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systemd/src/shared/mount-setup.c

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/statvfs.h>
#include <unistd.h>
#include "alloc-util.h"
#include "bus-util.h"
#include "cgroup-setup.h"
#include "cgroup-util.h"
#include "conf-files.h"
#include "dev-setup.h"
#include "dirent-util.h"
#include "efi-loader.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "label-util.h"
#include "log.h"
#include "macro.h"
#include "mkdir-label.h"
#include "mount-setup.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "nulstr-util.h"
#include "path-util.h"
#include "recurse-dir.h"
#include "set.h"
#include "smack-util.h"
#include "strv.h"
#include "user-util.h"
#include "virt.h"
typedef enum MountMode {
MNT_NONE = 0,
MNT_FATAL = 1 << 0,
MNT_IN_CONTAINER = 1 << 1,
MNT_CHECK_WRITABLE = 1 << 2,
MNT_FOLLOW_SYMLINK = 1 << 3,
} MountMode;
typedef struct MountPoint {
const char *what;
const char *where;
const char *type;
const char *options;
unsigned long flags;
bool (*condition_fn)(void);
MountMode mode;
} MountPoint;
/* The first three entries we might need before SELinux is up. The
* fourth (securityfs) is needed by IMA to load a custom policy. The
* other ones we can delay until SELinux and IMA are loaded. When
* SMACK is enabled we need smackfs, too, so it's a fifth one. */
#if ENABLE_SMACK
#define N_EARLY_MOUNT 5
#else
#define N_EARLY_MOUNT 4
#endif
static bool check_recursiveprot_supported(void) {
int r;
if (!cg_is_unified_wanted())
return false;
r = mount_option_supported("cgroup2", "memory_recursiveprot", NULL);
if (r < 0)
log_debug_errno(r, "Failed to determiner whether the 'memory_recursiveprot' mount option is supported, assuming not: %m");
else if (r == 0)
log_debug("This kernel version does not support 'memory_recursiveprot', not using mount option.");
return r > 0;
}
static const MountPoint mount_table[] = {
{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_FATAL|MNT_IN_CONTAINER|MNT_FOLLOW_SYMLINK },
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devtmpfs", "/dev", "devtmpfs", "mode=0755" TMPFS_LIMITS_DEV, MS_NOSUID|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "securityfs", "/sys/kernel/security", "securityfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },
#if ENABLE_SMACK
{ "smackfs", "/sys/fs/smackfs", "smackfs", "smackfsdef=*", MS_NOSUID|MS_NOEXEC|MS_NODEV,
mac_smack_use, MNT_FATAL },
{ "tmpfs", "/dev/shm", "tmpfs", "mode=01777,smackfsroot=*", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
mac_smack_use, MNT_FATAL },
#endif
{ "tmpfs", "/dev/shm", "tmpfs", "mode=01777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devpts", "/dev/pts", "devpts", "mode=0620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC,
NULL, MNT_IN_CONTAINER },
#if ENABLE_SMACK
{ "tmpfs", "/run", "tmpfs", "mode=0755,smackfsroot=*" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
mac_smack_use, MNT_FATAL },
#endif
{ "tmpfs", "/run", "tmpfs", "mode=0755" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "cgroup2", "/sys/fs/cgroup", "cgroup2", "nsdelegate,memory_recursiveprot", MS_NOSUID|MS_NOEXEC|MS_NODEV,
check_recursiveprot_supported, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
