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Systemd/src/core/namespace.c
Lennart Poettering 2d3a5a73e0 nspawn: make sure images containing an ESP are compatible with userns -U mode 
In -U mode we might need to re-chown() all files and directories to
match the UID shift we want for the image. That's problematic on fat
partitions, such as the ESP (and which is generated by mkosi's
--bootable switch), because fat of course knows no UID/GID file
ownership natively.

With this change we take benefit of the uid= and gid= mount options FAT
knows: instead of chown()ing all files and directories we can just
specify the right UID/GID to use at mount time.

This beefs up the image dissection logic in two ways:

1. First of all support for mounting relevant file systems with
   uid=/gid= is added: when a UID is specified during mount it is used for
   all applicable file systems.

2. Secondly, two new mount flags are added:
   DISSECT_IMAGE_MOUNT_ROOT_ONLY and DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY.
   If one is specified the mount routine will either only mount the root
   partition of an image, or all partitions except the root partition.
   This is used by nspawn: first the root partition is mounted, so that
   we can determine the UID shift in use so far, based on ownership of
   the image's root directory. Then, we mount the remaining partitions
   in a second go, this time with the right UID/GID information.
2017-12-05 13:49:12 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
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 <sched.h>
#include <stdio.h>
#include <string.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <unistd.h>
#include <linux/fs.h>
#include "alloc-util.h"
#include "base-filesystem.h"
#include "dev-setup.h"
#include "fd-util.h"
#include "fs-util.h"
#include "label.h"
#include "loop-util.h"
#include "loopback-setup.h"
#include "missing.h"
#include "mkdir.h"
#include "mount-util.h"
#include "namespace.h"
#include "path-util.h"
#include "selinux-util.h"
#include "socket-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "umask-util.h"
#include "user-util.h"
#include "util.h"
#define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC)
typedef enum MountMode {
/* This is ordered by priority! */
INACCESSIBLE,
BIND_MOUNT,
BIND_MOUNT_RECURSIVE,
PRIVATE_TMP,
PRIVATE_VAR_TMP,
PRIVATE_DEV,
BIND_DEV,
EMPTY_DIR,
SYSFS,
PROCFS,
READONLY,
READWRITE,
} 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? */
char *path_malloc; /* Use this instead of 'path' if we had to allocate memory */
const char *source_const; /* The source path, for bind mounts */
char *source_malloc;
} 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 overriden 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/sys", READONLY, false },
{ "/proc/sysrq-trigger", READONLY, true },
{ "/proc/latency_stats", READONLY, true },
{ "/proc/mtrr", READONLY, true },
{ "/proc/apm", READONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */
{ "/proc/acpi", READONLY, true },
{ "/proc/timer_stats", READONLY, true },
{ "/proc/asound", READONLY, true },
{ "/proc/bus", READONLY, true },
{ "/proc/fs", READONLY, true },
{ "/proc/irq", READONLY, true },
{ "/sys", READONLY, false },
{ "/sys/kernel/debug", READONLY, true },
{ "/sys/kernel/tracing", READONLY, true },
{ "/sys/fs/cgroup", READWRITE, false }, /* READONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", READWRITE, true },
};
/* ProtectKernelModules= option */
static const MountEntry protect_kernel_modules_table[] = {
#if HAVE_SPLIT_USR
{ "/lib/modules", INACCESSIBLE, true },
#endif
{ "/usr/lib/modules", INACCESSIBLE, true },
};
/*
* ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of
* system should be protected by ProtectSystem=
*/
static const MountEntry protect_home_read_only_table[] = {
{ "/home", READONLY, true },
{ "/run/user", READONLY, true },
{ "/root", READONLY, true },
};
/* ProtectHome=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 },
};
/* ProtectSystem=full includes ProtectSystem=yes */
static const MountEntry protect_system_full_table[] = {
{ "/usr", READONLY, false },
{ "/boot", READONLY, true },
{ "/efi", READONLY, true },
{ "/etc", READONLY, false },
};
/*
* ProtectSystem=strict table. In this strict mode, we mount everything
* read-only, except for /proc, /dev, /sys which are the kernel API VFS,
* which are left writable, but PrivateDevices= + ProtectKernelTunables=
* protect those, and these options should be fully orthogonal.
* (And of course /home and friends are also left writable, as ProtectHome=
* shall manage those, orthogonally).
