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-rw-r--r--src/nspawn/nspawn-mount.c1338
1 files changed, 1338 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
new file mode 100644
index 0000000..63f59fe
--- /dev/null
+++ b/src/nspawn/nspawn-mount.c
@@ -0,0 +1,1338 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/mount.h>
+#include <linux/magic.h>
+
+#include "alloc-util.h"
+#include "chase-symlinks.h"
+#include "escape.h"
+#include "fd-util.h"
+#include "format-util.h"
+#include "fs-util.h"
+#include "label.h"
+#include "mkdir-label.h"
+#include "mount-util.h"
+#include "mountpoint-util.h"
+#include "nspawn-mount.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "rm-rf.h"
+#include "set.h"
+#include "sort-util.h"
+#include "stat-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tmpfile-util.h"
+#include "user-util.h"
+
+CustomMount* custom_mount_add(CustomMount **l, size_t *n, CustomMountType t) {
+ CustomMount *c, *ret;
+
+ assert(l);
+ assert(n);
+ assert(t >= 0);
+ assert(t < _CUSTOM_MOUNT_TYPE_MAX);
+
+ c = reallocarray(*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, size_t n) {
+ for (size_t 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);
+ }
+
+ if (m->rm_rf_tmpdir) {
+ (void) rm_rf(m->rm_rf_tmpdir, REMOVE_ROOT|REMOVE_PHYSICAL);
+ free(m->rm_rf_tmpdir);
+ }
+
+ strv_free(m->lower);
+ free(m->type_argument);
+ }
+
+ free(l);
+}
+
+static int custom_mount_compare(const CustomMount *a, const CustomMount *b) {
+ int r;
+
+ r = path_compare(a->destination, b->destination);
+ if (r != 0)
+ return r;
+
+ return CMP(a->type, b->type);
+}
+
+static int source_path_parse(const char *p, char **ret) {
+ assert(p);
+ assert(ret);
+
+ if (isempty(p))
+ return -EINVAL;
+
+ if (*p == '+') {
+ if (!path_is_absolute(p + 1))
+ return -EINVAL;
+
+ char *s = strdup(p);
+ if (!s)
+ return -ENOMEM;
+
+ *ret = TAKE_PTR(s);
+ return 0;
+ }
+
+ return path_make_absolute_cwd(p, ret);
+}
+
+static int source_path_parse_nullable(const char *p, char **ret) {
+ assert(p);
+ assert(ret);
+
+ if (isempty(p)) {
+ *ret = NULL;
+ return 0;
+ }
+
+ return source_path_parse(p, ret);
+}
+
+static char *resolve_source_path(const char *dest, const char *source) {
+ if (!source)
+ return NULL;
+
+ if (source[0] == '+')
+ return path_join(dest, source + 1);
+
+ return strdup(source);
+}
+
+static int allocate_temporary_source(CustomMount *m) {
+ assert(m);
+ assert(!m->source);
+ assert(!m->rm_rf_tmpdir);
+
+ m->rm_rf_tmpdir = strdup("/var/tmp/nspawn-temp-XXXXXX");
+ if (!m->rm_rf_tmpdir)
+ return log_oom();
+
+ if (!mkdtemp(m->rm_rf_tmpdir)) {
+ m->rm_rf_tmpdir = mfree(m->rm_rf_tmpdir);
+ return log_error_errno(errno, "Failed to acquire temporary directory: %m");
+ }
+
+ m->source = path_join(m->rm_rf_tmpdir, "src");
+ if (!m->source)
+ return log_oom();
+
+ if (mkdir(m->source, 0755) < 0)
+ return log_error_errno(errno, "Failed to create %s: %m", m->source);
+
+ return 0;
+}
+
+int custom_mount_prepare_all(const char *dest, CustomMount *l, size_t n) {
+ int r;
+
+ /* Prepare all custom mounts. This will make source we know all temporary directories. This is called in the
+ * parent process, so that we know the temporary directories to remove on exit before we fork off the
+ * children. */
+
+ assert(l || n == 0);
+
+ /* Order the custom mounts, and make sure we have a working directory */
+ typesafe_qsort(l, n, custom_mount_compare);
+
+ for (size_t i = 0; i < n; i++) {
+ CustomMount *m = l + i;
+
+ /* /proc we mount in the inner child, i.e. when we acquired CLONE_NEWPID. All other mounts we mount
+ * already in the outer child, so that the mounts are already established before CLONE_NEWPID and in
+ * particular CLONE_NEWUSER. This also means any custom mounts below /proc also need to be mounted in
+ * the inner child, not the outer one. Determine this here. */
+ m->in_userns = path_startswith(m->destination, "/proc");
+
+ if (m->type == CUSTOM_MOUNT_BIND) {
+ if (m->source) {
+ char *s;
+
+ s = resolve_source_path(dest, m->source);
+ if (!s)
+ return log_oom();
+
+ free_and_replace(m->source, s);
+ } else {
+ /* No source specified? In that case, use a throw-away temporary directory in /var/tmp */
+
+ r = allocate_temporary_source(m);
+ if (r < 0)
+ return r;
+ }
+ }
+
+ if (m->type == CUSTOM_MOUNT_OVERLAY) {
+ STRV_FOREACH(j, m->lower) {
+ char *s;
+
+ s = resolve_source_path(dest, *j);
+ if (!s)
+ return log_oom();
+
+ free_and_replace(*j, s);
+ }
+
+ if (m->source) {
+ char *s;
+
+ s = resolve_source_path(dest, m->source);
+ if (!s)
+ return log_oom();
+
+ free_and_replace(m->source, s);
+ } else {
+ r = allocate_temporary_source(m);
+ if (r < 0)
+ return r;
+ }
+
+ if (m->work_dir) {
+ char *s;
+
+ s = resolve_source_path(dest, m->work_dir);
+ if (!s)
+ return log_oom();
+
+ free_and_replace(m->work_dir, s);
+ } else {
+ r = tempfn_random(m->source, NULL, &m->work_dir);
+ if (r < 0)
