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namespace.c
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namespace.c
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <linux/loop.h>
#include <sched.h>
#include <stdio.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <unistd.h>
#if WANT_LINUX_FS_H
#include <linux/fs.h>
#endif
#include "alloc-util.h"
#include "base-filesystem.h"
#include "chase.h"
#include "dev-setup.h"
#include "devnum-util.h"
#include "env-util.h"
#include "escape.h"
#include "extension-util.h"
#include "fd-util.h"
#include "format-util.h"
#include "glyph-util.h"
#include "label-util.h"
#include "list.h"
#include "lock-util.h"
#include "loop-util.h"
#include "loopback-setup.h"
#include "missing_syscall.h"
#include "mkdir-label.h"
#include "mount-util.h"
#include "mountpoint-util.h"
#include "namespace-util.h"
#include "namespace.h"
#include "nsflags.h"
#include "nulstr-util.h"
#include "os-util.h"
#include "path-util.h"
#include "selinux-util.h"
#include "socket-util.h"
#include "sort-util.h"
#include "stat-util.h"
#include "string-table.h"
#include "string-util.h"
#include "strv.h"
#include "tmpfile-util.h"
#include "umask-util.h"
#include "user-util.h"
#define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC)
typedef enum MountMode {
/* This is ordered by priority! */
MOUNT_INACCESSIBLE,
MOUNT_OVERLAY,
MOUNT_IMAGE,
MOUNT_BIND,
MOUNT_BIND_RECURSIVE,
MOUNT_PRIVATE_TMP,
MOUNT_PRIVATE_TMP_READ_ONLY,
MOUNT_PRIVATE_DEV,
MOUNT_BIND_DEV,
MOUNT_EMPTY_DIR,
MOUNT_PRIVATE_SYSFS,
MOUNT_BIND_SYSFS,
MOUNT_PROCFS,
MOUNT_READ_ONLY,
MOUNT_READ_WRITE,
MOUNT_NOEXEC,
MOUNT_EXEC,
MOUNT_TMPFS,
MOUNT_RUN,
MOUNT_EXTENSION_DIRECTORY, /* Bind-mounted outside the root directory, and used by subsequent mounts */
MOUNT_EXTENSION_IMAGE, /* Mounted outside the root directory, and used by subsequent mounts */
MOUNT_MQUEUEFS,
MOUNT_READ_WRITE_IMPLICIT, /* Should have the lowest priority. */
_MOUNT_MODE_MAX,
_MOUNT_MODE_INVALID = -EINVAL,
} MountMode;
typedef enum MountEntryState {
MOUNT_PENDING,
MOUNT_APPLIED,
MOUNT_SKIPPED,
_MOUNT_ENTRY_STATE_MAX,
_MOUNT_ENTRY_STATE_INVALID = -EINVAL,
} MountEntryState;
typedef struct MountEntry {
const char *path_const; /* Memory allocated on stack or static */
MountMode mode;
bool ignore:1; /* Ignore if path does not exist? */
bool has_prefix:1; /* Already is prefixed by the root dir? */
bool read_only:1; /* Shall this mount point be read-only? */
bool nosuid:1; /* Shall set MS_NOSUID on the mount itself */
bool noexec:1; /* Shall set MS_NOEXEC on the mount itself */
bool exec:1; /* Shall clear MS_NOEXEC on the mount itself */
MountEntryState state; /* Whether it was already processed or skipped */
char *path_malloc; /* Use this instead of 'path_const' if we had to allocate memory */
const char *unprefixed_path_const; /* If the path was amended with a prefix, these will save the original */
char *unprefixed_path_malloc;
const char *source_const; /* The source path, for bind mounts or images */
char *source_malloc;
const char *options_const;/* Mount options for tmpfs */
char *options_malloc;
unsigned long flags; /* Mount flags used by EMPTY_DIR and TMPFS. Do not include MS_RDONLY here, but please use read_only. */
unsigned n_followed;
LIST_HEAD(MountOptions, image_options_const);
char **overlay_layers;
} MountEntry;
typedef struct MountList {
