/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include #include #include #include #if WANT_LINUX_FS_H #include #endif #include "alloc-util.h" #include "base-filesystem.h" #include "chase.h" #include "dev-setup.h" #include "devnum-util.h" #include "env-util.h" #include "escape.h" #include "extension-util.h" #include "fd-util.h" #include "format-util.h" #include "glyph-util.h" #include "label-util.h" #include "list.h" #include "lock-util.h" #include "loop-util.h" #include "loopback-setup.h" #include "missing_syscall.h" #include "mkdir-label.h" #include "mount-util.h" #include "mountpoint-util.h" #include "namespace-util.h" #include "namespace.h" #include "nsflags.h" #include "nulstr-util.h" #include "os-util.h" #include "path-util.h" #include "selinux-util.h" #include "socket-util.h" #include "sort-util.h" #include "stat-util.h" #include "string-table.h" #include "string-util.h" #include "strv.h" #include "tmpfile-util.h" #include "umask-util.h" #include "user-util.h" #include "vpick.h" #define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC) typedef enum MountMode { /* This is ordered by priority! */ MOUNT_INACCESSIBLE, MOUNT_OVERLAY, MOUNT_IMAGE, MOUNT_BIND, MOUNT_BIND_RECURSIVE, MOUNT_PRIVATE_TMP, MOUNT_PRIVATE_TMP_READ_ONLY, MOUNT_PRIVATE_DEV, MOUNT_BIND_DEV, MOUNT_EMPTY_DIR, MOUNT_PRIVATE_SYSFS, MOUNT_BIND_SYSFS, MOUNT_PROCFS, MOUNT_READ_ONLY, MOUNT_READ_WRITE, MOUNT_NOEXEC, MOUNT_EXEC, MOUNT_TMPFS, MOUNT_RUN, MOUNT_EXTENSION_DIRECTORY, /* Bind-mounted outside the root directory, and used by subsequent mounts */ MOUNT_EXTENSION_IMAGE, /* Mounted outside the root directory, and used by subsequent mounts */ MOUNT_MQUEUEFS, MOUNT_READ_WRITE_IMPLICIT, /* Should have the lowest priority. */ _MOUNT_MODE_MAX, _MOUNT_MODE_INVALID = -EINVAL, } MountMode; typedef enum MountEntryState { MOUNT_PENDING, MOUNT_APPLIED, MOUNT_SKIPPED, _MOUNT_ENTRY_STATE_MAX, _MOUNT_ENTRY_STATE_INVALID = -EINVAL, } MountEntryState; typedef struct MountEntry { const char *path_const; /* Memory allocated on stack or static */ MountMode mode; bool ignore:1; /* Ignore if path does not exist? */ bool has_prefix:1; /* Already is prefixed by the root dir? */ bool read_only:1; /* Shall this mount point be read-only? */ bool nosuid:1; /* Shall set MS_NOSUID on the mount itself */ bool noexec:1; /* Shall set MS_NOEXEC on the mount itself */ bool exec:1; /* Shall clear MS_NOEXEC on the mount itself */ MountEntryState state; /* Whether it was already processed or skipped */ char *path_malloc; /* Use this instead of 'path_const' if we had to allocate memory */ const char *unprefixed_path_const; /* If the path was amended with a prefix, these will save the original */ char *unprefixed_path_malloc; const char *source_const; /* The source path, for bind mounts or images */ char *source_malloc; const char *options_const;/* Mount options for tmpfs */ char *options_malloc; unsigned long flags; /* Mount flags used by EMPTY_DIR and TMPFS. Do not include MS_RDONLY here, but please use read_only. */ unsigned n_followed; LIST_HEAD(MountOptions, image_options_const); char **overlay_layers; } MountEntry; typedef struct MountList { MountEntry *mounts; size_t n_mounts; } MountList; /* If MountAPIVFS= is used, let's mount /sys, /proc, /dev and /run into the it, but only as a fallback if the user hasn't mounted * something there already. These mounts are hence overridden by any other explicitly configured mounts. */ static const MountEntry apivfs_table[] = { { "/proc", MOUNT_PROCFS, false }, { "/dev", MOUNT_BIND_DEV, false }, { "/sys", MOUNT_BIND_SYSFS, false }, { "/run", MOUNT_RUN, false, .options_const = "mode=0755" TMPFS_LIMITS_RUN, .flags = MS_NOSUID|MS_NODEV|MS_STRICTATIME }, }; /* ProtectKernelTunables= option and the related filesystem APIs */ static const MountEntry protect_kernel_tunables_proc_table[] = { { "/proc/acpi", MOUNT_READ_ONLY, true }, { "/proc/apm", MOUNT_READ_ONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */ { "/proc/asound", MOUNT_READ_ONLY, true }, { "/proc/bus", MOUNT_READ_ONLY, true }, { "/proc/fs", MOUNT_READ_ONLY, true }, { "/proc/irq", MOUNT_READ_ONLY, true }, { "/proc/kallsyms", MOUNT_INACCESSIBLE, true }, { "/proc/kcore", MOUNT_INACCESSIBLE, true }, { "/proc/latency_stats", MOUNT_READ_ONLY, true }, { "/proc/mtrr", MOUNT_READ_ONLY, true }, { "/proc/scsi", MOUNT_READ_ONLY, true }, { "/proc/sys", MOUNT_READ_ONLY, true }, { "/proc/sysrq-trigger", MOUNT_READ_ONLY, true }, { "/proc/timer_stats", MOUNT_READ_ONLY, true }, }; static const MountEntry protect_kernel_tunables_sys_table[] = { { "/sys", MOUNT_READ_ONLY, false }, { "/sys/fs/bpf", MOUNT_READ_ONLY, true }, { "/sys/fs/cgroup", MOUNT_READ_WRITE_IMPLICIT, false }, /* READ_ONLY is set by ProtectControlGroups= option */ { "/sys/fs/selinux", MOUNT_READ_WRITE_IMPLICIT, true }, { "/sys/kernel/debug", MOUNT_READ_ONLY, true }, { "/sys/kernel/tracing", MOUNT_READ_ONLY, true }, }; /* ProtectKernelModules= option */ static const MountEntry protect_kernel_modules_table[] = { { "/usr/lib/modules", MOUNT_INACCESSIBLE, true }, }; /* ProtectKernelLogs= option */ static const MountEntry protect_kernel_logs_proc_table[] = { { "/proc/kmsg", MOUNT_INACCESSIBLE, true }, }; static const MountEntry protect_kernel_logs_dev_table[] = { { "/dev/kmsg", MOUNT_INACCESSIBLE, true }, }; /* * ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of * system should be protected by ProtectSystem= */ static const MountEntry protect_home_read_only_table[] = { { "/home", MOUNT_READ_ONLY, true }, { "/run/user", MOUNT_READ_ONLY, true }, { "/root", MOUNT_READ_ONLY, true }, }; /* ProtectHome=tmpfs table */ static const MountEntry protect_home_tmpfs_table[] = { { "/home", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME }, { "/run/user", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME }, { "/root", MOUNT_TMPFS, true, .read_only = true, .options_const = "mode=0700" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME }, }; /* ProtectHome=yes table */ static const MountEntry protect_home_yes_table[] = { { "/home", MOUNT_INACCESSIBLE, true }, { "/run/user", MOUNT_INACCESSIBLE, true }, { "/root", MOUNT_INACCESSIBLE, true }, }; /* ProtectSystem=yes table */ static const MountEntry protect_system_yes_table[] = { { "/usr", MOUNT_READ_ONLY, false }, { "/boot", MOUNT_READ_ONLY, true }, { "/efi", MOUNT_READ_ONLY, true }, }; /* ProtectSystem=full includes ProtectSystem=yes */ static const MountEntry protect_system_full_table[] = { { "/usr", MOUNT_READ_ONLY, false }, { "/boot", MOUNT_READ_ONLY, true }, { "/efi", MOUNT_READ_ONLY, true }, { "/etc", MOUNT_READ_ONLY, false }, }; /* ProtectSystem=strict table. In this strict mode, we mount everything read-only, except for /proc, /dev, * /sys which are the kernel API VFS, which are left writable, but PrivateDevices= + ProtectKernelTunables= * protect those, and these options should be fully orthogonal. (And of course /home and friends are also * left writable, as ProtectHome= shall manage those, orthogonally). */ static const MountEntry protect_system_strict_table[] = { { "/", MOUNT_READ_ONLY, false }, { "/proc", MOUNT_READ_WRITE_IMPLICIT, false }, /* ProtectKernelTunables= */ { "/sys", MOUNT_READ_WRITE_IMPLICIT, false }, /* ProtectKernelTunables= */ { "/dev", MOUNT_READ_WRITE_IMPLICIT, false }, /* PrivateDevices= */ { "/home", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */ { "/run/user", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */ { "/root", MOUNT_READ_WRITE_IMPLICIT, true }, /* ProtectHome= */ }; /* ProtectHostname=yes able */ static const MountEntry protect_hostname_table[] = { { "/proc/sys/kernel/hostname", MOUNT_READ_ONLY, false }, { "/proc/sys/kernel/domainname", MOUNT_READ_ONLY, false }, }; static const char * const mount_mode_table[_MOUNT_MODE_MAX] = { [MOUNT_INACCESSIBLE] = "inaccessible", [MOUNT_OVERLAY] = "overlay", [MOUNT_IMAGE] = "image", [MOUNT_BIND] = "bind", [MOUNT_BIND_RECURSIVE] = "bind-recursive", [MOUNT_PRIVATE_TMP] = "private-tmp", [MOUNT_PRIVATE_TMP_READ_ONLY] = "private-tmp-read-only", [MOUNT_PRIVATE_DEV] = "private-dev", [MOUNT_BIND_DEV] = "bind-dev", [MOUNT_EMPTY_DIR] = "empty-dir", [MOUNT_PRIVATE_SYSFS] = "private-sysfs", [MOUNT_BIND_SYSFS] = "bind-sysfs", [MOUNT_PROCFS] = "procfs", [MOUNT_READ_ONLY] = "read-only", [MOUNT_READ_WRITE] = "read-write", [MOUNT_NOEXEC] = "noexec", [MOUNT_EXEC] = "exec", [MOUNT_TMPFS] = "tmpfs", [MOUNT_RUN] = "run", [MOUNT_EXTENSION_DIRECTORY] = "extension-directory", [MOUNT_EXTENSION_IMAGE] = "extension-image", [MOUNT_MQUEUEFS] = "mqueuefs", [MOUNT_READ_WRITE_IMPLICIT] = "read-write-implicit", }; /* Helper