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systemd/src/shared/mount-util.c
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Lennart Poettering ba8dced2a6 mount-util: store mount flags in "todo" list in + handle submounts gracefully 
This replaces the "todo" set with a "todo" hash map that stores the
mount flags we found. This makes an explicit call to get_mount_flags()
unncessary, since we have the flags handy right-away, and lowers our
work from O(n^2) to O(n). Nice!

The "done" set is also improved slightly: we'll use more modern ways to
allocate it, via set_ensure_consume(), and freeing-via-hash_ops.

Finally, failures on submount remounts are now handled gracefully,
there are just too many reasons why they might fail, given NFS, autofs,
FUSE which weird access controls, where even root might lack the privs
to do something.

Fixes: #16156
2021-03-26 11:51:26 +01:00

1029 lines
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <linux/loop.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <unistd.h>
#include "alloc-util.h"
#include "dissect-image.h"
#include "extract-word.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hashmap.h"
#include "libmount-util.h"
#include "mkdir.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) {
char path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
xsprintf(path, "/proc/self/fd/%i", target_fd);
if (mount(source, path, 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;
}
static int get_mount_flags(
struct libmnt_table *table,
const char *path,
unsigned long *ret) {
_cleanup_close_ int fd = -1;
struct libmnt_fs *fs;
struct statvfs buf;
const char *opts;
int r;
/* Get the mount flags for the mountpoint at "path" from "table". We have a fallback using statvfs()
* in place (which provides us with mostly the same info), but it's just a fallback, since using it
* means triggering autofs or NFS mounts, which we'd rather avoid needlessly.
*
* This generally doesn't follow symlinks. */
fs = mnt_table_find_target(table, path, MNT_ITER_FORWARD);
if (!fs) {
log_debug("Could not find '%s' in mount table, ignoring.", path);
goto fallback;
}
opts = mnt_fs_get_vfs_options(fs);
if (!opts) {
*ret = 0;
return 0;
}
r = mnt_optstr_get_flags(opts, ret, mnt_get_builtin_optmap(MNT_LINUX_MAP));
if (r != 0) {
log_debug_errno(r, "Could not get flags for '%s', ignoring: %m", path);
goto fallback;
}
/* MS_RELATIME is default and trying to set it in an unprivileged container causes EPERM */
*ret &= ~MS_RELATIME;
return 0;
fallback:
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
if (fd < 0)
return -errno;
if (fstatvfs(fd, &buf) < 0)
return -errno;
/* The statvfs() flags and the mount flags mostly have the same values, but for some cases do
* not. Hence map the flags manually. (Strictly speaking, ST_RELATIME/MS_RELATIME is the most
* prominent one that doesn't match, but that's the one we mask away anyway, see above.) */
*ret =
FLAGS_SET(buf.f_flag, ST_RDONLY) * MS_RDONLY |
FLAGS_SET(buf.f_flag, ST_NODEV) * MS_NODEV |
FLAGS_SET(buf.f_flag, ST_NOEXEC) * MS_NOEXEC |
FLAGS_SET(buf.f_flag, ST_NOSUID) * MS_NOSUID |
FLAGS_SET(buf.f_flag, ST_NOATIME) * MS_NOATIME |
FLAGS_SET(buf.f_flag, ST_NODIRATIME) * MS_NODIRATIME;
return 0;
}
/* 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_set_free_ Set *done = NULL;
unsigned n_tries = 0;
int r;
assert(prefix);
assert(proc_self_mountinfo);
/* 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;
char **i;
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)
continue;
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_recursive(
const char *prefix,
unsigned long new_flags,
unsigned long flags_mask,
char **deny_list) {
_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
int r;
r = fopen_unlocked("/proc/self/mountinfo", "re", &proc_self_mountinfo);
if (r < 0)
return r;
return bind_remount_recursive_with_mountinfo(prefix, new_flags, flags_mask, deny_list, proc_self_mountinfo);
}
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 orig_flags = 0;
int r;
assert(path);
assert(proc_self_mountinfo);
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;
/* Try to reuse the original flag set */
(void) get_mount_flags(table, path, &orig_flags);
r = mount_nofollow(NULL, path, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL);
if (r < 0)
return r;
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;
if (chdir("/") < 0)
return -errno;
return 0;
}
int repeat_unmount(const char *path, int flags) {
bool done = false;
assert(path);
/* If there are multiple mounts on a mount point, this
* removes them all */
for (;;) {
if (umount2(path, flags) < 0) {
if (errno == EINVAL)
return done;
return -errno;
}
done = true;
}
}
