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Diffstat (limited to '')
| -rw-r--r-- | src/shared/mount-util.c | 1161 |
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); +} |