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Systemd/src/core/namespace.c

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <errno.h>
#include <linux/loop.h>
#include <sched.h>
#include <stdio.h>
#include <sys/mount.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 "format-util.h"
#include "fs-util.h"
#include "label.h"
#include "list.h"
#include "loop-util.h"
#include "loopback-setup.h"
#include "mkdir.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "namespace-util.h"
#include "namespace.h"
#include "nulstr-util.h"
#include "path-util.h"
#include "selinux-util.h"
#include "socket-util.h"
#include "sort-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "tmpfile-util.h"
#include "umask-util.h"
#include "user-util.h"
#define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC)
typedef enum MountMode {
/* This is ordered by priority! */
INACCESSIBLE,
MOUNT_IMAGES,
BIND_MOUNT,
BIND_MOUNT_RECURSIVE,
PRIVATE_TMP,
PRIVATE_TMP_READONLY,
PRIVATE_DEV,
BIND_DEV,
EMPTY_DIR,
SYSFS,
PROCFS,
READONLY,
READWRITE,
TMPFS,
READWRITE_IMPLICIT, /* Should have the lowest priority. */
_MOUNT_MODE_MAX,
} 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 nosuid:1; /* Shall set MS_NOSUID on the mount itself */
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 or images */
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;
LIST_FIELDS(MountEntry, mount_entry);
} 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_IMPLICIT, false }, /* READONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", READWRITE_IMPLICIT, 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 },
};
/* ProtectKernelLogs= option */
static const MountEntry protect_kernel_logs_table[] = {
{ "/proc/kmsg", INACCESSIBLE, true },
{ "/dev/kmsg", 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" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME },
{ "/run/user", TMPFS, true, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME },
{ "/root", TMPFS, true, .read_only = true, .options_const = "mode=0700" TMPFS_LIMITS_EMPTY_OR_ALMOST, .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_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/sys", READWRITE_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/dev", READWRITE_IMPLICIT, false }, /* PrivateDevices= */
{ "/home", READWRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/run/user", READWRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/root", READWRITE_IMPLICIT, true }, /* ProtectHome= */
};
static const char * const mount_mode_table[_MOUNT_MODE_MAX] = {
[INACCESSIBLE] = "inaccessible",
[BIND_MOUNT] = "bind",
[BIND_MOUNT_RECURSIVE] = "rbind",
[PRIVATE_TMP] = "private-tmp",
[PRIVATE_DEV] = "private-dev",
[BIND_DEV] = "bind-dev",
[EMPTY_DIR] = "empty",
[SYSFS] = "sysfs",
[PROCFS] = "procfs",
[READONLY] = "read-only",
[READWRITE] = "read-write",
[TMPFS] = "tmpfs",
[MOUNT_IMAGES] = "mount-images",
[READWRITE_IMPLICIT] = "rw-implicit",
};
DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(mount_mode, MountMode);
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, PRIVATE_TMP_READONLY);
}
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/READWRITE_IMPLICIT/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 log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"Path is not absolute: %s", e);
*((*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,
.read_only = true,
.options_const = "mode=755" TMPFS_LIMITS_EMPTY_OR_ALMOST,
.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,
.nosuid = b->nosuid,
.source_const = b->source,
.ignore = b->ignore_enoent,
};
}
return 0;
}
static int append_mount_images(MountEntry **p, const MountImage *mount_images, size_t n) {
assert(p);
for (size_t i = 0; i < n; i++) {
const MountImage *m = mount_images + i;
*((*p)++) = (MountEntry) {
.path_const = m->destination,
.mode = MOUNT_IMAGES,
.source_const = m->source,
.ignore = m->ignore_enoent,
};
}
return 0;
}
static int append_tmpfs_mounts(MountEntry **p, const TemporaryFileSystem *tmpfs, size_t n) {
