/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <unistd.h>
#include <linux/fs.h>
#include "alloc-util.h"
#include "base-filesystem.h"
#include "dev-setup.h"
#include "fd-util.h"
#include "fs-util.h"
#include "label.h"
#include "loop-util.h"
#include "loopback-setup.h"
#include "missing.h"
#include "mkdir.h"
#include "mount-util.h"
#include "namespace.h"
#include "path-util.h"
#include "selinux-util.h"
#include "socket-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "umask-util.h"
#include "user-util.h"
#include "util.h"
#define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC)
typedef enum MountMode {
/* This is ordered by priority! */
INACCESSIBLE,
BIND_MOUNT,
BIND_MOUNT_RECURSIVE,
PRIVATE_TMP,
PRIVATE_DEV,
BIND_DEV,
EMPTY_DIR,
SYSFS,
PROCFS,
READONLY,
READWRITE,
TMPFS,
} MountMode;
typedef struct MountEntry {
const char *path_const; /* Memory allocated on stack or static */
MountMode mode:5;
bool ignore:1; /* Ignore if path does not exist? */
bool has_prefix:1; /* Already is prefixed by the root dir? */
bool read_only:1; /* Shall this mount point be read-only? */
bool applied:1; /* Already applied */
char *path_malloc; /* Use this instead of 'path_const' if we had to allocate memory */
const char *source_const; /* The source path, for bind mounts */
char *source_malloc;
const char *options_const;/* Mount options for tmpfs */
char *options_malloc;
unsigned long flags; /* Mount flags used by EMPTY_DIR and TMPFS. Do not include MS_RDONLY here, but please use read_only. */
unsigned n_followed;
} MountEntry;
/* If MountAPIVFS= is used, let's mount /sys and /proc into the it, but only as a fallback if the user hasn't mounted
* something there already. These mounts are hence overridden by any other explicitly configured mounts. */
static const MountEntry apivfs_table[] = {
{ "/proc", PROCFS, false },
{ "/dev", BIND_DEV, false },
{ "/sys", SYSFS, false },
};
/* ProtectKernelTunables= option and the related filesystem APIs */
static const MountEntry protect_kernel_tunables_table[] = {
{ "/proc/acpi", READONLY, true },
{ "/proc/apm", READONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */
{ "/proc/asound", READONLY, true },
{ "/proc/bus", READONLY, true },
{ "/proc/fs", READONLY, true },
{ "/proc/irq", READONLY, true },
{ "/proc/kallsyms", INACCESSIBLE, true },
{ "/proc/kcore", INACCESSIBLE, true },
{ "/proc/latency_stats", READONLY, true },
{ "/proc/mtrr", READONLY, true },
{ "/proc/scsi", READONLY, true },
{ "/proc/sys", READONLY, false },
{ "/proc/sysrq-trigger", READONLY, true },
{ "/proc/timer_stats", READONLY, true },
{ "/sys", READONLY, false },
{ "/sys/fs/bpf", READONLY, true },
{ "/sys/fs/cgroup", READWRITE, false }, /* READONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", READWRITE, true },
{ "/sys/kernel/debug", READONLY, true },
{ "/sys/kernel/tracing", READONLY, true },
};
/* ProtectKernelModules= option */
static const MountEntry protect_kernel_modules_table[] = {
#if HAVE_SPLIT_USR
{ "/lib/modules", INACCESSIBLE, true },
#endif
{ "/usr/lib/modules", INACCESSIBLE, true },
};
/*
* ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of
* system should be protected by ProtectSystem=
*/
static const MountEntry protect_home_read_only_table[] = {
{ "/home", READONLY, true },
{ "/run/user", READONLY, true },
{ "/root", READONLY, true },
};
/* ProtectHome=tmpfs table */
static const MountEntry protect_home_tmpfs_table[] = {
{ "/home", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME },
{ "/run/user", TMPFS, true, .read_only = true, .options_const = "mode=0755", .flags = MS_NODEV|MS_STRICTATIME },
{ "/root", TMPFS, true, .read_only = true, .options_const = "mode=0700", .flags = MS_NODEV|MS_STRICTATIME },
};
/* ProtectHome=yes table */
static const MountEntry protect_home_yes_table[] = {
{ "/home", INACCESSIBLE, true },
{ "/run/user", INACCESSIBLE, true },
{ "/root", INACCESSIBLE, true },
};
/* ProtectSystem=yes table */
static const MountEntry protect_system_yes_table[] = {
{ "/usr", READONLY, false },
{ "/boot", READONLY, true },
{ "/efi", READONLY, true },
#if HAVE_SPLIT_USR
{ "/lib", READONLY, true },
{ "/lib64", READONLY, true },
{ "/bin", READONLY, true },
# if HAVE_SPLIT_BIN
{ "/sbin", READONLY, true },
# endif
#endif
};
/* ProtectSystem=full includes ProtectSystem=yes */
static const MountEntry protect_system_full_table[] = {
{ "/usr", READONLY, false },
{ "/boot", READONLY, true },
{ "/efi", READONLY, true },
{ "/etc", READONLY, false },
#if HAVE_SPLIT_USR
{ "/lib", READONLY, true },
{ "/lib64", READONLY, true },
{ "/bin", READONLY, true },
# if HAVE_SPLIT_BIN
{ "/sbin", READONLY, true },
# endif
#endif
};
/*
* ProtectSystem=strict table. In this strict mode, we mount everything
* read-only, except for /proc, /dev, /sys which are the kernel API VFS,
* which are left writable, but PrivateDevices= + ProtectKernelTunables=
* protect those, and these options should be fully orthogonal.
* (And of course /home and friends are also left writable, as ProtectHome=
* shall manage those, orthogonally).