+ return log_error_errno(r, "Failed to acquire working directory: %m");
+ }
+
+ (void) mkdir_label(m->work_dir, 0700);
+ }
+ }
+
+ return 0;
+}
+
+int bind_mount_parse(CustomMount **l, size_t *n, const char *s, bool read_only) {
+ _cleanup_free_ char *source = NULL, *destination = NULL, *opts = NULL, *p = NULL;
+ CustomMount *m;
+ int r;
+
+ assert(l);
+ assert(n);
+
+ r = extract_many_words(&s, ":", EXTRACT_DONT_COALESCE_SEPARATORS, &source, &destination, NULL);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL;
+ if (r == 1) {
+ destination = strdup(source[0] == '+' ? source+1 : source);
+ if (!destination)
+ return -ENOMEM;
+ }
+ if (r == 2 && !isempty(s)) {
+ opts = strdup(s);
+ if (!opts)
+ return -ENOMEM;
+ }
+
+ r = source_path_parse_nullable(source, &p);
+ if (r < 0)
+ return r;
+
+ if (!path_is_absolute(destination))
+ return -EINVAL;
+
+ m = custom_mount_add(l, n, CUSTOM_MOUNT_BIND);
+ if (!m)
+ return -ENOMEM;
+
+ m->source = TAKE_PTR(p);
+ m->destination = TAKE_PTR(destination);
+ m->read_only = read_only;
+ m->options = TAKE_PTR(opts);
+
+ return 0;
+}
+
+int tmpfs_mount_parse(CustomMount **l, size_t *n, const char *s) {
+ _cleanup_free_ char *path = NULL, *opts = NULL;
+ const char *p = ASSERT_PTR(s);
+ CustomMount *m;
+ int r;
+
+ assert(l);
+ assert(n);
+
+ 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 = TAKE_PTR(path);
+ m->options = TAKE_PTR(opts);
+
+ return 0;
+}
+
+int overlay_mount_parse(CustomMount **l, size_t *n, const char *s, bool read_only) {
+ _cleanup_free_ char *upper = NULL, *destination = NULL;
+ _cleanup_strv_free_ char **lower = NULL;
+ CustomMount *m;
+ int r, k;
+
+ k = strv_split_full(&lower, s, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
+ if (k < 0)
+ return k;
+ if (k < 2)
+ return -EADDRNOTAVAIL;
+ if (k == 2) {
+ _cleanup_free_ char *p = NULL;
+
+ /* If two parameters are specified, the first one is the lower, the second one the upper directory. And
+ * we'll also define the destination mount point the same as the upper. */
+
+ r = source_path_parse(lower[0], &p);
+ if (r < 0)
+ return r;
+
+ free_and_replace(lower[0], p);
+
+ r = source_path_parse(lower[1], &p);
+ if (r < 0)
+ return r;
+
+ free_and_replace(lower[1], p);
+
+ upper = TAKE_PTR(lower[1]);
+
+ destination = strdup(upper[0] == '+' ? upper+1 : upper); /* take the destination without "+" prefix */
+ if (!destination)
+ return -ENOMEM;
+ } else {
+ _cleanup_free_ char *p = NULL;
+
+ /* If more than two parameters are specified, the last one is the destination, the second to last one
+ * the "upper", and all before that the "lower" directories. */
+
+ destination = lower[k - 1];
+ upper = TAKE_PTR(lower[k - 2]);
+
+ STRV_FOREACH(i, lower) {
+ r = source_path_parse(*i, &p);
+ if (r < 0)
+ return r;
+
+ free_and_replace(*i, p);
+ }
+
+ /* If the upper directory is unspecified, then let's create it automatically as a throw-away directory
+ * in /var/tmp */
+ r = source_path_parse_nullable(upper, &p);
+ if (r < 0)
+ return r;
+
+ free_and_replace(upper, p);
+
+ if (!path_is_absolute(destination))
+ return -EINVAL;
+ }
+
+ m = custom_mount_add(l, n, CUSTOM_MOUNT_OVERLAY);
+ if (!m)
+ return -ENOMEM;
+
+ m->destination = TAKE_PTR(destination);
+ m->source = TAKE_PTR(upper);
+ m->lower = TAKE_PTR(lower);
+ m->read_only = read_only;
+
+ return 0;
+}
+
+int inaccessible_mount_parse(CustomMount **l, size_t *n, const char *s) {
+ _cleanup_free_ char *path = NULL;
+ CustomMount *m;
+
+ assert(l);
+ assert(n);
+ assert(s);
+
+ if (!path_is_absolute(s))
+ return -EINVAL;
+
+ path = strdup(s);
+ if (!path)
+ return -ENOMEM;
+
+ m = custom_mount_add(l, n, CUSTOM_MOUNT_INACCESSIBLE);
+ if (!m)
+ return -ENOMEM;
+
+ m->destination = TAKE_PTR(path);
+ return 0;
+}
+
+int tmpfs_patch_options(
+ const char *options,
+ uid_t uid_shift,
+ const char *selinux_apifs_context,
+ char **ret) {
+
+ _cleanup_free_ char *buf = NULL;
+
+ assert(ret);
+
+ if (options) {
+ buf = strdup(options);
+ if (!buf)
+ return -ENOMEM;
+ }
+
+ if (uid_shift != UID_INVALID)
+ if (strextendf_with_separator(&buf, ",", "uid=" UID_FMT ",gid=" UID_FMT, uid_shift, uid_shift) < 0)
+ return -ENOMEM;
+
+#if HAVE_SELINUX
+ if (selinux_apifs_context)
+ if (strextendf_with_separator(&buf, ",", "context=\"%s\"", selinux_apifs_context) < 0)
+ return -ENOMEM;
+#endif
+
+ *ret = TAKE_PTR(buf);
+ return !!*ret;
+}
+
+int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
+ const char *full, *top;
+ int r;
+ unsigned long extra_flags = 0;
+
+ top = prefix_roota(dest, "/sys");
+ r = path_is_fs_type(top, SYSFS_MAGIC);
+ if (r < 0)
+ return log_error_errno(r, "Failed to determine filesystem type of %s: %m", top);
+ /* /sys might already be mounted as sysfs by the outer child in the
+ * !netns case. In this case, it's all good. Don't touch it because we
+ * don't have the right to do so, see https://github.com/systemd/systemd/issues/1555.