assert(p);
for (size_t i = 0; i < n; i++) {
const TemporaryFileSystem *t = tmpfs + i;
_cleanup_free_ char *o = NULL, *str = NULL;
unsigned long flags;
bool ro = false;
int r;
if (!path_is_absolute(t->path))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"Path is not absolute: %s",
t->path);
str = strjoin("mode=0755" NESTED_TMPFS_LIMITS ",", t->options);
if (!str)
return -ENOMEM;
r = mount_option_mangle(str, MS_NODEV|MS_STRICTATIME, &flags, &o);
if (r < 0)
return log_debug_errno(r, "Failed to parse mount option '%s': %m", str);
ro = flags & MS_RDONLY;
if (ro)
flags ^= MS_RDONLY;
*((*p)++) = (MountEntry) {
.path_const = t->path,
.mode = TMPFS,
.read_only = ro,
.options_malloc = TAKE_PTR(o),
.flags = flags,
};
}
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 MountEntry *a, const MountEntry *b) {
int d;
/* If the paths are not equal, then order prefixes first */
d = path_compare(mount_entry_path(a), mount_entry_path(b));
if (d != 0)
return d;
/* If the paths are equal, check the mode */
return CMP((int) a->mode, (int) b->mode);
}
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 the entry needs that. */
for (i = 0; i < n; i++) {
char *s;
if (m[i].has_prefix)
continue;
s = path_join(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 (%s) is duplicate.", mount_entry_path(f), mount_mode_to_string(f->mode));
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, READWRITE and READWRITE_IMPLICIT entries */
if (IN_SET(f->mode, READONLY, READWRITE, READWRITE_IMPLICIT)) {
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 (%s) is made redundant by %s (%s)",
mount_entry_path(f), mount_mode_to_string(f->mode),
mount_entry_path(p), mount_mode_to_string(p->mode));
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) {
_cleanup_free_ char *sl = NULL;
const char *dn, *bn, *t;
struct stat st;
int r;
if (stat(d, &st) < 0) {
if (errno == ENOENT) {
log_debug_errno(errno, "Device node '%s' to clone does not exist, ignoring.", d);
return -ENXIO;
}
return log_debug_errno(errno, "Failed to stat() device node '%s' to clone, ignoring: %m", d);
}
if (!S_ISBLK(st.st_mode) &&
!S_ISCHR(st.st_mode))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"Device node '%s' to clone is not a device node, ignoring.",
d);
dn = strjoina(temporary_mount, d);
/* First, try to create device node properly */
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)
goto add_symlink;
if (errno != EPERM)
return log_debug_errno(errno, "mknod failed for %s: %m", d);
/* This didn't work, let's not try this again for the next iterations. */
*make_devnode = false;
}
/* We're about to fall back to bind-mounting the device
* node. So create a dummy bind-mount target.
* Do not prepare device-node SELinux label (see issue 13762) */
r = mknod(dn, S_IFREG, 0);
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, "Bind mounting failed for '%s': %m", d);
add_symlink:
bn = path_startswith(d, "/dev/");
if (!bn)
return 0;
/* Create symlinks like /dev/char/1:9 → ../urandom */
if (asprintf(&sl, "%s/dev/%s/%u:%u",
temporary_mount,
S_ISCHR(st.st_mode) ? "char" : "block",
major(st.st_rdev), minor(st.st_rdev)) < 0)
return log_oom();
(void) mkdir_parents(sl, 0755);
t = strjoina("../", bn);
if (symlink(t, sl) < 0)
log_debug_errno(errno, "Failed to symlink '%s' to '%s', ignoring: %m", t, sl);
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 log_debug_errno(errno, "Failed to create temporary directory '%s': %m", temporary_mount);
dev = strjoina(temporary_mount, "/dev");
(void) mkdir(dev, 0755);
if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755" TMPFS_LIMITS_DEV) < 0) {
r = log_debug_errno(errno, "Failed to mount tmpfs on '%s': %m", dev);
goto fail;
}
r = label_fix_container(dev, "/dev", 0);
if (r < 0) {
log_debug_errno(errno, "Failed to fix label of '%s' as /dev: %m", dev);
goto fail;
}
devpts = strjoina(temporary_mount, "/dev/pts");
(void) mkdir(devpts, 0755);
if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) {