*/
static const MountEntry protect_system_strict_table[] = {
{ "/", READONLY, false },
{ "/proc", READWRITE, false }, /* ProtectKernelTunables= */
{ "/sys", READWRITE, false }, /* ProtectKernelTunables= */
{ "/dev", READWRITE, false }, /* PrivateDevices= */
{ "/home", READWRITE, true }, /* ProtectHome= */
{ "/run/user", READWRITE, true }, /* ProtectHome= */
{ "/root", READWRITE, true }, /* ProtectHome= */
};
static const char *mount_entry_path(const MountEntry *p) {
assert(p);
/* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that,
* otherwise the stack/static ->path field is returned. */
return p->path_malloc ?: p->path_const;
}
static bool mount_entry_read_only(const MountEntry *p) {
assert(p);
return p->read_only || IN_SET(p->mode, READONLY, INACCESSIBLE);
}
static const char *mount_entry_source(const MountEntry *p) {
assert(p);
return p->source_malloc ?: p->source_const;
}
static const char *mount_entry_options(const MountEntry *p) {
assert(p);
return p->options_malloc ?: p->options_const;
}
static void mount_entry_done(MountEntry *p) {
assert(p);
p->path_malloc = mfree(p->path_malloc);
p->source_malloc = mfree(p->source_malloc);
p->options_malloc = mfree(p->options_malloc);
}
static int append_access_mounts(MountEntry **p, char **strv, MountMode mode, bool forcibly_require_prefix) {
char **i;
assert(p);
/* Adds a list of user-supplied READWRITE/READONLY/INACCESSIBLE entries */
STRV_FOREACH(i, strv) {
bool ignore = false, needs_prefix = false;
const char *e = *i;
/* Look for any prefixes */
if (startswith(e, "-")) {
e++;
ignore = true;
}
if (startswith(e, "+")) {
e++;
needs_prefix = true;
}
if (!path_is_absolute(e))
return -EINVAL;
*((*p)++) = (MountEntry) {
.path_const = e,
.mode = mode,
.ignore = ignore,
.has_prefix = !needs_prefix && !forcibly_require_prefix,
};
}
return 0;
}
static int append_empty_dir_mounts(MountEntry **p, char **strv) {
char **i;
assert(p);
/* Adds tmpfs mounts to provide readable but empty directories. This is primarily used to implement the
* "/private/" boundary directories for DynamicUser=1. */
STRV_FOREACH(i, strv) {
*((*p)++) = (MountEntry) {
.path_const = *i,
.mode = EMPTY_DIR,
.ignore = false,
.has_prefix = false,
.read_only = true,
.options_const = "mode=755",
.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
};
}
return 0;
}
static int append_bind_mounts(MountEntry **p, const BindMount *binds, size_t n) {
size_t i;
assert(p);
for (i = 0; i < n; i++) {
const BindMount *b = binds + i;
*((*p)++) = (MountEntry) {
.path_const = b->destination,
.mode = b->recursive ? BIND_MOUNT_RECURSIVE : BIND_MOUNT,
.read_only = b->read_only,
.source_const = b->source,
.ignore = b->ignore_enoent,
};
}
return 0;
}
static int append_tmpfs_mounts(MountEntry **p, const TemporaryFileSystem *tmpfs, size_t n) {
size_t i;
int r;
assert(p);
for (i = 0; i < n; i++) {
const TemporaryFileSystem *t = tmpfs + i;
_cleanup_free_ char *o = NULL, *str = NULL;
unsigned long flags = MS_NODEV|MS_STRICTATIME;
bool ro = false;
if (!path_is_absolute(t->path))
return -EINVAL;
if (!isempty(t->options)) {
str = strjoin("mode=0755,", t->options);
if (!str)
return -ENOMEM;
r = mount_option_mangle(str, MS_NODEV|MS_STRICTATIME, &flags, &o);
if (r < 0)
return r;
ro = flags & MS_RDONLY;
if (ro)
flags ^= MS_RDONLY;
}
*((*p)++) = (MountEntry) {
.path_const = t->path,
.mode = TMPFS,
.read_only = ro,
.options_malloc = o,
.flags = flags,
};
o = NULL;
}
return 0;
}
static int append_static_mounts(MountEntry **p, const MountEntry *mounts, size_t n, bool ignore_protect) {
size_t i;
assert(p);
assert(mounts);
/* Adds a list of static pre-defined entries */
for (i = 0; i < n; i++)
*((*p)++) = (MountEntry) {
.path_const = mount_entry_path(mounts+i),
.mode = mounts[i].mode,
.ignore = mounts[i].ignore || ignore_protect,
};
return 0;
}
static int append_protect_home(MountEntry **p, ProtectHome protect_home, bool ignore_protect) {
assert(p);
switch (protect_home) {
case PROTECT_HOME_NO:
return 0;
case PROTECT_HOME_READ_ONLY:
return append_static_mounts(p, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect);
case PROTECT_HOME_TMPFS:
return append_static_mounts(p, protect_home_tmpfs_table, ELEMENTSOF(protect_home_tmpfs_table), ignore_protect);
case PROTECT_HOME_YES:
return append_static_mounts(p, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect);
default:
assert_not_reached("Unexpected ProtectHome= value");
}
}
static int append_protect_system(MountEntry **p, ProtectSystem protect_system, bool ignore_protect) {
assert(p);
switch (protect_system) {
case PROTECT_SYSTEM_NO:
return 0;
case PROTECT_SYSTEM_STRICT:
return append_static_mounts(p, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect);
case PROTECT_SYSTEM_YES:
return append_static_mounts(p, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect);
case PROTECT_SYSTEM_FULL:
return append_static_mounts(p, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect);
default:
assert_not_reached("Unexpected ProtectSystem= value");
}
}
static int mount_path_compare(const void *a, const void *b) {
const MountEntry *p = a, *q = b;
int d;
/* If the paths are not equal, then order prefixes first */
d = path_compare(mount_entry_path(p), mount_entry_path(q));