*/
static const MountEntry protect_system_strict_table[] = {
{ "/", READONLY, false },
{ "/proc", READWRITE, false }, /* ProtectKernelTunables= */
{ "/sys", READWRITE, false }, /* ProtectKernelTunables= */
{ "/dev", READWRITE, false }, /* PrivateDevices= */
{ "/home", READWRITE, true }, /* ProtectHome= */
{ "/run/user", READWRITE, true }, /* ProtectHome= */
{ "/root", READWRITE, true }, /* ProtectHome= */
};
static const char *mount_entry_path(const MountEntry *p) {
assert(p);
/* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that,
* otherwise the stack/static ->path field is returned. */
return p->path_malloc ?: p->path_const;
}
static bool mount_entry_read_only(const MountEntry *p) {
assert(p);
return p->read_only || IN_SET(p->mode, READONLY, INACCESSIBLE);
}
static const char *mount_entry_source(const MountEntry *p) {
assert(p);
return p->source_malloc ?: p->source_const;
}
static void mount_entry_done(MountEntry *p) {
assert(p);
p->path_malloc = mfree(p->path_malloc);
p->source_malloc = mfree(p->source_malloc);
}
static int append_access_mounts(MountEntry **p, char **strv, MountMode mode, bool forcibly_require_prefix) {
char **i;
assert(p);
/* Adds a list of user-supplied READWRITE/READONLY/INACCESSIBLE entries */
STRV_FOREACH(i, strv) {
bool ignore = false, needs_prefix = false;
const char *e = *i;
/* Look for any prefixes */
if (startswith(e, "-")) {
e++;
ignore = true;
}
if (startswith(e, "+")) {
e++;
needs_prefix = true;
}
if (!path_is_absolute(e))
return -EINVAL;
*((*p)++) = (MountEntry) {
.path_const = e,
.mode = mode,
.ignore = ignore,
.has_prefix = !needs_prefix && !forcibly_require_prefix,
};
}
return 0;
}
static int append_empty_dir_mounts(MountEntry **p, char **strv) {
char **i;
assert(p);
/* Adds tmpfs mounts to provide readable but empty directories. This is primarily used to implement the
* "/private/" boundary directories for DynamicUser=1. */
STRV_FOREACH(i, strv) {
*((*p)++) = (MountEntry) {
.path_const = *i,
.mode = EMPTY_DIR,
.ignore = false,
.has_prefix = false,
.read_only = true,
};
}
return 0;
}
static int append_bind_mounts(MountEntry **p, const BindMount *binds, unsigned n) {
unsigned i;
assert(p);
for (i = 0; i < n; i++) {
const BindMount *b = binds + i;
*((*p)++) = (MountEntry) {
.path_const = b->destination,
.mode = b->recursive ? BIND_MOUNT_RECURSIVE : BIND_MOUNT,
.read_only = b->read_only,
.source_const = b->source,
};
}
return 0;
}
static int append_static_mounts(MountEntry **p, const MountEntry *mounts, unsigned n, bool ignore_protect) {
unsigned 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_YES:
return append_static_mounts(p, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect);
default:
assert_not_reached("Unexpected ProtectHome= value");
}
}
static int append_protect_system(MountEntry **p, ProtectSystem protect_system, bool ignore_protect) {
assert(p);
switch (protect_system) {
case PROTECT_SYSTEM_NO:
return 0;
case PROTECT_SYSTEM_STRICT:
return append_static_mounts(p, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect);
case PROTECT_SYSTEM_YES:
return append_static_mounts(p, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect);
case PROTECT_SYSTEM_FULL:
return append_static_mounts(p, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect);
default:
assert_not_reached("Unexpected ProtectSystem= value");
}
}
static int mount_path_compare(const void *a, const void *b) {
const MountEntry *p = a, *q = b;
int d;
/* If the paths are not equal, then order prefixes first */
d = path_compare(mount_entry_path(p), mount_entry_path(q));
if (d != 0)
return d;
/* If the paths are equal, check the mode */
if (p->mode < q->mode)
return -1;
if (p->mode > q->mode)
return 1;
return 0;
}
static int prefix_where_needed(MountEntry *m, unsigned n, const char *root_directory) {