+ */
+ if (r > 0)
+ return 0;
+
+ full = prefix_roota(top, "/full");
+
+ (void) mkdir(full, 0755);
+
+ if (FLAGS_SET(mount_settings, MOUNT_APPLY_APIVFS_RO))
+ extra_flags |= MS_RDONLY;
+
+ r = mount_nofollow_verbose(LOG_ERR, "sysfs", full, "sysfs",
+ MS_NOSUID|MS_NOEXEC|MS_NODEV|extra_flags, NULL);
+ if (r < 0)
+ return r;
+
+ FOREACH_STRING(x, "block", "bus", "class", "dev", "devices", "kernel") {
+ _cleanup_free_ char *from = NULL, *to = NULL;
+
+ from = path_join(full, x);
+ if (!from)
+ return log_oom();
+
+ to = path_join(top, x);
+ if (!to)
+ return log_oom();
+
+ (void) mkdir(to, 0755);
+
+ r = mount_nofollow_verbose(LOG_ERR, from, to, NULL, MS_BIND, NULL);
+ if (r < 0)
+ return r;
+
+ r = mount_nofollow_verbose(LOG_ERR, NULL, to, NULL,
+ MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
+ if (r < 0)
+ return r;
+ }
+
+ r = umount_verbose(LOG_ERR, full, UMOUNT_NOFOLLOW);
+ if (r < 0)
+ return r;
+
+ if (rmdir(full) < 0)
+ return log_error_errno(errno, "Failed to remove %s: %m", full);
+
+ /* Create mountpoint for cgroups. Otherwise we are not allowed since we
+ * remount /sys read-only.
+ */
+ const char *x = prefix_roota(top, "/fs/cgroup");
+ (void) mkdir_p(x, 0755);
+
+ return mount_nofollow_verbose(LOG_ERR, NULL, top, NULL,
+ MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
+}
+
+int mount_all(const char *dest,
+ MountSettingsMask mount_settings,
+ uid_t uid_shift,
+ const char *selinux_apifs_context) {
+
+#define PROC_INACCESSIBLE_REG(path) \
+ { "/run/systemd/inaccessible/reg", (path), NULL, NULL, MS_BIND, \
+ MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* Bind mount first ... */ \
+ { NULL, (path), NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, \
+ MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO } /* Then, make it r/o */
+
+#define PROC_READ_ONLY(path) \
+ { (path), (path), NULL, NULL, MS_BIND, \
+ MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* Bind mount first ... */ \
+ { NULL, (path), NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, \
+ MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO } /* Then, make it r/o */
+
+ typedef struct MountPoint {
+ const char *what;
+ const char *where;
+ const char *type;
+ const char *options;
+ unsigned long flags;
+ MountSettingsMask mount_settings;
+ } MountPoint;
+
+ static const MountPoint mount_table[] = {
+ /* First we list inner child mounts (i.e. mounts applied *after* entering user namespacing) */
+ { "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_MKDIR|MOUNT_FOLLOW_SYMLINKS }, /* we follow symlinks here since not following them requires /proc/ already being mounted, which we don't have here. */
+
+ { "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND,
+ MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* Bind mount first ... */
+
+ { "/proc/sys/net", "/proc/sys/net", NULL, NULL, MS_BIND,
+ MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO|MOUNT_APPLY_APIVFS_NETNS }, /* (except for this) */
+
+ { NULL, "/proc/sys", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
+ MOUNT_FATAL|MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO }, /* ... then, make it r/o */
+
+ /* Make these files inaccessible to container payloads: they potentially leak information about kernel
+ * internals or the host's execution environment to the container */
+ PROC_INACCESSIBLE_REG("/proc/kallsyms"),
+ PROC_INACCESSIBLE_REG("/proc/kcore"),
+ PROC_INACCESSIBLE_REG("/proc/keys"),
+ PROC_INACCESSIBLE_REG("/proc/sysrq-trigger"),
+ PROC_INACCESSIBLE_REG("/proc/timer_list"),
+
+ /* Make these directories read-only to container payloads: they show hardware information, and in some
+ * cases contain tunables the container really shouldn't have access to. */
+ PROC_READ_ONLY("/proc/acpi"),
+ PROC_READ_ONLY("/proc/apm"),
+ PROC_READ_ONLY("/proc/asound"),
+ PROC_READ_ONLY("/proc/bus"),
+ PROC_READ_ONLY("/proc/fs"),
+ PROC_READ_ONLY("/proc/irq"),
+ PROC_READ_ONLY("/proc/scsi"),
+
+ { "mqueue", "/dev/mqueue", "mqueue", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ MOUNT_IN_USERNS|MOUNT_MKDIR },
+
+ /* Then we list outer child mounts (i.e. mounts applied *before* entering user namespacing) */
+ { "tmpfs", "/tmp", "tmpfs", "mode=1777" NESTED_TMPFS_LIMITS, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ MOUNT_FATAL|MOUNT_APPLY_TMPFS_TMP|MOUNT_MKDIR },