if (d != 0)
return d;
/* If the paths are equal, check the mode */
if (p->mode < q->mode)
return -1;
if (p->mode > q->mode)
return 1;
return 0;
}
static int prefix_where_needed(MountEntry *m, size_t n, const char *root_directory) {
size_t i;
/* Prefixes all paths in the bind mount table with the root directory if it is specified and the entry needs
* that. */
if (!root_directory)
return 0;
for (i = 0; i < n; i++) {
char *s;
if (m[i].has_prefix)
continue;
s = prefix_root(root_directory, mount_entry_path(m+i));
if (!s)
return -ENOMEM;
free_and_replace(m[i].path_malloc, s);
m[i].has_prefix = true;
}
return 0;
}
static void drop_duplicates(MountEntry *m, size_t *n) {
MountEntry *f, *t, *previous;
assert(m);
assert(n);
/* Drops duplicate entries. Expects that the array is properly ordered already. */
for (f = m, t = m, previous = NULL; f < m + *n; f++) {
/* The first one wins (which is the one with the more restrictive mode), see mount_path_compare()
* above. Note that we only drop duplicates that haven't been mounted yet. */
if (previous &&
path_equal(mount_entry_path(f), mount_entry_path(previous)) &&
!f->applied && !previous->applied) {
log_debug("%s is duplicate.", mount_entry_path(f));
previous->read_only = previous->read_only || mount_entry_read_only(f); /* Propagate the read-only flag to the remaining entry */
mount_entry_done(f);
continue;
}
*t = *f;
previous = t;
t++;
}
*n = t - m;
}
static void drop_inaccessible(MountEntry *m, size_t *n) {
MountEntry *f, *t;
const char *clear = NULL;
assert(m);
assert(n);
/* Drops all entries obstructed by another entry further up the tree. Expects that the array is properly
* ordered already. */
for (f = m, t = m; f < m + *n; f++) {
/* If we found a path set for INACCESSIBLE earlier, and this entry has it as prefix we should drop
* it, as inaccessible paths really should drop the entire subtree. */
if (clear && path_startswith(mount_entry_path(f), clear)) {
log_debug("%s is masked by %s.", mount_entry_path(f), clear);
mount_entry_done(f);
continue;
}
clear = f->mode == INACCESSIBLE ? mount_entry_path(f) : NULL;
*t = *f;
t++;
}
*n = t - m;
}
static void drop_nop(MountEntry *m, size_t *n) {
MountEntry *f, *t;
assert(m);
assert(n);
/* Drops all entries which have an immediate parent that has the same type, as they are redundant. Assumes the
* list is ordered by prefixes. */
for (f = m, t = m; f < m + *n; f++) {
/* Only suppress such subtrees for READONLY and READWRITE entries */
if (IN_SET(f->mode, READONLY, READWRITE)) {
MountEntry *p;
bool found = false;
/* Now let's find the first parent of the entry we are looking at. */
for (p = t-1; p >= m; p--) {
if (path_startswith(mount_entry_path(f), mount_entry_path(p))) {
found = true;
break;
}
}
/* We found it, let's see if it's the same mode, if so, we can drop this entry */
if (found && p->mode == f->mode) {
log_debug("%s is redundant by %s", mount_entry_path(f), mount_entry_path(p));
mount_entry_done(f);
continue;
}
}
*t = *f;
t++;
}
*n = t - m;
}
static void drop_outside_root(const char *root_directory, MountEntry *m, size_t *n) {
MountEntry *f, *t;
assert(m);
assert(n);
/* Nothing to do */
if (!root_directory)
return;
/* Drops all mounts that are outside of the root directory. */
for (f = m, t = m; f < m + *n; f++) {
if (!path_startswith(mount_entry_path(f), root_directory)) {
log_debug("%s is outside of root directory.", mount_entry_path(f));
mount_entry_done(f);
continue;
}
*t = *f;
t++;
}
*n = t - m;
}
static int clone_device_node(const char *d, const char *temporary_mount, bool *make_devnode) {
const char *dn;
struct stat st;
int r;
if (stat(d, &st) < 0) {
if (errno == ENOENT)
return -ENXIO;
return -errno;
}
if (!S_ISBLK(st.st_mode) &&
!S_ISCHR(st.st_mode))
return -EINVAL;
if (st.st_rdev == 0)
return -ENXIO;
dn = strjoina(temporary_mount, d);
if (*make_devnode) {
mac_selinux_create_file_prepare(d, st.st_mode);
r = mknod(dn, st.st_mode, st.st_rdev);
mac_selinux_create_file_clear();
if (r == 0)
return 0;
if (errno != EPERM)
return log_debug_errno(errno, "mknod failed for %s: %m", d);
*make_devnode = false;
}
/* We're about to fallback to bind-mounting the device
* node. So create a dummy bind-mount target. */
mac_selinux_create_file_prepare(d, 0);
r = mknod(dn, S_IFREG, 0);
mac_selinux_create_file_clear();
if (r < 0 && errno != EEXIST)
return log_debug_errno(errno, "mknod fallback failed for %s: %m", d);
/* Fallback to bind-mounting:
* The assumption here is that all used device nodes carry standard
* properties. Specifically, the devices nodes we bind-mount should
* either be owned by root:root or root:tty (e.g. /dev/tty, /dev/ptmx)
* and should not carry ACLs. */
if (mount(d, dn, NULL, MS_BIND, NULL) < 0)
return log_debug_errno(errno, "mount failed for %s: %m", d);
return 0;
}
static int mount_private_dev(MountEntry *m) {
static const char devnodes[] =
"/dev/null\0"
"/dev/zero\0"
"/dev/full\0"
"/dev/random\0"
"/dev/urandom\0"
"/dev/tty\0";
char temporary_mount[] = "/tmp/namespace-dev-XXXXXX";
const char *d, *dev = NULL, *devpts = NULL, *devshm = NULL, *devhugepages = NULL, *devmqueue = NULL, *devlog = NULL, *devptmx = NULL;
bool can_mknod = true;
_cleanup_umask_ mode_t u;
int r;