unsigned i;
/* Prefixes all paths in the bind mount table with the root directory if it is specified and the entry needs
* that. */
if (!root_directory)
return 0;
for (i = 0; i < n; i++) {
char *s;
if (m[i].has_prefix)
continue;
s = prefix_root(root_directory, mount_entry_path(m+i));
if (!s)
return -ENOMEM;
free(m[i].path_malloc);
m[i].path_malloc = s;
m[i].has_prefix = true;
}
return 0;
}
static void drop_duplicates(MountEntry *m, unsigned *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. */
if (previous && path_equal(mount_entry_path(f), mount_entry_path(previous))) {
log_debug("%s is duplicate.", mount_entry_path(f));
previous->read_only = previous->read_only || mount_entry_read_only(f); /* Propagate the read-only flag to the remaining entry */
mount_entry_done(f);
continue;
}
*t = *f;
previous = t;
t++;
}
*n = t - m;
}
static void drop_inaccessible(MountEntry *m, unsigned *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, unsigned *n) {
MountEntry *f, *t;
assert(m);
assert(n);
/* Drops all entries which have an immediate parent that has the same type, as they are redundant. Assumes the
* list is ordered by prefixes. */
for (f = m, t = m; f < m + *n; f++) {
/* Only suppress such subtrees for READONLY and READWRITE entries */
if (IN_SET(f->mode, READONLY, READWRITE)) {
MountEntry *p;
bool found = false;
/* Now let's find the first parent of the entry we are looking at. */
for (p = t-1; p >= m; p--) {
if (path_startswith(mount_entry_path(f), mount_entry_path(p))) {
found = true;
break;
}
}
/* We found it, let's see if it's the same mode, if so, we can drop this entry */
if (found && p->mode == f->mode) {
log_debug("%s is redundant by %s", mount_entry_path(f), mount_entry_path(p));
mount_entry_done(f);
continue;
}
}
*t = *f;
t++;
}
*n = t - m;
}
static void drop_outside_root(const char *root_directory, MountEntry *m, unsigned *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 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;
_cleanup_umask_ mode_t u;
int r;
assert(m);
u = umask(0000);
if (!mkdtemp(temporary_mount))
return -errno;
dev = strjoina(temporary_mount, "/dev");
(void) mkdir(dev, 0755);
if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755") < 0) {
r = -errno;
goto fail;
}
devpts = strjoina(temporary_mount, "/dev/pts");
(void) mkdir(devpts, 0755);
if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) {
r = -errno;
goto fail;
}
devptmx = strjoina(temporary_mount, "/dev/ptmx");
if (symlink("pts/ptmx", devptmx) < 0) {
r = -errno;
goto fail;
}
devshm = strjoina(temporary_mount, "/dev/shm");
(void) mkdir(devshm, 01777);
r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL);
if (r < 0) {
r = -errno;
goto fail;
}
devmqueue = strjoina(temporary_mount, "/dev/mqueue");
(void) mkdir(devmqueue, 0755);
(void) mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL);
devhugepages = strjoina(temporary_mount, "/dev/hugepages");
(void) mkdir(devhugepages, 0755);
(void) mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL);
devlog = strjoina(temporary_mount, "/dev/log");
(void) symlink("/run/systemd/journal/dev-log", devlog);
NULSTR_FOREACH(d, devnodes) {
_cleanup_free_ char *dn = NULL;
struct stat st;
r = stat(d, &st);
if (r < 0) {
if (errno == ENOENT)
continue;
r = -errno;
goto fail;
}
if (!S_ISBLK(st.st_mode) &&
!S_ISCHR(st.st_mode)) {
r = -EINVAL;
goto fail;
}
if (st.st_rdev == 0)
continue;
dn = strappend(temporary_mount, d);
if (!dn) {
r = -ENOMEM;
goto fail;
}
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) {
r = -errno;
goto fail;
}
}
dev_setup(temporary_mount, UID_INVALID, GID_INVALID);
/* Create the /dev directory if missing. It is more likely to be
* missing when the service is started with RootDirectory. This is
* consistent with mount units creating the mount points when missing.