MountEntry *mounts;
size_t n_mounts;
} MountList;
/* If MountAPIVFS= is used, let's mount /sys, /proc, /dev and /run into the it, but only as a fallback if the user hasn't mounted
* something there already. These mounts are hence overridden by any other explicitly configured mounts. */
static const MountEntry apivfs_table[] = {
{ "/proc", MOUNT_PROCFS, false },
{ "/dev", MOUNT_BIND_DEV, false },
{ "/sys", MOUNT_BIND_SYSFS, false },
{ "/run", MOUNT_RUN, false, .options_const = "mode=0755" TMPFS_LIMITS_RUN, .flags = MS_NOSUID|MS_NODEV|MS_STRICTATIME },
};
/* ProtectKernelTunables= option and the related filesystem APIs */
static const MountEntry protect_kernel_tunables_proc_table[] = {
{ "/proc/acpi", MOUNT_READ_ONLY, true },
{ "/proc/apm", MOUNT_READ_ONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */
{ "/proc/asound", MOUNT_READ_ONLY, true },
{ "/proc/bus", MOUNT_READ_ONLY, true },
{ "/proc/fs", MOUNT_READ_ONLY, true },
{ "/proc/irq", MOUNT_READ_ONLY, true },
{ "/proc/kallsyms", MOUNT_INACCESSIBLE, true },
{ "/proc/kcore", MOUNT_INACCESSIBLE, true },
{ "/proc/latency_stats", MOUNT_READ_ONLY, true },
{ "/proc/mtrr", MOUNT_READ_ONLY, true },
{ "/proc/scsi", MOUNT_READ_ONLY, true },
{ "/proc/sys", MOUNT_READ_ONLY, true },
{ "/proc/sysrq-trigger", MOUNT_READ_ONLY, true },
{ "/proc/timer_stats", MOUNT_READ_ONLY, true },
};
static const MountEntry protect_kernel_tunables_sys_table[] = {
{ "/sys", MOUNT_READ_ONLY, false },
{ "/sys/fs/bpf", MOUNT_READ_ONLY, true },
{ "/sys/fs/cgroup", MOUNT_READ_WRITE_IMPLICIT, false }, /* READ_ONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", MOUNT_READ_WRITE_IMPLICIT, true },
{ "/sys/kernel/debug", MOUNT_READ_ONLY, true },
{ "/sys/kernel/tracing", MOUNT_READ_ONLY, true },
};
/* ProtectKernelModules= option */
static const MountEntry protect_kernel_modules_table[] = {
{ "/usr/lib/modules", MOUNT_INACCESSIBLE, true },
};
/* ProtectKernelLogs= option */
static const MountEntry protect_kernel_logs_proc_table[] = {
{ "/proc/kmsg", MOUNT_INACCESSIBLE, true },
};
static const MountEntry protect_kernel_logs_dev_table[] = {
{ "/dev/kmsg", MOUNT_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", MOUNT_READ_ONLY, true },
{ "/run/user", MOUNT_READ_ONLY, true },
{ "/root", MOUNT_READ_ONLY, true },
};
/* ProtectHome=tmpfs table */
static const MountEntry protect_home_tmpfs_table[] = {
{ "/home", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME },
{ "/run/user", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME },
{ "/root", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0700" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME },
};
/* ProtectHome=yes table */
static const MountEntry protect_home_yes_table[] = {
{ "/home", MOUNT_INACCESSIBLE, true },
{ "/run/user", MOUNT_INACCESSIBLE, true },
{ "/root", MOUNT_INACCESSIBLE, true },
};
/* ProtectSystem=yes table */
static const MountEntry protect_system_yes_table[] = {
{ "/usr", MOUNT_READ_ONLY, false },
{ "/boot", MOUNT_READ_ONLY, true },
{ "/efi", MOUNT_READ_ONLY, true },
};
/* ProtectSystem=full includes ProtectSystem=yes */
static const MountEntry protect_system_full_table[] = {
{ "/usr", MOUNT_READ_ONLY, false },
{ "/boot", MOUNT_READ_ONLY, true },
{ "/efi", MOUNT_READ_ONLY, true },
{ "/etc", MOUNT_READ_ONLY, 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[] = {