assert(m);
u = umask(0000);
if (!mkdtemp(temporary_mount))
return -errno;
dev = strjoina(temporary_mount, "/dev");
(void) mkdir(dev, 0755);
if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755") < 0) {
r = -errno;
goto fail;
}
devpts = strjoina(temporary_mount, "/dev/pts");
(void) mkdir(devpts, 0755);
if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) {
r = -errno;
goto fail;
}
/* /dev/ptmx can either be a device node or a symlink to /dev/pts/ptmx
* when /dev/ptmx a device node, /dev/pts/ptmx has 000 permissions making it inaccessible
* thus, in that case make a clone
*
* in nspawn and other containers it will be a symlink, in that case make it a symlink
*/
r = is_symlink("/dev/ptmx");
if (r < 0)
goto fail;
if (r > 0) {
devptmx = strjoina(temporary_mount, "/dev/ptmx");
if (symlink("pts/ptmx", devptmx) < 0) {
r = -errno;
goto fail;
}
} else {
r = clone_device_node("/dev/ptmx", temporary_mount, &can_mknod);
if (r < 0)
goto fail;
}
devshm = strjoina(temporary_mount, "/dev/shm");
(void) mkdir(devshm, 0755);
r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL);
if (r < 0) {
r = -errno;
goto fail;
}
devmqueue = strjoina(temporary_mount, "/dev/mqueue");
(void) mkdir(devmqueue, 0755);
(void) mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL);
devhugepages = strjoina(temporary_mount, "/dev/hugepages");
(void) mkdir(devhugepages, 0755);
(void) mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL);
devlog = strjoina(temporary_mount, "/dev/log");
(void) symlink("/run/systemd/journal/dev-log", devlog);
NULSTR_FOREACH(d, devnodes) {
r = clone_device_node(d, temporary_mount, &can_mknod);
/* ENXIO means the the *source* is not a device file, skip creation in that case */
if (r < 0 && r != -ENXIO)
goto fail;
}
dev_setup(temporary_mount, UID_INVALID, GID_INVALID);
/* Create the /dev directory if missing. It is more likely to be
* missing when the service is started with RootDirectory. This is
* consistent with mount units creating the mount points when missing.
*/
(void) mkdir_p_label(mount_entry_path(m), 0755);
/* Unmount everything in old /dev */
umount_recursive(mount_entry_path(m), 0);
if (mount(dev, mount_entry_path(m), NULL, MS_MOVE, NULL) < 0) {
r = -errno;
goto fail;
}
rmdir(dev);
rmdir(temporary_mount);
return 0;
fail:
if (devpts)
umount(devpts);
if (devshm)
umount(devshm);
if (devhugepages)
umount(devhugepages);
if (devmqueue)
umount(devmqueue);
umount(dev);
rmdir(dev);
rmdir(temporary_mount);
return r;
}
static int mount_bind_dev(const MountEntry *m) {
int r;
assert(m);
/* Implements the little brother of mount_private_dev(): simply bind mounts the host's /dev into the service's
* /dev. This is only used when RootDirectory= is set. */
(void) mkdir_p_label(mount_entry_path(m), 0755);
r = path_is_mount_point(mount_entry_path(m), NULL, 0);
if (r < 0)
return log_debug_errno(r, "Unable to determine whether /dev is already mounted: %m");
if (r > 0) /* make this a NOP if /dev is already a mount point */
return 0;
if (mount("/dev", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0)
return log_debug_errno(errno, "Failed to bind mount %s: %m", mount_entry_path(m));
return 1;
}
static int mount_sysfs(const MountEntry *m) {
int r;
assert(m);
(void) mkdir_p_label(mount_entry_path(m), 0755);
r = path_is_mount_point(mount_entry_path(m), NULL, 0);
if (r < 0)
return log_debug_errno(r, "Unable to determine whether /sys is already mounted: %m");
if (r > 0) /* make this a NOP if /sys is already a mount point */
return 0;
/* Bind mount the host's version so that we get all child mounts of it, too. */
if (mount("/sys", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
return 1;
}
static int mount_procfs(const MountEntry *m) {
int r;
assert(m);
(void) mkdir_p_label(mount_entry_path(m), 0755);
r = path_is_mount_point(mount_entry_path(m), NULL, 0);
if (r < 0)
return log_debug_errno(r, "Unable to determine whether /proc is already mounted: %m");
if (r > 0) /* make this a NOP if /proc is already a mount point */
return 0;
/* Mount a new instance, so that we get the one that matches our user namespace, if we are running in one */
if (mount("proc", mount_entry_path(m), "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
return 1;
}
static int mount_tmpfs(const MountEntry *m) {
assert(m);
/* First, get rid of everything that is below if there is anything. Then, overmount with our new tmpfs */
(void) mkdir_p_label(mount_entry_path(m), 0755);
(void) umount_recursive(mount_entry_path(m), 0);
if (mount("tmpfs", mount_entry_path(m), "tmpfs", m->flags, mount_entry_options(m)) < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
return 1;
}
static int follow_symlink(
const char *root_directory,
MountEntry *m) {
_cleanup_free_ char *target = NULL;
int r;
/* Let's chase symlinks, but only one step at a time. That's because depending where the symlink points we
* might need to change the order in which we mount stuff. Hence: let's normalize piecemeal, and do one step at
* a time by specifying CHASE_STEP. This function returns 0 if we resolved one step, and > 0 if we reached the
* end and already have a fully normalized name. */
r = chase_symlinks(mount_entry_path(m), root_directory, CHASE_STEP|CHASE_NONEXISTENT, &target);