*/
(void) mkdir_p_label(mount_entry_path(m), 0755);
/* Unmount everything in old /dev */
umount_recursive(mount_entry_path(m), 0);
if (mount(dev, mount_entry_path(m), NULL, MS_MOVE, NULL) < 0) {
r = -errno;
goto fail;
}
rmdir(dev);
rmdir(temporary_mount);
return 0;
fail:
if (devpts)
umount(devpts);
if (devshm)
umount(devshm);
if (devhugepages)
umount(devhugepages);
if (devmqueue)
umount(devmqueue);
umount(dev);
rmdir(dev);
rmdir(temporary_mount);
return r;
}
static int mount_bind_dev(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(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(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_empty_dir(MountEntry *m) {
assert(m);
/* First, get rid of everything that is below if there is anything. Then, overmount with our new empty dir */
(void) mkdir_p_label(mount_entry_path(m), 0755);
(void) umount_recursive(mount_entry_path(m), 0);
if (mount("tmpfs", mount_entry_path(m), "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, "mode=755") < 0)
return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
return 1;
}
static int mount_entry_chase(
const char *root_directory,
MountEntry *m,
const char *path,
char **location) {
char *chased;
int r;
assert(m);
/* Since mount() will always follow symlinks and we need to take the different root directory into account we
* chase the symlinks on our own first. This is called for the destination path, as well as the source path (if
* that applies). The result is stored in "location". */
r = chase_symlinks(path, root_directory,
IN_SET(m->mode, BIND_MOUNT, BIND_MOUNT_RECURSIVE, PRIVATE_TMP, PRIVATE_VAR_TMP, PRIVATE_DEV, BIND_DEV, EMPTY_DIR, SYSFS, PROCFS) ? CHASE_NONEXISTENT : 0,
&chased);
if (r == -ENOENT && m->ignore) {
log_debug_errno(r, "Path %s does not exist, ignoring.", path);
return 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to follow symlinks on %s: %m", path);
log_debug("Followed symlinks %s → %s.", path, chased);
free(*location);
*location = chased;
return 1;
}
static int apply_mount(
const char *root_directory,
MountEntry *m,
const char *tmp_dir,
const char *var_tmp_dir) {
bool rbind = true, make = false;
const char *what;
int r;
assert(m);
r = mount_entry_chase(root_directory, m, mount_entry_path(m), &m->path_malloc);
if (r <= 0)
return r;
log_debug("Applying namespace mount on %s", mount_entry_path(m));
switch (m->mode) {
case INACCESSIBLE: {
struct stat target;
/* First, get rid of everything that is below if there
* is anything... Then, overmount it with an
* inaccessible path. */
(void) umount_recursive(mount_entry_path(m), 0);
if (lstat(mount_entry_path(m), &target) < 0)
return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", mount_entry_path(m));
what = mode_to_inaccessible_node(target.st_mode);
if (!what) {
log_debug("File type not supported for inaccessible mounts. Note that symlinks are not allowed");
return -ELOOP;
}
break;
}
case READONLY:
case READWRITE:
r = path_is_mount_point(mount_entry_path(m), root_directory, 0);
if (r < 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:
/* Also chase the source mount */
r = mount_entry_chase(root_directory, m, mount_entry_source(m), &m->source_malloc);
if (r <= 0)
return r;
what = mount_entry_source(m);
make = true;
break;
case EMPTY_DIR:
return mount_empty_dir(m);
case PRIVATE_TMP:
what = tmp_dir;
make = true;
break;
case PRIVATE_VAR_TMP:
what = var_tmp_dir;
make = true;
break;
case PRIVATE_DEV:
return mount_private_dev(m);
case BIND_DEV:
return mount_bind_dev(m);
case SYSFS:
return mount_sysfs(m);
case PROCFS:
return mount_procfs(m);
default:
assert_not_reached("Unknown mode");
}
assert(what);
if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0) {
bool try_again = false;
r = -errno;
if (r == -ENOENT && make) {
struct stat st;
/* Hmm, either the source or the destination are missing. Let's see if we can create the destination, then try again */
if (stat(what, &st) >= 0) {
(void) mkdir_parents(mount_entry_path(m), 0755);
if (S_ISDIR(st.st_mode))
try_again = mkdir(mount_entry_path(m), 0755) >= 0;
else
try_again = touch(mount_entry_path(m)) >= 0;
}
}
if (try_again) {
if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0)
r = -errno;
else
r = 0;
}
if (r < 0)
return log_debug_errno(r, "Failed to mount %s to %s: %m", what, mount_entry_path(m));
}
log_debug("Successfully mounted %s to %s", what, mount_entry_path(m));
return 0;
}
static int make_read_only(MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) {
int r = 0;
assert(m);
assert(proc_self_mountinfo);
if (mount_entry_read_only(m))
r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), true, blacklist, proc_self_mountinfo);
else if (m->mode == PRIVATE_DEV) { /* Superblock can be readonly but the submounts can't */
if (mount(NULL, mount_entry_path(m), NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0)
r = -errno;
} else
return 0;
/* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked read-only
* already stays this way. This improves compatibility with container managers, where we won't attempt to undo
* read-only mounts already applied. */
if (r == -ENOENT && m->ignore)
r = 0;
return r;
}
static bool namespace_info_mount_apivfs(const char *root_directory, const NamespaceInfo *ns_info) {
assert(ns_info);
/*
* ProtectControlGroups= and ProtectKernelTunables= imply MountAPIVFS=,
* since to protect the API VFS mounts, they need to be around in the
* first place... and RootDirectory= or RootImage= need to be set.
