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Systemd/src/core/mount-setup.c
Tejun Heo 4095205ecc core: support "nsdelegate" cgroup v2 mount option (#6294) 
cgroup namespace wasn't useful for delegation because it allowed resource
control interface files (e.g. memory.high) to be written from inside the
namespace - this allowed the namespace parent's resource distribution to be
disturbed by its namespace-scoped children.

A new mount option, "nsdelegate", was added to cgroup v2 to address this issue.
The flag is meangingful only when mounting cgroup v2 in the init namespace and
makes a cgroup namespace a delegation boundary.  The kernel feature is pending
for v4.13.

This should have been the default behavior on cgroup namespaces and this commit
makes systemd try "nsdelegate" first when trying to mount cgroup v2 and fall
back if the option is not supported.

Note that this has danger of breaking usages which depend on modifying the
parent's resource settings from the namespace root, which isn't a valid thing
to do, but such usages may still exist.
2017-07-14 19:27:13 +02:00

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/***
This file is part of systemd.
Copyright 2010 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 <errno.h>
#include <ftw.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <unistd.h>
#include "alloc-util.h"
#include "bus-util.h"
#include "cgroup-util.h"
#include "dev-setup.h"
#include "efivars.h"
#include "fs-util.h"
#include "label.h"
#include "log.h"
#include "macro.h"
#include "missing.h"
#include "mkdir.h"
#include "mount-setup.h"
#include "mount-util.h"
#include "path-util.h"
#include "set.h"
#include "smack-util.h"
#include "strv.h"
#include "user-util.h"
#include "util.h"
#include "virt.h"
typedef enum MountMode {
MNT_NONE = 0,
MNT_FATAL = 1 << 0,
MNT_IN_CONTAINER = 1 << 1,
} MountMode;
typedef struct MountPoint {
const char *what;
const char *where;
const char *type;
const char *options;
unsigned long flags;
bool (*condition_fn)(void);
MountMode mode;
} MountPoint;
/* The first three entries we might need before SELinux is up. The
* fourth (securityfs) is needed by IMA to load a custom policy. The
* other ones we can delay until SELinux and IMA are loaded. When
* SMACK is enabled we need smackfs, too, so it's a fifth one. */
#ifdef HAVE_SMACK
#define N_EARLY_MOUNT 5
#else
#define N_EARLY_MOUNT 4
#endif
static const MountPoint mount_table[] = {
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devtmpfs", "/dev", "devtmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "securityfs", "/sys/kernel/security", "securityfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },
#ifdef HAVE_SMACK
{ "smackfs", "/sys/fs/smackfs", "smackfs", "smackfsdef=*", MS_NOSUID|MS_NOEXEC|MS_NODEV,
mac_smack_use, MNT_FATAL },
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777,smackfsroot=*", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
mac_smack_use, MNT_FATAL },
#endif
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "devpts", "/dev/pts", "devpts", "mode=620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC,
NULL, MNT_IN_CONTAINER },
#ifdef HAVE_SMACK
{ "tmpfs", "/run", "tmpfs", "mode=755,smackfsroot=*", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
mac_smack_use, MNT_FATAL },
#endif
{ "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
NULL, MNT_FATAL|MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_unified_wanted, MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_unified_wanted, MNT_IN_CONTAINER },
{ "tmpfs", "/sys/fs/cgroup", "tmpfs", "mode=755", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup/unified", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_hybrid_wanted, MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup/unified", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_hybrid_wanted, MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd,xattr", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_legacy_wanted, MNT_IN_CONTAINER },