+ { "tmpfs", "/sys", "tmpfs", "mode=555" TMPFS_LIMITS_SYS, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ MOUNT_FATAL|MOUNT_APPLY_APIVFS_NETNS|MOUNT_MKDIR },
+ { "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ MOUNT_FATAL|MOUNT_APPLY_APIVFS_RO|MOUNT_MKDIR }, /* skipped if above was mounted */
+ { "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ MOUNT_FATAL|MOUNT_MKDIR }, /* skipped if above was mounted */
+ { "tmpfs", "/dev", "tmpfs", "mode=755" TMPFS_LIMITS_PRIVATE_DEV, MS_NOSUID|MS_STRICTATIME,
+ MOUNT_FATAL|MOUNT_MKDIR },
+ { "tmpfs", "/dev/shm", "tmpfs", "mode=1777" NESTED_TMPFS_LIMITS, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ MOUNT_FATAL|MOUNT_MKDIR },
+ { "tmpfs", "/run", "tmpfs", "mode=755" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ MOUNT_FATAL|MOUNT_MKDIR },
+ { "/run/host", "/run/host", NULL, NULL, MS_BIND,
+ MOUNT_FATAL|MOUNT_MKDIR|MOUNT_PREFIX_ROOT }, /* Prepare this so that we can make it read-only when we are done */
+ { "/etc/os-release", "/run/host/os-release", NULL, NULL, MS_BIND,
+ MOUNT_TOUCH }, /* As per kernel interface requirements, bind mount first (creating mount points) and make read-only later */
+ { "/usr/lib/os-release", "/run/host/os-release", NULL, NULL, MS_BIND,
+ MOUNT_FATAL }, /* If /etc/os-release doesn't exist use the version in /usr/lib as fallback */
+ { NULL, "/run/host/os-release", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
+ MOUNT_FATAL },
+ { NULL, "/run/host", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
+ MOUNT_FATAL|MOUNT_IN_USERNS },
+#if HAVE_SELINUX
+ { "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND,
+ MOUNT_MKDIR }, /* Bind mount first (mkdir/chown the mount point in case /sys/ is mounted as minimal skeleton tmpfs) */
+ { NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
+ 0 }, /* Then, make it r/o (don't mkdir/chown the mount point here, the previous entry already did that) */
+#endif
+ };
+
+ bool use_userns = FLAGS_SET(mount_settings, MOUNT_USE_USERNS);
+ bool netns = FLAGS_SET(mount_settings, MOUNT_APPLY_APIVFS_NETNS);
+ bool ro = FLAGS_SET(mount_settings, MOUNT_APPLY_APIVFS_RO);
+ bool in_userns = FLAGS_SET(mount_settings, MOUNT_IN_USERNS);
+ bool tmpfs_tmp = FLAGS_SET(mount_settings, MOUNT_APPLY_TMPFS_TMP);
+ int r;
+
+ for (size_t k = 0; k < ELEMENTSOF(mount_table); k++) {
+ _cleanup_free_ char *where = NULL, *options = NULL, *prefixed = NULL;
+ bool fatal = FLAGS_SET(mount_table[k].mount_settings, MOUNT_FATAL);
+ const char *o;
+
+ if (in_userns != FLAGS_SET(mount_table[k].mount_settings, MOUNT_IN_USERNS))
+ continue;
+
+ if (!netns && FLAGS_SET(mount_table[k].mount_settings, MOUNT_APPLY_APIVFS_NETNS))
+ continue;
+
+ if (!ro && FLAGS_SET(mount_table[k].mount_settings, MOUNT_APPLY_APIVFS_RO))
+ continue;
+
+ if (!tmpfs_tmp && FLAGS_SET(mount_table[k].mount_settings, MOUNT_APPLY_TMPFS_TMP))
+ continue;
+
+ r = chase_symlinks(mount_table[k].where, dest, CHASE_NONEXISTENT|CHASE_PREFIX_ROOT, &where, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s%s: %m", strempty(dest), mount_table[k].where);
+
+ /* Skip this entry if it is not a remount. */
+ if (mount_table[k].what) {
+ r = path_is_mount_point(where, NULL, 0);
+ if (r < 0 && r != -ENOENT)
+ return log_error_errno(r, "Failed to detect whether %s is a mount point: %m", where);
+ if (r > 0)
+ continue;
+ }
+
+ if ((mount_table[k].mount_settings & (MOUNT_MKDIR|MOUNT_TOUCH)) != 0) {
+ uid_t u = (use_userns && !in_userns) ? uid_shift : UID_INVALID;
+
+ if (FLAGS_SET(mount_table[k].mount_settings, MOUNT_TOUCH))
+ r = mkdir_parents_safe(dest, where, 0755, u, u, 0);
+ else
+ r = mkdir_p_safe(dest, where, 0755, u, u, 0);
+ if (r < 0 && r != -EEXIST) {
+ if (fatal && r != -EROFS)
+ return log_error_errno(r, "Failed to create directory %s: %m", where);
+
+ log_debug_errno(r, "Failed to create directory %s: %m", where);
+
+ /* If we failed mkdir() or chown() due to the root directory being read only,
+ * attempt to mount this fs anyway and let mount_verbose log any errors */
+ if (r != -EROFS)
+ continue;
+ }
+ }
+
+ if (FLAGS_SET(mount_table[k].mount_settings, MOUNT_TOUCH)) {
+ r = touch(where);
+ if (r < 0 && r != -EEXIST) {
+ if (fatal && r != -EROFS)
+ return log_error_errno(r, "Failed to create file %s: %m", where);
+
+ log_debug_errno(r, "Failed to create file %s: %m", where);
+ if (r != -EROFS)
+ continue;
+ }
+ }
+
+ o = mount_table[k].options;
+ if (streq_ptr(mount_table[k].type, "tmpfs")) {