int mode_to_inaccessible_node(
const char *runtime_dir,
mode_t mode,
char **ret) {
/* This function maps a node type to a corresponding inaccessible file node. These nodes are created
* during early boot by PID 1. In some cases we lacked the privs to create the character and block
* devices (maybe because we run in an userns environment, or miss CAP_SYS_MKNOD, or run with a
* devices policy that excludes device nodes with major and minor of 0), but that's fine, in that
* case we use an AF_UNIX file node instead, which is not the same, but close enough for most
* uses. And most importantly, the kernel allows bind mounts from socket nodes to any non-directory
* file nodes, and that's the most important thing that matters.
*
* Note that the runtime directory argument shall be the top-level runtime directory, i.e. /run/ if
* we operate in system context and $XDG_RUNTIME_DIR if we operate in user context. */
_cleanup_free_ char *d = NULL;
const char *node = NULL;
assert(ret);
if (!runtime_dir)
runtime_dir = "/run";
switch(mode & S_IFMT) {
case S_IFREG:
node = "/systemd/inaccessible/reg";
break;
case S_IFDIR:
node = "/systemd/inaccessible/dir";
break;
case S_IFCHR:
node = "/systemd/inaccessible/chr";
break;
case S_IFBLK:
node = "/systemd/inaccessible/blk";
break;
case S_IFIFO:
node = "/systemd/inaccessible/fifo";
break;
case S_IFSOCK:
node = "/systemd/inaccessible/sock";
break;
}
if (!node)
return -EINVAL;
d = path_join(runtime_dir, node);
if (!d)
return -ENOMEM;
/* On new kernels unprivileged users are permitted to create 0:0 char device nodes (because they also
* act as whiteout inode for overlayfs), but no other char or block device nodes. On old kernels no
* device node whatsoever may be created by unprivileged processes. Hence, if the caller asks for the
* inaccessible block device node let's see if the block device node actually exists, and if not,
* fall back to the character device node. From there fall back to the socket device node. This means
* in the best case we'll get the right device node type — but if not we'll hopefully at least get a
* device node at all. */
if (S_ISBLK(mode) &&
access(d, F_OK) < 0 && errno == ENOENT) {
free(d);
d = path_join(runtime_dir, "/systemd/inaccessible/chr");
if (!d)
return -ENOMEM;
}
if (IN_SET(mode & S_IFMT, S_IFBLK, S_IFCHR) &&
access(d, F_OK) < 0 && errno == ENOENT) {
free(d);
d = path_join(runtime_dir, "/systemd/inaccessible/sock");
if (!d)
return -ENOMEM;
}
*ret = TAKE_PTR(d);
return 0;
}
#define FLAG(name) (flags & name ? STRINGIFY(name) "|" : "")
static char* mount_flags_to_string(long unsigned flags) {
char *x;
_cleanup_free_ char *y = NULL;
long unsigned overflow;
overflow = flags & ~(MS_RDONLY |
MS_NOSUID |
MS_NODEV |
MS_NOEXEC |
MS_SYNCHRONOUS |
MS_REMOUNT |
MS_MANDLOCK |
MS_DIRSYNC |
MS_NOATIME |
MS_NODIRATIME |
MS_BIND |
MS_MOVE |
MS_REC |
MS_SILENT |
MS_POSIXACL |
MS_UNBINDABLE |
MS_PRIVATE |
MS_SLAVE |
MS_SHARED |
MS_RELATIME |
MS_KERNMOUNT |
MS_I_VERSION |
MS_STRICTATIME |
MS_LAZYTIME);
if (flags == 0 || overflow != 0)
if (asprintf(&y, "%lx", overflow) < 0)
return NULL;
x = strjoin(FLAG(MS_RDONLY),
FLAG(MS_NOSUID),
FLAG(MS_NODEV),
FLAG(MS_NOEXEC),
FLAG(MS_SYNCHRONOUS),
FLAG(MS_REMOUNT),
FLAG(MS_MANDLOCK),
FLAG(MS_DIRSYNC),
FLAG(MS_NOATIME),
FLAG(MS_NODIRATIME),
FLAG(MS_BIND),
FLAG(MS_MOVE),
FLAG(MS_REC),
FLAG(MS_SILENT),
FLAG(MS_POSIXACL),
FLAG(MS_UNBINDABLE),
FLAG(MS_PRIVATE),
FLAG(MS_SLAVE),
FLAG(MS_SHARED),
FLAG(MS_RELATIME),
FLAG(MS_KERNMOUNT),
FLAG(MS_I_VERSION),
FLAG(MS_STRICTATIME),
FLAG(MS_LAZYTIME),
y);
if (!x)
return NULL;
if (!y)
x[strlen(x) - 1] = '\0'; /* truncate the last | */
return x;
}
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));
fl = mount_flags_to_string(f);
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 = mount(what, where, type, f, o) < 0 ? -errno : 0;
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;
const char *p;
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;
p = options;
for (;;) {
_cleanup_free_ char *word = NULL;
const struct libmnt_optmap *ent;
r = extract_first_word(&p, &word, ",", EXTRACT_UNQUOTE);
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,
chased_src[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int)];
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 (st.st_ino == self_mntns_st.st_ino && st.st_dev == self_mntns_st.st_dev)
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);
xsprintf(chased_src, "/proc/self/fd/%i", chased_src_fd);
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, mount_tmp, options, NULL, NULL, NULL);
else
r = mount_follow_verbose(LOG_DEBUG, chased_src, 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);
}
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