{ "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd", MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
{ "pstore", "/sys/fs/pstore", "pstore", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
NULL, MNT_NONE },
#ifdef ENABLE_EFI
{ "efivarfs", "/sys/firmware/efi/efivars", "efivarfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
is_efi_boot, MNT_NONE },
#endif
};
/* These are API file systems that might be mounted by other software,
* we just list them here so that we know that we should ignore them */
static const char ignore_paths[] =
/* SELinux file systems */
"/sys/fs/selinux\0"
/* Container bind mounts */
"/proc/sys\0"
"/dev/console\0"
"/proc/kmsg\0";
bool mount_point_is_api(const char *path) {
unsigned i;
/* Checks if this mount point is considered "API", and hence
* should be ignored */
for (i = 0; i < ELEMENTSOF(mount_table); i ++)
if (path_equal(path, mount_table[i].where))
return true;
return path_startswith(path, "/sys/fs/cgroup/");
}
bool mount_point_ignore(const char *path) {
const char *i;
NULSTR_FOREACH(i, ignore_paths)
if (path_equal(path, i))
return true;
return false;
}
static int mount_one(const MountPoint *p, bool relabel) {
int r;
assert(p);
if (p->condition_fn && !p->condition_fn())
return 0;
/* Relabel first, just in case */
if (relabel)
(void) label_fix(p->where, true, true);
r = path_is_mount_point(p->where, NULL, AT_SYMLINK_FOLLOW);
if (r < 0 && r != -ENOENT) {
log_full_errno((p->mode & MNT_FATAL) ? LOG_ERR : LOG_DEBUG, r, "Failed to determine whether %s is a mount point: %m", p->where);
return (p->mode & MNT_FATAL) ? r : 0;
}
if (r > 0)
return 0;
/* Skip securityfs in a container */
if (!(p->mode & MNT_IN_CONTAINER) && detect_container() > 0)
return 0;
/* The access mode here doesn't really matter too much, since
* the mounted file system will take precedence anyway. */
if (relabel)
(void) mkdir_p_label(p->where, 0755);
else
(void) mkdir_p(p->where, 0755);
log_debug("Mounting %s to %s of type %s with options %s.",
p->what,
p->where,
p->type,
strna(p->options));
if (mount(p->what,
p->where,
p->type,
p->flags,
p->options) < 0) {
log_full_errno((p->mode & MNT_FATAL) ? LOG_ERR : LOG_DEBUG, errno, "Failed to mount %s at %s: %m", p->type, p->where);
return (p->mode & MNT_FATAL) ? -errno : 0;
}
/* Relabel again, since we now mounted something fresh here */
if (relabel)
(void) label_fix(p->where, false, false);
return 1;
}
static int mount_points_setup(unsigned n, bool loaded_policy) {
unsigned i;
int r = 0;
for (i = 0; i < n; i ++) {
int j;
j = mount_one(mount_table + i, loaded_policy);
if (j != 0 && r >= 0)
r = j;
}
return r;
}
int mount_setup_early(void) {
assert_cc(N_EARLY_MOUNT <= ELEMENTSOF(mount_table));
/* Do a minimal mount of /proc and friends to enable the most
* basic stuff, such as SELinux */
return mount_points_setup(N_EARLY_MOUNT, false);
}
int mount_cgroup_controllers(char ***join_controllers) {
_cleanup_set_free_free_ Set *controllers = NULL;
int r;
if (!cg_is_legacy_wanted())
return 0;
/* Mount all available cgroup controllers that are built into the kernel. */
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 enumerate cgroup controllers: %m");
for (;;) {
_cleanup_free_ char *options = NULL, *controller = NULL, *where = NULL;
MountPoint p = {
.what = "cgroup",
.type = "cgroup",
.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV,
.mode = MNT_IN_CONTAINER,
};
char ***k = NULL;
controller = set_steal_first(controllers);
if (!controller)
break;
if (join_controllers)
for (k = join_controllers; *k; k++)
if (strv_find(*k, controller))
break;
if (k && *k) {
char **i, **j;
for (i = *k, j = *k; *i; i++) {
if (!streq(*i, controller)) {
_cleanup_free_ char *t;
t = set_remove(controllers, *i);
if (!t) {
free(*i);
continue;
}
}
*(j++) = *i;
}
*j = NULL;
options = strv_join(*k, ",");
if (!options)
return log_oom();
} else {
options = controller;
controller = NULL;
}
where = strappend("/sys/fs/cgroup/", options);
if (!where)
return log_oom();
p.where = where;
p.options = options;
r = mount_one(&p, true);
if (r < 0)
return r;
if (r > 0 && k && *k) {
char **i;