*/
/* root_directory should point to a mount point */
return root_directory &&
(ns_info->mount_apivfs ||
ns_info->protect_control_groups ||
ns_info->protect_kernel_tunables);
}
static unsigned namespace_calculate_mounts(
const char* root_directory,
const NamespaceInfo *ns_info,
char** read_write_paths,
char** read_only_paths,
char** inaccessible_paths,
char** empty_directories,
const BindMount *bind_mounts,
unsigned n_bind_mounts,
const char* tmp_dir,
const char* var_tmp_dir,
ProtectHome protect_home,
ProtectSystem protect_system) {
unsigned protect_home_cnt;
unsigned 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) : 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 +
ns_info->private_dev +
(ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
(ns_info->protect_control_groups ? 1 : 0) +
(ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) +
protect_home_cnt + protect_system_cnt +
(namespace_info_mount_apivfs(root_directory, ns_info) ? ELEMENTSOF(apivfs_table) : 0);
}
int setup_namespace(
const char* root_directory,
const char* root_image,
const NamespaceInfo *ns_info,
char** read_write_paths,
char** read_only_paths,
char** inaccessible_paths,
char** empty_directories,
const BindMount *bind_mounts,
unsigned n_bind_mounts,
const char* tmp_dir,
const char* var_tmp_dir,
ProtectHome protect_home,
ProtectSystem protect_system,
unsigned long mount_flags,
DissectImageFlags dissect_image_flags) {
_cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL;
_cleanup_(decrypted_image_unrefp) DecryptedImage *decrypted_image = NULL;
_cleanup_(dissected_image_unrefp) DissectedImage *dissected_image = NULL;
_cleanup_free_ void *root_hash = NULL;
MountEntry *m, *mounts = NULL;
size_t root_hash_size = 0;
bool make_slave = false;
const char *root;
unsigned n_mounts;
bool require_prefix = false;
int r = 0;
assert(ns_info);
if (mount_flags == 0)
mount_flags = MS_SHARED;
if (root_image) {
dissect_image_flags |= DISSECT_IMAGE_REQUIRE_ROOT;
if (protect_system == PROTECT_SYSTEM_STRICT && strv_isempty(read_write_paths))
dissect_image_flags |= DISSECT_IMAGE_READ_ONLY;
r = loop_device_make_by_path(root_image,
dissect_image_flags & DISSECT_IMAGE_READ_ONLY ? O_RDONLY : O_RDWR,
&loop_device);
if (r < 0)
return r;
r = root_hash_load(root_image, &root_hash, &root_hash_size);
if (r < 0)
return r;
r = dissect_image(loop_device->fd, root_hash, root_hash_size, dissect_image_flags, &dissected_image);
if (r < 0)
return r;
r = dissected_image_decrypt(dissected_image, NULL, root_hash, root_hash_size, dissect_image_flags, &decrypted_image);
if (r < 0)
return r;
}
if (root_directory)
root = root_directory;
else if (root_image || n_bind_mounts > 0) {
/* If we are booting from an image, create a mount point for the image, if it's still missing. 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. We also use such a root directory whenever there are bind
* mounts configured, so that their source mounts are never obstructed by mounts we already applied
* while we are applying them. */
root = "/run/systemd/unit-root";
(void) mkdir_label(root, 0700);
require_prefix = true;
} else
root = NULL;
n_mounts = namespace_calculate_mounts(
root,
ns_info,
read_write_paths,
read_only_paths,
inaccessible_paths,
empty_directories,
bind_mounts, n_bind_mounts,
tmp_dir, var_tmp_dir,
protect_home, protect_system);
/* Set mount slave mode */
if (root || n_mounts > 0)
make_slave = true;
if (n_mounts > 0) {
