| /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
| |
| #include <errno.h> |
| #include <stdlib.h> |
| #include <sys/mount.h> |
| #include <sys/stat.h> |
| #include <sys/statvfs.h> |
| #include <unistd.h> |
| #include <linux/loop.h> |
| #if WANT_LINUX_FS_H |
| #include <linux/fs.h> |
| #endif |
| |
| #include "alloc-util.h" |
| #include "chase-symlinks.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.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 "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(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; |
| } |
| |
| #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_debug("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_debug("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) { |
| if (laccess(path, F_OK) < 0) /* Hmm, it's not in the mount table, but does it exist at all? */ |
| return -errno; |
| |
| 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(const char *path, int fd_newroot) { |
| _cleanup_close_ int fd_oldroot = -EBADF; |
| |
| fd_oldroot = open("/", O_PATH|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW); |
| if (fd_oldroot < 0) |
| return log_debug_errno(errno, "Failed to open old rootfs"); |
| |
| /* 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); |
| |
| /* At this point the new root is tucked under the old root. If we want |
| * to unmount it we cannot be fchdir()ed into it. So escape back to the |
| * old root. */ |
| if (fchdir(fd_oldroot) < 0) |
| return log_debug_errno(errno, "Failed to change back to old rootfs: %m"); |
| |
| /* Note, usually we should set mount propagation up here but we'll |
| * assume that the caller has already done that. */ |
| |
| /* Get rid of the old root and reveal our brand new root. */ |
| if (umount2(".", MNT_DETACH) < 0) |
| return log_debug_errno(errno, "Failed to unmount old rootfs: %m"); |
| |
| if (fchdir(fd_newroot) < 0) |
| return log_debug_errno(errno, "Failed to switch to new rootfs '%s': %m", path); |
| |
| return 0; |
| } |
| |
| static int mount_switch_root_move(const char *path) { |
| if (mount(path, "/", NULL, MS_MOVE, NULL) < 0) |
| return log_debug_errno(errno, "Failed to move new rootfs '%s': %m", path); |
| |
| if (chroot(".") < 0) |
| return log_debug_errno(errno, "Failed to chroot to new rootfs '%s': %m", path); |
| |
| if (chdir("/")) |
| return log_debug_errno(errno, "Failed to chdir to new rootfs '%s': %m", path); |
| |
| return 0; |
| } |
| |
| int mount_switch_root(const char *path, unsigned long mount_propagation_flag) { |
| _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); |
| |
| /* Change into the new rootfs. */ |
| if (fchdir(fd_newroot) < 0) |
| return log_debug_errno(errno, "Failed to change into new rootfs '%s': %m", path); |
| |
| r = mount_switch_root_pivot(path, fd_newroot); |
| if (r < 0) { |
| /* 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. */ |
| log_debug_errno(r, "Failed to pivot into new rootfs '%s': %m", path); |
| r = mount_switch_root_move(path); |
| } |
| if (r < 0) |
| return log_debug_errno(r, "Failed to switch to new rootfs '%s': %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 = 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; |
| } |
| |
| 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 ((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 \"%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_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( |
| pid_t 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, |
| bool is_image) { |
| |
| _cleanup_close_pair_ int errno_pipe_fd[2] = PIPE_EBADF; |
| _cleanup_close_ int mntns_fd = -EBADF, root_fd = -EBADF, pidns_fd = -EBADF, chased_src_fd = -EBADF; |
| 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; |
| _cleanup_free_ char *chased_src_path = NULL; |
| struct stat st; |
| pid_t child; |
| int r; |
| |
| assert(target > 0); |
| assert(propagate_path); |
| assert(incoming_path); |
| assert(src); |
| assert(dest); |
| assert(!options || is_image); |
| |
| r = namespace_open(target, &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, 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"); |
| |
| /* One day, when bind mounting /proc/self/fd/n works across namespace boundaries we should rework |
| * this logic to make use of it... */ |
| |
| 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"); |
| |
| r = chase_symlinks(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); |
| |
| /* 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(&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, NULL, NULL, NULL, 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(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(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, |
| 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(&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(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(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; |
| } |
| |
| int bind_mount_in_namespace( |
| pid_t 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, NULL, false); |
| } |
| |
| int mount_image_in_namespace( |
| pid_t 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) { |
| |
| return mount_in_namespace(target, propagate_path, incoming_path, src, dest, read_only, make_file_or_directory, options, 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; |
| } |
| |
| static 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 (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( |
| const char *p, |
| uid_t uid_shift, |
| uid_t uid_range, |
| uid_t owner, |
| RemountIdmapping idmapping) { |
| |
| _cleanup_close_ int mount_fd = -EBADF, userns_fd = -EBADF; |
| int r; |
| |
| assert(p); |
| |
| if (!userns_shift_range_valid(uid_shift, uid_range)) |
| return -EINVAL; |
| |
| /* Clone the mount point */ |
| mount_fd = open_tree(-1, p, OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC); |
| if (mount_fd < 0) |
| return log_debug_errno(errno, "Failed to open tree of mounted filesystem '%s': %m", p); |
| |
| /* Create a user namespace mapping */ |
| userns_fd = make_userns(uid_shift, uid_range, owner, idmapping); |
| if (userns_fd < 0) |
| return userns_fd; |
| |
| /* Set the user namespace mapping attribute on the cloned mount point */ |
| if (mount_setattr(mount_fd, "", AT_EMPTY_PATH | AT_RECURSIVE, |
| &(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 '%s': %m", p); |
| |
| /* Remove the old mount point */ |
| r = umount_verbose(LOG_DEBUG, p, UMOUNT_NOFOLLOW); |
| if (r < 0) |
| return r; |
| |
| /* And place the cloned version in its place */ |
| if (move_mount(mount_fd, "", -1, p, MOVE_MOUNT_F_EMPTY_PATH) < 0) |
| return log_debug_errno(errno, "Failed to attach UID mapped mount to '%s': %m", p); |
| |
| return 0; |
| } |
| |
| 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); |
| } |