{ "cgroup2", "/sys/fs/cgroup", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
{ "cgroup2", "/sys/fs/cgroup", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
#if ENABLE_PSTORE
{ "pstore", "/sys/fs/pstore", "pstore", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },
#endif
#if ENABLE_EFI
{ "efivarfs", "/sys/firmware/efi/efivars", "efivarfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
is_efi_boot, MNT_NONE },
#endif
{ "bpf", "/sys/fs/bpf", "bpf", "mode=0700", MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE, },
};
assert_cc(N_EARLY_MOUNT <= ELEMENTSOF(mount_table));
bool mount_point_is_api(const char *path) {
/* Checks if this mount point is considered "API", and hence
* should be ignored */
FOREACH_ARRAY(i, mount_table, ELEMENTSOF(mount_table))
if (path_equal(path, i->where))
return true;
return path_startswith(path, "/sys/fs/cgroup/");
}
bool mount_point_ignore(const char *path) {
/* These are API file systems that might be mounted by other software, we just list them here so that
* we know that we should ignore them. */
FOREACH_STRING(i,
/* SELinux file systems */
"/sys/fs/selinux",
/* Container bind mounts */
"/dev/console",
"/proc/kmsg",
"/proc/sys",
"/proc/sys/kernel/random/boot_id")
if (path_equal(path, i))
return true;
if (path_startswith(path, "/run/host")) /* All mounts passed in from the container manager are
* something we better ignore. */
return true;
return false;
}
static int mount_one(const MountPoint *p, bool relabel) {
int r, priority;
assert(p);
assert(p->what);
assert(p->where);
assert(p->type);
priority = FLAGS_SET(p->mode, MNT_FATAL) ? LOG_ERR : LOG_DEBUG;
if (p->condition_fn && !p->condition_fn())
return 0;
/* Relabel first, just in case */
if (relabel)
(void) label_fix(p->where, LABEL_IGNORE_ENOENT|LABEL_IGNORE_EROFS);
r = path_is_mount_point_full(p->where, /* root = */ NULL, AT_SYMLINK_FOLLOW);
if (r < 0 && r != -ENOENT) {
log_full_errno(priority, r, "Failed to determine whether %s is a mount point: %m", p->where);
return FLAGS_SET(p->mode, MNT_FATAL) ? r : 0;
}
if (r > 0)
return 0;
/* Skip securityfs in a container */
if (!FLAGS_SET(p->mode, MNT_IN_CONTAINER) && detect_container() > 0)
return 0;
/* The access mode here doesn't really matter too much, since
* the mounted file system will take precedence anyway. */
if (relabel)
(void) mkdir_p_label(p->where, 0755);
else
(void) mkdir_p(p->where, 0755);
log_debug("Mounting %s to %s of type %s with options %s.",
p->what,
p->where,
p->type,
strna(p->options));
if (FLAGS_SET(p->mode, MNT_FOLLOW_SYMLINK))
r = mount_follow_verbose(priority, p->what, p->where, p->type, p->flags, p->options);
else
r = mount_nofollow_verbose(priority, p->what, p->where, p->type, p->flags, p->options);
if (r < 0)
return FLAGS_SET(p->mode, MNT_FATAL) ? r : 0;
/* Relabel again, since we now mounted something fresh here */
if (relabel)
(void) label_fix(p->where, 0);
if (FLAGS_SET(p->mode, MNT_CHECK_WRITABLE))
if (access(p->where, W_OK) < 0) {
r = -errno;
(void) umount2(p->where, UMOUNT_NOFOLLOW);
(void) rmdir(p->where);
log_full_errno(priority, r, "Mount point '%s' not writable after mounting, undoing: %m", p->where);
return FLAGS_SET(p->mode, MNT_FATAL) ? r : 0;
}