{ "/", MOUNT_READ_ONLY, false },
{ "/proc", MOUNT_READ_WRITE_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/sys", MOUNT_READ_WRITE_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/dev", MOUNT_READ_WRITE_IMPLICIT, false }, /* PrivateDevices= */
{ "/home", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/run/user", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/root", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */
};
/* ProtectHostname=yes able */
static const MountEntry protect_hostname_table[] = {
{ "/proc/sys/kernel/hostname", MOUNT_READ_ONLY, false },
{ "/proc/sys/kernel/domainname", MOUNT_READ_ONLY, false },
};
static const char * const mount_mode_table[_MOUNT_MODE_MAX] = {
[MOUNT_INACCESSIBLE] = "inaccessible",
[MOUNT_OVERLAY] = "overlay",
[MOUNT_IMAGE] = "image",
[MOUNT_BIND] = "bind",
[MOUNT_BIND_RECURSIVE] = "bind-recursive",
[MOUNT_PRIVATE_TMP] = "private-tmp",
[MOUNT_PRIVATE_TMP_READ_ONLY] = "private-tmp-read-only",
[MOUNT_PRIVATE_DEV] = "private-dev",
[MOUNT_BIND_DEV] = "bind-dev",
[MOUNT_EMPTY_DIR] = "empty-dir",
[MOUNT_PRIVATE_SYSFS] = "private-sysfs",
[MOUNT_BIND_SYSFS] = "bind-sysfs",
[MOUNT_PROCFS] = "procfs",
[MOUNT_READ_ONLY] = "read-only",
[MOUNT_READ_WRITE] = "read-write",
[MOUNT_NOEXEC] = "noexec",
[MOUNT_EXEC] = "exec",
[MOUNT_TMPFS] = "tmpfs",
[MOUNT_RUN] = "run",
[MOUNT_EXTENSION_DIRECTORY] = "extension-directory",
[MOUNT_EXTENSION_IMAGE] = "extension-image",
[MOUNT_MQUEUEFS] = "mqueuefs",
[MOUNT_READ_WRITE_IMPLICIT] = "read-write-implicit",
};
/* Helper struct for naming simplicity and reusability */
static const struct {
const char *level_env;
const char *level_env_print;
} image_class_info[_IMAGE_CLASS_MAX] = {
[IMAGE_SYSEXT] = {
.level_env = "SYSEXT_LEVEL",
.level_env_print = " SYSEXT_LEVEL=",
},
[IMAGE_CONFEXT] = {
.level_env = "CONFEXT_LEVEL",
.level_env_print = " CONFEXT_LEVEL=",
}
};
DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(mount_mode, MountMode);
static const char *mount_entry_path(const MountEntry *p) {
assert(p);
/* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that,
* otherwise the stack/static ->path field is returned. */
return p->path_malloc ?: p->path_const;
}
static const char *mount_entry_unprefixed_path(const MountEntry *p) {
assert(p);
/* Returns the unprefixed path (ie: before prefix_where_needed() ran), if any */
return p->unprefixed_path_malloc ?: p->unprefixed_path_const ?: mount_entry_path(p);
}
static void mount_entry_consume_prefix(MountEntry *p, char *new_path) {
assert(p);
assert(p->path_malloc || p->path_const);
assert(new_path);
/* Saves current path in unprefixed_ variable, and takes over new_path */
free_and_replace(p->unprefixed_path_malloc, p->path_malloc);
/* If we didn't have a path on the heap, then it's a static one */
if (!p->unprefixed_path_malloc)
p->unprefixed_path_const = p->path_const;
p->path_malloc = new_path;
p->has_prefix = true;
}
static bool mount_entry_read_only(const MountEntry *p) {
assert(p);
return p->read_only || IN_SET(p->mode, MOUNT_READ_ONLY, MOUNT_INACCESSIBLE, MOUNT_PRIVATE_TMP_READ_ONLY);
}
static bool mount_entry_noexec(const MountEntry *p) {
assert(p);
return p->noexec || IN_SET(p->mode, MOUNT_NOEXEC, MOUNT_INACCESSIBLE, MOUNT_PRIVATE_SYSFS, MOUNT_BIND_SYSFS, MOUNT_PROCFS);
}
static bool mount_entry_exec(const MountEntry *p) {
assert(p);
return p->exec || p->mode == MOUNT_EXEC;