r = log_debug_errno(errno, "Failed to bind mount /dev/pts on '%s': %m", devpts);
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) {
log_debug_errno(r, "Failed to detect whether /dev/ptmx is a symlink or not: %m");
goto fail;
} else if (r > 0) {
devptmx = strjoina(temporary_mount, "/dev/ptmx");
if (symlink("pts/ptmx", devptmx) < 0) {
r = log_debug_errno(errno, "Failed to create a symlink '%s' to pts/ptmx: %m", devptmx);
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 = log_debug_errno(errno, "Failed to bind mount /dev/shm on '%s': %m", devshm);
goto fail;
}
devmqueue = strjoina(temporary_mount, "/dev/mqueue");
(void) mkdir(devmqueue, 0755);
if (mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL) < 0)
log_debug_errno(errno, "Failed to bind mount /dev/mqueue on '%s', ignoring: %m", devmqueue);
devhugepages = strjoina(temporary_mount, "/dev/hugepages");
(void) mkdir(devhugepages, 0755);
if (mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL) < 0)
log_debug_errno(errno, "Failed to bind mount /dev/hugepages on '%s', ignoring: %m", devhugepages);
devlog = strjoina(temporary_mount, "/dev/log");
if (symlink("/run/systemd/journal/dev-log", devlog) < 0)
log_debug_errno(errno, "Failed to create a symlink '%s' to /run/systemd/journal/dev-log, ignoring: %m", devlog);
NULSTR_FOREACH(d, devnodes) {
r = clone_device_node(d, temporary_mount, &can_mknod);
/* ENXIO means the *source* is not a device file, skip creation in that case */
if (r < 0 && r != -ENXIO)
goto fail;
}
r = dev_setup(temporary_mount, UID_INVALID, GID_INVALID);
if (r < 0)
log_debug_errno(r, "Failed to set up basic device tree at '%s', ignoring: %m", temporary_mount);
/* 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 */
r = umount_recursive(mount_entry_path(m), 0);
if (r < 0)
log_debug_errno(r, "Failed to unmount directories below '%s', ignoring: %m", mount_entry_path(m));
if (mount(dev, mount_entry_path(m), NULL, MS_MOVE, NULL) < 0) {
r = log_debug_errno(errno, "Failed to move mount point '%s' to '%s': %m", dev, mount_entry_path(m));
goto fail;
}
(void) rmdir(dev);
(void) rmdir(temporary_mount);
return 0;
fail:
if (devpts)
(void) umount(devpts);
if (devshm)
(void) umount(devshm);
if (devhugepages)
(void) umount(devhugepages);
if (devmqueue)
(void) umount(devmqueue);
(void) umount(dev);
(void) rmdir(dev);
(void) 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) {
int r;
const char *entry_path = mount_entry_path(m);
const char *source_path = m->path_const;
assert(m);
/* First, get rid of everything that is below if there is anything. Then, overmount with our new tmpfs */
(void) mkdir_p_label(entry_path, 0755);
(void) umount_recursive(entry_path, 0);
if (mount("tmpfs", entry_path, "tmpfs", m->flags, mount_entry_options(m)) < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", entry_path);
r = label_fix_container(entry_path, source_path, 0);
if (r < 0)
return log_debug_errno(r, "Failed to fix label of '%s' as '%s': %m", entry_path, source_path);
return 1;
}
static int mount_images(const MountEntry *m) {
_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_decoded = NULL;
_cleanup_free_ char *verity_data = NULL, *hash_sig = NULL;
DissectImageFlags dissect_image_flags = m->read_only ? DISSECT_IMAGE_READ_ONLY : 0;
size_t root_hash_size = 0;
int r;
r = verity_metadata_load(mount_entry_source(m), NULL, &root_hash_decoded, &root_hash_size, &verity_data, &hash_sig);
if (r < 0)
return log_debug_errno(r, "Failed to load root hash: %m");
dissect_image_flags |= verity_data ? DISSECT_IMAGE_NO_PARTITION_TABLE : 0;
r = loop_device_make_by_path(mount_entry_source(m),
m->read_only ? O_RDONLY : -1 /* < 0 means writable if possible, read-only as fallback */,
verity_data ? 0 : LO_FLAGS_PARTSCAN,
&loop_device);
if (r < 0)
return log_debug_errno(r, "Failed to create loop device for image: %m");
r = dissect_image(loop_device->fd, root_hash_decoded, root_hash_size, verity_data, NULL, dissect_image_flags, &dissected_image);