return 1;
}
static int mount_points_setup(size_t n, bool loaded_policy) {
int r = 0;
assert(n <= ELEMENTSOF(mount_table));
FOREACH_ARRAY(mp, mount_table, n)
RET_GATHER(r, mount_one(mp, loaded_policy));
return r;
}
int mount_setup_early(void) {
/* Do a minimal mount of /proc and friends to enable the most basic stuff, such as SELinux */
return mount_points_setup(N_EARLY_MOUNT, /* loaded_policy= */ false);
}
static const char *join_with(const char *controller) {
static const char* const pairs[] = {
"cpu", "cpuacct",
"net_cls", "net_prio",
NULL
};
assert(controller);
/* This will lookup which controller to mount another controller with. Input is a controller name, and output
* is the other controller name. The function works both ways: you can input one and get the other, and input
* the other to get the one. */
STRV_FOREACH_PAIR(x, y, pairs) {
if (streq(controller, *x))
return *y;
if (streq(controller, *y))
return *x;
}
return NULL;
}
static int symlink_controller(const char *target, const char *alias) {
const char *a;
int r;
assert(target);
assert(alias);
a = strjoina("/sys/fs/cgroup/", alias);
r = symlink_idempotent(target, a, false);
if (r < 0)
return log_error_errno(r, "Failed to create symlink %s: %m", a);
#if HAVE_SMACK_RUN_LABEL
const char *p;
p = strjoina("/sys/fs/cgroup/", target);
r = mac_smack_copy(a, p);
if (r < 0 && !ERRNO_IS_NOT_SUPPORTED(r))
return log_error_errno(r, "Failed to copy smack label from %s to %s: %m", p, a);
#endif
return 0;
}
#if HAVE_SELINUX || ENABLE_SMACK
static int relabel_cb(
RecurseDirEvent event,
const char *path,
int dir_fd,
int inode_fd,
const struct dirent *de,
const struct statx *sx,
void *userdata) {
switch (event) {
case RECURSE_DIR_LEAVE:
case RECURSE_DIR_SKIP_MOUNT:
/* If we already saw this dirent when entering it or this is a dirent that on a different
* mount, don't relabel it. */
return RECURSE_DIR_CONTINUE;
case RECURSE_DIR_ENTER:
/* /run/initramfs/ + /run/nextroot/ are static data and big, no need to dynamically relabel
* its contents at boot... */
if (PATH_STARTSWITH_SET(path, "/run/initramfs", "/run/nextroot"))
return RECURSE_DIR_SKIP_ENTRY;
_fallthrough_;
default:
/* Otherwise, label it, even if we had trouble stat()ing it and similar. SELinux can figure this out */
(void) label_fix(path, 0);
return RECURSE_DIR_CONTINUE;
}
}
static int relabel_tree(const char *path) {
int r;
r = recurse_dir_at(AT_FDCWD, path, 0, UINT_MAX, RECURSE_DIR_ENSURE_TYPE|RECURSE_DIR_SAME_MOUNT, relabel_cb, NULL);
if (r < 0)
log_debug_errno(r, "Failed to recursively relabel '%s': %m", path);
return r;
}
static int relabel_extra(void) {
_cleanup_strv_free_ char **files = NULL;
int r, c = 0;
/* Support for relabelling additional files or directories after loading the policy. For this, code in the
* initrd simply has to drop in *.relabel files into /run/systemd/relabel-extra.d/. We'll read all such files
* expecting one absolute path by line and will relabel each (and everyone below that in case the path refers
* to a directory). These drop-in files are supposed to be absolutely minimal, and do not understand comments
* and such. After the operation succeeded the files are removed, and the drop-in directory as well, if
* possible.