+ r = tmpfs_patch_options(o, in_userns ? 0 : uid_shift, selinux_apifs_context, &options);
+ if (r < 0)
+ return log_oom();
+ if (r > 0)
+ o = options;
+ }
+
+ if (FLAGS_SET(mount_table[k].mount_settings, MOUNT_PREFIX_ROOT)) {
+ /* Optionally prefix the mount source with the root dir. This is useful in bind
+ * mounts to be created within the container image before we transition into it. Note
+ * that MOUNT_IN_USERNS is run after we transitioned hence prefixing is not ncessary
+ * for those. */
+ r = chase_symlinks(mount_table[k].what, dest, CHASE_PREFIX_ROOT, &prefixed, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s%s: %m", strempty(dest), mount_table[k].what);
+ }
+
+ r = mount_verbose_full(
+ fatal ? LOG_ERR : LOG_DEBUG,
+ prefixed ?: mount_table[k].what,
+ where,
+ mount_table[k].type,
+ mount_table[k].flags,
+ o,
+ FLAGS_SET(mount_table[k].mount_settings, MOUNT_FOLLOW_SYMLINKS));
+ if (r < 0 && fatal)
+ return r;
+ }
+
+ return 0;
+}
+
+static int parse_mount_bind_options(const char *options, unsigned long *mount_flags, char **mount_opts, RemountIdmapping *idmapping) {
+ unsigned long flags = *mount_flags;
+ char *opts = NULL;
+ RemountIdmapping new_idmapping = *idmapping;
+ int r;
+
+ assert(options);
+
+ for (;;) {
+ _cleanup_free_ char *word = NULL;
+
+ r = extract_first_word(&options, &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 if (streq(word, "idmap"))
+ new_idmapping = REMOUNT_IDMAPPING_HOST_ROOT;
+ else if (streq(word, "noidmap"))
+ new_idmapping = REMOUNT_IDMAPPING_NONE;
+ else if (streq(word, "rootidmap"))
+ new_idmapping = REMOUNT_IDMAPPING_HOST_OWNER;
+ else
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+ "Invalid bind mount option: %s", word);
+ }
+
+ *mount_flags = flags;
+ *idmapping = new_idmapping;
+ /* 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, uid_t uid_shift, uid_t uid_range) {
+ _cleanup_free_ char *mount_opts = NULL, *where = NULL;
+ unsigned long mount_flags = MS_BIND | MS_REC;
+ struct stat source_st, dest_st;
+ int r;
+ RemountIdmapping idmapping = REMOUNT_IDMAPPING_NONE;
+
+ assert(dest);
+ assert(m);
+
+ if (m->options) {
+ r = parse_mount_bind_options(m->options, &mount_flags, &mount_opts, &idmapping);
+ if (r < 0)
+ return r;
+ }
+
+ /* If this is a bind mount from a temporary sources change ownership of the source to the container's
+ * root UID. Otherwise it would always show up as "nobody" if user namespacing is used. */
+ if (m->rm_rf_tmpdir && chown(m->source, uid_shift, uid_shift) < 0)
+ return log_error_errno(errno, "Failed to chown %s: %m", m->source);
+
+ if (stat(m->source, &source_st) < 0)
+ return log_error_errno(errno, "Failed to stat %s: %m", m->source);
+
+ r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
+ if (r > 0) { /* Path exists already? */
+
+ if (stat(where, &dest_st) < 0)
+ return log_error_errno(errno, "Failed to stat %s: %m", where);
+
+ if (S_ISDIR(source_st.st_mode) && !S_ISDIR(dest_st.st_mode))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+ "Cannot bind mount directory %s on file %s.",
+ m->source, where);
+
+ if (!S_ISDIR(source_st.st_mode) && S_ISDIR(dest_st.st_mode))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+ "Cannot bind mount file %s on directory %s.",
+ m->source, where);
+
+ } else { /* Path doesn't exist yet? */
+ r = mkdir_parents_label(where, 0755);
+ if (r < 0)
+ return log_error_errno(r, "Failed to make parents of %s: %m", where);
+
+ /* 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)
+ return log_error_errno(r, "Failed to create mount point %s: %m", where);
+ }
+
+ r = mount_nofollow_verbose(LOG_ERR, m->source, where, NULL, mount_flags, mount_opts);
+ if (r < 0)
+ return r;
+
+ if (m->read_only) {
+ r = bind_remount_recursive(where, MS_RDONLY, MS_RDONLY, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Read-only bind mount failed: %m");
+ }
+
+ if (idmapping != REMOUNT_IDMAPPING_NONE) {
+ r = remount_idmap(where, uid_shift, uid_range, source_st.st_uid, idmapping);
+ if (r < 0)
+ return log_error_errno(r, "Failed to map ids for bind mount %s: %m", where);
+ }
+
+ return 0;
+}
+
+static int mount_tmpfs(const char *dest, CustomMount *m, uid_t uid_shift, const char *selinux_apifs_context) {
+ const char *options;
+ _cleanup_free_ char *buf = NULL, *where = NULL;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
+ if (r == 0) { /* Doesn't exist yet? */
+ r = mkdir_p_label(where, 0755);
+ if (r < 0)
