0) { log_debug_errno(r, "Failed to pivot into new rootfs '%s', will try to use MS_MOVE instead: %m", path); force_ms_move = true; } } if (force_ms_move) { /* Failed to pivot_root() fallback to MS_MOVE. For example, this may happen if the rootfs is * an initramfs in which case pivot_root() isn't supported. */ r = mount_switch_root_move(fd_newroot, path); if (r < 0) return log_debug_errno(r, "Failed to switch to new rootfs '%s' with MS_MOVE: %m", path); } /* Finally, let's establish the requested propagation flags. */ if (mount_propagation_flag == 0) return 0; if (mount(NULL, ".", NULL, mount_propagation_flag | MS_REC, 0) < 0) return log_debug_errno(errno, "Failed to turn new rootfs '%s' into %s mount: %m", mount_propagation_flag_to_string(mount_propagation_flag), path); 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; assert(ret); if (!runtime_dir) runtime_dir = "/run"; if (S_ISLNK(mode)) return -EINVAL; node = inode_type_to_string(mode); if (!node) return -EINVAL; d = path_join(runtime_dir, "systemd/inaccessible", 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; } int mount_flags_to_string(unsigned long flags, char **ret) { static const struct { unsigned long flag; const char *name; } map[] = { { .flag = MS_RDONLY, .name = "MS_RDONLY", }, { .flag = MS_NOSUID, .name = "MS_NOSUID", }, { .flag = MS_NODEV, .name = "MS_NODEV", }, { .flag = MS_NOEXEC, .name = "MS_NOEXEC", }, { .flag = MS_SYNCHRONOUS, .name = "MS_SYNCHRONOUS", }, { .flag = MS_REMOUNT, .name = "MS_REMOUNT", }, { .flag = MS_MANDLOCK, .name = "MS_MANDLOCK", }, { .flag = MS_DIRSYNC, .name = "MS_DIRSYNC", }, { .flag = MS_NOSYMFOLLOW, .name = "MS_NOSYMFOLLOW", }, { .flag = MS_NOATIME, .name = "MS_NOATIME", }, { .flag = MS_NODIRATIME, .name = "MS_NODIRATIME", }, { .flag = MS_BIND, .name = "MS_BIND", }, { .flag = MS_MOVE, .name = "MS_MOVE", }, { .flag = MS_REC, .name = "MS_REC", }, { .flag = MS_SILENT, .name = "MS_SILENT", }, { .flag = MS_POSIXACL, .name = "MS_POSIXACL", }, { .flag = MS_UNBINDABLE, .name = "MS_UNBINDABLE", }, { .flag = MS_PRIVATE, .name = "MS_PRIVATE", }, { .flag = MS_SLAVE, .name = "MS_SLAVE", }, { .flag = MS_SHARED, .name = "MS_SHARED", }, { .flag = MS_RELATIME, .name = "MS_RELATIME", }, { .flag = MS_KERNMOUNT, .name = "MS_KERNMOUNT", }, { .flag = MS_I_VERSION, .name = "MS_I_VERSION", }, { .flag = MS_STRICTATIME, .name = "MS_STRICTATIME", }, { .flag = MS_LAZYTIME, .name = "MS_LAZYTIME", }, }; _cleanup_free_ char *str = NULL; assert(ret); for (size_t i = 0; i < ELEMENTSOF(map); i++) if (flags & map[i].flag) { if (!strextend_with_separator(&str, "|", map[i].name)) return -ENOMEM; flags &= ~map[i].flag; } if (!str || flags != 0) if (strextendf_with_separator(&str, "|", "%lx", flags) < 0) return -ENOMEM; *ret = TAKE_PTR(str); return 0; } 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)); (void) mount_flags_to_string(f, &fl); if (FLAGS_SET(f, MS_REMOUNT|MS_BIND)) log_debug("Changing mount flags %s (%s \"%s\")...", where, strnull(fl), strempty(o)); else if (f & MS_REMOUNT) log_debug("Remounting superblock %s (%s \"%s\")...", where, strnull(fl), strempty(o)); else if (f & (MS_SHARED|MS_PRIVATE|MS_SLAVE|MS_UNBINDABLE)) log_debug("Changing mount propagation %s (%s \"%s\")", where, strnull(fl), strempty(o)); else if (f & MS_BIND) 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 \"%s\")...", what, special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), 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 = RET_NERRNO(mount(what, where, type, f, o)); 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_exchange_graceful(int fsmount_fd, const char *dest, bool mount_beneath) { int r; assert(fsmount_fd >= 0); assert(dest); /* First, try to mount beneath an existing mount point, and if that works, umount the old mount, * which is now at the top. This will ensure we can atomically replace a mount. Note that this