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Systemd/src/nspawn/nspawn-mount.c

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/***
This file is part of systemd.
Copyright 2015 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <sys/mount.h>
#include <linux/magic.h>
#include "alloc-util.h"
#include "escape.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "label.h"
#include "mkdir.h"
#include "mount-util.h"
#include "nspawn-mount.h"
#include "parse-util.h"
#include "path-util.h"
#include "rm-rf.h"
#include "set.h"
#include "stat-util.h"
#include "string-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
CustomMount* custom_mount_add(CustomMount **l, unsigned *n, CustomMountType t) {
CustomMount *c, *ret;
assert(l);
assert(n);
assert(t >= 0);
assert(t < _CUSTOM_MOUNT_TYPE_MAX);
c = realloc_multiply(*l, (*n + 1), sizeof(CustomMount));
if (!c)
return NULL;
*l = c;
ret = *l + *n;
(*n)++;
*ret = (CustomMount) { .type = t };
return ret;
}
void custom_mount_free_all(CustomMount *l, unsigned n) {
unsigned i;
for (i = 0; i < n; i++) {
CustomMount *m = l + i;
free(m->source);
free(m->destination);
free(m->options);
if (m->work_dir) {
(void) rm_rf(m->work_dir, REMOVE_ROOT|REMOVE_PHYSICAL);
free(m->work_dir);
}
if (m->rm_rf_tmpdir) {
(void) rm_rf(m->rm_rf_tmpdir, REMOVE_ROOT|REMOVE_PHYSICAL);
free(m->rm_rf_tmpdir);
}
strv_free(m->lower);
}
free(l);
}
static int custom_mount_compare(const void *a, const void *b) {
const CustomMount *x = a, *y = b;
int r;
r = path_compare(x->destination, y->destination);
if (r != 0)
return r;
if (x->type < y->type)
return -1;
if (x->type > y->type)
return 1;
return 0;
}
static bool source_path_is_valid(const char *p) {
assert(p);
if (*p == '+')
p++;
return path_is_absolute(p);
}
static char *resolve_source_path(const char *dest, const char *source) {
if (!source)
return NULL;
if (source[0] == '+')
return prefix_root(dest, source + 1);
return strdup(source);
}
int custom_mount_prepare_all(const char *dest, CustomMount *l, unsigned n) {
unsigned i;
int r;
/* Prepare all custom mounts. This will make source we know all temporary directories. This is called in the
* parent process, so that we know the temporary directories to remove on exit before we fork off the
* children. */
assert(l || n == 0);
/* Order the custom mounts, and make sure we have a working directory */
qsort_safe(l, n, sizeof(CustomMount), custom_mount_compare);
for (i = 0; i < n; i++) {
CustomMount *m = l + i;
if (m->source) {
char *s;
s = resolve_source_path(dest, m->source);
if (!s)
return log_oom();
free(m->source);
m->source = s;
} else {
/* No source specified? In that case, use a throw-away temporary directory in /var/tmp */
m->rm_rf_tmpdir = strdup("/var/tmp/nspawn-temp-XXXXXX");
if (!m->rm_rf_tmpdir)
return log_oom();
if (!mkdtemp(m->rm_rf_tmpdir)) {
m->rm_rf_tmpdir = mfree(m->rm_rf_tmpdir);
return log_error_errno(errno, "Failed to acquire temporary directory: %m");
}
m->source = strjoin(m->rm_rf_tmpdir, "/src");
if (!m->source)
return log_oom();
if (mkdir(m->source, 0755) < 0)
return log_error_errno(errno, "Failed to create %s: %m", m->source);
}
if (m->type == CUSTOM_MOUNT_OVERLAY) {
char **j;
STRV_FOREACH(j, m->lower) {
char *s;
s = resolve_source_path(dest, *j);
if (!s)
return log_oom();
free(*j);
*j = s;
}
if (m->work_dir) {
char *s;
s = resolve_source_path(dest, m->work_dir);
if (!s)
return log_oom();
free(m->work_dir);
m->work_dir = s;
} else {
assert(m->source);
r = tempfn_random(m->source, NULL, &m->work_dir);
if (r < 0)
return log_error_errno(r, "Failed to acquire working directory: %m");
}
(void) mkdir_label(m->work_dir, 0700);
}
}
return 0;
}
int bind_mount_parse(CustomMount **l, unsigned *n, const char *s, bool read_only) {
_cleanup_free_ char *source = NULL, *destination = NULL, *opts = NULL;
const char *p = s;
CustomMount *m;
int r;
assert(l);
assert(n);
r = extract_many_words(&p, ":", EXTRACT_DONT_COALESCE_SEPARATORS, &source, &destination, NULL);
if (r < 0)
return r;
if (r == 0)
return -EINVAL;