+ return log_error_errno(r, "Creating mount point for tmpfs %s failed: %m", where);
+ }
+
+ r = tmpfs_patch_options(m->options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
+ if (r < 0)
+ return log_oom();
+ options = r > 0 ? buf : m->options;
+
+ return mount_nofollow_verbose(LOG_ERR, "tmpfs", where, "tmpfs", MS_NODEV|MS_STRICTATIME, options);
+}
+
+static char *joined_and_escaped_lower_dirs(char **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, *where = NULL, *escaped_source = NULL;
+ const char *options;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
+ if (r == 0) { /* Doesn't exist yet? */
+ r = mkdir_label(where, 0755);
+ if (r < 0)
+ 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();
+
+ escaped_source = shell_escape(m->source, ",:");
+ if (!escaped_source)
+ return log_oom();
+
+ if (m->read_only)
+ options = strjoina("lowerdir=", escaped_source, ":", lower);
+ else {
+ _cleanup_free_ char *escaped_work_dir = NULL;
+
+ 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);
+ }
+
+ return mount_nofollow_verbose(LOG_ERR, "overlay", where, "overlay", m->read_only ? MS_RDONLY : 0, options);
+}
+
+static int mount_inaccessible(const char *dest, CustomMount *m) {
+ _cleanup_free_ char *where = NULL, *source = NULL;
+ struct stat st;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ r = chase_symlinks_and_stat(m->destination, dest, CHASE_PREFIX_ROOT, &where, &st, NULL);
+ if (r < 0) {
+ log_full_errno(m->graceful ? LOG_DEBUG : LOG_ERR, r, "Failed to resolve %s/%s: %m", dest, m->destination);
+ return m->graceful ? 0 : r;
+ }
+
+ r = mode_to_inaccessible_node(NULL, st.st_mode, &source);
+ if (r < 0)
+ return m->graceful ? 0 : r;
+
+ r = mount_nofollow_verbose(m->graceful ? LOG_DEBUG : LOG_ERR, source, where, NULL, MS_BIND, NULL);
+ if (r < 0)
+ return m->graceful ? 0 : r;
+
+ r = mount_nofollow_verbose(m->graceful ? LOG_DEBUG : LOG_ERR, NULL, where, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL);
+ if (r < 0) {
+ (void) umount_verbose(m->graceful ? LOG_DEBUG : LOG_ERR, where, UMOUNT_NOFOLLOW);
+ return m->graceful ? 0 : r;
+ }
+
+ return 0;
+}
+
+static int mount_arbitrary(const char *dest, CustomMount *m) {
+ _cleanup_free_ char *where = NULL;
+ int r;
+
+ assert(dest);
+ assert(m);
+
+ r = chase_symlinks(m->destination, dest, CHASE_PREFIX_ROOT|CHASE_NONEXISTENT, &where, NULL);
+ if (r < 0)
+ return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, m->destination);
+ if (r == 0) { /* Doesn't exist yet? */
+ r = mkdir_p_label(where, 0755);
+ if (r < 0)
+ return log_error_errno(r, "Creating mount point for mount %s failed: %m", where);
+ }
+
+ return mount_nofollow_verbose(LOG_ERR, m->source, where, m->type_argument, 0, m->options);
+}
+
+int mount_custom(
+ const char *dest,
+ CustomMount *mounts, size_t n,
+ uid_t uid_shift,
+ uid_t uid_range,
+ const char *selinux_apifs_context,
+ MountSettingsMask mount_settings) {
+ int r;
+
+ assert(dest);
+
+ for (size_t i = 0; i < n; i++) {
+ CustomMount *m = mounts + i;
+
+ if (FLAGS_SET(mount_settings, MOUNT_IN_USERNS) != m->in_userns)
+ continue;
+
+ if (FLAGS_SET(mount_settings, MOUNT_ROOT_ONLY) && !path_equal(m->destination, "/"))
+ continue;
+
+ if (FLAGS_SET(mount_settings, MOUNT_NON_ROOT_ONLY) && path_equal(m->destination, "/"))
+ continue;
+
+ switch (m->type) {
+
+ case CUSTOM_MOUNT_BIND:
+ r = mount_bind(dest, m, uid_shift, uid_range);
+ break;
+
+ case CUSTOM_MOUNT_TMPFS:
+ r = mount_tmpfs(dest, m, uid_shift, selinux_apifs_context);
+ break;
+
+ case CUSTOM_MOUNT_OVERLAY:
+ r = mount_overlay(dest, m);
+ break;
+
+ case CUSTOM_MOUNT_INACCESSIBLE:
+ r = mount_inaccessible(dest, m);
+ break;
+
+ case CUSTOM_MOUNT_ARBITRARY:
+ r = mount_arbitrary(dest, m);
+ break;
+
+ default:
+ assert_not_reached();
+ }
+
+ if (r < 0)
+ return r;
+ }
+
+ return 0;
+}
+
+bool has_custom_root_mount(const CustomMount *mounts, size_t n) {
+ for (size_t i = 0; i < n; i++)
+ if (path_equal(mounts[i].destination, "/"))
+ return true;
+
+ return false;
+}
+
+static int setup_volatile_state(const char *directory, uid_t uid_shift, const char *selinux_apifs_context) {
+ _cleanup_free_ char *buf = NULL;
+ const char *p, *options;
+ int r;
+
+ assert(directory);
+
+ /* --volatile=state means we simply overmount /var with a tmpfs, and the rest read-only. */
+
+ r = bind_remount_recursive(directory, MS_RDONLY, MS_RDONLY, NULL);
+ 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" TMPFS_LIMITS_VOLATILE_STATE;