works * also in the case where there are submounts down the tree. Mount propagation is allowed but * restricted to layouts that don't end up propagation the new mount on top of the mount stack. If * this is not supported (minimum kernel v6.5), or if there is no mount on the mountpoint, we get * -EINVAL and then we fallback to normal mounting. */ r = RET_NERRNO(move_mount( fsmount_fd, /* from_path= */ "", /* to_fd= */ -EBADF, dest, MOVE_MOUNT_F_EMPTY_PATH | (mount_beneath ? MOVE_MOUNT_BENEATH : 0))); if (mount_beneath) { if (r == -EINVAL) { /* Fallback if mount_beneath is not supported */ log_debug_errno(r, "Failed to mount beneath '%s', falling back to overmount", dest); return RET_NERRNO(move_mount( fsmount_fd, /* from_path= */ "", /* to_fd= */ -EBADF, dest, MOVE_MOUNT_F_EMPTY_PATH)); } if (r >= 0) /* If it is, now remove the old mount */ return umount_verbose(LOG_DEBUG, dest, UMOUNT_NOFOLLOW|MNT_DETACH); } return r; } 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; int r; /* This extracts mount flags from the mount options, and stores * non-mount-flag options to '*ret_remaining_options'. * E.g., * "rw,nosuid,nodev,relatime,size=1630748k,mode=0700,uid=1000,gid=1000" * is split to MS_NOSUID|MS_NODEV|MS_RELATIME and * "size=1630748k,mode=0700,uid=1000,gid=1000". * See more examples in test-mount-util.c. * * If 'options' does not contain any non-mount-flag options, * then '*ret_remaining_options' is set to NULL instead of empty string. * The validity of options stored in '*ret_remaining_options' is not checked. * If 'options' is NULL, 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; for (const char *p = options;;) { _cleanup_free_ char *word = NULL; const struct libmnt_optmap *ent; r = extract_first_word(&p, &word, ",", EXTRACT_KEEP_QUOTE); 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 && !startswith_no_case(word, "x-") && !strextend_with_separator(&ret, ",", word)) return -ENOMEM; } *ret_mount_flags = mount_flags; *ret_remaining_options = TAKE_PTR(ret); return 0; } static int mount_in_namespace_legacy( const char *chased_src_path, int chased_src_fd, struct stat *chased_src_st, const char *propagate_path, const char *incoming_path, const char *dest, int pidns_fd, int mntns_fd, int root_fd, bool read_only, bool make_file_or_directory, const MountOptions *options, const ImagePolicy *image_policy, bool is_image) { _cleanup_close_pair_ int errno_pipe_fd[2] = EBADF_PAIR; char mount_slave[] = "/tmp/propagate.XXXXXX", *mount_tmp, *mount_outside, *p; bool mount_slave_created = false, mount_slave_mounted = false, mount_tmp_created = false, mount_tmp_mounted = false, mount_outside_created = false, mount_outside_mounted = false; pid_t child; int r; assert(chased_src_path); assert(chased_src_fd >= 0); assert(chased_src_st); assert(propagate_path); assert(incoming_path); assert(dest); assert(pidns_fd >= 0); assert(mntns_fd >= 0); assert(root_fd >= 0); assert(!options || is_image); p = strjoina(propagate_path, "/"); r = laccess(p, F_OK); if (r < 0) return log_debug_errno(r == -ENOENT ? SYNTHETIC_ERRNO(EOPNOTSUPP) : r, "Target does not allow propagation of mount points"); /* Our goal is to install a new bind mount into the container, possibly read-only. This is irritatingly complex unfortunately, currently. First, we start by creating a private playground in /tmp, that we can mount MS_SLAVE. (Which is necessary, since MS_MOVE cannot be applied to mounts with MS_SHARED parent mounts.) */ if (!mkdtemp(mount_slave)) return log_debug_errno(errno, "Failed to create playground %s: %m", mount_slave); mount_slave_created = true; r = mount_nofollow_verbose(LOG_DEBUG, mount_slave, mount_slave, NULL, MS_BIND, NULL); if (r < 0) goto finish; mount_slave_mounted = true; r = mount_nofollow_verbose(LOG_DEBUG, NULL, mount_slave, NULL, MS_SLAVE, NULL); if (r < 0) goto finish; /* Second, we mount the source file