if (r < 0)
return log_debug_errno(r, "Failed to chase symlinks '%s': %m", mount_entry_path(m));
if (r > 0) /* Reached the end, nothing more to resolve */
return 1;
if (m->n_followed >= CHASE_SYMLINKS_MAX) { /* put a boundary on things */
log_debug("Symlink loop on '%s'.", mount_entry_path(m));
return -ELOOP;
}
log_debug("Followed mount entry path symlink %s → %s.", mount_entry_path(m), target);
free_and_replace(m->path_malloc, target);
m->has_prefix = true;
m->n_followed ++;
return 0;
}
static int apply_mount(
const char *root_directory,
MountEntry *m) {
bool rbind = true, make = false;
const char *what;
int r;
assert(m);
log_debug("Applying namespace mount on %s", mount_entry_path(m));
switch (m->mode) {
case INACCESSIBLE: {
struct stat target;
/* First, get rid of everything that is below if there
* is anything... Then, overmount it with an
* inaccessible path. */
(void) umount_recursive(mount_entry_path(m), 0);
if (lstat(mount_entry_path(m), &target) < 0) {
if (errno == ENOENT && m->ignore)
return 0;
return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", mount_entry_path(m));
}
what = mode_to_inaccessible_node(target.st_mode);
if (!what) {
log_debug("File type not supported for inaccessible mounts. Note that symlinks are not allowed");
return -ELOOP;
}
break;
}
case READONLY:
case READWRITE:
r = path_is_mount_point(mount_entry_path(m), root_directory, 0);
if (r == -ENOENT && m->ignore)
return 0;
if (r < 0)
return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", mount_entry_path(m));
if (r > 0) /* Nothing to do here, it is already a mount. We just later toggle the MS_RDONLY bit for the mount point if needed. */
return 0;
/* This isn't a mount point yet, let's make it one. */
what = mount_entry_path(m);
break;
case BIND_MOUNT:
rbind = false;
_fallthrough_;
case BIND_MOUNT_RECURSIVE: {
_cleanup_free_ char *chased = NULL;
/* Since mount() will always follow symlinks we chase the symlinks on our own first. Note that bind
* mount source paths are always relative to the host root, hence we pass NULL as root directory to
* chase_symlinks() here. */
r = chase_symlinks(mount_entry_source(m), NULL, CHASE_TRAIL_SLASH, &chased);
if (r == -ENOENT && m->ignore) {
log_debug_errno(r, "Path %s does not exist, ignoring.", mount_entry_source(m));
return 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to follow symlinks on %s: %m", mount_entry_source(m));
log_debug("Followed source symlinks %s → %s.", mount_entry_source(m), chased);
free_and_replace(m->source_malloc, chased);
what = mount_entry_source(m);
make = true;
break;
}
case EMPTY_DIR:
case TMPFS:
return mount_tmpfs(m);
case PRIVATE_TMP:
what = mount_entry_source(m);
make = true;
break;
case PRIVATE_DEV:
return mount_private_dev(m);
case BIND_DEV:
return mount_bind_dev(m);
case SYSFS:
return mount_sysfs(m);
case PROCFS:
return mount_procfs(m);
default:
assert_not_reached("Unknown mode");
}
assert(what);
if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0) {
bool try_again = false;
r = -errno;
if (r == -ENOENT && make) {
struct stat st;
/* Hmm, either the source or the destination are missing. Let's see if we can create the destination, then try again */
if (stat(what, &st) < 0)
log_debug_errno(errno, "Mount point source '%s' is not accessible: %m", what);
else {
int q;
(void) mkdir_parents(mount_entry_path(m), 0755);
if (S_ISDIR(st.st_mode))
q = mkdir(mount_entry_path(m), 0755) < 0 ? -errno : 0;
else
q = touch(mount_entry_path(m));
if (q < 0)
log_debug_errno(q, "Failed to create destination mount point node '%s': %m", mount_entry_path(m));
else
try_again = true;
}
}
if (try_again) {
if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0)
r = -errno;
else
r = 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to mount %s to %s: %m", what, mount_entry_path(m));
}
log_debug("Successfully mounted %s to %s", what, mount_entry_path(m));
return 0;
}
static int make_read_only(const MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) {
int r = 0;
assert(m);
assert(proc_self_mountinfo);
if (mount_entry_read_only(m)) {
if (IN_SET(m->mode, EMPTY_DIR, TMPFS)) {
/* Make superblock readonly */
if (mount(NULL, mount_entry_path(m), NULL, MS_REMOUNT | MS_RDONLY | m->flags, mount_entry_options(m)) < 0)
r = -errno;
} else
r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), true, blacklist, proc_self_mountinfo);
} else if (m->mode == PRIVATE_DEV) {
/* Superblock can be readonly but the submounts can't */
if (mount(NULL, mount_entry_path(m), NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0)
r = -errno;
} else
return 0;
/* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked read-only
* already stays this way. This improves compatibility with container managers, where we won't attempt to undo
* read-only mounts already applied. */
if (r == -ENOENT && m->ignore)
r = 0;
return r;
}
static bool namespace_info_mount_apivfs(const char *root_directory, const NamespaceInfo *ns_info) {
assert(ns_info);
/*
* ProtectControlGroups= and ProtectKernelTunables= imply MountAPIVFS=,
* since to protect the API VFS mounts, they need to be around in the
* first place... and RootDirectory= or RootImage= need to be set.