+ r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
+ if (r < 0)
+ return log_oom();
+ if (r > 0)
+ options = buf;
+
+ return mount_nofollow_verbose(LOG_ERR, "tmpfs", p, "tmpfs", MS_STRICTATIME, options);
+}
+
+static int setup_volatile_yes(const char *directory, uid_t uid_shift, const char *selinux_apifs_context) {
+ bool tmpfs_mounted = false, bind_mounted = false;
+ char template[] = "/tmp/nspawn-volatile-XXXXXX";
+ _cleanup_free_ char *buf = NULL, *bindir = NULL;
+ const char *f, *t, *options;
+ struct stat st;
+ int r;
+
+ assert(directory);
+
+ /* --volatile=yes means we mount a tmpfs to the root dir, and the original /usr to use inside it, and
+ * that read-only. Before we start setting this up let's validate if the image has the /usr merge
+ * implemented, and let's output a friendly log message if it hasn't. */
+
+ bindir = path_join(directory, "/bin");
+ if (!bindir)
+ return log_oom();
+ if (lstat(bindir, &st) < 0) {
+ if (errno != ENOENT)
+ return log_error_errno(errno, "Failed to stat /bin directory below image: %m");
+
+ /* ENOENT is fine, just means the image is probably just a naked /usr and we can create the
+ * rest. */
+ } else if (S_ISDIR(st.st_mode))
+ return log_error_errno(SYNTHETIC_ERRNO(EISDIR),
+ "Sorry, --volatile=yes mode is not supported with OS images that have not merged /bin/, /sbin/, /lib/, /lib64/ into /usr/. "
+ "Please work with your distribution and help them adopt the merged /usr scheme.");
+ else if (!S_ISLNK(st.st_mode))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+ "Error starting image: if --volatile=yes is used /bin must be a symlink (for merged /usr support) or non-existent (in which case a symlink is created automatically).");
+
+ if (!mkdtemp(template))
+ return log_error_errno(errno, "Failed to create temporary directory: %m");
+
+ options = "mode=755" TMPFS_LIMITS_ROOTFS;
+ r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
+ if (r < 0)
+ goto fail;
+ if (r > 0)
+ options = buf;
+
+ r = mount_nofollow_verbose(LOG_ERR, "tmpfs", template, "tmpfs", MS_STRICTATIME, options);
+ if (r < 0)
+ 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;
+ }
+
+ r = mount_nofollow_verbose(LOG_ERR, f, t, NULL, MS_BIND|MS_REC, NULL);
+ if (r < 0)
+ goto fail;
+
+ bind_mounted = true;
+
+ r = bind_remount_recursive(t, MS_RDONLY, MS_RDONLY, NULL);
+ if (r < 0) {
+ log_error_errno(r, "Failed to remount %s read-only: %m", t);
+ goto fail;
+ }
+
+ r = mount_nofollow_verbose(LOG_ERR, template, directory, NULL, MS_MOVE, NULL);
+ if (r < 0)
+ goto fail;
+
+ (void) rmdir(template);
+
+ return 0;
+
+fail:
+ if (bind_mounted)
+ (void) umount_verbose(LOG_ERR, t, UMOUNT_NOFOLLOW);
+
+ if (tmpfs_mounted)
+ (void) umount_verbose(LOG_ERR, template, UMOUNT_NOFOLLOW);
+
+ (void) rmdir(template);
+ return r;
+}
+
+static int setup_volatile_overlay(const char *directory, uid_t uid_shift, const char *selinux_apifs_context) {
+ _cleanup_free_ char *buf = NULL, *escaped_directory = NULL, *escaped_upper = NULL, *escaped_work = NULL;
+ char template[] = "/tmp/nspawn-volatile-XXXXXX";
+ const char *upper, *work, *options;
+ bool tmpfs_mounted = false;
+ int r;
+
+ assert(directory);
+
+ /* --volatile=overlay means we mount an overlayfs to the root dir. */
+
+ if (!mkdtemp(template))
+ return log_error_errno(errno, "Failed to create temporary directory: %m");
+
+ options = "mode=755" TMPFS_LIMITS_ROOTFS;
+ r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
+ if (r < 0)
+ goto finish;
+ if (r > 0)
+ options = buf;
+
+ r = mount_nofollow_verbose(LOG_ERR, "tmpfs", template, "tmpfs", MS_STRICTATIME, options);
+ if (r < 0)
+ goto finish;
+
+ tmpfs_mounted = true;
+
+ upper = strjoina(template, "/upper");
+ work = strjoina(template, "/work");
+
+ if (mkdir(upper, 0755) < 0) {
+ r = log_error_errno(errno, "Failed to create %s: %m", upper);
+ goto finish;
+ }
+ if (mkdir(work, 0755) < 0) {
+ r = log_error_errno(errno, "Failed to create %s: %m", work);
+ goto finish;
+ }
+
+ /* And now, let's overmount the root dir with an overlayfs that uses the root dir as lower dir. It's kinda nice
+ * that the kernel allows us to do that without going through some mount point rearrangements. */
+
+ escaped_directory = shell_escape(directory, ",:");
+ escaped_upper = shell_escape(upper, ",:");
+ escaped_work = shell_escape(work, ",:");
+ if (!escaped_directory || !escaped_upper || !escaped_work) {
+ r = -ENOMEM;
+ goto finish;
+ }
+