}
static const char *mount_entry_source(const MountEntry *p) {
assert(p);
return p->source_malloc ?: p->source_const;
}
static const char *mount_entry_options(const MountEntry *p) {
assert(p);
return p->options_malloc ?: p->options_const;
}
static void mount_entry_done(MountEntry *p) {
assert(p);
p->path_malloc = mfree(p->path_malloc);
p->unprefixed_path_malloc = mfree(p->unprefixed_path_malloc);
p->source_malloc = mfree(p->source_malloc);
p->options_malloc = mfree(p->options_malloc);
p->overlay_layers = strv_free(p->overlay_layers);
}
static void mount_list_done(MountList *ml) {
assert(ml);
FOREACH_ARRAY(m, ml->mounts, ml->n_mounts)
mount_entry_done(m);
ml->mounts = mfree(ml->mounts);
ml->n_mounts = 0;
}
static MountEntry *mount_list_extend(MountList *ml) {
assert(ml);
if (!GREEDY_REALLOC0(ml->mounts, ml->n_mounts+1))
return NULL;
return ml->mounts + ml->n_mounts++;
}
static int append_access_mounts(MountList *ml, char **strv, MountMode mode, bool forcibly_require_prefix) {
assert(ml);
/* Adds a list of user-supplied READ_WRITE/READ_WRITE_IMPLICIT/READ_ONLY/INACCESSIBLE entries */
STRV_FOREACH(i, strv) {
bool ignore = false, needs_prefix = false;
const char *e = *i;
/* Look for any prefixes */
if (startswith(e, "-")) {
e++;
ignore = true;
}
if (startswith(e, "+")) {
e++;
needs_prefix = true;
}
if (!path_is_absolute(e))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Path is not absolute: %s", e);
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = e,
.mode = mode,
.ignore = ignore,
.has_prefix = !needs_prefix && !forcibly_require_prefix,
};
}
return 0;
}
static int append_empty_dir_mounts(MountList *ml, char **strv) {
assert(ml);
/* 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) {
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = *i,
.mode = MOUNT_EMPTY_DIR,
.ignore = false,
.read_only = true,
.options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST,
.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
};
}
return 0;
}
static int append_bind_mounts(MountList *ml, const BindMount *binds, size_t n) {
assert(ml);
assert(binds || n == 0);
FOREACH_ARRAY(b, binds, n) {
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = b->destination,
.mode = b->recursive ? MOUNT_BIND_RECURSIVE : MOUNT_BIND,
.read_only = b->read_only,
.nosuid = b->nosuid,
.source_const = b->source,
.ignore = b->ignore_enoent,
};
}
return 0;
}
static int append_mount_images(MountList *ml, const MountImage *mount_images, size_t n) {
assert(ml);
assert(mount_images || n == 0);
FOREACH_ARRAY(m, mount_images, n) {
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = m->destination,
.mode = MOUNT_IMAGE,
.source_const = m->source,
.image_options_const = m->mount_options,
.ignore = m->ignore_enoent,
};
}
return 0;
}
static int append_extensions(
MountList *ml,
const char *root,
const char *extension_dir,
char **hierarchies,
const MountImage *mount_images,
size_t n,
char **extension_directories) {
char ***overlays = NULL;
size_t n_overlays = 0;
int r;
assert(ml);
if (n == 0 && strv_isempty(extension_directories))
return 0;
assert(extension_dir);
n_overlays = strv_length(hierarchies);
if (n_overlays == 0)
return 0;
/* Prepare a list of overlays, that will have as each element a strv containing all the layers that
* will later be concatenated as a lowerdir= parameter for the mount operation.
