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systemd/src/core/mount-setup.c
Alessandro Puccetti c4b4170746 namespace: unify limit behavior on non-directory paths 
Despite the name, `Read{Write,Only}Directories=` already allows for
regular file paths to be masked. This commit adds the same behavior
to `InaccessibleDirectories=` and makes it explicit in the doc.
This patch introduces `/run/systemd/inaccessible/{reg,dir,chr,blk,fifo,sock}`
{dile,device}nodes and mounts on the appropriate one the paths specified
in `InacessibleDirectories=`.

Based on Luca's patch from https://github.com/systemd/systemd/pull/3327
2016-07-19 17:22:02 +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", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
cg_is_unified_wanted, MNT_FATAL|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/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, 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. */
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);
(void) mkdir_label("/run/systemd/inaccessible", 0000);
/* Set up inaccessible items */
(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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