/* No partition table? Might be a single-filesystem image, try again */
if (!verity_data && r < 0 && r == -ENOPKG)
r = dissect_image(loop_device->fd, root_hash_decoded, root_hash_size, verity_data, NULL, dissect_image_flags|DISSECT_IMAGE_NO_PARTITION_TABLE, &dissected_image);
if (r < 0)
return log_debug_errno(r, "Failed to dissect image: %m");
r = dissected_image_decrypt(dissected_image, NULL, root_hash_decoded, root_hash_size, verity_data, hash_sig, NULL, 0, dissect_image_flags, &decrypted_image);
if (r < 0)
return log_debug_errno(r, "Failed to decrypt dissected image: %m");
r = mkdir_p_label(mount_entry_path(m), 0755);
if (r < 0)
return log_debug_errno(r, "Failed to create destination directory %s: %m", mount_entry_path(m));
r = umount_recursive(mount_entry_path(m), 0);
if (r < 0)
return log_debug_errno(r, "Failed to umount under destination directory %s: %m", mount_entry_path(m));
r = dissected_image_mount(dissected_image, mount_entry_path(m), UID_INVALID, dissect_image_flags);
if (r < 0)
return log_debug_errno(r, "Failed to mount image: %m");
if (decrypted_image) {
r = decrypted_image_relinquish(decrypted_image);
if (r < 0)
return log_debug_errno(r, "Failed to relinquish decrypted image: %m");
}
loop_device_relinquish(loop_device);
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, NULL);
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 */
return log_debug_errno(SYNTHETIC_ERRNO(ELOOP),
"Symlink loop on '%s'.",
mount_entry_path(m));
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) {
_cleanup_free_ char *inaccessible = NULL;
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: {
_cleanup_free_ char *tmp = NULL;
const char *runtime_dir;
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));
}
if (geteuid() == 0)
runtime_dir = "/run";
else {
if (asprintf(&tmp, "/run/user/" UID_FMT, geteuid()) < 0)
return -ENOMEM;
runtime_dir = tmp;
}
r = mode_to_inaccessible_node(runtime_dir, target.st_mode, &inaccessible);
if (r < 0)
return log_debug_errno(SYNTHETIC_ERRNO(ELOOP),
"File type not supported for inaccessible mounts. Note that symlinks are not allowed");
what = inaccessible;
break;
}
case READONLY:
case READWRITE:
case READWRITE_IMPLICIT:
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, NULL);
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:
case PRIVATE_TMP_READONLY:
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);
case MOUNT_IMAGES:
return mount_images(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_error_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_error_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_error_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 **deny_list, FILE *proc_self_mountinfo) {
unsigned long new_flags = 0, flags_mask = 0;
bool submounts = false;
int r = 0;
assert(m);
assert(proc_self_mountinfo);
if (mount_entry_read_only(m) || m->mode == PRIVATE_DEV) {
new_flags |= MS_RDONLY;
flags_mask |= MS_RDONLY;
}
if (m->nosuid) {
new_flags |= MS_NOSUID;
flags_mask |= MS_NOSUID;
}
if (flags_mask == 0) /* No Change? */
return 0;
/* We generally apply these changes recursively, except for /dev, and the cases we know there's
* nothing further down. Set /dev readonly, but not submounts like /dev/shm. Also, we only set the
* per-mount read-only flag. We can't set it on the superblock, if we are inside a user namespace
* and running Linux <= 4.17. */
submounts =
mount_entry_read_only(m) &&
!IN_SET(m->mode, EMPTY_DIR, TMPFS);
if (submounts)
r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, deny_list, proc_self_mountinfo);
else
r = bind_remount_one_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, proc_self_mountinfo);
/* 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)
return 0;
if (r < 0)
return log_debug_errno(r, "Failed to re-mount '%s'%s: %m", mount_entry_path(m),
submounts ? " and its submounts" : "");
return 0;
}
static bool namespace_info_mount_apivfs(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...
