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authorLennart Poettering <lennart@poettering.net>2015-09-07 15:59:52 +0200
committerLennart Poettering <lennart@poettering.net>2015-09-07 18:44:30 +0200
commite83bebeff7d9d734e17c3e38ac13daabc09518e1 (patch)
treef8f744cadfa0fe75c1897fbef4d8ab500646e897 /src/nspawn/nspawn-mount.c
parent1dc0b4e4b0dd5d59fbfc37410825c4b9a716e2b9 (diff)
nspawn: split out mount related functions into a new nspawn-mount.c file
Diffstat (limited to 'src/nspawn/nspawn-mount.c')
-rw-r--r--src/nspawn/nspawn-mount.c870
1 files changed, 870 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
new file mode 100644
index 0000000000..5521e1bbe0
--- /dev/null
+++ b/src/nspawn/nspawn-mount.c
@@ -0,0 +1,870 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ 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 "util.h"
+#include "rm-rf.h"
+#include "strv.h"
+#include "path-util.h"
+#include "mkdir.h"
+#include "label.h"
+#include "set.h"
+#include "cgroup-util.h"
+
+#include "nspawn.h"
+#include "nspawn-mount.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(*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);
+ }
+
+ strv_free(m->lower);
+ }
+
+ free(l);
+}
+
+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;
+}
+
+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);
+ if (!destination)
+ return -ENOMEM;
+ }
+
+ if (r == 2 && !isempty(p)) {
+ opts = strdup(p);
+ if (!opts)
+ return -ENOMEM;
+ }
+
+ if (!path_is_absolute(source))
+ return -EINVAL;
+
+ if (!path_is_absolute(destination))
+ return -EINVAL;
+
+ m = custom_mount_add(l, n, CUSTOM_MOUNT_BIND);
+ if (!m)
+ return log_oom();
+
+ 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;
+}
+
+static int tmpfs_patch_options(
+ const char *options,
+ bool userns, uid_t uid_shift, uid_t uid_range,
+ const char *selinux_apifs_context,
+ char **ret) {
+
+ char *buf = NULL;
+
+ if (userns && uid_shift != 0) {
+ assert(uid_shift != UID_INVALID);
+
+ if (options)
+ (void) asprintf(&buf, "%s,uid=" UID_FMT ",gid=" UID_FMT, options, uid_shift, uid_shift);
+ else
+ (void) asprintf(&buf, "uid=" UID_FMT ",gid=" UID_FMT, uid_shift, uid_shift);
+ if (!buf)
+ return -ENOMEM;
+
+ options = buf;
+ }
+
+#ifdef HAVE_SELINUX
+ if (selinux_apifs_context) {
+ char *t;
+
+ if (options)
+ t = strjoin(options, ",context=\"", selinux_apifs_context, "\"", NULL);
+ else
+ t = strjoin("context=\"", selinux_apifs_context, "\"", NULL);
+ if (!t) {
+ free(buf);
+ return -ENOMEM;
+ }
+
+ free(buf);
+ buf = t;
+ }
+#endif
+
+ *ret = buf;
+ return !!buf;
+}
+
+int mount_all(const char *dest,
+ bool userns, 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;
+ bool fatal;
+ bool userns;
+ } MountPoint;
+
+ static const MountPoint mount_table[] = {
+ { "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, true, true },
+ { "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND, true, true }, /* Bind mount first */
+ { NULL, "/proc/sys", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, true, true }, /* Then, make it r/o */
+ { "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV, true, false },
+ { "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME, true, false },
+ { "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME, true, false },
+ { "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV|MS_STRICTATIME, true, false },
+ { "tmpfs", "/tmp", "tmpfs", "mode=1777", MS_STRICTATIME, true, false },
+#ifdef HAVE_SELINUX
+ { "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND, false, false }, /* Bind mount first */
+ { NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, false, false }, /* Then, make it r/o */
+#endif
+ };
+
+ unsigned k;
+ int r;
+
+ for (k = 0; k < ELEMENTSOF(mount_table); k++) {
+ _cleanup_free_ char *where = NULL, *options = NULL;
+ const char *o;
+
+ if (userns != mount_table[k].userns)
+ continue;
+
+ where = prefix_root(dest, mount_table[k].where);
+ if (!where)
+ return log_oom();
+
+ r = path_is_mount_point(where, AT_SYMLINK_FOLLOW);
+ 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_p(where, 0755);
+ if (r < 0) {
+ if (mount_table[k].fatal)
+ return log_error_errno(r, "Failed to create directory %s: %m", where);
+
+ log_warning_errno(r, "Failed to create directory %s: %m", where);
