/* SPDX-License-Identifier: LGPL-2.1+ */ /*** This file is part of systemd. Copyright 2015 Lennart Poettering ***/ #include #include #include "alloc-util.h" #include "escape.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "label.h" #include "mkdir.h" #include "mount-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 "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 void *a, const void *b) { const CustomMount *x = a, *y = b; int r; r = path_compare(x->destination, y->destination); if (r != 0) return r; if (x->type < y->type) return -1; if (x->type > y->type) return 1; return 0; } 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 */ qsort_safe(l, n, sizeof(CustomMount), 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; } static int tmpfs_patch_options( const char *options, bool userns, uid_t uid_shift, uid_t uid_range, bool patch_ids, const char *selinux_apifs_context, char **ret) { char *buf = NULL; if ((userns && uid_shift != 0) || patch_ids) { assert(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. */ if (cg_ns_supported()) { 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, MountSettingsMask mask, uid_t uid_shift) { int r; assert(path); r = mkdir_errno_wrapper(path, mode); if (r < 0 && r != -EEXIST) return r; if ((mask & MOUNT_USE_USERNS) == 0) return 0; if (mask & MOUNT_IN_USERNS) 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, MountSettingsMask mask, 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, mask, uid_shift); if (r < 0) return r; } return mkdir_userns(path, mode, mask, uid_shift); } int mount_all(const char *dest, MountSettingsMask mount_settings, uid_t uid_shift, uid_t uid_range, 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 }, { "tmpfs", "/sys", "tmpfs", "mode=755", 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 }, #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); 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; 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, mount_settings, uid_shift); 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")) { if (in_userns) r = tmpfs_patch_options(o, use_userns, 0, uid_range, true, selinux_apifs_context, &options); else r = tmpfs_patch_options(o, use_userns, uid_shift, uid_range, false, 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)) { log_error("Cannot bind mount directory %s on file %s.", m->source, where); return -EINVAL; } if (!S_ISDIR(source_st.st_mode) && S_ISDIR(dest_st.st_mode)) { log_error("Cannot bind mount file %s on directory %s.", m->source, where); return -EINVAL; } } else { /* 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, userns, uid_shift, uid_range, false, 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; } /* Retrieve existing subsystems. This function is called in a new cgroup * namespace. */ static int get_process_controllers(Set **ret) { _cleanup_set_free_free_ Set *controllers = NULL; _cleanup_fclose_ FILE *f = NULL; int r; assert(ret); controllers = set_new(&string_hash_ops); if (!controllers) return -ENOMEM; f = fopen("/proc/self/cgroup", "re"); if (!f) return errno == ENOENT ? -ESRCH : -errno; for (;;) { _cleanup_free_ char *line = NULL; char *e, *l; r = read_line(f, LONG_LINE_MAX, &line); if (r < 0) return r; if (r == 0) break; l = strchr(line, ':'); if (!l) continue; l++; e = strchr(l, ':'); if (!e) continue; *e = 0; if (STR_IN_SET(l, "", "name=systemd", "name=unified")) continue; r = set_put_strdup(controllers, l); if (r < 0) return r; } *ret = TAKE_PTR(controllers); return 0; } static int mount_legacy_cgroup_hierarchy( const char *dest, const char *controller, const char *hierarchy, bool read_only) { const char *to, *fstype, *opts; int r; to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy); r = path_is_mount_point(to, dest, 0); if (r < 0 && r != -ENOENT) return log_error_errno(r, "Failed to determine if %s is mounted already: %m", to); if (r > 0) return 0; mkdir_p(to, 0755); /* The superblock mount options of the mount point need to be * identical to the hosts', and hence writable... */ if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_HYBRID)) { fstype = "cgroup2"; opts = NULL; } else if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_LEGACY)) { fstype = "cgroup"; opts = "none,name=systemd,xattr"; } else { fstype = "cgroup"; opts = controller; } r = mount_verbose(LOG_ERR, "cgroup", to, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts); if (r < 0) return r; /* ... hence let's only make the bind mount read-only, not the superblock. */ if (read_only) { r = mount_verbose(LOG_ERR, NULL, to, NULL, MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL); if (r < 0) return r; } return 1; } /* Mount a legacy cgroup hierarchy when cgroup namespaces are supported. */ static int mount_legacy_cgns_supported( const char *dest, CGroupUnified unified_requested, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context) { _cleanup_set_free_free_ Set *controllers = NULL; const char *cgroup_root = "/sys/fs/cgroup", *c; int r; (void) mkdir_p(cgroup_root, 0755); /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */ r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW); if (r < 0) return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m"); if (r == 0) { _cleanup_free_ char *options = NULL; /* When cgroup namespaces are enabled and user namespaces are * used then the mount of the cgroupfs is done *inside* the new * user namespace. We're root in the new user namespace and the * kernel will happily translate our uid/gid to the correct * uid/gid as seen from e.g. /proc/1/mountinfo. So we simply * pass uid 0 and not uid_shift to tmpfs_patch_options(). */ r = tmpfs_patch_options("mode=755", userns, 0, uid_range, true, selinux_apifs_context, &options); if (r < 0) return log_oom(); r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options); if (r < 0) return r; } r = cg_all_unified(); if (r < 0) return r; if (r > 0) goto skip_controllers; r = get_process_controllers(&controllers); if (r < 0) return log_error_errno(r, "Failed to determine cgroup controllers: %m"); for (;;) { _cleanup_free_ const char *controller = NULL; controller = set_steal_first(controllers); if (!controller) break; r = mount_legacy_cgroup_hierarchy("", controller, controller, !userns); if (r < 0) return r; /* When multiple