* The overlays vector will have the same number of elements and will correspond to the
* hierarchies vector, so they can be iterated upon together. */
overlays = new0(char**, n_overlays);
if (!overlays)
return -ENOMEM;
CLEANUP_ARRAY(overlays, n_overlays, strv_free_many);
/* First, prepare a mount for each image, but these won't be visible to the unit, instead
* they will be mounted in our propagate directory, and used as a source for the overlay. */
for (size_t i = 0; i < n; i++) {
_cleanup_free_ char *mount_point = NULL;
const MountImage *m = mount_images + i;
if (asprintf(&mount_point, "%s/%zu", extension_dir, i) < 0)
return -ENOMEM;
for (size_t j = 0; hierarchies && hierarchies[j]; ++j) {
char *prefixed_hierarchy = path_join(mount_point, hierarchies[j]);
if (!prefixed_hierarchy)
return -ENOMEM;
r = strv_consume(&overlays[j], TAKE_PTR(prefixed_hierarchy));
if (r < 0)
return r;
}
MountEntry *me = mount_list_extend(ml);
if (!me)
return -ENOMEM;
*me = (MountEntry) {
.path_malloc = TAKE_PTR(mount_point),
.image_options_const = m->mount_options,
.ignore = m->ignore_enoent,
.source_const = m->source,
.mode = MOUNT_EXTENSION_IMAGE,
.has_prefix = true,
};
}
/* Secondly, extend the lowerdir= parameters with each ExtensionDirectory.
* Bind mount them in the same location as the ExtensionImages, so that we
* can check that they are valid trees (extension-release.d). */
STRV_FOREACH(extension_directory, extension_directories) {
_cleanup_free_ char *mount_point = NULL, *source = NULL;
const char *e = *extension_directory;
bool ignore_enoent = false;
/* Pick up the counter where the ExtensionImages left it. */
if (asprintf(&mount_point, "%s/%zu", extension_dir, n++) < 0)
return -ENOMEM;
/* Look for any prefixes */
if (startswith(e, "-")) {
e++;
ignore_enoent = true;
}
/* Ignore this for now */
if (startswith(e, "+"))
e++;
source = strdup(e);
if (!source)
return -ENOMEM;
for (size_t j = 0; hierarchies && hierarchies[j]; ++j) {
char *prefixed_hierarchy = path_join(mount_point, hierarchies[j]);
if (!prefixed_hierarchy)
return -ENOMEM;
r = strv_consume(&overlays[j], TAKE_PTR(prefixed_hierarchy));
if (r < 0)
return r;
}
MountEntry *me = mount_list_extend(ml);
if (!me)
return -ENOMEM;
*me = (MountEntry) {
.path_malloc = TAKE_PTR(mount_point),
.source_malloc = TAKE_PTR(source),
.mode = MOUNT_EXTENSION_DIRECTORY,
.ignore = ignore_enoent,
.has_prefix = true,
.read_only = true,
};
}
/* Then, for each hierarchy, prepare an overlay with the list of lowerdir= strings
* set up earlier. */
for (size_t i = 0; hierarchies && hierarchies[i]; ++i) {
_cleanup_free_ char *prefixed_hierarchy = NULL;
prefixed_hierarchy = path_join(root, hierarchies[i]);
if (!prefixed_hierarchy)
return -ENOMEM;
MountEntry *me = mount_list_extend(ml);
if (!me)
return -ENOMEM;
*me = (MountEntry) {
.path_malloc = TAKE_PTR(prefixed_hierarchy),
.overlay_layers = TAKE_PTR(overlays[i]),
.mode = MOUNT_OVERLAY,
.has_prefix = true,
.ignore = true, /* If the source image doesn't set the ignore bit it will fail earlier. */
};
}
return 0;
}
static int append_tmpfs_mounts(MountList *ml, const TemporaryFileSystem *tmpfs, size_t n) {
assert(ml);
assert(tmpfs || n == 0);
FOREACH_ARRAY(t, tmpfs, n) {
_cleanup_free_ char *o = NULL, *str = NULL;
unsigned long flags;
bool ro = false;
int r;
if (!path_is_absolute(t->path))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Path is not absolute: %s", t->path);
str = strjoin("mode=0755" NESTED_TMPFS_LIMITS ",", t->options);
if (!str)
return -ENOMEM;
r = mount_option_mangle(str, MS_NODEV|MS_STRICTATIME, &flags, &o);