*/
return ns_info->mount_apivfs ||
ns_info->protect_control_groups ||
ns_info->protect_kernel_tunables;
}
static size_t namespace_calculate_mounts(
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,
size_t n_mount_images,
const char* tmp_dir,
const char* var_tmp_dir,
const char* log_namespace,
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_mount_images +
n_temporary_filesystems +
ns_info->private_dev +
(ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
(ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) +
(ns_info->protect_kernel_logs ? ELEMENTSOF(protect_kernel_logs_table) : 0) +
(ns_info->protect_control_groups ? 1 : 0) +
protect_home_cnt + protect_system_cnt +
(ns_info->protect_hostname ? 2 : 0) +
(namespace_info_mount_apivfs(ns_info) ? ELEMENTSOF(apivfs_table) : 0) +
!!log_namespace;
}
static void normalize_mounts(const char *root_directory, MountEntry *mounts, size_t *n_mounts) {
assert(root_directory);
assert(n_mounts);
assert(mounts || *n_mounts == 0);
typesafe_qsort(mounts, *n_mounts, 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);
}
static bool root_read_only(
char **read_only_paths,
ProtectSystem protect_system) {
/* Determine whether the root directory is going to be read-only given the configured settings. */
if (protect_system == PROTECT_SYSTEM_STRICT)
return true;
if (prefixed_path_strv_contains(read_only_paths, "/"))
return true;
return false;
}
static bool home_read_only(
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,
ProtectHome protect_home) {
size_t i;
/* Determine whether the /home directory is going to be read-only given the configured settings. Yes,
* this is a bit sloppy, since we don't bother checking for cases where / is affected by multiple
* settings. */
if (protect_home != PROTECT_HOME_NO)
return true;
if (prefixed_path_strv_contains(read_only_paths, "/home") ||
prefixed_path_strv_contains(inaccessible_paths, "/home") ||
prefixed_path_strv_contains(empty_directories, "/home"))
return true;
for (i = 0; i < n_temporary_filesystems; i++)
if (path_equal(temporary_filesystems[i].path, "/home"))
return true;
/* If /home is overmounted with some dir from the host it's not writable. */
for (i = 0; i < n_bind_mounts; i++)
if (path_equal(bind_mounts[i].destination, "/home"))
return true;
return false;
}
int setup_namespace(
const char* root_directory,
const char* root_image,
const MountOptions *root_image_options,
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 MountImage *mount_images,
size_t n_mount_images,
const char* tmp_dir,
const char* var_tmp_dir,
const char *log_namespace,
ProtectHome protect_home,
ProtectSystem protect_system,
unsigned long mount_flags,
const void *root_hash,
size_t root_hash_size,
const char *root_hash_path,
const void *root_hash_sig,
size_t root_hash_sig_size,
const char *root_hash_sig_path,
const char *root_verity,
DissectImageFlags dissect_image_flags,
char **error_path) {
_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_decoded = NULL;
_cleanup_free_ char *verity_data = NULL, *hash_sig_path = NULL;
MountEntry *m = NULL, *mounts = NULL;
size_t n_mounts;
bool require_prefix = false;
const char *root;
int r = 0;
assert(ns_info);
if (mount_flags == 0)
mount_flags = MS_SHARED;
if (root_image) {
dissect_image_flags |= DISSECT_IMAGE_REQUIRE_ROOT;
/* Make the whole image read-only if we can determine that we only access it in a read-only fashion. */
if (root_read_only(read_only_paths,
protect_system) &&
home_read_only(read_only_paths, inaccessible_paths, empty_directories,