or directory to a directory inside of our MS_SLAVE playground. */ mount_tmp = strjoina(mount_slave, "/mount"); if (is_image) r = mkdir_p(mount_tmp, 0700); else r = make_mount_point_inode_from_stat(chased_src_st, mount_tmp, 0700); if (r < 0) { log_debug_errno(r, "Failed to create temporary mount point %s: %m", mount_tmp); goto finish; } mount_tmp_created = true; if (is_image) r = verity_dissect_and_mount( chased_src_fd, chased_src_path, mount_tmp, options, image_policy, /* required_host_os_release_id= */ NULL, /* required_host_os_release_version_id= */ NULL, /* required_host_os_release_sysext_level= */ NULL, /* required_host_os_release_confext_level= */ NULL, /* required_sysext_scope= */ NULL, /* ret_image= */ NULL); else r = mount_follow_verbose(LOG_DEBUG, FORMAT_PROC_FD_PATH(chased_src_fd), mount_tmp, NULL, MS_BIND, NULL); if (r < 0) goto finish; mount_tmp_mounted = true; /* Third, we remount the new bind mount read-only if requested. */ if (read_only) { r = mount_nofollow_verbose(LOG_DEBUG, NULL, mount_tmp, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY, NULL); if (r < 0) goto finish; } /* Fourth, we move the new bind mount into the propagation directory. This way it will appear there read-only * right-away. */ mount_outside = strjoina(propagate_path, "/XXXXXX"); if (is_image || S_ISDIR(chased_src_st->st_mode)) r = mkdtemp(mount_outside) ? 0 : -errno; else { r = mkostemp_safe(mount_outside); safe_close(r); } if (r < 0) { log_debug_errno(r, "Cannot create propagation file or directory %s: %m", mount_outside); goto finish; } mount_outside_created = true; r = mount_nofollow_verbose(LOG_DEBUG, mount_tmp, mount_outside, NULL, MS_MOVE, NULL); if (r < 0) goto finish; mount_outside_mounted = true; mount_tmp_mounted = false; if (is_image || S_ISDIR(chased_src_st->st_mode)) (void) rmdir(mount_tmp); else (void) unlink(mount_tmp); mount_tmp_created = false; (void) umount_verbose(LOG_DEBUG, mount_slave, UMOUNT_NOFOLLOW); mount_slave_mounted = false; (void) rmdir(mount_slave); mount_slave_created = false; if (pipe2(errno_pipe_fd, O_CLOEXEC|O_NONBLOCK) < 0) { log_debug_errno(errno, "Failed to create pipe: %m"); goto finish; } r = namespace_fork("(sd-bindmnt)", "(sd-bindmnt-inner)", NULL, 0, FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM, pidns_fd, mntns_fd, -1, -1, root_fd, &child); if (r < 0) goto finish; if (r == 0) { _cleanup_free_ char *mount_outside_fn = NULL, *mount_inside = NULL; errno_pipe_fd[0] = safe_close(errno_pipe_fd[0]); if (make_file_or_directory) { if (!is_image) { (void) mkdir_parents(dest, 0755); (void) make_mount_point_inode_from_stat(chased_src_st, dest, 0700); } else (void) mkdir_p(dest, 0755); } /* Fifth, move the mount to the right place inside */ r = path_extract_filename(mount_outside, &mount_outside_fn); if (r < 0) { log_debug_errno(r, "Failed to extract filename from propagation file or directory '%s': %m", mount_outside); goto child_fail; } mount_inside = path_join(incoming_path, mount_outside_fn); if (!mount_inside) { r = log_oom_debug(); goto child_fail; } r = mount_nofollow_verbose(LOG_DEBUG, mount_inside, dest, NULL, MS_MOVE, NULL); if (r < 0) goto child_fail; _exit(EXIT_SUCCESS); child_fail: (void) write(errno_pipe_fd[1], &r, sizeof(r)); errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]); _exit(EXIT_FAILURE); } errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]); r = wait_for_terminate_and_check("(sd-bindmnt)", child, 0); if (r < 0) { log_debug_errno(r, "Failed to wait for child: %m"); goto finish; } if (r != EXIT_SUCCESS) { if (read(errno_pipe_fd[0], &r, sizeof(r)) == sizeof(r)) log_debug_errno(r, "Failed to mount: %m"); else log_debug("Child failed."); goto finish; } finish: if (mount_outside_mounted) (void) umount_verbose(LOG_DEBUG, mount_outside, UMOUNT_NOFOLLOW); if (mount_outside_created) { if (is_image || S_ISDIR(chased_src_st->st_mode)) (void) rmdir(mount_outside); else (void) unlink(mount_outside); } if (mount_tmp_mounted) (void) umount_verbose(LOG_DEBUG, mount_tmp, UMOUNT_NOFOLLOW); if (mount_tmp_created) { if (is_image || S_ISDIR(chased_src_st->st_mode)) (void) rmdir(mount_tmp); else (void) unlink(mount_tmp); } if (mount_slave_mounted) (void) umount_verbose(LOG_DEBUG, mount_slave, UMOUNT_NOFOLLOW); if (mount_slave_created) (void) rmdir(mount_slave); return r; } static int mount_in_namespace( const PidRef *target, const char *propagate_path, const char *incoming_path, const char *src, const char *dest, bool read_only, bool make_file_or_directory, const MountOptions *options, const ImagePolicy *image_policy, bool is_image) { _cleanup_(dissected_image_unrefp) DissectedImage *img = NULL; _cleanup_close_pair_ int errno_pipe_fd[2] = EBADF_PAIR; _cleanup_close_ int mntns_fd = -EBADF, root_fd = -EBADF, pidns_fd = -EBADF, chased_src_fd = -EBADF, new_mount_fd = -EBADF; _cleanup_free_ char *chased_src_path = NULL; struct stat st; pid_t child; int r; assert(propagate_path); assert(incoming_path); assert(src); assert(dest); assert(!options || is_image); if (!pidref_is_set(target)) return -ESRCH; r = namespace_open(target->pid, &pidns_fd, &mntns_fd, NULL, NULL, &root_fd); if (r < 0) return log_debug_errno(r, "Failed to retrieve FDs of the target process' namespace: %m"); r = in_same_namespace(target->pid, 0, NAMESPACE_MOUNT); if (r < 0) return log_debug_errno(r, "Failed to determine if mount namespaces are equal: %m"); /* We can't add new mounts at runtime if the process wasn't started in a namespace */ if (r > 0) return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to activate bind mount in target, not running in a mount namespace"); r = pidref_verify(target); if (r < 0) return log_debug_errno(r, "Failed to verify target process '" PID_FMT "': %m", target->pid); r = chase(src, NULL, 0, &chased_src_path, &chased_src_fd); if (r < 0) return log_debug_errno(r, "Failed to resolve source path of %s: %m", src); log_debug("Chased source path of %s to %s", src, chased_src_path); if (fstat(chased_src_fd, &st) < 0) return log_debug_errno(errno, "Failed to stat() resolved source path %s: %m", src); if (S_ISLNK(st.st_mode)) /* This shouldn't really happen, given that we just chased the symlinks above, but let's better be safe… */ return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP), "Source directory %s can't be a symbolic link", src); if (!mount_new_api_supported()) /* Fallback if we can't use the new mount API */ return mount_in_namespace_legacy( chased_src_path, chased_src_fd, &st, propagate_path, incoming_path, dest, pidns_fd, mntns_fd, root_fd, read_only, make_file_or_directory, options, image_policy, is_image); if (is_image) { r = verity_dissect_and_mount( chased_src_fd, chased_src_path, /* dest= */ NULL, options, image_policy, /* required_host_os_release_id= */ NULL, /* required_host_os_release_version_id= */ NULL, /* required_host_os_release_sysext_level= */ NULL, /* required_host_os_release_confext_level= */ NULL, /* required_sysext_scope= */ NULL, &img); if (r < 0) return log_debug_errno( r, "Failed to dissect and mount image %s: %m", chased_src_path); } else { new_mount_fd = open_tree( chased_src_fd, "", OPEN_TREE_CLONE|OPEN_TREE_CLOEXEC|AT_SYMLINK_NOFOLLOW|AT_EMPTY_PATH); if (new_mount_fd < 0) return log_debug_errno( errno, "Failed to open mount point \"%s\": %m", chased_src_path); if (read_only && mount_setattr(new_mount_fd, "", AT_EMPTY_PATH, &(struct mount_attr) { .attr_set = MOUNT_ATTR_RDONLY, }, MOUNT_ATTR_SIZE_VER0) < 0) return log_debug_errno( errno, "Failed to set mount flags for \"%s\": %m", chased_src_path); } if (pipe2(errno_pipe_fd, O_CLOEXEC|O_NONBLOCK) < 0) return log_debug_errno(errno, "Failed to create pipe: %m"); r = namespace_fork("(sd-bindmnt)", "(sd-bindmnt-inner)", /* except_fds= */ NULL, /* n_except_fds= */ 0, FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM, pidns_fd, mntns_fd, /* netns_fd= */ -1, /* userns_fd= */ -1, root_fd, &child); if (r < 0) return log_debug_errno(r, "Failed to fork off: %m"); if (r == 0) { errno_pipe_fd[0] = safe_close(errno_pipe_fd[0]); if (make_file_or_directory) (void) mkdir_parents(dest, 0755); if (img) { DissectImageFlags f = DISSECT_IMAGE_TRY_ATOMIC_MOUNT_EXCHANGE; if (make_file_or_directory) f |= DISSECT_IMAGE_MKDIR; if (read_only) f |= DISSECT_IMAGE_READ_ONLY; r = dissected_image_mount( img, dest, /* uid_shift= */ UID_INVALID, /* uid_range= */ UID_INVALID, /* userns_fd= */ -EBADF, f); } else { if (make_file_or_directory) (void) make_mount_point_inode_from_stat(&st, dest, 0700); r = mount_exchange_graceful(new_mount_fd, dest, /* mount_beneath= */ true); } if (r < 0) { (void) write(errno_pipe_fd[1], &r, sizeof(r)); errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]); _exit(EXIT_FAILURE); } _exit(EXIT_SUCCESS); } errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]); r = wait_for_terminate_and_check("(sd-bindmnt)", child, 0); if (r < 0) return log_debug_errno(r, "Failed to wait for child: %m"); if (r != EXIT_SUCCESS) { if (read(errno_pipe_fd[0], &r, sizeof(r)) == sizeof(r)) return log_debug_errno(r, "Failed to mount: %m"); return log_debug_errno(SYNTHETIC_ERRNO(EPROTO), "Child failed."); } return 0; } int bind_mount_in_namespace( PidRef * target, const char *propagate_path, const char *incoming_path, const char *src, const char *dest, bool read_only, bool make_file_or_directory) { return mount_in_namespace(target, propagate_path, incoming_path, src, dest, read_only, make_file_or_directory, /* options= */ NULL, /* image_policy= */ NULL, /* is_image= */ false); } int mount_image_in_namespace( PidRef * target, const char *propagate_path, const char *incoming_path, const char *src, const char *dest, bool read_only, bool make_file_or_directory, const MountOptions *options, const ImagePolicy *image_policy) { return mount_in_namespace(target, propagate_path, incoming_path, src, dest, read_only, make_file_or_directory, options, image_policy, /* is_image=*/ true); } int make_mount_point(const char *path) { int r; assert(path); /* If 'path' is already a mount point, does nothing and returns 0. If it is not it makes it one, and returns 1. */ r = path_is_mount_point(path, NULL, 0); if (r < 0) return log_debug_errno(r, "Failed to determine whether '%s' is a mount point: %m", path); if (r > 0) return 0; r = mount_nofollow_verbose(LOG_DEBUG, path, path, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; return 1; } int fd_make_mount_point(int fd) { int r; assert(fd >= 0); r = fd_is_mount_point(fd, NULL, 0); if (r < 0) return log_debug_errno(r, "Failed to determine whether file descriptor is a mount point: %m"); if (r > 0) return 0; r = mount_follow_verbose(LOG_DEBUG, FORMAT_PROC_FD_PATH(fd), FORMAT_PROC_FD_PATH(fd), NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; return 1; } int make_userns(uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping) { _cleanup_close_ int userns_fd = -EBADF; _cleanup_free_ char *line = NULL; /* Allocates a userns file descriptor with the mapping we need. For this we'll fork off a child * process whose only purpose is to give us a new user namespace. It's killed when we got it. */ if (!userns_shift_range_valid(uid_shift, uid_range)) return -EINVAL; if (IN_SET(idmapping, REMOUNT_IDMAPPING_NONE, REMOUNT_IDMAPPING_HOST_ROOT)) { if (asprintf(&line, UID_FMT " " UID_FMT " " UID_FMT "\n", 0u, uid_shift, uid_range) < 0) return log_oom_debug(); /* If requested we'll include an entry in the mapping so that the host root user can make * changes to the uidmapped mount like it normally would. Specifically, we'll map the user * with UID_MAPPED_ROOT on the backing fs to UID 0. This is useful, since nspawn code wants * to create various