struct for naming simplicity and reusability */ static const struct { const char *level_env; const char *level_env_print; } image_class_info[_IMAGE_CLASS_MAX] = { [IMAGE_SYSEXT] = { .level_env = "SYSEXT_LEVEL", .level_env_print = " SYSEXT_LEVEL=", }, [IMAGE_CONFEXT] = { .level_env = "CONFEXT_LEVEL", .level_env_print = " CONFEXT_LEVEL=", } }; DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(mount_mode, MountMode); static const char *mount_entry_path(const MountEntry *p) { assert(p); /* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that, * otherwise the stack/static ->path field is returned. */ return p->path_malloc ?: p->path_const; } static const char *mount_entry_unprefixed_path(const MountEntry *p) { assert(p); /* Returns the unprefixed path (ie: before prefix_where_needed() ran), if any */ return p->unprefixed_path_malloc ?: p->unprefixed_path_const ?: mount_entry_path(p); } static void mount_entry_consume_prefix(MountEntry *p, char *new_path) { assert(p); assert(p->path_malloc || p->path_const); assert(new_path); /* Saves current path in unprefixed_ variable, and takes over new_path */ free_and_replace(p->unprefixed_path_malloc, p->path_malloc); /* If we didn't have a path on the heap, then it's a static one */ if (!p->unprefixed_path_malloc) p->unprefixed_path_const = p->path_const; p->path_malloc = new_path; p->has_prefix = true; } static bool mount_entry_read_only(const MountEntry *p) { assert(p); return p->read_only || IN_SET(p->mode, MOUNT_READ_ONLY, MOUNT_INACCESSIBLE, MOUNT_PRIVATE_TMP_READ_ONLY); } static bool mount_entry_noexec(const MountEntry *p) { assert(p); return p->noexec || IN_SET(p->mode, MOUNT_NOEXEC, MOUNT_INACCESSIBLE, MOUNT_PRIVATE_SYSFS, MOUNT_BIND_SYSFS, MOUNT_PROCFS); } static bool mount_entry_exec(const MountEntry *p) { assert(p); return p->exec || p->mode == MOUNT_EXEC; } static const char *mount_entry_source(const MountEntry *p) { assert(p); return p->source_malloc ?: p->source_const; } static const char *mount_entry_options(const MountEntry *p) { assert(p); return p->options_malloc ?: p->options_const; } static void mount_entry_done(MountEntry *p) { assert(p); p->path_malloc = mfree(p->path_malloc); p->unprefixed_path_malloc = mfree(p->unprefixed_path_malloc); p->source_malloc = mfree(p->source_malloc); p->options_malloc = mfree(p->options_malloc); p->overlay_layers = strv_free(p->overlay_layers); } static void mount_list_done(MountList *ml) { assert(ml); FOREACH_ARRAY(m, ml->mounts, ml->n_mounts) mount_entry_done(m); ml->mounts = mfree(ml->mounts); ml->n_mounts = 0; } static MountEntry *mount_list_extend(MountList *ml) { assert(ml); if (!GREEDY_REALLOC0(ml->mounts, ml->n_mounts+1)) return NULL; return ml->mounts + ml->n_mounts++; } static int append_access_mounts(MountList *ml, char **strv, MountMode mode, bool forcibly_require_prefix) { assert(ml); /* Adds a list of user-supplied READ_WRITE/READ_WRITE_IMPLICIT/READ_ONLY/INACCESSIBLE entries */ STRV_FOREACH(i, strv) { bool ignore = false, needs_prefix = false; const char *e = *i; /* Look for any prefixes */ if (startswith(e, "-")) { e++; ignore = true; } if (startswith(e, "+")) { e++; needs_prefix = true; } if (!path_is_absolute(e)) return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Path is not absolute: %s", e); MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = e, .mode = mode, .ignore = ignore, .has_prefix = !needs_prefix && !forcibly_require_prefix, }; } return 0; } static int append_empty_dir_mounts(MountList *ml, char **strv) { assert(ml); /* Adds tmpfs mounts to provide readable but empty directories. This is primarily used to implement the * "/private/" boundary directories for DynamicUser=1. */ STRV_FOREACH(i, strv) { MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = *i, .mode = MOUNT_EMPTY_DIR, .ignore = false, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, }; } return 0; } static int append_bind_mounts(MountList *ml, const