bind_mounts, n_bind_mounts, temporary_filesystems, n_temporary_filesystems,
protect_home) &&
strv_isempty(read_write_paths))
dissect_image_flags |= DISSECT_IMAGE_READ_ONLY;
r = loop_device_make_by_path(root_image,
FLAGS_SET(dissect_image_flags, DISSECT_IMAGE_READ_ONLY) ? O_RDONLY : -1 /* < 0 means writable if possible, read-only as fallback */,
LO_FLAGS_PARTSCAN,
&loop_device);
if (r < 0)
return log_debug_errno(r, "Failed to create loop device for root image: %m");
r = verity_metadata_load(root_image,
root_hash_path,
root_hash ? NULL : &root_hash_decoded,
root_hash ? NULL : &root_hash_size,
root_verity ? NULL : &verity_data,
root_hash_sig || root_hash_sig_path ? NULL : &hash_sig_path);
if (r < 0)
return log_debug_errno(r, "Failed to load root hash: %m");
dissect_image_flags |= root_verity || verity_data ? DISSECT_IMAGE_NO_PARTITION_TABLE : 0;
r = dissect_image(loop_device->fd,
root_hash ?: root_hash_decoded,
root_hash_size,
root_verity ?: verity_data,
root_image_options,
dissect_image_flags,
&dissected_image);
if (r < 0)
return log_debug_errno(r, "Failed to dissect image: %m");
r = dissected_image_decrypt(dissected_image,
NULL,
root_hash ?: root_hash_decoded,
root_hash_size,
root_verity ?: verity_data,
root_hash_sig_path ?: hash_sig_path,
root_hash_sig,
root_hash_sig_size,
dissect_image_flags,
&decrypted_image);
if (r < 0)
return log_debug_errno(r, "Failed to decrypt dissected image: %m");
}
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(
ns_info,
read_write_paths,
read_only_paths,
inaccessible_paths,
empty_directories,
n_bind_mounts,
n_temporary_filesystems,
n_mount_images,
tmp_dir, var_tmp_dir,
log_namespace,
protect_home, protect_system);
if (n_mounts > 0) {
m = mounts = new0(MountEntry, n_mounts);
if (!mounts)
return -ENOMEM;
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) {
bool ro = streq(tmp_dir, RUN_SYSTEMD_EMPTY);
*(m++) = (MountEntry) {
.path_const = "/tmp",
.mode = ro ? PRIVATE_TMP_READONLY : PRIVATE_TMP,
.source_const = tmp_dir,
};
}
if (var_tmp_dir) {
bool ro = streq(var_tmp_dir, RUN_SYSTEMD_EMPTY);
*(m++) = (MountEntry) {
.path_const = "/var/tmp",
.mode = ro ? PRIVATE_TMP_READONLY : PRIVATE_TMP,
.source_const = var_tmp_dir,
};
}
r = append_mount_images(&m, mount_images, n_mount_images);
if (r < 0)
goto finish;
if (ns_info->private_dev) {
*(m++) = (MountEntry) {
.path_const = "/dev",
.mode = PRIVATE_DEV,
.flags = DEV_MOUNT_OPTIONS,
};
}
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_kernel_logs) {
r = append_static_mounts(&m,
protect_kernel_logs_table,
ELEMENTSOF(protect_kernel_logs_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(ns_info)) {
r = append_static_mounts(&m,
apivfs_table,
ELEMENTSOF(apivfs_table),
ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
if (ns_info->protect_hostname) {
*(m++) = (MountEntry) {
.path_const = "/proc/sys/kernel/hostname",
.mode = READONLY,
};
*(m++) = (MountEntry) {
.path_const = "/proc/sys/kernel/domainname",
.mode = READONLY,
};
}
if (log_namespace) {
_cleanup_free_ char *q;
q = strjoin("/run/systemd/journal.", log_namespace);
if (!q) {
r = -ENOMEM;
goto finish;
}
*(m++) = (MountEntry) {
.path_const = "/run/systemd/journal",
.mode = BIND_MOUNT_RECURSIVE,
.read_only = true,
.source_malloc = TAKE_PTR(q),
};
}
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, mounts, &n_mounts);
}
/* All above is just preparation, figuring out what to do. Let's now actually start doing something. */
if (unshare(CLONE_NEWNS) < 0) {
r = log_debug_errno(errno, "Failed to unshare the mount namespace: %m");
if (IN_SET(r, -EACCES, -EPERM, -EOPNOTSUPP, -ENOSYS))