if (r == 1) {
destination = strdup(source[0] == '+' ? source+1 : source);
if (!destination)
return -ENOMEM;
}
if (r == 2 && !isempty(p)) {
opts = strdup(p);
if (!opts)
return -ENOMEM;
}
if (isempty(source))
source = NULL;
else if (!source_path_is_valid(source))
return -EINVAL;
if (!path_is_absolute(destination))
return -EINVAL;
m = custom_mount_add(l, n, CUSTOM_MOUNT_BIND);
if (!m)
return -ENOMEM;
m->source = source;
m->destination = destination;
m->read_only = read_only;
m->options = opts;
source = destination = opts = NULL;
return 0;
}
int tmpfs_mount_parse(CustomMount **l, unsigned *n, const char *s) {
_cleanup_free_ char *path = NULL, *opts = NULL;
const char *p = s;
CustomMount *m;
int r;
assert(l);
assert(n);
assert(s);
r = extract_first_word(&p, &path, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
if (r < 0)
return r;
if (r == 0)
return -EINVAL;
if (isempty(p))
opts = strdup("mode=0755");
else
opts = strdup(p);
if (!opts)
return -ENOMEM;
if (!path_is_absolute(path))
return -EINVAL;
m = custom_mount_add(l, n, CUSTOM_MOUNT_TMPFS);
if (!m)
return -ENOMEM;
m->destination = path;
m->options = opts;
path = opts = NULL;
return 0;
}
int overlay_mount_parse(CustomMount **l, unsigned *n, const char *s, bool read_only) {
_cleanup_free_ char *upper = NULL, *destination = NULL;
_cleanup_strv_free_ char **lower = NULL;
CustomMount *m;
int k;
k = strv_split_extract(&lower, s, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
if (k < 0)
return k;
if (k < 2)
return -EADDRNOTAVAIL;
if (k == 2) {
/* If two parameters are specified, the first one is the lower, the second one the upper directory. And
* we'll also define the destination mount point the same as the upper. */
if (!source_path_is_valid(lower[0]) ||
!source_path_is_valid(lower[1]))
return -EINVAL;
upper = lower[1];
lower[1] = NULL;
destination = strdup(upper[0] == '+' ? upper+1 : upper); /* take the destination without "+" prefix */
if (!destination)
return -ENOMEM;
} else {
char **i;
/* If more than two parameters are specified, the last one is the destination, the second to last one
* the "upper", and all before that the "lower" directories. */
destination = lower[k - 1];
upper = lower[k - 2];
lower[k - 2] = NULL;
STRV_FOREACH(i, lower)
if (!source_path_is_valid(*i))
return -EINVAL;
/* If the upper directory is unspecified, then let's create it automatically as a throw-away directory
* in /var/tmp */
if (isempty(upper))
upper = NULL;
else if (!source_path_is_valid(upper))
return -EINVAL;
if (!path_is_absolute(destination))
return -EINVAL;
}
m = custom_mount_add(l, n, CUSTOM_MOUNT_OVERLAY);
if (!m)
return -ENOMEM;
m->destination = destination;
m->source = upper;
m->lower = lower;
m->read_only = read_only;
upper = destination = NULL;
lower = NULL;
return 0;
}
static int tmpfs_patch_options(
const char *options,
bool userns,
uid_t uid_shift, uid_t uid_range,
bool patch_ids,
const char *selinux_apifs_context,
char **ret) {
char *buf = NULL;
if ((userns && uid_shift != 0) || patch_ids) {
assert(uid_shift != UID_INVALID);
if (asprintf(&buf, "%s%suid=" UID_FMT ",gid=" UID_FMT,
options ?: "", options ? "," : "",
uid_shift, uid_shift) < 0)
return -ENOMEM;
options = buf;
}
#ifdef HAVE_SELINUX
if (selinux_apifs_context) {
char *t;
t = strjoin(options ?: "", options ? "," : "",
"context=\"", selinux_apifs_context, "\"");
free(buf);
if (!t)
return -ENOMEM;
buf = t;
}
#endif
if (!buf && options) {
buf = strdup(options);
if (!buf)
return -ENOMEM;
}
*ret = buf;
return !!buf;
}
int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
const char *full, *top, *x;
int r;
unsigned long extra_flags = 0;
top = prefix_roota(dest, "/sys");
r = path_check_fstype(top, SYSFS_MAGIC);
if (r < 0)
return log_error_errno(r, "Failed to determine filesystem type of %s: %m", top);
/* /sys might already be mounted as sysfs by the outer child in the
* !netns case. In this case, it's all good. Don't touch it because we
* don't have the right to do so, see https://github.com/systemd/systemd/issues/1555.