if (r < 0)
return log_debug_errno(r, "Failed to parse mount option '%s': %m", str);
ro = flags & MS_RDONLY;
if (ro)
flags ^= MS_RDONLY;
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = t->path,
.mode = MOUNT_TMPFS,
.read_only = ro,
.options_malloc = TAKE_PTR(o),
.flags = flags,
};
}
return 0;
}
static int append_static_mounts(MountList *ml, const MountEntry *mounts, size_t n, bool ignore_protect) {
assert(ml);
assert(mounts || n == 0);
/* Adds a list of static pre-defined entries */
FOREACH_ARRAY(m, mounts, n) {
MountEntry *me = mount_list_extend(ml);
if (!me)
return log_oom_debug();
*me = (MountEntry) {
.path_const = mount_entry_path(m),
.mode = m->mode,
.ignore = m->ignore || ignore_protect,
};
}
return 0;
}
static int append_protect_home(MountList *ml, ProtectHome protect_home, bool ignore_protect) {
assert(ml);
switch (protect_home) {
case PROTECT_HOME_NO:
return 0;
case PROTECT_HOME_READ_ONLY:
return append_static_mounts(ml, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect);
case PROTECT_HOME_TMPFS:
return append_static_mounts(ml, protect_home_tmpfs_table, ELEMENTSOF(protect_home_tmpfs_table), ignore_protect);
case PROTECT_HOME_YES:
return append_static_mounts(ml, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect);
default:
assert_not_reached();
}
}
static int append_protect_system(MountList *ml, ProtectSystem protect_system, bool ignore_protect) {
assert(ml);
switch (protect_system) {
case PROTECT_SYSTEM_NO:
return 0;
case PROTECT_SYSTEM_STRICT:
return append_static_mounts(ml, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect);
case PROTECT_SYSTEM_YES:
return append_static_mounts(ml, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect);
case PROTECT_SYSTEM_FULL:
return append_static_mounts(ml, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect);
default:
assert_not_reached();
}
}
static int mount_path_compare(const MountEntry *a, const MountEntry *b) {
int d;
/* ExtensionImages/Directories will be used by other mounts as a base, so sort them first
* regardless of the prefix - they are set up in the propagate directory anyway */
d = -CMP(a->mode == MOUNT_EXTENSION_IMAGE, b->mode == MOUNT_EXTENSION_IMAGE);
if (d != 0)
return d;
d = -CMP(a->mode == MOUNT_EXTENSION_DIRECTORY, b->mode == MOUNT_EXTENSION_DIRECTORY);
if (d != 0)
return d;
/* If the paths are not equal, then order prefixes first */
d = path_compare(mount_entry_path(a), mount_entry_path(b));
if (d != 0)
return d;
/* If the paths are equal, check the mode */
return CMP((int) a->mode, (int) b->mode);
}
static int prefix_where_needed(MountList *ml, const char *root_directory) {
/* Prefixes all paths in the bind mount table with the root directory if the entry needs that. */
assert(ml);
FOREACH_ARRAY(me, ml->mounts, ml->n_mounts) {
char *s;
if (me->has_prefix)
continue;
s = path_join(root_directory, mount_entry_path(me));
if (!s)
return -ENOMEM;
mount_entry_consume_prefix(me, s);
}
return 0;
}
static void drop_duplicates(MountList *ml) {
MountEntry *f, *t, *previous;
assert(ml);
/* Drops duplicate entries. Expects that the array is properly ordered already. */
for (f = ml->mounts, t = ml->mounts, previous = NULL; f < ml->mounts + ml->n_mounts; f++) {
/* The first one wins (which is the one with the more restrictive mode), see mount_path_compare()
* above. Note that we only drop duplicates that haven't been mounted yet. */
if (previous &&
path_equal(mount_entry_path(f), mount_entry_path(previous)) &&
f->state == MOUNT_PENDING && previous->state == MOUNT_PENDING) {