*/
r = conf_files_list(&files, ".relabel", NULL,
CONF_FILES_FILTER_MASKED | CONF_FILES_REGULAR,
"/run/systemd/relabel-extra.d/");
if (r < 0)
return log_error_errno(r, "Failed to enumerate /run/systemd/relabel-extra.d/, ignoring: %m");
STRV_FOREACH(file, files) {
_cleanup_fclose_ FILE *f = NULL;
f = fopen(*file, "re");
if (!f) {
log_warning_errno(errno, "Failed to open %s, ignoring: %m", *file);
continue;
}
for (;;) {
_cleanup_free_ char *line = NULL;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0) {
log_warning_errno(r, "Failed to read %s, ignoring: %m", *file);
break;
}
if (r == 0) /* EOF */
break;
path_simplify(line);
if (!path_is_normalized(line)) {
log_warning("Path to relabel is not normalized, ignoring: %s", line);
continue;
}
if (!path_is_absolute(line)) {
log_warning("Path to relabel is not absolute, ignoring: %s", line);
continue;
}
log_debug("Relabelling additional file/directory '%s'.", line);
(void) label_fix(line, 0);
(void) relabel_tree(line);
c++;
}
if (unlink(*file) < 0)
log_warning_errno(errno, "Failed to remove %s, ignoring: %m", *file);
}
/* Remove when we complete things. */
if (rmdir("/run/systemd/relabel-extra.d") < 0 &&
errno != ENOENT)
log_warning_errno(errno, "Failed to remove /run/systemd/relabel-extra.d/ directory: %m");
return c;
}
#endif
int mount_setup(bool loaded_policy, bool leave_propagation) {
int r;
r = mount_points_setup(ELEMENTSOF(mount_table), loaded_policy);
if (r < 0)
return r;
#if HAVE_SELINUX || ENABLE_SMACK
/* Nodes in devtmpfs and /run need to be manually updated for
* the appropriate labels, after mounting. The other virtual
* API file systems like /sys and /proc do not need that, they
* use the same label for all their files. */
if (loaded_policy) {
usec_t before_relabel, after_relabel;
int n_extra;
before_relabel = now(CLOCK_MONOTONIC);
FOREACH_STRING(i, "/dev", "/dev/shm", "/run")
(void) relabel_tree(i);
n_extra = relabel_extra();
after_relabel = now(CLOCK_MONOTONIC);
log_info("Relabeled /dev/, /dev/shm/, /run/%s in %s.",
n_extra > 0 ? ", and additional files" : "",
FORMAT_TIMESPAN(after_relabel - before_relabel, 0));
}
#endif
/* Create a few default symlinks, which are normally created
* by udevd, but some scripts might need them before we start
* udevd. */
dev_setup(NULL, UID_INVALID, GID_INVALID);
/* Mark the root directory as shared in regards to mount propagation. The kernel defaults to "private", but we
* think it makes more sense to have a default of "shared" so that nspawn and the container tools work out of
* the box. If specific setups need other settings they can reset the propagation mode to private if
* needed. Note that we set this only when we are invoked directly by the kernel. If we are invoked by a
* container manager we assume the container manager knows what it is doing (for example, because it set up
* some directories with different propagation modes). */
if (detect_container() <= 0 && !leave_propagation)
if (mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL) < 0)
log_warning_errno(errno, "Failed to set up the root directory for shared mount propagation: %m");
/* Create a few directories we always want around, Note that sd_booted() checks for /run/systemd/system, so
* this mkdir really needs to stay for good, otherwise software that copied sd-daemon.c into their sources will
* misdetect systemd. */
(void) mkdir_label("/run/systemd", 0755);
(void) mkdir_label("/run/systemd/system", 0755);
/* Make sure there's always a place where sandboxed environments can mount root file systems they are
* about to move into, even when unprivileged, without having to create a temporary one in /tmp/
* (which they then have to keep track of and clean) */
(void) mkdir_label("/run/systemd/mount-rootfs", 0555);
/* Make sure we have a mount point to hide in sandboxes */
(void) mkdir_label("/run/credentials", 0755);
/* Also create /run/systemd/inaccessible nodes, so that we always have something to mount
* inaccessible nodes from. If we run in a container the host might have created these for us already
* in /run/host/inaccessible/. Use those if we can, since that way we likely get access to block/char