*/
/* root_directory should point to a mount point */
return root_directory &&
(ns_info->mount_apivfs ||
ns_info->protect_control_groups ||
ns_info->protect_kernel_tunables);
}
static size_t namespace_calculate_mounts(
const char* root_directory,
const NamespaceInfo *ns_info,
char** read_write_paths,
char** read_only_paths,
char** inaccessible_paths,
char** empty_directories,
size_t n_bind_mounts,
size_t n_temporary_filesystems,
const char* tmp_dir,
const char* var_tmp_dir,
ProtectHome protect_home,
ProtectSystem protect_system) {
size_t protect_home_cnt;
size_t protect_system_cnt =
(protect_system == PROTECT_SYSTEM_STRICT ?
ELEMENTSOF(protect_system_strict_table) :
((protect_system == PROTECT_SYSTEM_FULL) ?
ELEMENTSOF(protect_system_full_table) :
((protect_system == PROTECT_SYSTEM_YES) ?
ELEMENTSOF(protect_system_yes_table) : 0)));
protect_home_cnt =
(protect_home == PROTECT_HOME_YES ?
ELEMENTSOF(protect_home_yes_table) :
((protect_home == PROTECT_HOME_READ_ONLY) ?
ELEMENTSOF(protect_home_read_only_table) :
((protect_home == PROTECT_HOME_TMPFS) ?
ELEMENTSOF(protect_home_tmpfs_table) : 0)));
return !!tmp_dir + !!var_tmp_dir +
strv_length(read_write_paths) +
strv_length(read_only_paths) +
strv_length(inaccessible_paths) +
strv_length(empty_directories) +
n_bind_mounts +
n_temporary_filesystems +
ns_info->private_dev +
(ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
(ns_info->protect_control_groups ? 1 : 0) +
(ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) +
protect_home_cnt + protect_system_cnt +
(namespace_info_mount_apivfs(root_directory, ns_info) ? ELEMENTSOF(apivfs_table) : 0);
}
static void normalize_mounts(const char *root_directory, MountEntry *mounts, size_t *n_mounts) {
assert(n_mounts);
assert(mounts || *n_mounts == 0);
qsort_safe(mounts, *n_mounts, sizeof(MountEntry), mount_path_compare);
drop_duplicates(mounts, n_mounts);
drop_outside_root(root_directory, mounts, n_mounts);
drop_inaccessible(mounts, n_mounts);
drop_nop(mounts, n_mounts);
}
int setup_namespace(
const char* root_directory,
const char* root_image,
const NamespaceInfo *ns_info,
char** read_write_paths,
char** read_only_paths,
char** inaccessible_paths,
char** empty_directories,
const BindMount *bind_mounts,
size_t n_bind_mounts,
const TemporaryFileSystem *temporary_filesystems,
size_t n_temporary_filesystems,
const char* tmp_dir,
const char* var_tmp_dir,
ProtectHome protect_home,
ProtectSystem protect_system,
unsigned long mount_flags,
DissectImageFlags dissect_image_flags) {
_cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL;
_cleanup_(decrypted_image_unrefp) DecryptedImage *decrypted_image = NULL;
_cleanup_(dissected_image_unrefp) DissectedImage *dissected_image = NULL;
_cleanup_free_ void *root_hash = NULL;
MountEntry *m, *mounts = NULL;
size_t root_hash_size = 0;
const char *root;
size_t n_mounts;
bool make_slave;
bool require_prefix = false;
int r = 0;
assert(ns_info);
if (mount_flags == 0)
mount_flags = MS_SHARED;
if (root_image) {
dissect_image_flags |= DISSECT_IMAGE_REQUIRE_ROOT;
if (protect_system == PROTECT_SYSTEM_STRICT &&
protect_home != PROTECT_HOME_NO &&
strv_isempty(read_write_paths))
dissect_image_flags |= DISSECT_IMAGE_READ_ONLY;
r = loop_device_make_by_path(root_image,
dissect_image_flags & DISSECT_IMAGE_READ_ONLY ? O_RDONLY : O_RDWR,
&loop_device);
if (r < 0)
return r;
r = root_hash_load(root_image, &root_hash, &root_hash_size);
if (r < 0)
return r;
r = dissect_image(loop_device->fd, root_hash, root_hash_size, dissect_image_flags, &dissected_image);
if (r < 0)
return r;
r = dissected_image_decrypt(dissected_image, NULL, root_hash, root_hash_size, dissect_image_flags, &decrypted_image);
if (r < 0)
return r;
}
if (root_directory)
root = root_directory;
else {
/* Always create the mount namespace in a temporary directory, instead of operating
* directly in the root. The temporary directory prevents any mounts from being
* potentially obscured my other mounts we already applied.