+ options = strjoina("lowerdir=", escaped_directory, ",upperdir=", escaped_upper, ",workdir=", escaped_work);
+ r = mount_nofollow_verbose(LOG_ERR, "overlay", directory, "overlay", 0, options);
+
+finish:
+ if (tmpfs_mounted)
+ (void) umount_verbose(LOG_ERR, template, UMOUNT_NOFOLLOW);
+
+ (void) rmdir(template);
+ return r;
+}
+
+int setup_volatile_mode(
+ const char *directory,
+ VolatileMode mode,
+ uid_t uid_shift,
+ const char *selinux_apifs_context) {
+
+ switch (mode) {
+
+ case VOLATILE_YES:
+ return setup_volatile_yes(directory, uid_shift, selinux_apifs_context);
+
+ case VOLATILE_STATE:
+ return setup_volatile_state(directory, uid_shift, selinux_apifs_context);
+
+ case VOLATILE_OVERLAY:
+ return setup_volatile_overlay(directory, uid_shift, selinux_apifs_context);
+
+ default:
+ return 0;
+ }
+}
+
+/* Expects *pivot_root_new and *pivot_root_old to be initialised to allocated memory or NULL. */
+int pivot_root_parse(char **pivot_root_new, char **pivot_root_old, const char *s) {
+ _cleanup_free_ char *root_new = NULL, *root_old = NULL;
+ const char *p = s;
+ int r;
+
+ assert(pivot_root_new);
+ assert(pivot_root_old);
+
+ r = extract_first_word(&p, &root_new, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL;
+
+ if (isempty(p))
+ root_old = NULL;
+ else {
+ root_old = strdup(p);
+ if (!root_old)
+ return -ENOMEM;
+ }
+
+ if (!path_is_absolute(root_new))
+ return -EINVAL;
+ if (root_old && !path_is_absolute(root_old))
+ return -EINVAL;
+
+ free_and_replace(*pivot_root_new, root_new);
+ free_and_replace(*pivot_root_old, root_old);
+
+ return 0;
+}
+
+int setup_pivot_root(const char *directory, const char *pivot_root_new, const char *pivot_root_old) {
+ _cleanup_free_ char *directory_pivot_root_new = NULL;
+ _cleanup_free_ char *pivot_tmp_pivot_root_old = NULL;
+ char pivot_tmp[] = "/tmp/nspawn-pivot-XXXXXX";
+ bool remove_pivot_tmp = false;
+ int r;
+
+ assert(directory);
+
+ if (!pivot_root_new)
+ return 0;
+
+ /* Pivot pivot_root_new to / and the existing / to pivot_root_old.
+ * If pivot_root_old is NULL, the existing / disappears.
+ * This requires a temporary directory, pivot_tmp, which is
+ * not a child of either.
+ *
+ * This is typically used for OSTree-style containers, where the root partition contains several
+ * sysroots which could be run. Normally, one would be chosen by the bootloader and pivoted to / by
+ * initrd.
+ *
+ * For example, for an OSTree deployment, pivot_root_new
+ * would be: /ostree/deploy/$os/deploy/$checksum. Note that this
+ * code doesn’t do the /var mount which OSTree expects: use
+ * --bind +/sysroot/ostree/deploy/$os/var:/var for that.
+ *
+ * So in the OSTree case, we’ll end up with something like:
+ * - directory = /tmp/nspawn-root-123456
+ * - pivot_root_new = /ostree/deploy/os/deploy/123abc
+ * - pivot_root_old = /sysroot
+ * - directory_pivot_root_new =
+ * /tmp/nspawn-root-123456/ostree/deploy/os/deploy/123abc
+ * - pivot_tmp = /tmp/nspawn-pivot-123456
+ * - pivot_tmp_pivot_root_old = /tmp/nspawn-pivot-123456/sysroot
+ *
+ * Requires all file systems at directory and below to be mounted
+ * MS_PRIVATE or MS_SLAVE so they can be moved.
+ */
+ directory_pivot_root_new = path_join(directory, pivot_root_new);
+ if (!directory_pivot_root_new)
+ return log_oom();
+
+ /* Remount directory_pivot_root_new to make it movable. */
+ r = mount_nofollow_verbose(LOG_ERR, directory_pivot_root_new, directory_pivot_root_new, NULL, MS_BIND, NULL);
+ if (r < 0)
+ goto done;
+
+ if (pivot_root_old) {
+ if (!mkdtemp(pivot_tmp)) {
+ r = log_error_errno(errno, "Failed to create temporary directory: %m");
+ goto done;
+ }
+
+ remove_pivot_tmp = true;
+ pivot_tmp_pivot_root_old = path_join(pivot_tmp, pivot_root_old);
+ if (!pivot_tmp_pivot_root_old) {
+ r = log_oom();
+ goto done;
+ }
+
+ r = mount_nofollow_verbose(LOG_ERR, directory_pivot_root_new, pivot_tmp, NULL, MS_MOVE, NULL);
+ if (r < 0)
+ goto done;
+
+ r = mount_nofollow_verbose(LOG_ERR, directory, pivot_tmp_pivot_root_old, NULL, MS_MOVE, NULL);
+ if (r < 0)
+ goto done;
+
+ r = mount_nofollow_verbose(LOG_ERR, pivot_tmp, directory, NULL, MS_MOVE, NULL);
+ if (r < 0)
+ goto done;
+ } else {
+ r = mount_nofollow_verbose(LOG_ERR, directory_pivot_root_new, directory, NULL, MS_MOVE, NULL);
+ if (r < 0)
+ goto done;
+ }
+
+done:
+ if (remove_pivot_tmp)
+ (void) rmdir(pivot_tmp);
+
+ return r;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-30 21:08:02 +0000