for (i = *k; *i; i++) {
_cleanup_free_ char *t = NULL;
t = strappend("/sys/fs/cgroup/", *i);
if (!t)
return log_oom();
r = symlink(options, t);
if (r >= 0) {
#ifdef SMACK_RUN_LABEL
_cleanup_free_ char *src;
src = strappend("/sys/fs/cgroup/", options);
if (!src)
return log_oom();
r = mac_smack_copy(t, src);
if (r < 0 && r != -EOPNOTSUPP)
return log_error_errno(r, "Failed to copy smack label from %s to %s: %m", src, t);
#endif
} else if (errno != EEXIST)
return log_error_errno(errno, "Failed to create symlink %s: %m", t);
}
}
}
/* Now that we mounted everything, let's make the tmpfs the
* cgroup file systems are mounted into read-only. */
(void) mount("tmpfs", "/sys/fs/cgroup", "tmpfs", MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
return 0;
}
#if defined(HAVE_SELINUX) || defined(HAVE_SMACK)
static int nftw_cb(
const char *fpath,
const struct stat *sb,
int tflag,
struct FTW *ftwbuf) {
/* No need to label /dev twice in a row... */
if (_unlikely_(ftwbuf->level == 0))
return FTW_CONTINUE;
label_fix(fpath, false, false);
/* /run/initramfs is static data and big, no need to
* dynamically relabel its contents at boot... */
if (_unlikely_(ftwbuf->level == 1 &&
tflag == FTW_D &&
streq(fpath, "/run/initramfs")))
return FTW_SKIP_SUBTREE;
return FTW_CONTINUE;
};
#endif
int mount_setup(bool loaded_policy) {
int r = 0;
r = mount_points_setup(ELEMENTSOF(mount_table), loaded_policy);
if (r < 0)
return r;
#if defined(HAVE_SELINUX) || defined(HAVE_SMACK)
/* Nodes in devtmpfs and /run need to be manually updated for
* the appropriate labels, after mounting. The other virtual
* API file systems like /sys and /proc do not need that, they
* use the same label for all their files. */
if (loaded_policy) {
usec_t before_relabel, after_relabel;
char timespan[FORMAT_TIMESPAN_MAX];
before_relabel = now(CLOCK_MONOTONIC);
nftw("/dev", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
nftw("/dev/shm", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
nftw("/run", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
after_relabel = now(CLOCK_MONOTONIC);
log_info("Relabelled /dev and /run in %s.",
format_timespan(timespan, sizeof(timespan), after_relabel - before_relabel, 0));
}
#endif
/* Create a few default symlinks, which are normally created
* by udevd, but some scripts might need them before we start
* udevd. */
dev_setup(NULL, UID_INVALID, GID_INVALID);
/* Mark the root directory as shared in regards to mount propagation. The kernel defaults to "private", but we
* think it makes more sense to have a default of "shared" so that nspawn and the container tools work out of
* the box. If specific setups need other settings they can reset the propagation mode to private if
* needed. Note that we set this only when we are invoked directly by the kernel. If we are invoked by a
* container manager we assume the container manager knows what it is doing (for example, because it set up
* some directories with different propagation modes). */
if (detect_container() <= 0)
if (mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL) < 0)
log_warning_errno(errno, "Failed to set up the root directory for shared mount propagation: %m");
/* Create a few directories we always want around, Note that sd_booted() checks for /run/systemd/system, so
* this mkdir really needs to stay for good, otherwise software that copied sd-daemon.c into their sources will
* misdetect systemd. */
(void) mkdir_label("/run/systemd", 0755);
(void) mkdir_label("/run/systemd/system", 0755);
/* Set up inaccessible items */
(void) mkdir_label("/run/systemd/inaccessible", 0000);
(void) mknod("/run/systemd/inaccessible/reg", S_IFREG | 0000, 0);
(void) mkdir_label("/run/systemd/inaccessible/dir", 0000);
(void) mknod("/run/systemd/inaccessible/chr", S_IFCHR | 0000, makedev(0, 0));
(void) mknod("/run/systemd/inaccessible/blk", S_IFBLK | 0000, makedev(0, 0));
(void) mkfifo("/run/systemd/inaccessible/fifo", 0000);
(void) mknod("/run/systemd/inaccessible/sock", S_IFSOCK | 0000, 0);
return 0;
}
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