* We use the same mount point for all images, which is safe, since they all live
* in their own namespaces after all, and hence won't see each other. */
root = "/run/systemd/unit-root";
(void) mkdir_label(root, 0700);
require_prefix = true;
}
n_mounts = namespace_calculate_mounts(
root,
ns_info,
read_write_paths,
read_only_paths,
inaccessible_paths,
empty_directories,
n_bind_mounts,
n_temporary_filesystems,
tmp_dir, var_tmp_dir,
protect_home, protect_system);
/* Set mount slave mode */
make_slave = root || n_mounts > 0 || ns_info->private_mounts;
if (n_mounts > 0) {
m = mounts = (MountEntry *) alloca0(n_mounts * sizeof(MountEntry));
r = append_access_mounts(&m, read_write_paths, READWRITE, require_prefix);
if (r < 0)
goto finish;
r = append_access_mounts(&m, read_only_paths, READONLY, require_prefix);
if (r < 0)
goto finish;
r = append_access_mounts(&m, inaccessible_paths, INACCESSIBLE, require_prefix);
if (r < 0)
goto finish;
r = append_empty_dir_mounts(&m, empty_directories);
if (r < 0)
goto finish;
r = append_bind_mounts(&m, bind_mounts, n_bind_mounts);
if (r < 0)
goto finish;
r = append_tmpfs_mounts(&m, temporary_filesystems, n_temporary_filesystems);
if (r < 0)
goto finish;
if (tmp_dir) {
*(m++) = (MountEntry) {
.path_const = "/tmp",
.mode = PRIVATE_TMP,
.source_const = tmp_dir,
};
}
if (var_tmp_dir) {
*(m++) = (MountEntry) {
.path_const = "/var/tmp",
.mode = PRIVATE_TMP,
.source_const = var_tmp_dir,
};
}
if (ns_info->private_dev) {
*(m++) = (MountEntry) {
.path_const = "/dev",
.mode = PRIVATE_DEV,
};
}
if (ns_info->protect_kernel_tunables) {
r = append_static_mounts(&m, protect_kernel_tunables_table, ELEMENTSOF(protect_kernel_tunables_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
if (ns_info->protect_kernel_modules) {
r = append_static_mounts(&m, protect_kernel_modules_table, ELEMENTSOF(protect_kernel_modules_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
if (ns_info->protect_control_groups) {
*(m++) = (MountEntry) {
.path_const = "/sys/fs/cgroup",
.mode = READONLY,
};
}
r = append_protect_home(&m, protect_home, ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
r = append_protect_system(&m, protect_system, false);
if (r < 0)
goto finish;
if (namespace_info_mount_apivfs(root, ns_info)) {
r = append_static_mounts(&m, apivfs_table, ELEMENTSOF(apivfs_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
assert(mounts + n_mounts == m);
/* Prepend the root directory where that's necessary */
r = prefix_where_needed(mounts, n_mounts, root);
if (r < 0)
goto finish;
normalize_mounts(root_directory, mounts, &n_mounts);
}
if (unshare(CLONE_NEWNS) < 0) {
r = -errno;
goto finish;
}
if (make_slave) {
/* Remount / as SLAVE so that nothing now mounted in the namespace
shows up in the parent */
if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
if (root_image) {
/* A root image is specified, mount it to the right place */
r = dissected_image_mount(dissected_image, root, UID_INVALID, dissect_image_flags);
if (r < 0)
goto finish;
if (decrypted_image) {
r = decrypted_image_relinquish(decrypted_image);
if (r < 0)
goto finish;
}
loop_device_relinquish(loop_device);
} else if (root_directory) {
/* A root directory is specified. Turn its directory into bind mount, if it isn't one yet. */
r = path_is_mount_point(root, NULL, AT_SYMLINK_FOLLOW);
if (r < 0)
goto finish;
if (r == 0) {
if (mount(root, root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
} else if (root) {
/* Let's mount the main root directory to the root directory to use */
if (mount("/", root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
/* Try to set up the new root directory before mounting anything else there. */
if (root_image || root_directory)
(void) base_filesystem_create(root, UID_INVALID, GID_INVALID);
if (n_mounts > 0) {
_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
char **blacklist;
size_t j;
/* Open /proc/self/mountinfo now as it may become unavailable if we mount anything on top of /proc.
* For example, this is the case with the option: 'InaccessiblePaths=/proc' */
proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
if (!proc_self_mountinfo) {
r = -errno;
goto finish;
}
/* First round, establish all mounts we need */
for (;;) {
bool again = false;
for (m = mounts; m < mounts + n_mounts; ++m) {
if (m->applied)
continue;
r = follow_symlink(root, m);
if (r < 0)
goto finish;
if (r == 0) {
/* We hit a symlinked mount point. The entry got rewritten and might point to a
* very different place now. Let's normalize the changed list, and start from
* the beginning. After all to mount the entry at the new location we might
* need some other mounts first */
again = true;
break;
}
r = apply_mount(root, m);
if (r < 0)
goto finish;
m->applied = true;
}
if (!again)
break;
normalize_mounts(root_directory, mounts, &n_mounts);
}
/* Create a blacklist we can pass to bind_mount_recursive() */
blacklist = newa(char*, n_mounts+1);
for (j = 0; j < n_mounts; j++)
blacklist[j] = (char*) mount_entry_path(mounts+j);
blacklist[j] = NULL;
/* Second round, flip the ro bits if necessary. */
for (m = mounts; m < mounts + n_mounts; ++m) {
r = make_read_only(m, blacklist, proc_self_mountinfo);
if (r < 0)
goto finish;
}
}
if (root) {
/* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */
r = mount_move_root(root);
if (r < 0)
goto finish;
}
/* Remount / as the desired mode. Note that this will not
* reestablish propagation from our side to the host, since
* what's disconnected is disconnected. */
if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
r = 0;
finish:
for (m = mounts; m < mounts + n_mounts; m++)
mount_entry_done(m);
return r;
}
void bind_mount_free_many(BindMount *b, size_t n) {
size_t i;
assert(b || n == 0);
for (i = 0; i < n; i++) {
free(b[i].source);
free(b[i].destination);
}
free(b);
}
int bind_mount_add(BindMount **b, size_t *n, const BindMount *item) {
_cleanup_free_ char *s = NULL, *d = NULL;
BindMount *c;
assert(b);
assert(n);
assert(item);
s = strdup(item->source);
if (!s)
return -ENOMEM;
d = strdup(item->destination);
if (!d)
return -ENOMEM;
c = reallocarray(*b, *n + 1, sizeof(BindMount));
if (!c)
return -ENOMEM;
*b = c;
c[(*n) ++] = (BindMount) {
.source = TAKE_PTR(s),
.destination = TAKE_PTR(d),
.read_only = item->read_only,
.recursive = item->recursive,
.ignore_enoent = item->ignore_enoent,
};
return 0;
}
void temporary_filesystem_free_many(TemporaryFileSystem *t, size_t n) {
size_t i;
assert(t || n == 0);
for (i = 0; i < n; i++) {
free(t[i].path);
free(t[i].options);
}
free(t);
}
int temporary_filesystem_add(
TemporaryFileSystem **t,
size_t *n,
const char *path,
const char *options) {
_cleanup_free_ char *p = NULL, *o = NULL;
TemporaryFileSystem *c;
assert(t);
assert(n);
assert(path);
p = strdup(path);
if (!p)
return -ENOMEM;
if (!isempty(options)) {
o = strdup(options);
if (!o)
return -ENOMEM;
}
c = reallocarray(*t, *n + 1, sizeof(TemporaryFileSystem));
if (!c)
return -ENOMEM;
*t = c;
c[(*n) ++] = (TemporaryFileSystem) {
.path = TAKE_PTR(p),
.options = TAKE_PTR(o),
};
return 0;
}
static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
_cleanup_free_ char *x = NULL;
char bid[SD_ID128_STRING_MAX];
sd_id128_t boot_id;
int r;
assert(id);
assert(prefix);
assert(path);
/* We include the boot id in the directory so that after a
* reboot we can easily identify obsolete directories. */
r = sd_id128_get_boot(&boot_id);
if (r < 0)
return r;
x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX");
if (!x)
return -ENOMEM;
RUN_WITH_UMASK(0077)
if (!mkdtemp(x))
return -errno;
RUN_WITH_UMASK(0000) {
char *y;
y = strjoina(x, "/tmp");
if (mkdir(y, 0777 | S_ISVTX) < 0)
return -errno;
}
*path = TAKE_PTR(x);
return 0;
}
int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
char *a, *b;
int r;
assert(id);
assert(tmp_dir);
assert(var_tmp_dir);
r = setup_one_tmp_dir(id, "/tmp", &a);
if (r < 0)
return r;
r = setup_one_tmp_dir(id, "/var/tmp", &b);
if (r < 0) {
char *t;
t = strjoina(a, "/tmp");
rmdir(t);
rmdir(a);
free(a);
return r;
}
*tmp_dir = a;
*var_tmp_dir = b;
return 0;
}
int setup_netns(int netns_storage_socket[2]) {
_cleanup_close_ int netns = -1;
int r, q;
assert(netns_storage_socket);
assert(netns_storage_socket[0] >= 0);
assert(netns_storage_socket[1] >= 0);
/* We use the passed socketpair as a storage buffer for our
* namespace reference fd. Whatever process runs this first
* shall create a new namespace, all others should just join
* it. To serialize that we use a file lock on the socket
* pair.
*
* It's a bit crazy, but hey, works great! */
if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0)
return -errno;
netns = receive_one_fd(netns_storage_socket[0], MSG_DONTWAIT);
if (netns == -EAGAIN) {
/* Nothing stored yet, so let's create a new namespace */
if (unshare(CLONE_NEWNET) < 0) {
r = -errno;
goto fail;
}
loopback_setup();
netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (netns < 0) {
r = -errno;
goto fail;
}
r = 1;
} else if (netns < 0) {
r = netns;
goto fail;
} else {
/* Yay, found something, so let's join the namespace */
if (setns(netns, CLONE_NEWNET) < 0) {
r = -errno;
goto fail;
}
r = 0;
}
q = send_one_fd(netns_storage_socket[1], netns, MSG_DONTWAIT);
if (q < 0) {
r = q;
goto fail;
}
fail:
(void) lockf(netns_storage_socket[0], F_ULOCK, 0);
return r;
}
bool ns_type_supported(NamespaceType type) {
const char *t, *ns_proc;
t = namespace_type_to_string(type);
if (!t) /* Don't know how to translate this? Then it's not supported */
return false;
ns_proc = strjoina("/proc/self/ns/", t);
return access(ns_proc, F_OK) == 0;
}
static const char *const protect_home_table[_PROTECT_HOME_MAX] = {
[PROTECT_HOME_NO] = "no",
[PROTECT_HOME_YES] = "yes",
[PROTECT_HOME_READ_ONLY] = "read-only",
[PROTECT_HOME_TMPFS] = "tmpfs",
};
DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(protect_home, ProtectHome, PROTECT_HOME_YES);
static const char *const protect_system_table[_PROTECT_SYSTEM_MAX] = {
[PROTECT_SYSTEM_NO] = "no",
[PROTECT_SYSTEM_YES] = "yes",
[PROTECT_SYSTEM_FULL] = "full",
[PROTECT_SYSTEM_STRICT] = "strict",
};
DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(protect_system, ProtectSystem, PROTECT_SYSTEM_YES);
static const char* const namespace_type_table[] = {
[NAMESPACE_MOUNT] = "mnt",
[NAMESPACE_CGROUP] = "cgroup",
[NAMESPACE_UTS] = "uts",
[NAMESPACE_IPC] = "ipc",
[NAMESPACE_USER] = "user",
[NAMESPACE_PID] = "pid",
[NAMESPACE_NET] = "net",
};
DEFINE_STRING_TABLE_LOOKUP(namespace_type, NamespaceType);