+ continue;
+ }
+
+ o = mount_table[k].options;
+ if (streq_ptr(mount_table[k].type, "tmpfs")) {
+ r = tmpfs_patch_options(o, userns, uid_shift, uid_range, selinux_apifs_context, &options);
+ if (r < 0)
+ return log_oom();
+ if (r > 0)
+ o = options;
+ }
+
+ if (mount(mount_table[k].what,
+ where,
+ mount_table[k].type,
+ mount_table[k].flags,
+ o) < 0) {
+
+ if (mount_table[k].fatal)
+ return log_error_errno(errno, "mount(%s) failed: %m", where);
+
+ log_warning_errno(errno, "mount(%s) failed, ignoring: %m", where);
+ }
+ }
+
+ 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;
+
+ assert(options);
+
+ for (;;) {
+ _cleanup_free_ char *word = NULL;
+ int 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) {
+ struct stat source_st, dest_st;
+ const char *where;
+ unsigned long mount_flags = MS_BIND | MS_REC;
+ _cleanup_free_ char *mount_opts = NULL;
+ int r;
+
+ 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);
+
+ where = prefix_roota(dest, m->destination);
+
+ if (stat(where, &dest_st) >= 0) {
+ 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 if (errno == ENOENT) {
+ r = mkdir_parents_label(where, 0755);
+ if (r < 0)
+ return log_error_errno(r, "Failed to make parents of %s: %m", where);
+ } else {
+ log_error_errno(errno, "Failed to stat %s: %m", where);
+ return -errno;
+ }
+
+ /* 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 && r != -EEXIST)
+ return log_error_errno(r, "Failed to create mount point %s: %m", where);
+
+ if (mount(m->source, where, NULL, mount_flags, mount_opts) < 0)
+ return log_error_errno(errno, "mount(%s) failed: %m", where);
+
+ if (m->read_only) {
+ r = bind_remount_recursive(where, true);
+ 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 *where, *options;
+ _cleanup_free_ char *buf = NULL;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ where = prefix_roota(dest, m->destination);
+
+ r = mkdir_p_label(where, 0755);
+ if (r < 0 && r != -EEXIST)
+ 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, selinux_apifs_context, &buf);
+ if (r < 0)
+ return log_oom();
+ options = r > 0 ? buf : m->options;
+
+ if (mount("tmpfs", where, "tmpfs", MS_NODEV|MS_STRICTATIME, options) < 0)
+ return log_error_errno(errno, "tmpfs mount to %s failed: %m", where);
+
+ return 0;
+}
+
+static char *joined_and_escaped_lower_dirs(char * const *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;
+ const char *where, *options;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ where = prefix_roota(dest, m->destination);
+
+ r = mkdir_label(where, 0755);
+ if (r < 0 && r != -EEXIST)
+ 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();
+
+ if (m->read_only) {
+ _cleanup_free_ char *escaped_source = NULL;
+
+ escaped_source = shell_escape(m->source, ",:");
+ if (!escaped_source)
+ return log_oom();
+
+ options = strjoina("lowerdir=", escaped_source, ":", lower);
+ } else {
+ _cleanup_free_ char *escaped_source = NULL, *escaped_work_dir = NULL;
+
+ assert(m->work_dir);
+ (void) mkdir_label(m->work_dir, 0700);
+
+ escaped_source = shell_escape(m->source, ",:");
+ if (!escaped_source)
+ return log_oom();
+ 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);
+ }
+
+ if (mount("overlay", where, "overlay", m->read_only ? MS_RDONLY : 0, options) < 0)
+ return log_error_errno(errno, "overlay mount to %s failed: %m", where);
+
+ return 0;
+}
+
+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;
+}
+
+static int mount_legacy_cgroup_hierarchy(const char *dest, const char *controller, const char *hierarchy, bool read_only) {
+ char *to;
+ int r;
+
+ to = strjoina(dest, "/sys/fs/cgroup/", hierarchy);
+
+ r = path_is_mount_point(to, 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 (mount("cgroup", to, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, controller) < 0)
+ return log_error_errno(errno, "Failed to mount to %s: %m", to);
+
+ /* ... hence let's only make the bind mount read-only, not the
+ * superblock. */
+ if (read_only) {
+ if (mount(NULL, to, NULL, MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL) < 0)
+ return log_error_errno(errno, "Failed to remount %s read-only: %m", to);
+ }
+ return 1;
+}
+
+static int mount_legacy_cgroups(
+ const char *dest,