missing inodes in the OS tree before booting into it, and this becomes * very easy and straightforward to do if it can just do it under its own regular UID. Note * that in that case the container's runtime uidmap (i.e. the one the container payload * processes run in) will leave this UID unmapped, i.e. if we accidentally leave files owned * by host root in the already uidmapped tree around they'll show up as owned by 'nobody', * which is safe. (Of course, we shouldn't leave such inodes around, but always chown() them * to the container's own UID range, but it's good to have a safety net, in case we * forget it.) */ if (idmapping == REMOUNT_IDMAPPING_HOST_ROOT) if (strextendf(&line, UID_FMT " " UID_FMT " " UID_FMT "\n", UID_MAPPED_ROOT, 0u, 1u) < 0) return log_oom_debug(); } if (idmapping == REMOUNT_IDMAPPING_HOST_OWNER) { /* Remap the owner of the bind mounted directory to the root user within the container. This * way every file written by root within the container to the bind-mounted directory will * be owned by the original user. All other user will remain unmapped. */ if (asprintf(&line, UID_FMT " " UID_FMT " " UID_FMT "\n", owner, uid_shift, 1u) < 0) return log_oom_debug(); } /* We always assign the same UID and GID ranges */ userns_fd = userns_acquire(line, line); if (userns_fd < 0) return log_debug_errno(userns_fd, "Failed to acquire new userns: %m"); return TAKE_FD(userns_fd); } int remount_idmap_fd( char **paths, int userns_fd) { int r; assert(userns_fd >= 0); /* This remounts all specified paths with the specified userns as idmap. It will do so in in the * order specified in the strv: the expectation is that the top-level directories are at the * beginning, and nested directories in the right, so that the tree can be built correctly from left * to right. */ size_t n = strv_length(paths); if (n == 0) /* Nothing to do? */ return 0; int *mount_fds = NULL; size_t n_mounts_fds = 0; mount_fds = new(int, n); if (!mount_fds) return log_oom_debug(); CLEANUP_ARRAY(mount_fds, n_mounts_fds, close_many_and_free); for (size_t i = 0; i < n; i++) { int mntfd; /* Clone the mount point */ mntfd = mount_fds[n_mounts_fds] = open_tree(-EBADF, paths[i], OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC); if (mount_fds[n_mounts_fds] < 0) return log_debug_errno(errno, "Failed to open tree of mounted filesystem '%s': %m", paths[i]); n_mounts_fds++; /* Set the user namespace mapping attribute on the cloned mount point */ if (mount_setattr(mntfd, "", AT_EMPTY_PATH, &(struct mount_attr) { .attr_set = MOUNT_ATTR_IDMAP, .userns_fd = userns_fd, }, sizeof(struct mount_attr)) < 0) return log_debug_errno(errno, "Failed to change bind mount attributes for clone of '%s': %m", paths[i]); } for (size_t i = n; i > 0; i--) { /* Unmount the paths right-to-left */ /* Remove the old mount points now that we have a idmapped mounts as replacement for all of them */ r = umount_verbose(LOG_DEBUG, paths[i-1], UMOUNT_NOFOLLOW); if (r < 0) return r; } for (size_t i = 0; i < n; i++) { /* Mount the replacement mounts left-to-right */ /* And place the cloned version in its place */ log_debug("Mounting idmapped fs to '%s'", paths[i]); if (move_mount(mount_fds[i], "", -EBADF, paths[i], MOVE_MOUNT_F_EMPTY_PATH) < 0) return log_debug_errno(errno, "Failed to attach UID mapped mount to '%s': %m", paths[i]); } return 0; } int remount_idmap(char **p, uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping) { _cleanup_close_ int userns_fd = -EBADF; userns_fd = make_userns(uid_shift, uid_range, owner, idmapping); if (userns_fd < 0) return userns_fd; return remount_idmap_fd(p, userns_fd); } typedef struct SubMount { char *path; int mount_fd; } SubMount; static void sub_mount_clear(SubMount *s) { assert(s); s->path = mfree(s->path); s->mount_fd = safe_close(s->mount_fd); } static void sub_mount_array_free(SubMount *s, size_t n) { assert(s || n == 0); for (size_t i = 0; i < n; i++) sub_mount_clear(s + i); free(s); } static int sub_mount_compare(const SubMount *a, const SubMount *b) { assert(a); assert(b); assert(a->path); assert(b->path); return path_compare(a->path, b->path); } static void sub_mount_drop(SubMount *s, size_t n) { assert(s || n == 0); for (size_t m = 0, i = 1; i < n; i++) { if (path_startswith(s[i].path, s[m].path)) sub_mount_clear(s + i); else m = i; } } static int get_sub_mounts( const char *prefix, SubMount **ret_mounts, size_t *ret_n_mounts) { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; SubMount *mounts = NULL; size_t n = 0; int r; CLEANUP_ARRAY(mounts, n, sub_mount_array_free); assert(prefix); assert(ret_mounts); assert(ret_n_mounts); 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 (;;) { _cleanup_close_ int mount_fd = -EBADF; _cleanup_free_ char *p = NULL; struct libmnt_fs *fs; const char *path; int id1, id2; r = mnt_table_next_fs(table, iter, &fs); if (r == 1) break; /* EOF */ 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 (isempty(path_startswith(path, prefix))) continue; id1 = mnt_fs_get_id(fs); r = path_get_mnt_id(path, &id2); if (r < 0) { log_debug_errno(r, "Failed to get mount ID of '%s', ignoring: %m", path); continue; } if (id1 != id2) { /* The path may be hidden by another over-mount or already remounted. */ log_debug("The mount IDs of '%s' obtained by libmount and path_get_mnt_id() are different (%i vs %i), ignoring.", path, id1, id2); continue; } mount_fd = open(path, O_CLOEXEC|O_PATH); if (mount_fd < 0) { if (errno == ENOENT) /* The path may be hidden by another over-mount or already unmounted. */ continue; return log_debug_errno(errno, "Failed to open subtree of mounted filesystem '%s': %m", path); } p = strdup(path); if (!p) return log_oom_debug(); if (!GREEDY_REALLOC(mounts, n + 1)) return log_oom_debug(); mounts[n++] = (SubMount) { .path = TAKE_PTR(p), .mount_fd = TAKE_FD(mount_fd), }; } typesafe_qsort(mounts, n, sub_mount_compare); sub_mount_drop(mounts, n); *ret_mounts = TAKE_PTR(mounts); *ret_n_mounts = n; return 0; } int bind_mount_submounts( const char *source, const char *target) { SubMount *mounts = NULL; size_t n = 0; int ret = 0, r; /* Bind mounts all child mounts of 'source' to 'target'. Useful when setting up a new procfs instance * with new mount options to copy the original submounts over. */ assert(source); assert(target); CLEANUP_ARRAY(mounts, n, sub_mount_array_free); r = get_sub_mounts(source, &mounts, &n); if (r < 0) return r; FOREACH_ARRAY(m, mounts, n) { _cleanup_free_ char *t = NULL; const char *suffix; if (isempty(m->path)) continue; assert_se(suffix = path_startswith(m->path, source)); t = path_join(target, suffix); if (!t) return -ENOMEM; r = path_is_mount_point(t, NULL, 0); if (r < 0) { log_debug_errno(r, "Failed to detect if '%s' already is a mount point, ignoring: %m", t); continue; } if (r > 0) { log_debug("Not bind mounting '%s' from '%s' to '%s', since there's already a mountpoint.", suffix, source, target); continue; } r = mount_follow_verbose(LOG_DEBUG, FORMAT_PROC_FD_PATH(m->mount_fd), t, NULL, MS_BIND|MS_REC, NULL); if (r < 0 && ret == 0) ret = r; } return ret; } int make_mount_point_inode_from_stat(const struct stat *st, const char *dest, mode_t mode) { assert(st); assert(dest); if (S_ISDIR(st->st_mode)) return mkdir_label(dest, mode); else return RET_NERRNO(mknod(dest, S_IFREG|(mode & ~0111), 0)); } int make_mount_point_inode_from_path(const char *source, const char *dest, mode_t mode) { struct stat st; assert(source); assert(dest); if (stat(source, &st) < 0) return -errno; return make_mount_point_inode_from_stat(&st, dest, mode); } int trigger_automount_at(int dir_fd, const char *path) { _cleanup_free_ char *nested = NULL; assert(dir_fd >= 0 || dir_fd == AT_FDCWD); nested = path_join(path, "a"); if (!nested) return -ENOMEM; (void) faccessat(dir_fd, nested, F_OK, 