blob: 83ce749d12782545d43a85dbb3c54c8db3191b5b [file] [log] [blame] [raw]
/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <unistd.h>
#include "alloc-util.h"
#include "extract-word.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hashmap.h"
#include "libmount-util.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "parse-util.h"
#include "path-util.h"
#include "set.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#include "strv.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_free_ Set *done = NULL;
_cleanup_free_ char *simplified = NULL;
int r;
assert(prefix);
assert(proc_self_mountinfo);
/* Recursively remount a directory (and all its submounts) read-only or read-write. 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). If it isn't we first make it one. Afterwards we apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) 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. This includes
* future submounts that have been triggered via autofs.
*
* 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. */
simplified = strdup(prefix);
if (!simplified)
return -ENOMEM;
path_simplify(simplified, false);
done = set_new(&path_hash_ops);
if (!done)
return -ENOMEM;
for (;;) {
_cleanup_set_free_free_ Set *todo = NULL;
_cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL;
_cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL;
bool top_autofs = false;
char *x;
unsigned long orig_flags;
todo = set_new(&path_hash_ops);
if (!todo)
return -ENOMEM;
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 (;;) {
struct libmnt_fs *fs;
const char *path, *type;
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);
type = mnt_fs_get_fstype(fs);
if (!path || !type)
continue;
if (!path_startswith(path, simplified))
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, simplified)) {
bool deny_listed = false;
char **i;
STRV_FOREACH(i, deny_list) {
if (path_equal(*i, simplified))
continue;
if (!path_startswith(*i, simplified))
continue;
if (path_startswith(path, *i)) {
deny_listed = true;
log_debug("Not remounting %s deny-listed by %s, called for %s",
path, *i, simplified);
break;
}
}
if (deny_listed)
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, simplified);
continue;
}
if (!set_contains(done, path)) {
r = set_put_strdup(&todo, path);
if (r < 0)
return r;
}
}
/* If we have no submounts to process anymore and if
* the root is either already done, or an autofs, we
* are done */
if (set_isempty(todo) &&
(top_autofs || set_contains(done, simplified)))
return 0;
if (!set_contains(done, simplified) &&
!set_contains(todo, simplified)) {
/* The prefix directory itself is not yet a mount, make it one. */
r = mount_nofollow(simplified, simplified, NULL, MS_BIND|MS_REC, NULL);
if (r < 0)
return r;
orig_flags = 0;
(void) get_mount_flags(table, simplified, &orig_flags);
r = mount_nofollow(NULL, simplified, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL);
if (r < 0)
return r;
log_debug("Made top-level directory %s a mount point.", prefix);
r = set_put_strdup(&done, simplified);
if (r < 0)
return r;
}
while ((x = set_steal_first(todo))) {
r = set_consume(done, x);
if (IN_SET(r, 0, -EEXIST))
continue;
if (r < 0)
return r;
/* Deal with mount points that are obstructed by a later mount */
r = path_is_mount_point(x, NULL, 0);
if (IN_SET(r, 0, -ENOENT))
continue;
if (r < 0) {
if (!ERRNO_IS_PRIVILEGE(r))
return r;
/* Even if root user invoke this, submounts under private FUSE or NFS mount points
* may not be acceessed. E.g.,
*
* $ bindfs --no-allow-other ~/mnt/mnt ~/mnt/mnt
* $ bindfs --no-allow-other ~/mnt ~/mnt
*
* Then, root user cannot access the mount point ~/mnt/mnt.
* In such cases, the submounts are ignored, as we have no way to manage them. */
log_debug_errno(r, "Failed to determine '%s' is mount point or not, ignoring: %m", x);
continue;
}
/* Try to reuse the original flag set */
orig_flags = 0;
(void) get_mount_flags(table, x, &orig_flags);
r = mount_nofollow(NULL, x, NULL, (orig_flags & ~flags_mask)|MS_BIND|MS_REMOUNT|new_flags, NULL);
if (r < 0)
return r;
log_debug("Remounted %s read-only.", 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, NULL))
return -ENOMEM;
}
*ret_mount_flags = mount_flags;
*ret_remaining_options = TAKE_PTR(ret);
return 0;
}