* device nodes that are inaccessible, and if userns is used to nodes that are on mounts owned by a
* userns outside the container and thus nicely read-only and not remountable. */
if (access("/run/host/inaccessible/", F_OK) < 0) {
if (errno != ENOENT)
log_debug_errno(errno, "Failed to check if /run/host/inaccessible exists, ignoring: %m");
(void) make_inaccessible_nodes("/run/systemd", UID_INVALID, GID_INVALID);
} else
(void) symlink("../host/inaccessible", "/run/systemd/inaccessible");
return 0;
}
static const MountPoint cgroupv1_mount_table[] = {
{ "tmpfs", "/sys/fs/cgroup", "tmpfs", "mode=0755" TMPFS_LIMITS_SYS_FS_CGROUP, MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
{ "cgroup2", "/sys/fs/cgroup/unified", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
{ "cgroup2", "/sys/fs/cgroup/unified", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
{ "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd,xattr", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_legacy_wanted, MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
};
static void relabel_cgroup_legacy_hierarchy(void) {
#if HAVE_SELINUX || ENABLE_SMACK
struct statfs st;
assert(cg_is_legacy_wanted());
/* Temporarily remount the root cgroup filesystem to give it a proper label. Do this
only when the filesystem has been already populated by a previous instance of systemd
running from initrd. Otherwise don't remount anything and leave the filesystem read-write
for the cgroup filesystems to be mounted inside. */
if (statfs("/sys/fs/cgroup", &st) < 0)
return (void) log_error_errno(errno, "Failed to determine mount flags for /sys/fs/cgroup/: %m");
if (st.f_flags & ST_RDONLY)
(void) mount_nofollow(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);
(void) label_fix("/sys/fs/cgroup", 0);
(void) relabel_tree("/sys/fs/cgroup");
if (st.f_flags & ST_RDONLY)
(void) mount_nofollow(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
#endif
}
int mount_cgroup_legacy_controllers(bool loaded_policy) {
_cleanup_set_free_ Set *controllers = NULL;
int r;
if (!cg_is_legacy_wanted())
return 0;
FOREACH_ARRAY(mp, cgroupv1_mount_table, ELEMENTSOF(cgroupv1_mount_table)) {
r = mount_one(mp, loaded_policy);
if (r < 0)
return r;
}
if (loaded_policy)
relabel_cgroup_legacy_hierarchy();
/* Mount all available cgroup controllers that are built into the kernel. */
r = cg_kernel_controllers(&controllers);
if (r < 0)
return log_error_errno(r, "Failed to enumerate cgroup controllers: %m");
for (;;) {
_cleanup_free_ char *options = NULL, *controller = NULL, *where = NULL;
const char *other_controller;
MountPoint p = {
.what = "cgroup",
.type = "cgroup",
.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV,
.mode = MNT_IN_CONTAINER,
};
controller = set_steal_first(controllers);
if (!controller)
break;
/* Check if we shall mount this together with another controller */
other_controller = join_with(controller);
if (other_controller) {
_cleanup_free_ char *c = NULL;
/* Check if the other controller is actually available in the kernel too */
c = set_remove(controllers, other_controller);
if (c) {
/* Join the two controllers into one string, and maintain a stable ordering */
if (strcmp(controller, other_controller) < 0)
options = strjoin(controller, ",", other_controller);
else
options = strjoin(other_controller, ",", controller);
if (!options)
return log_oom();
}
}
/* The simple case, where there's only one controller to mount together */
if (!options)
options = TAKE_PTR(controller);
where = path_join("/sys/fs/cgroup", options);
if (!where)
return log_oom();
p.where = where;
p.options = options;
r = mount_one(&p, true);
if (r < 0)
return r;
/* Create symlinks from the individual controller names, in case we have a joined mount */
if (controller)
(void) symlink_controller(options, controller);
if (other_controller)
(void) symlink_controller(options, other_controller);
}
/* Now that we mounted everything, let's make the tmpfs the cgroup file systems are mounted into read-only. */
(void) mount_nofollow("tmpfs", "/sys/fs/cgroup", "tmpfs",
MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY,
"mode=0755" TMPFS_LIMITS_SYS_FS_CGROUP);
return 1;
}
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