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48542eac39999f58f6c331b4b3cdf2d78bf15979
systemd/src/shared/mount-util.c
Yu Watanabe de010b0b2e strv: make iterator in STRV_FOREACH() declaread in the loop 
This also avoids multiple evaluations in STRV_FOREACH_BACKWARDS()
2022-03-19 08:33:33 +09:00

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/* 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>
#include <linux/fs.h>
#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 "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_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;
}
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\")...",
what, where, strnull(fl), strempty(o));
else
log_debug("Mounting %s (%s) on %s (%s \"%s\")...",
strna(what), strna(type), where, strnull(fl), strempty(o));
if (follow_symlink)
r = 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 && !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 self_mntns_fd = -1, 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;
struct stat st, self_mntns_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");
if (fstat(mntns_fd, &st) < 0)
return log_debug_errno(errno, "Failed to fstat mount namespace FD of target process: %m");
r = namespace_open(0, NULL, &self_mntns_fd, NULL, NULL, NULL);
if (r < 0)
return log_debug_errno(r, "Failed to retrieve FDs of systemd's namespace: %m");
if (fstat(self_mntns_fd, &self_mntns_st) < 0)
return log_debug_errno(errno, "Failed to fstat mount namespace FD of systemd: %m");
/* We can't add new mounts at runtime if the process wasn't started in a namespace */
if (stat_inode_same(&st, &self_mntns_st))
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, CHASE_TRAIL_SLASH, NULL, &chased_src_fd);
if (r < 0)
return log_debug_errno(r, "Failed to resolve source path of %s: %m", src);
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(FORMAT_PROC_FD_PATH(chased_src_fd), 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, RemountIdmapFlags flags) {
_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 (asprintf(&line, UID_FMT " " UID_FMT " " UID_FMT "\n", 0, 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_HOST_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 (flags & REMOUNT_IDMAP_HOST_ROOT)
if (strextendf(&line,
UID_FMT " " UID_FMT " " UID_FMT "\n",
UID_MAPPED_ROOT, 0, 1) < 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,
RemountIdmapFlags flags) {
_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, flags);
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 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);
}
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