diff options
Diffstat (limited to 'src/nspawn/nspawn-mount.c')
| -rw-r--r-- | src/nspawn/nspawn-mount.c | 1075 |
1 files changed, 1075 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c new file mode 100644 index 0000000..a9af889 --- /dev/null +++ b/src/nspawn/nspawn-mount.c @@ -0,0 +1,1075 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#include <sys/mount.h> +#include <linux/magic.h> + +#include "alloc-util.h" +#include "escape.h" +#include "fd-util.h" +#include "fs-util.h" +#include "label.h" +#include "mkdir.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 "stat-util.h" +#include "string-util.h" +#include "strv.h" +#include "tmpfile-util.h" +#include "user-util.h" +#include "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) { + size_t 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); + } + + 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(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 bool source_path_is_valid(const char *p) { + assert(p); + + if (*p == '+') + p++; + + return path_is_absolute(p); +} + +static char *resolve_source_path(const char *dest, const char *source) { + + if (!source) + return NULL; + + if (source[0] == '+') + return prefix_root(dest, source + 1); + + return strdup(source); +} + +int custom_mount_prepare_all(const char *dest, CustomMount *l, size_t n) { + size_t i; + 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 (i = 0; i < n; i++) { + CustomMount *m = l + i; + + 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 */ + + 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 = strjoin(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); + } + + if (m->type == CUSTOM_MOUNT_OVERLAY) { + char **j; + + 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->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 { + assert(m->source); + + 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; + 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[0] == '+' ? source+1 : source); + if (!destination) + return -ENOMEM; + } + if (r == 2 && !isempty(p)) { + opts = strdup(p); + if (!opts) + return -ENOMEM; + } + + if (isempty(source)) + source = NULL; + else if (!source_path_is_valid(source)) + return -EINVAL; + + if (!path_is_absolute(destination)) + return -EINVAL; + + m = custom_mount_add(l, n, CUSTOM_MOUNT_BIND); + if (!m) + return -ENOMEM; + + 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, size_t *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 = 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 k; + + k = strv_split_extract(&lower, s, ":", EXTRACT_DONT_COALESCE_SEPARATORS); + if (k < 0) + return k; + if (k < 2) + return -EADDRNOTAVAIL; + if (k == 2) { + /* 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. */ + + if (!source_path_is_valid(lower[0]) || + !source_path_is_valid(lower[1])) + return -EINVAL; + + upper = TAKE_PTR(lower[1]); + + destination = strdup(upper[0] == '+' ? upper+1 : upper); /* take the destination without "+" prefix */ + if (!destination) + return -ENOMEM; + } else { + char **i; + + /* 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) + if (!source_path_is_valid(*i)) + return -EINVAL; + + /* If the upper directory is unspecified, then let's create it automatically as a throw-away directory + * in /var/tmp */ + if (isempty(upper)) + upper = NULL; + else if (!source_path_is_valid(upper)) + return -EINVAL; + + 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 tmpfs_patch_options( + const char *options, + uid_t uid_shift, + const char *selinux_apifs_context, + char **ret) { + + char *buf = NULL; + + if (uid_shift != UID_INVALID) { + if (asprintf(&buf, "%s%suid=" UID_FMT ",gid=" UID_FMT, + strempty(options), options ? "," : "", + uid_shift, uid_shift) < 0) + return -ENOMEM; + + options = buf; + } + +#if HAVE_SELINUX + if (selinux_apifs_context) { + char *t; + + t = strjoin(strempty(options), options ? "," : "", + "context=\"", selinux_apifs_context, "\""); + free(buf); + if (!t) + return -ENOMEM; + + buf = t; + } +#endif + + if (!buf && options) { + buf = strdup(options); + if (!buf) + return -ENOMEM; + } + *ret = buf; + + return !!buf; +} + +int mount_sysfs(const char *dest, MountSettingsMask mount_settings) { + const char *full, *top, *x; + 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 (mount_settings & MOUNT_APPLY_APIVFS_RO) + extra_flags |= MS_RDONLY; + + r = mount_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 = prefix_root(full, x); + if (!from) + return log_oom(); + + to = prefix_root(top, x); + if (!to) + return log_oom(); + + (void) mkdir(to, 0755); + + r = mount_verbose(LOG_ERR, from, to, NULL, MS_BIND, NULL); + if (r < 0) + return r; + + r = mount_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(full); + 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. + */ + x = prefix_roota(top, "/fs/cgroup"); + (void) mkdir_p(x, 0755); + + return mount_verbose(LOG_ERR, NULL, top, NULL, + MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL); +} + +static int mkdir_userns(const char *path, mode_t mode, uid_t uid_shift) { + int r; + + assert(path); + + r = mkdir_errno_wrapper(path, mode); + if (r < 0 && r != -EEXIST) + return r; + + if (uid_shift == UID_INVALID) + return 0; + + if (lchown(path, uid_shift, uid_shift) < 0) + return -errno; + + return 0; +} + +static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, uid_t uid_shift) { + const char *p, *e; + int r; + + assert(path); + + if (prefix && !path_startswith(path, prefix)) + return -ENOTDIR; + + /* create every parent directory in the path, except the last component */ + p = path + strspn(path, "/"); + for (;;) { + char t[strlen(path) + 1]; + + e = p + strcspn(p, "/"); + p = e + strspn(e, "/"); + + /* Is this the last component? If so, then we're done */ + if (*p == 0) + break; + + memcpy(t, path, e - path); + t[e-path] = 0; + + if (prefix && path_startswith(prefix, t)) + continue; + + r = mkdir_userns(t, mode, uid_shift); + if (r < 0) + return r; + } + + return mkdir_userns(path, mode, uid_shift); +} + +int mount_all(const char *dest, + MountSettingsMask mount_settings, + uid_t uid_shift, + const char *selinux_apifs_context) { + +#define PROC_INACCESSIBLE(path) \ + { NULL, (path), NULL, NULL, MS_BIND, \ + MOUNT_IN_USERNS|MOUNT_APPLY_APIVFS_RO|MOUNT_INACCESSIBLE_REG }, /* 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 }, + + { "/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("/proc/kallsyms"), + PROC_INACCESSIBLE("/proc/kcore"), + PROC_INACCESSIBLE("/proc/keys"), + PROC_INACCESSIBLE("/proc/sysrq-trigger"), + PROC_INACCESSIBLE("/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"), + + /* Then we list outer child mounts (i.e. mounts applied *before* entering user namespacing) */ + { "tmpfs", "/tmp", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME, + MOUNT_FATAL|MOUNT_APPLY_TMPFS_TMP }, + { "tmpfs", "/sys", "tmpfs", "mode=555", MS_NOSUID|MS_NOEXEC|MS_NODEV, + MOUNT_FATAL|MOUNT_APPLY_APIVFS_NETNS }, + { "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV, + MOUNT_FATAL|MOUNT_APPLY_APIVFS_RO }, /* skipped if above was mounted */ + { "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, + MOUNT_FATAL }, /* skipped if above was mounted */ + { "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME, + MOUNT_FATAL }, + { "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME, + MOUNT_FATAL }, + { "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV|MS_STRICTATIME, + MOUNT_FATAL }, + { "mqueue", "/dev/mqueue", "mqueue", NULL, 0, + MOUNT_FATAL }, + +#if HAVE_SELINUX + { "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND, + 0 }, /* Bind mount first */ + { NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT, + 0 }, /* Then, make it r/o */ +#endif + }; + + _cleanup_(unlink_and_freep) char *inaccessible = NULL; + bool use_userns = (mount_settings & MOUNT_USE_USERNS); + bool netns = (mount_settings & MOUNT_APPLY_APIVFS_NETNS); + bool ro = (mount_settings & MOUNT_APPLY_APIVFS_RO); + bool in_userns = (mount_settings & MOUNT_IN_USERNS); + bool tmpfs_tmp = (mount_settings & MOUNT_APPLY_TMPFS_TMP); + size_t k; + int r; + + for (k = 0; k < ELEMENTSOF(mount_table); k++) { + _cleanup_free_ char *where = NULL, *options = NULL; + const char *o, *what; + bool fatal = (mount_table[k].mount_settings & MOUNT_FATAL); + + if (in_userns != (bool)(mount_table[k].mount_settings & MOUNT_IN_USERNS)) + continue; + + if (!netns && (bool)(mount_table[k].mount_settings & MOUNT_APPLY_APIVFS_NETNS)) + continue; + + if (!ro && (bool)(mount_table[k].mount_settings & MOUNT_APPLY_APIVFS_RO)) + continue; + + if (!tmpfs_tmp && (bool)(mount_table[k].mount_settings & MOUNT_APPLY_TMPFS_TMP)) + continue; + + r = chase_symlinks(mount_table[k].where, dest, CHASE_NONEXISTENT|CHASE_PREFIX_ROOT, &where); + if (r < 0) + return log_error_errno(r, "Failed to resolve %s/%s: %m", dest, mount_table[k].where); + + if (mount_table[k].mount_settings & MOUNT_INACCESSIBLE_REG) { + + if (!inaccessible) { + _cleanup_free_ char *np = NULL; + + r = tempfn_random_child(NULL, "inaccessible", &np); + if (r < 0) + return log_error_errno(r, "Failed to generate inaccessible file node path: %m"); + + r = touch_file(np, false, USEC_INFINITY, UID_INVALID, GID_INVALID, 0000); + if (r < 0) + return log_error_errno(r, "Failed to create inaccessible file node '%s': %m", np); + + inaccessible = TAKE_PTR(np); + } + + what = inaccessible; + } else + what = 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); + + /* Skip this entry if it is not a remount. */ + if (what && r > 0) + continue; + + r = mkdir_userns_p(dest, where, 0755, (use_userns && !in_userns) ? uid_shift : UID_INVALID); + 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; + } + + 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; + } + + r = mount_verbose(fatal ? LOG_ERR : LOG_DEBUG, + what, + where, + mount_table[k].type, + mount_table[k].flags, + o); + if (r < 0 && fatal) + return r; + } + + return 0; +} + +static int mount_bind(const char *dest, CustomMount *m) { + + _cleanup_free_ char *where = NULL; + struct stat source_st, dest_st; + int r; + + assert(dest); + assert(m); + + 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); + 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_verbose(LOG_ERR, m->source, where, NULL, MS_BIND | MS_REC, m->options); + if (r < 0) + return r; + + if (m->read_only) { + r = bind_remount_recursive(where, true, NULL); + 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 *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); + 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_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); + 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_verbose(LOG_ERR, "overlay", where, "overlay", m->read_only ? MS_RDONLY : 0, options); +} + +int mount_custom( + const char *dest, + CustomMount *mounts, size_t n, + bool userns, uid_t uid_shift, uid_t uid_range, + const char *selinux_apifs_context) { + + size_t 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; +} + +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, 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"; + 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_verbose(LOG_ERR, "tmpfs", p, "tmpfs", MS_STRICTATIME, options); +} + +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, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf); + if (r < 0) + return log_oom(); + if (r > 0) + options = buf; + + r = mount_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_verbose(LOG_ERR, f, t, NULL, MS_BIND|MS_REC, NULL); + if (r < 0) + goto fail; + + bind_mounted = true; + + r = bind_remount_recursive(t, true, NULL); + if (r < 0) { + log_error_errno(r, "Failed to remount %s read-only: %m", t); + goto fail; + } + + r = mount_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(t); + + if (tmpfs_mounted) + (void) umount_verbose(template); + (void) rmdir(template); + return r; +} + +/* 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 initramfs. + * + * 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 = prefix_root(directory, pivot_root_new); + + /* Remount directory_pivot_root_new to make it movable. */ + r = mount_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 = prefix_root(pivot_tmp, pivot_root_old); + + r = mount_verbose(LOG_ERR, directory_pivot_root_new, pivot_tmp, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + + r = mount_verbose(LOG_ERR, directory, pivot_tmp_pivot_root_old, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + + r = mount_verbose(LOG_ERR, pivot_tmp, directory, NULL, MS_MOVE, NULL); + if (r < 0) + goto done; + } else { + r = mount_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; +} |