0); return 0; } unsigned long credentials_fs_mount_flags(bool ro) { /* A tight set of mount flags for credentials mounts */ return MS_NODEV|MS_NOEXEC|MS_NOSUID|ms_nosymfollow_supported()|(ro ? MS_RDONLY : 0); } int mount_credentials_fs(const char *path, size_t size, bool ro) { _cleanup_free_ char *opts = NULL; int r, noswap_supported; /* Mounts a file system we can place credentials in, i.e. with tight access modes right from the * beginning, and ideally swapping turned off. In order of preference: * * 1. tmpfs if it supports "noswap" * 2. ramfs * 3. tmpfs if it doesn't support "noswap" */ noswap_supported = mount_option_supported("tmpfs", "noswap", NULL); /* Check explicitly to avoid kmsg noise */ if (noswap_supported > 0) { _cleanup_free_ char *noswap_opts = NULL; if (asprintf(&noswap_opts, "mode=0700,nr_inodes=1024,size=%zu,noswap", size) < 0) return -ENOMEM; /* Best case: tmpfs with noswap (needs kernel >= 6.3) */ r = mount_nofollow_verbose( LOG_DEBUG, "tmpfs", path, "tmpfs", credentials_fs_mount_flags(ro), noswap_opts); if (r >= 0) return r; } r = mount_nofollow_verbose( LOG_DEBUG, "ramfs", path, "ramfs", credentials_fs_mount_flags(ro), "mode=0700"); if (r >= 0) return r; if (asprintf(&opts, "mode=0700,nr_inodes=1024,size=%zu", size) < 0) return -ENOMEM; return mount_nofollow_verbose( LOG_DEBUG, "tmpfs", path, "tmpfs", credentials_fs_mount_flags(ro), opts); } int make_fsmount( int error_log_level, const char *what, const char *type, unsigned long flags, const char *options, int userns_fd) { _cleanup_close_ int fs_fd = -EBADF, mnt_fd = -EBADF; _cleanup_free_ char *o = NULL; unsigned long f; int r; assert(type); assert(what); 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)); if (DEBUG_LOGGING) { _cleanup_free_ char *fl = NULL; (void) mount_flags_to_string(f, &fl); log_debug("Creating mount fd for %s (%s) (%s \"%s\")...", strna(what), strna(type), strnull(fl), strempty(o)); } fs_fd = fsopen(type, FSOPEN_CLOEXEC); if (fs_fd < 0) return log_full_errno(error_log_level, errno, "Failed to open superblock for \"%s\": %m", type); if (fsconfig(fs_fd, FSCONFIG_SET_STRING, "source", what, 0) < 0) return log_full_errno(error_log_level, errno, "Failed to set mount source for \"%s\" to \"%s\": %m", type, what); if (FLAGS_SET(f, MS_RDONLY)) if (fsconfig(fs_fd, FSCONFIG_SET_FLAG, "ro", NULL, 0) < 0) return log_full_errno(error_log_level, errno, "Failed to set read only mount flag for \"%s\": %m", type); for (const char *p = o;;) { _cleanup_free_ char *word = NULL; char *eq; r = extract_first_word(&p, &word, ",", EXTRACT_KEEP_QUOTE); if (r < 0) return log_full_errno(error_log_level, r, "Failed to parse mount option string \"%s\": %m", o); if (r == 0) break; eq = strchr(word, '='); if (eq) { *eq = 0; eq++; if (fsconfig(fs_fd, FSCONFIG_SET_STRING, word, eq, 0) < 0) return log_full_errno(error_log_level, errno, "Failed to set mount option \"%s=%s\" for \"%s\": %m", word, eq, type); } else { if (fsconfig(fs_fd, FSCONFIG_SET_FLAG, word, NULL, 0) < 0) return log_full_errno(error_log_level, errno, "Failed to set mount flag \"%s\" for \"%s\": %m", word, type); } } if (fsconfig(fs_fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0) < 0) return log_full_errno(error_log_level, errno, "Failed to realize fs fd for \"%s\" (\"%s\"): %m", what, type); mnt_fd = fsmount(fs_fd, FSMOUNT_CLOEXEC, 0); if (mnt_fd < 0) return log_full_errno(error_log_level, errno, "Failed to create mount fd for \"%s\" (\"%s\"): %m", what, type); struct mount_attr ma = { .attr_set = ms_flags_to_mount_attr(f) | (userns_fd >= 0 ? MOUNT_ATTR_IDMAP : 0), .userns_fd = userns_fd, }; if (ma.attr_set != 0 && mount_setattr(mnt_fd, "", AT_EMPTY_PATH|AT_RECURSIVE, &ma, MOUNT_ATTR_SIZE_VER0) < 0) return log_full_errno(error_log_level, errno, "Failed to set mount flags for \"%s\" (\"%s\"): %m", what, type); return TAKE_FD(mnt_fd); }