/* If the kernel doesn't support namespaces, or when there's a MAC or seccomp filter
* in place that doesn't allow us to create namespaces (or a missing cap), then
* propagate a recognizable error back, which the caller can use to detect this case
* (and only this) and optionally continue without namespacing applied. */
r = -ENOANO;
goto finish;
}
/* 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 = log_debug_errno(errno, "Failed to remount '/' as SLAVE: %m");
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) {
log_debug_errno(r, "Failed to mount root image: %m");
goto finish;
}
if (decrypted_image) {
r = decrypted_image_relinquish(decrypted_image);
if (r < 0) {
log_debug_errno(r, "Failed to relinquish decrypted image: %m");
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) {
log_debug_errno(r, "Failed to detect that %s is a mount point or not: %m", root);
goto finish;
}
if (r == 0) {
if (mount(root, root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = log_debug_errno(errno, "Failed to bind mount '%s': %m", root);
goto finish;
}
}
} else {
/* Let's mount the main root directory to the root directory to use */
if (mount("/", root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = log_debug_errno(errno, "Failed to bind mount '/' on '%s': %m", root);
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;
_cleanup_free_ char **deny_list = NULL;
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 = log_debug_errno(errno, "Failed to open /proc/self/mountinfo: %m");
if (error_path)
*error_path = strdup("/proc/self/mountinfo");
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) {
if (error_path && mount_entry_path(m))
*error_path = strdup(mount_entry_path(m));
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) {
if (error_path && mount_entry_path(m))
*error_path = strdup(mount_entry_path(m));
goto finish;
}
m->applied = true;
}
if (!again)
break;
normalize_mounts(root, mounts, &n_mounts);
}
/* Create a deny list we can pass to bind_mount_recursive() */
deny_list = new(char*, n_mounts+1);
if (!deny_list) {
r = -ENOMEM;
goto finish;
}
for (j = 0; j < n_mounts; j++)
deny_list[j] = (char*) mount_entry_path(mounts+j);
deny_list[j] = NULL;
/* Second round, flip the ro bits if necessary. */
for (m = mounts; m < mounts + n_mounts; ++m) {
r = make_read_only(m, deny_list, proc_self_mountinfo);
if (r < 0) {
if (error_path && mount_entry_path(m))
*error_path = strdup(mount_entry_path(m));
goto finish;
}
}
}
/* 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) {
log_debug_errno(r, "Failed to mount root with MS_MOVE: %m");
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 = log_debug_errno(errno, "Failed to remount '/' with desired mount flags: %m");
goto finish;
}
r = 0;
finish:
if (n_mounts > 0)
for (m = mounts; m < mounts + n_mounts; m++)
mount_entry_done(m);
free(mounts);
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,
.nosuid = item->nosuid,
.recursive = item->recursive,
.ignore_enoent = item->ignore_enoent,
};
return 0;
}
MountImage* mount_image_free_many(MountImage *m, size_t *n) {
size_t i;
assert(n);
assert(m || *n == 0);
for (i = 0; i < *n; i++) {
free(m[i].source);
free(m[i].destination);
}
free(m);
*n = 0;
return NULL;
}
int mount_image_add(MountImage **m, size_t *n, const MountImage *item) {
_cleanup_free_ char *s = NULL, *d = NULL;
MountImage *c;
assert(m);
assert(n);
assert(item);
s = strdup(item->source);
if (!s)
return -ENOMEM;
d = strdup(item->destination);
if (!d)
return -ENOMEM;
c = reallocarray(*m, *n + 1, sizeof(MountImage));
if (!c)
return -ENOMEM;