*/
if (r > 0)
return 0;
full = prefix_roota(top, "/full");
(void) mkdir(full, 0755);
if (mount_settings & MOUNT_APPLY_APIVFS_RO)
extra_flags |= MS_RDONLY;
r = mount_verbose(LOG_ERR, "sysfs", full, "sysfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|extra_flags, NULL);
if (r < 0)
return r;
FOREACH_STRING(x, "block", "bus", "class", "dev", "devices", "kernel") {
_cleanup_free_ char *from = NULL, *to = NULL;
from = prefix_root(full, x);
if (!from)
return log_oom();
to = prefix_root(top, x);
if (!to)
return log_oom();
(void) mkdir(to, 0755);
r = mount_verbose(LOG_ERR, from, to, NULL, MS_BIND, NULL);
if (r < 0)
return r;
r = mount_verbose(LOG_ERR, NULL, to, NULL,
MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
if (r < 0)
return r;
}
r = umount_verbose(full);
if (r < 0)
return r;
if (rmdir(full) < 0)
return log_error_errno(errno, "Failed to remove %s: %m", full);
x = prefix_roota(top, "/fs/kdbus");
(void) mkdir_p(x, 0755);
/* Create mountpoint for cgroups. Otherwise we are not allowed since we
* remount /sys read-only.
*/
if (cg_ns_supported()) {
x = prefix_roota(top, "/fs/cgroup");
(void) mkdir_p(x, 0755);
}
return mount_verbose(LOG_ERR, NULL, top, NULL,
MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
}
static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
int r;
assert(path);
r = mkdir(path, mode);
if (r < 0 && errno != EEXIST)
return -errno;
if ((mask & MOUNT_USE_USERNS) == 0)
return 0;
if (mask & MOUNT_IN_USERNS)
return 0;
r = lchown(path, uid_shift, uid_shift);
if (r < 0)
return -errno;
return 0;
}
static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
const char *p, *e;
int r;
assert(path);
if (prefix && !path_startswith(path, prefix))
return -ENOTDIR;
/* create every parent directory in the path, except the last component */
p = path + strspn(path, "/");
for (;;) {
char t[strlen(path) + 1];
e = p + strcspn(p, "/");
p = e + strspn(e, "/");
/* Is this the last component? If so, then we're done */
if (*p == 0)
break;
memcpy(t, path, e - path);
t[e-path] = 0;
if (prefix && path_startswith(prefix, t))
continue;
r = mkdir_userns(t, mode, mask, uid_shift);
if (r < 0)
return r;
}
return mkdir_userns(path, mode, mask, uid_shift);
}
int mount_all(const char *dest,
MountSettingsMask mount_settings,
uid_t uid_shift, uid_t uid_range,
const char *selinux_apifs_context) {
typedef struct MountPoint {
const char *what;
const char *where;
const char *type;
const char *options;
unsigned long flags;
MountSettingsMask mount_settings;
} MountPoint;
static const MountPoint mount_table[] = {
/* inner child mounts */
{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, MOUNT_FATAL|MOUNT_IN_USERNS },
{ "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND, MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* Bind mount first ...*/
{ "/proc/sys/net", "/proc/sys/net", NULL, NULL, MS_BIND, MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO|MOUNT_APPLY_APIVFS_NETNS }, /* (except for this) */
{ NULL, "/proc/sys", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* ... then, make it r/o */
{ "/proc/sysrq-trigger", "/proc/sysrq-trigger", NULL, NULL, MS_BIND, MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* Bind mount first ...*/
{ NULL, "/proc/sysrq-trigger", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* ... then, make it r/o */
/* outer child mounts */
{ "tmpfs", "/tmp", "tmpfs", "mode=1777", MS_STRICTATIME, MOUNT_FATAL },
{ "tmpfs", "/sys", "tmpfs", "mode=755", MS_NOSUID|MS_NOEXEC|MS_NODEV, MOUNT_FATAL|MOUNT_APPLY_APIVFS_NETNS },
{ "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV, MOUNT_FATAL|MOUNT_APPLY_APIVFS_RO }, /* skipped if above was mounted */
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, MOUNT_FATAL }, /* skipped if above was mounted */