m = mounts = (MountEntry *) alloca0(n_mounts * sizeof(MountEntry));
r = append_access_mounts(&m, read_write_paths, READWRITE, require_prefix);
if (r < 0)
goto finish;
r = append_access_mounts(&m, read_only_paths, READONLY, require_prefix);
if (r < 0)
goto finish;
r = append_access_mounts(&m, inaccessible_paths, INACCESSIBLE, require_prefix);
if (r < 0)
goto finish;
r = append_empty_dir_mounts(&m, empty_directories);
if (r < 0)
goto finish;
r = append_bind_mounts(&m, bind_mounts, n_bind_mounts);
if (r < 0)
goto finish;
if (tmp_dir) {
*(m++) = (MountEntry) {
.path_const = "/tmp",
.mode = PRIVATE_TMP,
};
}
if (var_tmp_dir) {
*(m++) = (MountEntry) {
.path_const = "/var/tmp",
.mode = PRIVATE_VAR_TMP,
};
}
if (ns_info->private_dev) {
*(m++) = (MountEntry) {
.path_const = "/dev",
.mode = PRIVATE_DEV,
};
}
if (ns_info->protect_kernel_tunables) {
r = append_static_mounts(&m, protect_kernel_tunables_table, ELEMENTSOF(protect_kernel_tunables_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
if (ns_info->protect_kernel_modules) {
r = append_static_mounts(&m, protect_kernel_modules_table, ELEMENTSOF(protect_kernel_modules_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
if (ns_info->protect_control_groups) {
*(m++) = (MountEntry) {
.path_const = "/sys/fs/cgroup",
.mode = READONLY,
};
}
r = append_protect_home(&m, protect_home, ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
r = append_protect_system(&m, protect_system, false);
if (r < 0)
goto finish;
if (namespace_info_mount_apivfs(root, ns_info)) {
r = append_static_mounts(&m, apivfs_table, ELEMENTSOF(apivfs_table), ns_info->ignore_protect_paths);
if (r < 0)
goto finish;
}
assert(mounts + n_mounts == m);
/* Prepend the root directory where that's necessary */
r = prefix_where_needed(mounts, n_mounts, root);
if (r < 0)
goto finish;
qsort(mounts, n_mounts, sizeof(MountEntry), mount_path_compare);
drop_duplicates(mounts, &n_mounts);
drop_outside_root(root, mounts, &n_mounts);
drop_inaccessible(mounts, &n_mounts);
drop_nop(mounts, &n_mounts);
}
if (unshare(CLONE_NEWNS) < 0) {
r = -errno;
goto finish;
}
if (make_slave) {
/* Remount / as SLAVE so that nothing now mounted in the namespace
shows up in the parent */
if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
if (root_image) {
/* A root image is specified, mount it to the right place */
r = dissected_image_mount(dissected_image, root, UID_INVALID, dissect_image_flags);
if (r < 0)
goto finish;
if (decrypted_image) {
r = decrypted_image_relinquish(decrypted_image);
if (r < 0)
goto finish;
}
loop_device_relinquish(loop_device);
} else if (root_directory) {
/* A root directory is specified. Turn its directory into bind mount, if it isn't one yet. */
r = path_is_mount_point(root, NULL, AT_SYMLINK_FOLLOW);
if (r < 0)
goto finish;
if (r == 0) {
if (mount(root, root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
} else if (root) {
/* Let's mount the main root directory to the root directory to use */
if (mount("/", root, NULL, MS_BIND|MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
}
/* Try to set up the new root directory before mounting anything else there. */
if (root_image || root_directory)
(void) base_filesystem_create(root, UID_INVALID, GID_INVALID);
if (n_mounts > 0) {
_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
char **blacklist;
unsigned j;
/* Open /proc/self/mountinfo now as it may become unavailable if we mount anything on top of /proc.