BindMount *binds, size_t n) { assert(ml); assert(binds || n == 0); FOREACH_ARRAY(b, binds, n) { MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = b->destination, .mode = b->recursive ? MOUNT_BIND_RECURSIVE : MOUNT_BIND, .read_only = b->read_only, .nosuid = b->nosuid, .source_const = b->source, .ignore = b->ignore_enoent, }; } return 0; } static int append_mount_images(MountList *ml, const MountImage *mount_images, size_t n) { assert(ml); assert(mount_images || n == 0); FOREACH_ARRAY(m, mount_images, n) { MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = m->destination, .mode = MOUNT_IMAGE, .source_const = m->source, .image_options_const = m->mount_options, .ignore = m->ignore_enoent, }; } return 0; } static int append_extensions( MountList *ml, const char *root, const char *extension_dir, char **hierarchies, const MountImage *mount_images, size_t n, char **extension_directories) { char ***overlays = NULL; size_t n_overlays = 0; int r; assert(ml); if (n == 0 && strv_isempty(extension_directories)) return 0; assert(extension_dir); n_overlays = strv_length(hierarchies); if (n_overlays == 0) return 0; /* Prepare a list of overlays, that will have as each element a strv containing all the layers that * will later be concatenated as a lowerdir= parameter for the mount operation. * The overlays vector will have the same number of elements and will correspond to the * hierarchies vector, so they can be iterated upon together. */ overlays = new0(char**, n_overlays); if (!overlays) return -ENOMEM; CLEANUP_ARRAY(overlays, n_overlays, strv_free_many); /* First, prepare a mount for each image, but these won't be visible to the unit, instead * they will be mounted in our propagate directory, and used as a source for the overlay. */ for (size_t i = 0; i < n; i++) { _cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL; _cleanup_free_ char *mount_point = NULL; const MountImage *m = mount_images + i; r = path_pick(/* toplevel_path= */ NULL, /* toplevel_fd= */ AT_FDCWD, m->source, &pick_filter_image_raw, PICK_ARCHITECTURE|PICK_TRIES, &result); if (r < 0) return r; if (!result.path) return log_debug_errno( SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", m->source); if (asprintf(&mount_point, "%s/%zu", extension_dir, i) < 0) return -ENOMEM; for (size_t j = 0; hierarchies && hierarchies[j]; ++j) { char *prefixed_hierarchy = path_join(mount_point, hierarchies[j]); if (!prefixed_hierarchy) return -ENOMEM; r = strv_consume(&overlays[j], TAKE_PTR(prefixed_hierarchy)); if (r < 0) return r; } MountEntry *me = mount_list_extend(ml); if (!me) return -ENOMEM; *me = (MountEntry) { .path_malloc = TAKE_PTR(mount_point), .image_options_const = m->mount_options, .ignore = m->ignore_enoent, .source_malloc = TAKE_PTR(result.path), .mode = MOUNT_EXTENSION_IMAGE, .has_prefix = true, }; } /* Secondly, extend the lowerdir= parameters with each ExtensionDirectory. * Bind mount them in the same location as the ExtensionImages, so that we * can check that they are valid trees (extension-release.d). */ STRV_FOREACH(extension_directory, extension_directories) { _cleanup_(pick_result_done) PickResult result = PICK_RESULT_NULL; _cleanup_free_ char *mount_point = NULL; const char *e = *extension_directory; bool ignore_enoent = false; /* Pick up the counter where the ExtensionImages left it. */ if (asprintf(&mount_point, "%s/%zu", extension_dir, n++) < 0) return -ENOMEM; /* Look for any prefixes */ if (startswith(e, "-")) { e++; ignore_enoent = true; } /* Ignore this for now */ if (startswith(e, "+")) e++; r = path_pick(/* toplevel_path= */ NULL, /* toplevel_fd= */ AT_FDCWD, e, &pick_filter_image_dir, PICK_ARCHITECTURE|PICK_TRIES, &result); if (r < 0) return r; if (!result.path) return log_debug_errno( SYNTHETIC_ERRNO(ENOENT), "No matching entry in .v/ directory %s found.", e); for (size_t j = 0; hierarchies && hierarchies[j]; ++j) { char *prefixed_hierarchy = path_join(mount_point, hierarchies[j]); if (!prefixed_hierarchy) return -ENOMEM; r = strv_consume(&overlays[j], TAKE_PTR(prefixed_hierarchy)); if (r < 0) return r; } MountEntry *me = mount_list_extend(ml); if (!me) return -ENOMEM; *me = (MountEntry) { .path_malloc = TAKE_PTR(mount_point), .source_malloc = TAKE_PTR(result.path), .mode = MOUNT_EXTENSION_DIRECTORY, .ignore = ignore_enoent, .has_prefix = true, .read_only = true, }; } /* Then, for each hierarchy, prepare an overlay with the list of lowerdir= strings * set up earlier. */ for (size_t i = 0; hierarchies && hierarchies[i]; ++i) { _cleanup_free_ char *prefixed_hierarchy = NULL; prefixed_hierarchy = path_join(root, hierarchies[i]); if (!prefixed_hierarchy) return -ENOMEM; MountEntry *me = mount_list_extend(ml); if (!me) return -ENOMEM; *me = (MountEntry) { .path_malloc = TAKE_PTR(prefixed_hierarchy), .overlay_layers = TAKE_PTR(overlays[i]), .mode = MOUNT_OVERLAY, .has_prefix = true, .ignore = true, /* If the source image doesn't set the ignore bit it will fail earlier. */ }; } return 0; } static int append_tmpfs_mounts(MountList *ml, const TemporaryFileSystem *tmpfs, size_t n) { assert(ml); assert(tmpfs || n == 0); FOREACH_ARRAY(t, tmpfs, n) { _cleanup_free_ char *o = NULL, *str = NULL; unsigned long flags; bool ro = false; int r; if (!path_is_absolute(t->path)) return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Path is not absolute: %s", t->path); str = strjoin("mode=0755" NESTED_TMPFS_LIMITS ",", t->options); if (!str) return -ENOMEM; r = mount_option_mangle(str, MS_NODEV|MS_STRICTATIME, &flags, &o); if (r < 0) return log_debug_errno(r, "Failed to parse mount option '%s': %m", str); ro = flags & MS_RDONLY; flags &= ~MS_RDONLY; MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = t->path, .mode = MOUNT_TMPFS, .read_only = ro, .options_malloc = TAKE_PTR(o), .flags = flags, }; } return 0; } static int append_static_mounts(MountList *ml, const MountEntry *mounts, size_t n, bool ignore_protect) { assert(ml); assert(mounts || n == 0); /* Adds a list of static pre-defined entries */ FOREACH_ARRAY(m, mounts, n) { MountEntry *me = mount_list_extend(ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = mount_entry_path(m), .mode = m->mode, .ignore = m->ignore || ignore_protect, }; } return 0; } static int append_protect_home(MountList *ml, ProtectHome protect_home, bool ignore_protect) { assert(ml); switch (protect_home) { case PROTECT_HOME_NO: return 0; case PROTECT_HOME_READ_ONLY: return append_static_mounts(ml, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect); case PROTECT_HOME_TMPFS: return append_static_mounts(ml, protect_home_tmpfs_table, ELEMENTSOF(protect_home_tmpfs_table), ignore_protect); case PROTECT_HOME_YES: return append_static_mounts(ml, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect); default: assert_not_reached(); } } static int append_protect_system(MountList *ml, ProtectSystem protect_system, bool ignore_protect) { assert(ml); switch (protect_system) { case PROTECT_SYSTEM_NO: return 0; case PROTECT_SYSTEM_STRICT: return append_static_mounts(ml, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect); case PROTECT_SYSTEM_YES: return append_static_mounts(ml, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect); case PROTECT_SYSTEM_FULL: return append_static_mounts(ml, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect); default: assert_not_reached(); } } static int mount_path_compare(const MountEntry *a, const MountEntry *b) { int d; /* ExtensionImages/Directories will be used by other mounts as a base, so sort them first * regardless of the prefix - they are set up in the propagate directory anyway */ d = -CMP(a->mode == MOUNT_EXTENSION_IMAGE, b->mode == MOUNT_EXTENSION_IMAGE); if (d != 0) return d; d = -CMP(a->mode == MOUNT_EXTENSION_DIRECTORY, b->mode == MOUNT_EXTENSION_DIRECTORY); if (d != 0) return d; /* If the paths are not equal, then order prefixes first */ d = path_compare(mount_entry_path(a), mount_entry_path(b)); if (d != 0) return d; /* If the paths are equal, check the mode */ return CMP((int) a->mode, (int) b->mode); } static int prefix_where_needed(MountList *ml, const char *root_directory) { /* Prefixes all paths in the bind mount table with the root directory if the entry needs that. */ assert(ml); FOREACH_ARRAY(me, ml->mounts, ml->n_mounts) { char *s; if (me->has_prefix) continue; s = path_join(root_directory, mount_entry_path(me)); if (!s) return -ENOMEM; mount_entry_consume_prefix(me, s); } return 0; } static void drop_duplicates(MountList *ml) { MountEntry *f, *t, *previous; assert(ml); /* Drops duplicate entries. Expects that the array is properly ordered already. */ for (f = ml->mounts, t = ml->mounts, previous = NULL; f < ml->mounts + ml->n_mounts; f++) { /* The first one wins (which is the one with the more restrictive mode), see mount_path_compare() * above. Note that we only drop duplicates that haven't been mounted yet. */ if (previous && path_equal(mount_entry_path(f), mount_entry_path(previous)) && f->state == MOUNT_PENDING && previous->state == MOUNT_PENDING) { log_debug("%s (%s) is duplicate.", mount_entry_path(f), mount_mode_to_string(f->mode)); /* Propagate the flags to the remaining entry */ previous->read_only = previous->read_only || mount_entry_read_only(f); previous->noexec = previous->noexec || mount_entry_noexec(f); previous->exec = previous->exec || mount_entry_exec(f); mount_entry_done(f); continue; } *t = *f; previous = t; t++; } ml->n_mounts = t - ml->mounts; } static void drop_inaccessible(MountList *ml) { MountEntry *f, *t; const char *clear = NULL; assert(ml); /* Drops all entries obstructed by another entry further up the tree. Expects that the array is properly * ordered already. */ for (f = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; f++) { /* If we found a path set for INACCESSIBLE earlier, and this entry has it as prefix we should drop * it, as inaccessible paths really should drop the entire subtree. */ if (clear && path_startswith(mount_entry_path(f), clear)) { log_debug("%s is masked by %s.", mount_entry_path(f), clear); mount_entry_done(f); continue; } clear = f->mode == MOUNT_INACCESSIBLE ? mount_entry_path(f) : NULL; *t = *f; t++; } ml->n_mounts = t - ml->mounts; } static void drop_nop(MountList *ml) { MountEntry *f, *t; assert(ml); /* Drops all entries which have an immediate parent that has the same type, as they are redundant. Assumes the * list is ordered by prefixes. */ for (f = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; f++) { /* Only suppress such subtrees for READ_ONLY, READ_WRITE and READ_WRITE_IMPLICIT entries */ if (IN_SET(f->mode, MOUNT_READ_ONLY, MOUNT_READ_WRITE, MOUNT_READ_WRITE_IMPLICIT)) { MountEntry *found = NULL; /* Now let's find the first parent of the entry we are looking at. */ for (MountEntry *p = PTR_SUB1(t, ml->mounts); p; p = PTR_SUB1(p, ml->mounts)) if (path_startswith(mount_entry_path(f), mount_entry_path(p))) { found = p; break; } /* We found it, let's see if it's the same mode, if so, we can drop this entry */ if (found && found->mode == f->mode) { log_debug("%s (%s) is made redundant by %s (%s)", mount_entry_path(f), mount_mode_to_string(f->mode), mount_entry_path(found), mount_mode_to_string(found->mode)); mount_entry_done(f); continue; } } *t = *f; t++; } ml->n_mounts = t - ml->mounts; } static void drop_outside_root(MountList *ml, const char *root_directory) { MountEntry *f, *t; assert(ml); /* Nothing to do */ if (!root_directory) return; /* Drops all mounts that are outside of the root directory. */ for (f = ml->mounts, t = ml->mounts; f < ml->mounts + ml->n_mounts; f++) { /* ExtensionImages/Directories bases are opened in /run/systemd/unit-extensions on the host */ if (!IN_SET(f->mode, MOUNT_EXTENSION_IMAGE, MOUNT_EXTENSION_DIRECTORY) && !path_startswith(mount_entry_path(f), root_directory)) { log_debug("%s is outside of root directory.", mount_entry_path(f)); mount_entry_done(f); continue; } *t = *f; t++; } ml->n_mounts = t - ml->mounts; } static int clone_device_node(const char *node, const char *temporary_mount, bool *make_devnode) { _cleanup_free_ char *sl = NULL; const char *dn, *bn; struct stat st; int r; assert(node); assert(path_is_absolute(node)); assert(temporary_mount); assert(make_devnode); if (stat(node, &st) < 0) { if (errno == ENOENT) { log_debug_errno(errno, "Device node '%s' to clone does not exist.", node); return -ENXIO; } return log_debug_errno(errno, "Failed to stat() device node '%s' to clone: %m", node); } r = stat_verify_device_node(&st); if (r < 0) return log_debug_errno(r, "Cannot clone device