{ "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME, MOUNT_FATAL },
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME, MOUNT_FATAL },
{ "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV|MS_STRICTATIME, MOUNT_FATAL },
#ifdef HAVE_SELINUX
{ "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND, 0 }, /* Bind mount first */
{ NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, 0 }, /* Then, make it r/o */
#endif
};
unsigned k;
int r;
bool use_userns = (mount_settings & MOUNT_USE_USERNS);
bool netns = (mount_settings & MOUNT_APPLY_APIVFS_NETNS);
bool ro = (mount_settings & MOUNT_APPLY_APIVFS_RO);
bool in_userns = (mount_settings & MOUNT_IN_USERNS);
for (k = 0; k < ELEMENTSOF(mount_table); k++) {
_cleanup_free_ char *where = NULL, *options = NULL;
const char *o;
bool fatal = (mount_table[k].mount_settings & MOUNT_FATAL);
if (in_userns != (bool)(mount_table[k].mount_settings & MOUNT_IN_USERNS))
continue;
if (!netns && (bool)(mount_table[k].mount_settings & MOUNT_APPLY_APIVFS_NETNS))
continue;
if (!ro && (bool)(mount_table[k].mount_settings & MOUNT_APPLY_APIVFS_RO))
continue;
r = chase_symlinks(mount_table[k].where, dest, CHASE_NONEXISTENT|CHASE_PREFIX_ROOT, &where);
if (r < 0)
return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, mount_table[k].where);
r = path_is_mount_point(where, NULL, 0);
if (r < 0 && r != -ENOENT)
return log_error_errno(r, "Failed to detect whether %s is a mount point: %m", where);
/* Skip this entry if it is not a remount. */
if (mount_table[k].what && r > 0)
continue;
r = mkdir_userns_p(dest, where, 0755, mount_settings, uid_shift);
if (r < 0 && r != -EEXIST) {
if (fatal)
return log_error_errno(r, "Failed to create directory %s: %m", where);
log_debug_errno(r, "Failed to create directory %s: %m", where);
continue;
}
o = mount_table[k].options;
if (streq_ptr(mount_table[k].type, "tmpfs")) {
if (in_userns)
r = tmpfs_patch_options(o, use_userns, 0, uid_range, true, selinux_apifs_context, &options);
else
r = tmpfs_patch_options(o, use_userns, uid_shift, uid_range, false, selinux_apifs_context, &options);
if (r < 0)
return log_oom();
if (r > 0)
o = options;
}
r = mount_verbose(fatal ? LOG_ERR : LOG_DEBUG,
mount_table[k].what,
where,
mount_table[k].type,
mount_table[k].flags,
o);
if (r < 0 && fatal)
return r;
}
return 0;
}
static int parse_mount_bind_options(const char *options, unsigned long *mount_flags, char **mount_opts) {
const char *p = options;
unsigned long flags = *mount_flags;
char *opts = NULL;
int r;
assert(options);
for (;;) {
_cleanup_free_ char *word = NULL;
r = extract_first_word(&p, &word, ",", 0);
if (r < 0)
return log_error_errno(r, "Failed to extract mount option: %m");
if (r == 0)
break;
if (streq(word, "rbind"))
flags |= MS_REC;
else if (streq(word, "norbind"))
flags &= ~MS_REC;
else {
log_error("Invalid bind mount option: %s", word);
return -EINVAL;
}
}
*mount_flags = flags;
/* in the future mount_opts will hold string options for mount(2) */
*mount_opts = opts;
return 0;
}
static int mount_bind(const char *dest, CustomMount *m) {
_cleanup_free_ char *mount_opts = NULL, *where = NULL;
unsigned long mount_flags = MS_BIND | MS_REC;
struct stat source_st, dest_st;
int r;
assert(dest);
assert(m);
if (m->options) {
r = parse_mount_bind_options(m->options, &mount_flags, &mount_opts);
if (r < 0)
return r;
}
if (stat(m->source, &source_st) < 0)
return log_error_errno(errno, "Failed to stat %s: %m", m->source);
r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where);
if (r < 0)
return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
if (r > 0) { /* Path exists already? */
if (stat(where, &dest_st) < 0)
return log_error_errno(errno, "Failed to stat %s: %m", where);
if (S_ISDIR(source_st.st_mode) && !S_ISDIR(dest_st.st_mode)) {