log_debug("%s (%s) is duplicate.", mount_entry_path(f), mount_mode_to_string(f->mode));
/* Propagate the flags to the remaining entry */
previous->read_only = previous->read_only || mount_entry_read_only(f);
previous->noexec = previous->noexec || mount_entry_noexec(f);
previous->exec = previous->exec || mount_entry_exec(f);
mount_entry_done(f);
continue;
}
*t = *f;
previous = t;
t++;
}
ml->n_mounts = t - ml->mounts;
}
static void drop_inaccessible(MountList *ml) {
MountEntry *f, *t;
const char *clear = NULL;
assert(ml);
/* Drops all entries obstructed by another entry further up the tree. Expects that the array is properly
* ordered already. */
for (f = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; 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 == MOUNT_INACCESSIBLE ? mount_entry_path(f) : NULL;
*t = *f;
t++;
}
ml->n_mounts = t - ml->mounts;
}
static void drop_nop(MountList *ml) {
MountEntry *f, *t;
assert(ml);
/* 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 = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; f++) {
/* Only suppress such subtrees for READ_ONLY, READ_WRITE and READ_WRITE_IMPLICIT entries */
if (IN_SET(f->mode, MOUNT_READ_ONLY, MOUNT_READ_WRITE, MOUNT_READ_WRITE_IMPLICIT)) {
MountEntry *found = NULL;
/* Now let's find the first parent of the entry we are looking at. */
for (MountEntry *p = PTR_SUB1(t, ml->mounts); p; p = PTR_SUB1(p, ml->mounts))
if (path_startswith(mount_entry_path(f), mount_entry_path(p))) {
found = p;
break;
}
/* We found it, let's see if it's the same mode, if so, we can drop this entry */
if (found && found->mode == f->mode) {
log_debug("%s (%s) is made redundant by %s (%s)",
mount_entry_path(f), mount_mode_to_string(f->mode),
mount_entry_path(found), mount_mode_to_string(found->mode));
mount_entry_done(f);
continue;
}
}
*t = *f;
t++;
}
ml->n_mounts = t - ml->mounts;
}
static void drop_outside_root(MountList *ml, const char *root_directory) {
MountEntry *f, *t;
assert(ml);
/* Nothing to do */
if (!root_directory)
return;
/* Drops all mounts that are outside of the root directory. */
for (f = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; f++) {
/* ExtensionImages/Directories bases are opened in /run/systemd/unit-extensions on the host */
if (!IN_SET(f->mode, MOUNT_EXTENSION_IMAGE, MOUNT_EXTENSION_DIRECTORY) && !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++;
}
ml->n_mounts = t - ml->mounts;
}
static int clone_device_node(
const char *d,
const char *temporary_mount,
bool *make_devnode) {
_cleanup_free_ char *sl = NULL;
const char *dn, *bn, *t;
struct stat st;
int r;
if (stat(d, &st) < 0) {
if (errno == ENOENT) {
log_debug_errno(errno, "Device node '%s' to clone does not exist, ignoring.", d);
return -ENXIO;
}
return log_debug_errno(errno, "Failed to stat() device node '%s' to clone, ignoring: %m", d);
}
if (!S_ISBLK(st.st_mode) &&
!S_ISCHR(st.st_mode))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"Device node '%s' to clone is not a device node, ignoring.",
d);
dn = strjoina(temporary_mount, d);
/* First, try to create device node properly */
if (*make_devnode) {
mac_selinux_create_file_prepare(d, st.st_mode);
r = mknod(dn, st.st_mode, st.st_rdev);
mac_selinux_create_file_clear();
if (r >= 0)
goto add_symlink;
if (errno != EPERM)
return log_debug_errno(errno, "mknod failed for %s: %m", d);
/* This didn't work, let's not try this again for the next iterations. */
*make_devnode = false;
}
/* We're about to fall back to bind-mounting the device node. So create a dummy bind-mount target.