*m = c;
c[(*n) ++] = (MountImage) {
.source = TAKE_PTR(s),
.destination = TAKE_PTR(d),
.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 make_tmp_prefix(const char *prefix) {
_cleanup_free_ char *t = NULL;
int r;
/* Don't do anything unless we know the dir is actually missing */
r = access(prefix, F_OK);
if (r >= 0)
return 0;
if (errno != ENOENT)
return -errno;
r = mkdir_parents(prefix, 0755);
if (r < 0)
return r;
r = tempfn_random(prefix, NULL, &t);
if (r < 0)
return r;
if (mkdir(t, 0777) < 0)
return -errno;
if (chmod(t, 01777) < 0) {
r = -errno;
(void) rmdir(t);
return r;
}
if (rename(t, prefix) < 0) {
r = -errno;
(void) rmdir(t);
return r == -EEXIST ? 0 : r; /* it's fine if someone else created the dir by now */
}
return 0;
}
static int make_tmp_subdir(const char *parent, char **ret) {
_cleanup_free_ char *y = NULL;
y = path_join(parent, "/tmp");
if (!y)
return -ENOMEM;
RUN_WITH_UMASK(0000) {
if (mkdir(y, 0777 | S_ISVTX) < 0)
return -errno;
}
if (ret)
*ret = TAKE_PTR(y);
return 0;
}
static int setup_one_tmp_dir(const char *id, const char *prefix, char **path, char **tmp_path) {
_cleanup_free_ char *x = NULL;
char bid[SD_ID128_STRING_MAX];
sd_id128_t boot_id;
bool rw = true;
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;
r = make_tmp_prefix(prefix);
if (r < 0)
return r;
RUN_WITH_UMASK(0077)
if (!mkdtemp(x)) {
if (errno == EROFS || ERRNO_IS_DISK_SPACE(errno))
rw = false;
else
return -errno;
}
if (rw) {
r = make_tmp_subdir(x, tmp_path);
if (r < 0)
return r;
} else {
/* Trouble: we failed to create the directory. Instead of failing, let's simulate /tmp being
* read-only. This way the service will get the EROFS result as if it was writing to the real
* file system. */
r = mkdir_p(RUN_SYSTEMD_EMPTY, 0500);
if (r < 0)
return r;
r = free_and_strdup(&x, RUN_SYSTEMD_EMPTY);
if (r < 0)
return r;
}
*path = TAKE_PTR(x);
return 0;
}
int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
_cleanup_(namespace_cleanup_tmpdirp) char *a = NULL;
_cleanup_(rmdir_and_freep) char *a_tmp = NULL;
char *b;
int r;
assert(id);
assert(tmp_dir);
assert(var_tmp_dir);
r = setup_one_tmp_dir(id, "/tmp", &a, &a_tmp);
if (r < 0)
return r;
r = setup_one_tmp_dir(id, "/var/tmp", &b, NULL);
if (r < 0)
return r;
a_tmp = mfree(a_tmp); /* avoid rmdir */
*tmp_dir = TAKE_PTR(a);
*var_tmp_dir = TAKE_PTR(b);
return 0;
}
int setup_netns(const int netns_storage_socket[static 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;
}
(void) 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;
}
int open_netns_path(const int netns_storage_socket[static 2], const char *path) {
_cleanup_close_ int netns = -1;
int q, r;
assert(netns_storage_socket);
assert(netns_storage_socket[0] >= 0);
assert(netns_storage_socket[1] >= 0);
assert(path);
/* If the storage socket doesn't contain a netns fd yet, open one via the file system and store it in
* it. This is supposed to be called ahead of time, i.e. before setup_netns() which will allocate a
* new anonymous netns if needed. */
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. Open the file from the file system. */
netns = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC);
if (netns < 0) {
r = -errno;
goto fail;
}
r = fd_is_network_ns(netns);
if (r == 0) { /* Not a netns? Refuse early. */
r = -EINVAL;
goto fail;
}
if (r < 0 && r != -EUCLEAN) /* EUCLEAN: we don't know */
goto fail;
r = 1;
} else if (netns < 0) {
r = netns;
goto fail;
} else
r = 0; /* Already allocated */
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);
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