+ 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");
+
+ /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
+ r = path_is_mount_point(cgroup_root, 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, selinux_apifs_context, &options);
+ if (r < 0)
+ return log_oom();
+
+ if (mount("tmpfs", cgroup_root, "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options) < 0)
+ return log_error_errno(errno, "Failed to mount /sys/fs/cgroup: %m");
+ }
+
+ if (cg_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, 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, true);
+ if (r < 0)
+ return r;
+
+ r = symlink_idempotent(combined, target);
+ if (r == -EINVAL) {
+ log_error("Invalid existing symlink for combined hierarchy");
+ return r;
+ }
+ if (r < 0)
+ return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
+ }
+ }
+
+skip_controllers:
+ r = mount_legacy_cgroup_hierarchy(dest, "none,name=systemd,xattr", "systemd", false);
+ if (r < 0)
+ return r;
+
+ if (mount(NULL, cgroup_root, NULL, MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755") < 0)
+ return log_error_errno(errno, "Failed to remount %s read-only: %m", cgroup_root);
+
+ return 0;
+}
+
+static int mount_unified_cgroups(const char *dest) {
+ const char *p;
+ int r;
+
+ assert(dest);
+
+ p = strjoina(dest, "/sys/fs/cgroup");
+
+ r = path_is_mount_point(p, 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 = strjoina(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;
+ }
+
+ if (mount("cgroup", p, "cgroup", MS_NOSUID|MS_NOEXEC|MS_NODEV, "__DEVEL__sane_behavior") < 0)
+ return log_error_errno(errno, "Failed to mount unified cgroup hierarchy to %s: %m", p);
+
+ return 0;
+}
+
+int mount_cgroups(
+ const char *dest,
+ bool unified_requested,
+ bool userns, uid_t uid_shift, uid_t uid_range,
+ const char *selinux_apifs_context) {
+
+ if (unified_requested)
+ return mount_unified_cgroups(dest);
+ else
+ return mount_legacy_cgroups(dest, userns, uid_shift, uid_range, selinux_apifs_context);
+}
+
+int mount_systemd_cgroup_writable(
+ const char *dest,
+ bool 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) {
+ 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 */
+ if (mount(systemd_own, systemd_own, NULL, MS_BIND, NULL) < 0)
+ return log_error_errno(errno, "Failed to turn %s into a bind mount: %m", own_cgroup_path);
+
+ /* And then remount the systemd cgroup root read-only */
+ if (mount(NULL, systemd_root, NULL, MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL) < 0)
+ return log_error_errno(errno, "Failed to mount cgroup root read-only: %m");
+
+ return 0;
+}
+
+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);
+ 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, selinux_apifs_context, &buf);
+ if (r < 0)
+ return log_oom();
+ if (r > 0)
+ options = buf;
+
+ if (mount("tmpfs", p, "tmpfs", MS_STRICTATIME, options) < 0)
+ return log_error_errno(errno, "Failed to mount tmpfs to /var: %m");
+
+ return 0;
+}
+
+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, selinux_apifs_context, &buf);
+ if (r < 0)
+ return log_oom();
+ if (r > 0)
+ options = buf;
+
+ if (mount("tmpfs", template, "tmpfs", MS_STRICTATIME, options) < 0) {
+ r = log_error_errno(errno, "Failed to mount tmpfs for root directory: %m");
+ 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;
+ }
+
+ if (mount(f, t, NULL, MS_BIND|MS_REC, NULL) < 0) {
+ r = log_error_errno(errno, "Failed to create /usr bind mount: %m");
+ goto fail;
+ }
+
+ bind_mounted = true;
+
+ r = bind_remount_recursive(t, true);
+ if (r < 0) {
+ log_error_errno(r, "Failed to remount %s read-only: %m", t);
+ goto fail;
+ }
+
+ if (mount(template, directory, NULL, MS_MOVE, NULL) < 0) {
+ r = log_error_errno(errno, "Failed to move root mount: %m");
+ goto fail;
+ }
+
+ (void) rmdir(template);
+
+ return 0;
+
+fail:
+ if (bind_mounted)
+ (void) umount(t);
+
+ if (tmpfs_mounted)
+ (void) umount(template);
+ (void) rmdir(template);
+ return r;
+}
+
+VolatileMode volatile_mode_from_string(const char *s) {
+ int b;
+
+ if (isempty(s))
+ return _VOLATILE_MODE_INVALID;
+
+ b = parse_boolean(s);
+ if (b > 0)
+ return VOLATILE_YES;
+ if (b == 0)
+ return VOLATILE_NO;
+
+ if (streq(s, "state"))
+ return VOLATILE_STATE;
+
+ return _VOLATILE_MODE_INVALID;
+}