* Do not prepare device-node SELinux label (see issue 13762) */
r = mknod(dn, S_IFREG, 0);
if (r < 0 && errno != EEXIST)
return log_debug_errno(errno, "mknod() fallback failed for '%s': %m", d);
/* Fallback to bind-mounting: The assumption here is that all used device nodes carry standard
* properties. Specifically, the devices nodes we bind-mount should either be owned by root:root or
* root:tty (e.g. /dev/tty, /dev/ptmx) and should not carry ACLs. */
r = mount_nofollow_verbose(LOG_DEBUG, d, dn, NULL, MS_BIND, NULL);
if (r < 0)
return r;
add_symlink:
bn = path_startswith(d, "/dev/");
if (!bn)
return 0;
/* Create symlinks like /dev/char/1:9 → ../urandom */
if (asprintf(&sl, "%s/dev/%s/" DEVNUM_FORMAT_STR,
temporary_mount,
S_ISCHR(st.st_mode) ? "char" : "block",
DEVNUM_FORMAT_VAL(st.st_rdev)) < 0)
return log_oom_debug();
(void) mkdir_parents(sl, 0755);
t = strjoina("../", bn);
if (symlink(t, sl) < 0)
log_debug_errno(errno, "Failed to symlink '%s' to '%s', ignoring: %m", t, sl);
return 0;
}
static char *settle_runtime_dir(RuntimeScope scope) {
char *runtime_dir;
if (scope != RUNTIME_SCOPE_USER)
return strdup("/run/");
if (asprintf(&runtime_dir, "/run/user/" UID_FMT, geteuid()) < 0)
return NULL;
return runtime_dir;
}
static int create_temporary_mount_point(RuntimeScope scope, char **ret) {
_cleanup_free_ char *runtime_dir = NULL, *temporary_mount = NULL;
assert(ret);
runtime_dir = settle_runtime_dir(scope);
if (!runtime_dir)
return log_oom_debug();
temporary_mount = path_join(runtime_dir, "systemd/namespace-XXXXXX");
if (!temporary_mount)
return log_oom_debug();
if (!mkdtemp(temporary_mount))
return log_debug_errno(errno, "Failed to create temporary directory '%s': %m", temporary_mount);
*ret = TAKE_PTR(temporary_mount);
return 0;
}
static int mount_private_dev(MountEntry *m, RuntimeScope scope) {
static const char devnodes[] =
"/dev/null\0"
"/dev/zero\0"
"/dev/full\0"
"/dev/random\0"
"/dev/urandom\0"
"/dev/tty\0";
_cleanup_free_ char *temporary_mount = NULL;
const char *dev = NULL, *devpts = NULL, *devshm = NULL, *devhugepages = NULL, *devmqueue = NULL, *devlog = NULL, *devptmx = NULL;
bool can_mknod = true;
int r;
assert(m);