log_error("Cannot bind mount directory %s on file %s.", m->source, where);
return -EINVAL;
}
if (!S_ISDIR(source_st.st_mode) && S_ISDIR(dest_st.st_mode)) {
log_error("Cannot bind mount file %s on directory %s.", m->source, where);
return -EINVAL;
}
} else { /* Path doesn't exist yet? */
r = mkdir_parents_label(where, 0755);
if (r < 0)
return log_error_errno(r, "Failed to make parents of %s: %m", where);
/* Create the mount point. Any non-directory file can be
* mounted on any non-directory file (regular, fifo, socket,
* char, block).
*/
if (S_ISDIR(source_st.st_mode))
r = mkdir_label(where, 0755);
else
r = touch(where);
if (r < 0)
return log_error_errno(r, "Failed to create mount point %s: %m", where);
}
r = mount_verbose(LOG_ERR, m->source, where, NULL, mount_flags, mount_opts);
if (r < 0)
return r;
if (m->read_only) {
r = bind_remount_recursive(where, true, NULL);
if (r < 0)
return log_error_errno(r, "Read-only bind mount failed: %m");
}
return 0;
}
static int mount_tmpfs(
const char *dest,
CustomMount *m,
bool userns, uid_t uid_shift, uid_t uid_range,
const char *selinux_apifs_context) {
const char *options;
_cleanup_free_ char *buf = NULL, *where = NULL;
int r;
assert(dest);
assert(m);
r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where);
if (r < 0)
return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
if (r == 0) { /* Doesn't exist yet? */
r = mkdir_p_label(where, 0755);
if (r < 0)
return log_error_errno(r, "Creating mount point for tmpfs %s failed: %m", where);
}
r = tmpfs_patch_options(m->options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
if (r < 0)
return log_oom();
options = r > 0 ? buf : m->options;
return mount_verbose(LOG_ERR, "tmpfs", where, "tmpfs", MS_NODEV|MS_STRICTATIME, options);
}
static char *joined_and_escaped_lower_dirs(char **lower) {
_cleanup_strv_free_ char **sv = NULL;
sv = strv_copy(lower);
if (!sv)
return NULL;
strv_reverse(sv);
if (!strv_shell_escape(sv, ",:"))
return NULL;
return strv_join(sv, ":");
}
static int mount_overlay(const char *dest, CustomMount *m) {
_cleanup_free_ char *lower = NULL, *where = NULL, *escaped_source = NULL;
const char *options;
int r;
assert(dest);
assert(m);
r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where);
if (r < 0)
return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
if (r == 0) { /* Doesn't exist yet? */
r = mkdir_label(where, 0755);
if (r < 0)
return log_error_errno(r, "Creating mount point for overlay %s failed: %m", where);
}
(void) mkdir_p_label(m->source, 0755);
lower = joined_and_escaped_lower_dirs(m->lower);
if (!lower)
return log_oom();
escaped_source = shell_escape(m->source, ",:");
if (!escaped_source)
return log_oom();
if (m->read_only)
options = strjoina("lowerdir=", escaped_source, ":", lower);
else {
_cleanup_free_ char *escaped_work_dir = NULL;
escaped_work_dir = shell_escape(m->work_dir, ",:");
if (!escaped_work_dir)
return log_oom();
options = strjoina("lowerdir=", lower, ",upperdir=", escaped_source, ",workdir=", escaped_work_dir);
}
return mount_verbose(LOG_ERR, "overlay", where, "overlay", m->read_only ? MS_RDONLY : 0, options);
}
int mount_custom(
const char *dest,
CustomMount *mounts, unsigned n,
bool userns, uid_t uid_shift, uid_t uid_range,
const char *selinux_apifs_context) {
unsigned i;
int r;
assert(dest);
for (i = 0; i < n; i++) {
CustomMount *m = mounts + i;
switch (m->type) {
case CUSTOM_MOUNT_BIND:
r = mount_bind(dest, m);
break;
case CUSTOM_MOUNT_TMPFS:
r = mount_tmpfs(dest, m, userns, uid_shift, uid_range, selinux_apifs_context);
break;
case CUSTOM_MOUNT_OVERLAY:
r = mount_overlay(dest, m);
break;
default:
assert_not_reached("Unknown custom mount type");
}
if (r < 0)
return r;
}
return 0;
}
/* Retrieve existing subsystems. This function is called in a new cgroup
* namespace.