hierarchies are co-mounted, make their * constituting individual hierarchies a symlink to the * co-mount. */ c = controller; for (;;) { _cleanup_free_ char *target = NULL, *tok = NULL; r = extract_first_word(&c, &tok, ",", 0); if (r < 0) return log_error_errno(r, "Failed to extract co-mounted cgroup controller: %m"); if (r == 0) break; if (streq(controller, tok)) break; target = prefix_root("/sys/fs/cgroup/", tok); if (!target) return log_oom(); r = symlink_idempotent(controller, target); if (r == -EINVAL) return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m"); if (r < 0) return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m"); } } skip_controllers: if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) { r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false); if (r < 0) return r; } r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false); if (r < 0) return r; if (!userns) return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL, MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755"); return 0; } /* Mount legacy cgroup hierarchy when cgroup namespaces are unsupported. */ static int mount_legacy_cgns_unsupported( const char *dest, CGroupUnified unified_requested, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context) { _cleanup_set_free_free_ Set *controllers = NULL; const char *cgroup_root; int r; cgroup_root = prefix_roota(dest, "/sys/fs/cgroup"); (void) mkdir_p(cgroup_root, 0755); /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */ r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW); if (r < 0) return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m"); if (r == 0) { _cleanup_free_ char *options = NULL; r = tmpfs_patch_options("mode=755", userns, uid_shift, uid_range, false, selinux_apifs_context, &options); if (r < 0) return log_oom(); r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options); if (r < 0) return r; } r = cg_all_unified(); if (r < 0) return r; if (r > 0) goto skip_controllers; r = cg_kernel_controllers(&controllers); if (r < 0) return log_error_errno(r, "Failed to determine cgroup controllers: %m"); for (;;) { _cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL; controller = set_steal_first(controllers); if (!controller) break; origin = prefix_root("/sys/fs/cgroup/", controller); if (!origin) return log_oom(); r = readlink_malloc(origin, &combined); if (r == -EINVAL) { /* Not a symbolic link, but directly a single cgroup hierarchy */ r = mount_legacy_cgroup_hierarchy(dest, controller, controller, true); if (r < 0) return r; } else if (r < 0) return log_error_errno(r, "Failed to read link %s: %m", origin); else { _cleanup_free_ char *target = NULL; target = prefix_root(dest, origin); if (!target) return log_oom(); /* A symbolic link, a combination of controllers in one hierarchy */ if (!filename_is_valid(combined)) { log_warning("Ignoring invalid combined hierarchy %s.", combined); continue; } r = mount_legacy_cgroup_hierarchy(dest, combined, combined, true); if (r < 0) return r; r = symlink_idempotent(combined, target); if (r == -EINVAL) return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m"); if (r < 0) return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m"); } } skip_controllers: if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) { r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false); if (r < 0) return r; } r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false); if (r < 0) return r; return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL, MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755"); } static int mount_unified_cgroups(const char *dest) { const char *p; int r; assert(dest); p = prefix_roota(dest, "/sys/fs/cgroup"); (void) mkdir_p(p, 0755); r = path_is_mount_point(p, dest, AT_SYMLINK_FOLLOW); if (r < 0) return log_error_errno(r, "Failed to determine if %s is mounted already: %m", p); if (r > 0) { p = prefix_roota(dest, "/sys/fs/cgroup/cgroup.procs"); if (access(p, F_OK) >= 0) return 0; if (errno != ENOENT) return log_error_errno(errno, "Failed to determine if mount point %s contains the unified cgroup hierarchy: %m", p); log_error("%s is already mounted but not a unified cgroup hierarchy. Refusing.", p); return -EINVAL; } return mount_verbose(LOG_ERR, "cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL); } int mount_cgroups( const char *dest, CGroupUnified unified_requested, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context, bool use_cgns) { if (unified_requested >= CGROUP_UNIFIED_ALL) return mount_unified_cgroups(dest); if (use_cgns) return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context); return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context); } static int mount_systemd_cgroup_writable_one(const char *root, const char *own) { int r; assert(root); assert(own); /* Make our own cgroup a (writable) bind mount */ r = mount_verbose(LOG_ERR, own, own, NULL, MS_BIND, NULL); if (r < 0) return r; /* And then remount the systemd cgroup root read-only */ return mount_verbose(LOG_ERR, NULL, root, NULL, MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL); } int mount_systemd_cgroup_writable( const char *dest, CGroupUnified unified_requested) { _cleanup_free_ char *own_cgroup_path = NULL; const char *root, *own; int r; assert(dest); r = cg_pid_get_path(NULL, 0, &own_cgroup_path); if (r < 0) return log_error_errno(r, "Failed to determine our own cgroup path: %m"); /* If we are living in the top-level, then there's nothing to do... */ if (path_equal(own_cgroup_path, "/")) return 0; if (unified_requested >= CGROUP_UNIFIED_ALL) { root = prefix_roota(dest, "/sys/fs/cgroup"); own = strjoina(root, own_cgroup_path); } else { if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) { root = prefix_roota(dest, "/sys/fs/cgroup/unified"); own = strjoina(root, own_cgroup_path); r = mount_systemd_cgroup_writable_one(root, own); if (r < 0) return r; } root = prefix_roota(dest, "/sys/fs/cgroup/systemd"); own = strjoina(root, own_cgroup_path); } return mount_systemd_cgroup_writable_one(root, own); } 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, userns, uid_shift, uid_range, false, 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, userns, uid_shift, uid_range, false, 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; }