summaryrefslogtreecommitdiffstats
path: root/src/shared/mount-util.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
commitb750101eb236130cf056c675997decbac904cc49 (patch)
treea5df1a06754bdd014cb975c051c83b01c9a97532 /src/shared/mount-util.c
parentInitial commit. (diff)
downloadsystemd-b750101eb236130cf056c675997decbac904cc49.tar.xz
systemd-b750101eb236130cf056c675997decbac904cc49.zip
Adding upstream version 252.22.upstream/252.22
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/shared/mount-util.c')
-rw-r--r--src/shared/mount-util.c1161
1 files changed, 1161 insertions, 0 deletions
diff --git a/src/shared/mount-util.c b/src/shared/mount-util.c
new file mode 100644
index 0000000..dd3fd79
--- /dev/null
+++ b/src/shared/mount-util.c
@@ -0,0 +1,1161 @@
+/* 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 "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-util.h"
+#include "strv.h"
+#include "tmpfile-util.h"
+#include "user-util.h"
+
+int mount_fd(const char *source,
+ int target_fd,
+ const char *filesystemtype,
+ unsigned long mountflags,
+ const void *data) {
+
+ if (mount(source, FORMAT_PROC_FD_PATH(target_fd), 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_trace("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_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) {
+ 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;
+}
+
+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;
+
+ return RET_NERRNO(chdir("/"));
+}
+
+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 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;
+
+ 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] = { -1, -1 };
+ _cleanup_close_ int mntns_fd = -1, root_fd = -1, pidns_fd = -1, chased_src_fd = -1;
+ 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) {
+ const char *mount_inside;
+
+ 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 */
+ mount_inside = strjoina(incoming_path, basename(mount_outside));
+ r = mount_nofollow_verbose(LOG_ERR, 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 = -1;
+ _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 = -1, userns_fd = -1;
+ 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);
+}