* For example, this is the case with the option: 'InaccessiblePaths=/proc' */
proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
if (!proc_self_mountinfo) {
r = -errno;
goto finish;
}
/* First round, add in all special mounts we need */
for (m = mounts; m < mounts + n_mounts; ++m) {
r = apply_mount(root, m, tmp_dir, var_tmp_dir);
if (r < 0)
goto finish;
}
/* Create a blacklist we can pass to bind_mount_recursive() */
blacklist = newa(char*, n_mounts+1);
for (j = 0; j < n_mounts; j++)
blacklist[j] = (char*) mount_entry_path(mounts+j);
blacklist[j] = NULL;
/* Second round, flip the ro bits if necessary. */
for (m = mounts; m < mounts + n_mounts; ++m) {
r = make_read_only(m, blacklist, proc_self_mountinfo);
if (r < 0)
goto finish;
}
}
if (root) {
/* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */
r = mount_move_root(root);
if (r < 0)
goto finish;
}
/* Remount / as the desired mode. Not that this will not
* reestablish propagation from our side to the host, since
* what's disconnected is disconnected. */
if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {
r = -errno;
goto finish;
}
r = 0;
finish:
for (m = mounts; m < mounts + n_mounts; m++)
mount_entry_done(m);
return r;
}
void bind_mount_free_many(BindMount *b, unsigned n) {
unsigned 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, unsigned *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 = realloc_multiply(*b, sizeof(BindMount), *n + 1);
if (!c)
return -ENOMEM;
*b = c;
c[(*n) ++] = (BindMount) {
.source = s,
.destination = d,
.read_only = item->read_only,
.recursive = item->recursive,
.ignore_enoent = item->ignore_enoent,
};
s = d = NULL;
return 0;
}
static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
_cleanup_free_ char *x = NULL;
char bid[SD_ID128_STRING_MAX];
sd_id128_t boot_id;
int r;
assert(id);
assert(prefix);
assert(path);
/* We include the boot id in the directory so that after a
* reboot we can easily identify obsolete directories. */
r = sd_id128_get_boot(&boot_id);
if (r < 0)
return r;
x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX");
if (!x)
return -ENOMEM;
RUN_WITH_UMASK(0077)
if (!mkdtemp(x))
return -errno;
RUN_WITH_UMASK(0000) {
char *y;
y = strjoina(x, "/tmp");
if (mkdir(y, 0777 | S_ISVTX) < 0)
return -errno;
}
*path = x;
x = NULL;
return 0;
}
int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
char *a, *b;
int r;
assert(id);
assert(tmp_dir);
assert(var_tmp_dir);
r = setup_one_tmp_dir(id, "/tmp", &a);
if (r < 0)
return r;
r = setup_one_tmp_dir(id, "/var/tmp", &b);
if (r < 0) {
char *t;
t = strjoina(a, "/tmp");
rmdir(t);
rmdir(a);
free(a);
return r;
}
*tmp_dir = a;
*var_tmp_dir = b;
return 0;
}
int setup_netns(int netns_storage_socket[2]) {
_cleanup_close_ int netns = -1;
int r, q;
assert(netns_storage_socket);
assert(netns_storage_socket[0] >= 0);
assert(netns_storage_socket[1] >= 0);
/* We use the passed socketpair as a storage buffer for our
* namespace reference fd. Whatever process runs this first
* shall create a new namespace, all others should just join
* it. To serialize that we use a file lock on the socket
* pair.
*
* It's a bit crazy, but hey, works great! */
if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0)
return -errno;
netns = receive_one_fd(netns_storage_socket[0], MSG_DONTWAIT);
if (netns == -EAGAIN) {
/* Nothing stored yet, so let's create a new namespace */
if (unshare(CLONE_NEWNET) < 0) {
r = -errno;
goto fail;
}
loopback_setup();
netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (netns < 0) {
r = -errno;
goto fail;
}
r = 1;
} else if (netns < 0) {
r = netns;
goto fail;
} else {
/* Yay, found something, so let's join the namespace */
if (setns(netns, CLONE_NEWNET) < 0) {
r = -errno;
goto fail;
}
r = 0;
}
q = send_one_fd(netns_storage_socket[1], netns, MSG_DONTWAIT);
if (q < 0) {
r = q;
goto fail;
}
fail:
(void) lockf(netns_storage_socket[0], F_ULOCK, 0);
return r;
}
bool ns_type_supported(NamespaceType type) {
const char *t, *ns_proc;
t = namespace_type_to_string(type);
if (!t) /* Don't know how to translate this? Then it's not supported */
return false;
ns_proc = strjoina("/proc/self/ns/", t);
return access(ns_proc, F_OK) == 0;
}
static const char *const protect_home_table[_PROTECT_HOME_MAX] = {
[PROTECT_HOME_NO] = "no",
[PROTECT_HOME_YES] = "yes",
[PROTECT_HOME_READ_ONLY] = "read-only",
};
DEFINE_STRING_TABLE_LOOKUP(protect_home, ProtectHome);
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(protect_system, ProtectSystem);
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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