*/
static int get_controllers(Set *subsystems) {
_cleanup_fclose_ FILE *f = NULL;
char line[LINE_MAX];
assert(subsystems);
f = fopen("/proc/self/cgroup", "re");
if (!f)
return errno == ENOENT ? -ESRCH : -errno;
FOREACH_LINE(line, f, return -errno) {
int r;
char *e, *l, *p;
l = strchr(line, ':');
if (!l)
continue;
l++;
e = strchr(l, ':');
if (!e)
continue;
*e = 0;
if (STR_IN_SET(l, "", "name=systemd"))
continue;
p = strdup(l);
if (!p)
return -ENOMEM;
r = set_consume(subsystems, p);
if (r < 0)
return r;
}
return 0;
}
static int mount_legacy_cgroup_hierarchy(
const char *dest,
const char *controller,
const char *hierarchy,
CGroupUnified unified_requested,
bool read_only) {
const char *to, *fstype, *opts;
int r;
to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy);
r = path_is_mount_point(to, dest, 0);
if (r < 0 && r != -ENOENT)
return log_error_errno(r, "Failed to determine if %s is mounted already: %m", to);
if (r > 0)
return 0;
mkdir_p(to, 0755);
/* The superblock mount options of the mount point need to be
* identical to the hosts', and hence writable... */
if (streq(controller, SYSTEMD_CGROUP_CONTROLLER)) {
if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
fstype = "cgroup2";
opts = NULL;
} else {
fstype = "cgroup";
opts = "none,name=systemd,xattr";
}
} else {
fstype = "cgroup";
opts = controller;
}
r = mount_verbose(LOG_ERR, "cgroup", to, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts);
if (r < 0)
return r;
/* ... hence let's only make the bind mount read-only, not the superblock. */
if (read_only) {
r = mount_verbose(LOG_ERR, NULL, to, NULL,
MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
if (r < 0)
return r;
}
return 1;
}
/* Mount a legacy cgroup hierarchy when cgroup namespaces are supported. */
static int mount_legacy_cgns_supported(
const char *dest,
CGroupUnified unified_requested,
bool userns,
uid_t uid_shift,
uid_t uid_range,
const char *selinux_apifs_context) {
_cleanup_set_free_free_ Set *controllers = NULL;
const char *cgroup_root = "/sys/fs/cgroup", *c;
int r;
(void) mkdir_p(cgroup_root, 0755);
/* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
if (r == 0) {
_cleanup_free_ char *options = NULL;
/* When cgroup namespaces are enabled and user namespaces are
* used then the mount of the cgroupfs is done *inside* the new
* user namespace. We're root in the new user namespace and the
* kernel will happily translate our uid/gid to the correct
* uid/gid as seen from e.g. /proc/1/mountinfo. So we simply
* pass uid 0 and not uid_shift to tmpfs_patch_options().
*/
r = tmpfs_patch_options("mode=755", userns, 0, uid_range, true, selinux_apifs_context, &options);
if (r < 0)
return log_oom();
r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
if (r < 0)
return r;
}
if (cg_all_unified() > 0)
goto skip_controllers;
controllers = set_new(&string_hash_ops);
if (!controllers)
return log_oom();
r = get_controllers(controllers);
if (r < 0)
return log_error_errno(r, "Failed to determine cgroup controllers: %m");
for (;;) {
_cleanup_free_ const char *controller = NULL;
controller = set_steal_first(controllers);
if (!controller)
break;
r = mount_legacy_cgroup_hierarchy("", controller, controller, unified_requested, !userns);
if (r < 0)
return r;
/* When multiple hierarchies are co-mounted, make their
* constituting individual hierarchies a symlink to the
* co-mount.
