/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include "alloc-util.h" #include "chase.h" #include "escape.h" #include "fd-util.h" #include "format-util.h" #include "fs-util.h" #include "label-util.h" #include "mkdir-label.h" #include "mount-util.h" #include "mountpoint-util.h" #include "namespace-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); } #define PROC_DEFAULT_MOUNT_FLAGS (MS_NOSUID|MS_NOEXEC|MS_NODEV) #define SYS_DEFAULT_MOUNT_FLAGS (MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV) 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, PROC_DEFAULT_MOUNT_FLAGS, 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=01777" NESTED_TMPFS_LIMITS, MS_NOSUID|MS_NODEV|MS_STRICTATIME, MOUNT_FATAL|MOUNT_APPLY_TMPFS_TMP|MOUNT_MKDIR }, { "tmpfs", "/sys", "tmpfs", "mode=0555" TMPFS_LIMITS_SYS, MS_NOSUID|MS_NOEXEC|MS_NODEV, MOUNT_FATAL|MOUNT_APPLY_APIVFS_NETNS|MOUNT_MKDIR }, { "sysfs", "/sys", "sysfs", NULL, SYS_DEFAULT_MOUNT_FLAGS, 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=0755" TMPFS_LIMITS_PRIVATE_DEV, MS_NOSUID|MS_STRICTATIME, MOUNT_FATAL|MOUNT_MKDIR }, { "tmpfs", "/dev/shm", "tmpfs", "mode=01777" NESTED_TMPFS_LIMITS, MS_NOSUID|MS_NODEV|MS_STRICTATIME, MOUNT_FATAL|MOUNT_MKDIR }, { "tmpfs", "/run", "tmpfs", "mode=0755" 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/os-release", NULL, NULL, MS_PRIVATE, MOUNT_FATAL }, /* Turn off propagation (we only want that for the mount propagation tunnel dir) */ { 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) */ { NULL, "/sys/fs/selinux", NULL, NULL, MS_PRIVATE, 0 }, /* Turn off propagation (we only want that for the mount propagation tunnel dir) */ #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(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 necessary * for those. */ r = chase(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(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_safe_label(dest, where, 0755, uid_shift, uid_shift, MKDIR_IGNORE_EXISTING); 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); if (chown(where, uid_shift, uid_shift) < 0) return log_error_errno(errno, "Failed to chown %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(STRV_MAKE(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(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(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_and_stat(m->destination, dest, CHASE_PREFIX_ROOT, &where, &st); 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(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=0755" 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=0755" 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=0755" 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 (!path_is_normalized(root_new)) return -EINVAL; if (root_old && (!path_is_absolute(root_old) || !path_is_normalized(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; } #define NSPAWN_PRIVATE_FULLY_VISIBLE_PROCFS "/run/host/proc" #define NSPAWN_PRIVATE_FULLY_VISIBLE_SYSFS "/run/host/sys" int pin_fully_visible_fs(void) { int r; (void) mkdir_p(NSPAWN_PRIVATE_FULLY_VISIBLE_PROCFS, 0755); (void) mkdir_p(NSPAWN_PRIVATE_FULLY_VISIBLE_SYSFS, 0755); r = mount_follow_verbose(LOG_ERR, "proc", NSPAWN_PRIVATE_FULLY_VISIBLE_PROCFS, "proc", PROC_DEFAULT_MOUNT_FLAGS, NULL); if (r < 0) return r; r = mount_follow_verbose(LOG_ERR, "sysfs", NSPAWN_PRIVATE_FULLY_VISIBLE_SYSFS, "sysfs", SYS_DEFAULT_MOUNT_FLAGS, NULL); if (r < 0) return r; return 0; } static int do_wipe_fully_visible_fs(void) { if (umount2(NSPAWN_PRIVATE_FULLY_VISIBLE_PROCFS, MNT_DETACH) < 0) return log_error_errno(errno, "Failed to unmount temporary proc: %m"); if (rmdir(NSPAWN_PRIVATE_FULLY_VISIBLE_PROCFS) < 0) return log_error_errno(errno, "Failed to remove temporary proc mountpoint: %m"); if (umount2(NSPAWN_PRIVATE_FULLY_VISIBLE_SYSFS, MNT_DETACH) < 0) return log_error_errno(errno, "Failed to unmount temporary sys: %m"); if (rmdir(NSPAWN_PRIVATE_FULLY_VISIBLE_SYSFS) < 0) return log_error_errno(errno, "Failed to remove temporary sys mountpoint: %m"); return 0; } int wipe_fully_visible_fs(int mntns_fd) { _cleanup_close_ int orig_mntns_fd = -EBADF; int r, rr; r = namespace_open(0, NULL, &orig_mntns_fd, NULL, NULL, NULL); if (r < 0) return log_error_errno(r, "Failed to pin originating mount namespace: %m"); r = namespace_enter(-EBADF, mntns_fd, -EBADF, -EBADF, -EBADF); if (r < 0) return log_error_errno(r, "Failed to enter mount namespace: %m"); rr = do_wipe_fully_visible_fs(); r = namespace_enter(-EBADF, orig_mntns_fd, -EBADF, -EBADF, -EBADF); if (r < 0) return log_error_errno(r, "Failed to enter original mount namespace: %m"); return rr; }