*/
c = controller;
for (;;) {
_cleanup_free_ char *target = NULL, *tok = NULL;
r = extract_first_word(&c, &tok, ",", 0);
if (r < 0)
return log_error_errno(r, "Failed to extract co-mounted cgroup controller: %m");
if (r == 0)
break;
target = prefix_root("/sys/fs/cgroup", tok);
if (!target)
return log_oom();
if (streq(controller, tok))
break;
r = symlink_idempotent(controller, target);
if (r == -EINVAL)
return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
if (r < 0)
return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
}
}
skip_controllers:
r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER, "systemd", unified_requested, false);
if (r < 0)
return r;
if (!userns)
return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
return 0;
}
/* Mount legacy cgroup hierarchy when cgroup namespaces are unsupported. */
static int mount_legacy_cgns_unsupported(
const char *dest,
CGroupUnified unified_requested,
bool userns,
uid_t uid_shift,
uid_t uid_range,
const char *selinux_apifs_context) {
_cleanup_set_free_free_ Set *controllers = NULL;
const char *cgroup_root;
int r;
cgroup_root = prefix_roota(dest, "/sys/fs/cgroup");
(void) mkdir_p(cgroup_root, 0755);
/* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
if (r == 0) {
_cleanup_free_ char *options = NULL;
r = tmpfs_patch_options("mode=755", userns, uid_shift, uid_range, false, selinux_apifs_context, &options);
if (r < 0)
return log_oom();
r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
if (r < 0)
return r;
}
if (cg_all_unified() > 0)
goto skip_controllers;
controllers = set_new(&string_hash_ops);
if (!controllers)
return log_oom();
r = cg_kernel_controllers(controllers);
if (r < 0)
return log_error_errno(r, "Failed to determine cgroup controllers: %m");
for (;;) {
_cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL;
controller = set_steal_first(controllers);
if (!controller)
break;
origin = prefix_root("/sys/fs/cgroup/", controller);
if (!origin)
return log_oom();
r = readlink_malloc(origin, &combined);
if (r == -EINVAL) {
/* Not a symbolic link, but directly a single cgroup hierarchy */
r = mount_legacy_cgroup_hierarchy(dest, controller, controller, unified_requested, true);
if (r < 0)
return r;
} else if (r < 0)
return log_error_errno(r, "Failed to read link %s: %m", origin);
else {
_cleanup_free_ char *target = NULL;
target = prefix_root(dest, origin);
if (!target)
return log_oom();
/* A symbolic link, a combination of controllers in one hierarchy */
if (!filename_is_valid(combined)) {
log_warning("Ignoring invalid combined hierarchy %s.", combined);
continue;
}
r = mount_legacy_cgroup_hierarchy(dest, combined, combined, unified_requested, true);
if (r < 0)
return r;
r = symlink_idempotent(combined, target);
if (r == -EINVAL)
return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
if (r < 0)
return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
}
}
skip_controllers:
r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER, "systemd", unified_requested, false);
if (r < 0)
return r;
return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
}
static int mount_unified_cgroups(const char *dest) {
const char *p;
int r;
assert(dest);
p = prefix_roota(dest, "/sys/fs/cgroup");
(void) mkdir_p(p, 0755);
r = path_is_mount_point(p, dest, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Failed to determine if %s is mounted already: %m", p);
if (r > 0) {
p = prefix_roota(dest, "/sys/fs/cgroup/cgroup.procs");
if (access(p, F_OK) >= 0)
return 0;
if (errno != ENOENT)
return log_error_errno(errno, "Failed to determine if mount point %s contains the unified cgroup hierarchy: %m", p);
log_error("%s is already mounted but not a unified cgroup hierarchy. Refusing.", p);
return -EINVAL;
}
return mount_verbose(LOG_ERR, "cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
}
int mount_cgroups(
const char *dest,
CGroupUnified unified_requested,
bool userns,
uid_t uid_shift,
uid_t uid_range,
const char *selinux_apifs_context,
bool use_cgns) {
if (unified_requested >= CGROUP_UNIFIED_ALL)
return mount_unified_cgroups(dest);
else if (use_cgns)
return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
}
int mount_systemd_cgroup_writable(
const char *dest,
CGroupUnified unified_requested) {
_cleanup_free_ char *own_cgroup_path = NULL;
const char *systemd_root, *systemd_own;
int r;
assert(dest);
r = cg_pid_get_path(NULL, 0, &own_cgroup_path);
if (r < 0)
return log_error_errno(r, "Failed to determine our own cgroup path: %m");
/* If we are living in the top-level, then there's nothing to do... */
if (path_equal(own_cgroup_path, "/"))
return 0;
if (unified_requested >= CGROUP_UNIFIED_ALL) {
systemd_own = strjoina(dest, "/sys/fs/cgroup", own_cgroup_path);
systemd_root = prefix_roota(dest, "/sys/fs/cgroup");
} else {
systemd_own = strjoina(dest, "/sys/fs/cgroup/systemd", own_cgroup_path);
systemd_root = prefix_roota(dest, "/sys/fs/cgroup/systemd");
}
/* Make our own cgroup a (writable) bind mount */
r = mount_verbose(LOG_ERR, systemd_own, systemd_own, NULL, MS_BIND, NULL);
if (r < 0)
return r;
/* And then remount the systemd cgroup root read-only */
return mount_verbose(LOG_ERR, NULL, systemd_root, NULL,
MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
}
int setup_volatile_state(
const char *directory,
VolatileMode mode,
bool userns, uid_t uid_shift, uid_t uid_range,
const char *selinux_apifs_context) {
_cleanup_free_ char *buf = NULL;
const char *p, *options;
int r;
assert(directory);
if (mode != VOLATILE_STATE)
return 0;
/* --volatile=state means we simply overmount /var
with a tmpfs, and the rest read-only. */
r = bind_remount_recursive(directory, true, NULL);
if (r < 0)
return log_error_errno(r, "Failed to remount %s read-only: %m", directory);
p = prefix_roota(directory, "/var");
r = mkdir(p, 0755);
if (r < 0 && errno != EEXIST)
return log_error_errno(errno, "Failed to create %s: %m", directory);
options = "mode=755";
r = tmpfs_patch_options(options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
if (r < 0)
return log_oom();
if (r > 0)
options = buf;
return mount_verbose(LOG_ERR, "tmpfs", p, "tmpfs", MS_STRICTATIME, options);
}
int setup_volatile(
const char *directory,
VolatileMode mode,
bool userns, uid_t uid_shift, uid_t uid_range,
const char *selinux_apifs_context) {
bool tmpfs_mounted = false, bind_mounted = false;
char template[] = "/tmp/nspawn-volatile-XXXXXX";
_cleanup_free_ char *buf = NULL;
const char *f, *t, *options;
int r;
assert(directory);
if (mode != VOLATILE_YES)
return 0;
/* --volatile=yes means we mount a tmpfs to the root dir, and
the original /usr to use inside it, and that read-only. */
if (!mkdtemp(template))
return log_error_errno(errno, "Failed to create temporary directory: %m");
options = "mode=755";
r = tmpfs_patch_options(options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
if (r < 0)
return log_oom();
if (r > 0)
options = buf;
r = mount_verbose(LOG_ERR, "tmpfs", template, "tmpfs", MS_STRICTATIME, options);
if (r < 0)
goto fail;
tmpfs_mounted = true;
f = prefix_roota(directory, "/usr");
t = prefix_roota(template, "/usr");
r = mkdir(t, 0755);
if (r < 0 && errno != EEXIST) {
r = log_error_errno(errno, "Failed to create %s: %m", t);
goto fail;
}
r = mount_verbose(LOG_ERR, f, t, NULL, MS_BIND|MS_REC, NULL);
if (r < 0)
goto fail;
bind_mounted = true;
r = bind_remount_recursive(t, true, NULL);
if (r < 0) {
log_error_errno(r, "Failed to remount %s read-only: %m", t);
goto fail;
}
r = mount_verbose(LOG_ERR, template, directory, NULL, MS_MOVE, NULL);
if (r < 0)
goto fail;
(void) rmdir(template);
return 0;
fail:
if (bind_mounted)
(void) umount_verbose(t);
if (tmpfs_mounted)
(void) umount_verbose(template);
(void) rmdir(template);
return r;
}
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