node '%s': %m", node); dn = strjoina(temporary_mount, node); /* First, try to create device node properly */ if (*make_devnode) { mac_selinux_create_file_prepare(node, st.st_mode); r = mknod(dn, st.st_mode, st.st_rdev); mac_selinux_create_file_clear(); if (r >= 0) goto add_symlink; if (errno != EPERM) return log_debug_errno(errno, "Failed to mknod '%s': %m", node); /* This didn't work, let's not try this again for the next iterations. */ *make_devnode = false; } /* We're about to fall back to bind-mounting the device node. So create a dummy bind-mount target. * Do not prepare device-node SELinux label (see issue 13762) */ r = mknod(dn, S_IFREG, 0); if (r < 0 && errno != EEXIST) return log_debug_errno(errno, "Failed to mknod dummy device node for '%s': %m", node); /* Fallback to bind-mounting: The assumption here is that all used device nodes carry standard * properties. Specifically, the devices nodes we bind-mount should either be owned by root:root or * root:tty (e.g. /dev/tty, /dev/ptmx) and should not carry ACLs. */ r = mount_nofollow_verbose(LOG_DEBUG, node, dn, NULL, MS_BIND, NULL); if (r < 0) return r; add_symlink: bn = path_startswith(node, "/dev/"); if (!bn) return 0; /* Create symlinks like /dev/char/1:9 → ../urandom */ if (asprintf(&sl, "%s/dev/%s/" DEVNUM_FORMAT_STR, temporary_mount, S_ISCHR(st.st_mode) ? "char" : "block", DEVNUM_FORMAT_VAL(st.st_rdev)) < 0) return log_oom_debug(); (void) mkdir_parents(sl, 0755); const char *t = strjoina("../", bn); if (symlink(t, sl) < 0) log_debug_errno(errno, "Failed to symlink '%s' to '%s', ignoring: %m", t, sl); return 0; } static int bind_mount_device_dir(const char *temporary_mount, const char *dir) { const char *t; assert(temporary_mount); assert(dir); assert(path_is_absolute(dir)); t = strjoina(temporary_mount, dir); (void) mkdir(t, 0755); return mount_nofollow_verbose(LOG_DEBUG, dir, t, NULL, MS_BIND, NULL); } static char* settle_runtime_dir(RuntimeScope scope) { char *runtime_dir; if (scope != RUNTIME_SCOPE_USER) return strdup("/run/"); if (asprintf(&runtime_dir, "/run/user/" UID_FMT, geteuid()) < 0) return NULL; return runtime_dir; } static int create_temporary_mount_point(RuntimeScope scope, char **ret) { _cleanup_free_ char *runtime_dir = NULL, *temporary_mount = NULL; assert(ret); runtime_dir = settle_runtime_dir(scope); if (!runtime_dir) return log_oom_debug(); temporary_mount = path_join(runtime_dir, "systemd/namespace-XXXXXX"); if (!temporary_mount) return log_oom_debug(); if (!mkdtemp(temporary_mount)) return log_debug_errno(errno, "Failed to create temporary directory '%s': %m", temporary_mount); *ret = TAKE_PTR(temporary_mount); return 0; } static int mount_private_dev(MountEntry *m, RuntimeScope scope) { static const char devnodes[] = "/dev/null\0" "/dev/zero\0" "/dev/full\0" "/dev/random\0" "/dev/urandom\0" "/dev/tty\0"; _cleanup_(rmdir_and_freep) char *temporary_mount = NULL; _cleanup_(umount_and_rmdir_and_freep) char *dev = NULL; bool can_mknod = true; int r; assert(m); r = create_temporary_mount_point(scope, &temporary_mount); if (r < 0) return r; dev = path_join(temporary_mount, "dev"); if (!dev) return -ENOMEM; (void) mkdir(dev, 0755); r = mount_nofollow_verbose(LOG_DEBUG, "tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=0755" TMPFS_LIMITS_PRIVATE_DEV); if (r < 0) return r; r = label_fix_full(AT_FDCWD, dev, "/dev", 0); if (r < 0) return log_debug_errno(r, "Failed to fix label of '%s' as /dev/: %m", dev); r = bind_mount_device_dir(temporary_mount, "/dev/pts"); if (r < 0) return r; /* /dev/ptmx can either be a device node or a symlink to /dev/pts/ptmx. * When /dev/ptmx a device node, /dev/pts/ptmx has 000 permissions making it inaccessible. * Thus, in that case make a clone. * In nspawn and other containers it will be a symlink, in that case make it a symlink. */ r = is_symlink("/dev/ptmx"); if (r < 0) return log_debug_errno(r, "Failed to detect whether /dev/ptmx is a symlink or not: %m"); if (r > 0) { const char *devptmx = strjoina(temporary_mount, "/dev/ptmx"); if (symlink("pts/ptmx", devptmx) < 0) return log_debug_errno(errno, "Failed to create symlink '%s' to pts/ptmx: %m", devptmx); } else { r = clone_device_node("/dev/ptmx", temporary_mount, &can_mknod); if (r < 0) return r; } r = bind_mount_device_dir(temporary_mount, "/dev/shm"); if (r < 0) return r; FOREACH_STRING(d, "/dev/mqueue", "/dev/hugepages") (void) bind_mount_device_dir(temporary_mount, d); const char *devlog = strjoina(temporary_mount, "/dev/log"); if (symlink("/run/systemd/journal/dev-log", devlog) < 0) log_debug_errno(errno, "Failed to create symlink '%s' to /run/systemd/journal/dev-log, ignoring: %m", devlog); NULSTR_FOREACH(d, devnodes) { r = clone_device_node(d, temporary_mount, &can_mknod); /* ENXIO means the *source* is not a device file, skip creation in that case */ if (r < 0 && r != -ENXIO) return r; } r = dev_setup(temporary_mount, UID_INVALID, GID_INVALID); if (r < 0) log_debug_errno(r, "Failed to set up basic device tree at '%s', ignoring: %m", temporary_mount); /* Create the /dev directory if missing. It is more likely to be missing when the service is started * with RootDirectory. This is consistent with mount units creating the mount points when missing. */ (void) mkdir_p_label(mount_entry_path(m), 0755); /* Unmount everything in old /dev */ r = umount_recursive(mount_entry_path(m), 0); if (r < 0) log_debug_errno(r, "Failed to unmount directories below '%s', ignoring: %m", mount_entry_path(m)); r = mount_nofollow_verbose(LOG_DEBUG, dev, mount_entry_path(m), NULL, MS_MOVE, NULL); if (r < 0) return r; dev = rmdir_and_free(dev); /* Mount is successfully moved, do not umount() */ return 1; } static int mount_bind_dev(const MountEntry *m) { int r; assert(m); /* Implements the little brother of mount_private_dev(): simply bind mounts the host's /dev into the * service's /dev. This is only used when RootDirectory= is set. */ (void) mkdir_p_label(mount_entry_path(m), 0755); r = path_is_mount_point(mount_entry_path(m)); if (r < 0) return log_debug_errno(r, "Unable to determine whether /dev is already mounted: %m"); if (r > 0) /* make this a NOP if /dev is already a mount point */ return 0; r = mount_nofollow_verbose(LOG_DEBUG, "/dev", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; return 1; } static int mount_bind_sysfs(const MountEntry *m) { int r; assert(m); (void) mkdir_p_label(mount_entry_path(m), 0755); r = path_is_mount_point(mount_entry_path(m)); if (r < 0) return log_debug_errno(r, "Unable to determine whether /sys is already mounted: %m"); if (r > 0) /* make this a NOP if /sys is already a mount point */ return 0; /* Bind mount the host's version so that we get all child mounts of it, too. */ r = mount_nofollow_verbose(LOG_DEBUG, "/sys", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; return 1; } static int mount_private_apivfs( const char *fstype, const char *entry_path, const char *bind_source, const char *opts, RuntimeScope scope) { _cleanup_(rmdir_and_freep) char *temporary_mount = NULL; int r; assert(fstype); assert(entry_path); assert(bind_source); (void) mkdir_p_label(entry_path, 0755); /* First, check if we have enough privileges to mount a new instance. Note, a new sysfs instance * cannot be mounted on an already existing mount. Let's use a temporary place. */ r = create_temporary_mount_point(scope, &temporary_mount); if (r < 0) return r; r = mount_nofollow_verbose(LOG_DEBUG, fstype, temporary_mount, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts); if (r == -EINVAL && opts) /* If this failed with EINVAL then this likely means the textual hidepid= stuff for procfs is * not supported by the kernel, and thus the per-instance hidepid= neither, which means we * really don't want to use it, since it would affect our host's /proc mount. Hence let's * gracefully fallback to a classic, unrestricted version. */ r = mount_nofollow_verbose(LOG_DEBUG, fstype, temporary_mount, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, /* opts = */ NULL); if (ERRNO_IS_NEG_PRIVILEGE(r)) { /* When we do not have enough privileges to mount a new instance, fall back to use an * existing mount. */ r = path_is_mount_point(entry_path); if (r < 0) return log_debug_errno(r, "Unable to determine whether '%s' is already mounted: %m", entry_path); if (r > 0) return 0; /* Use the current mount as is. */ /* We lack permissions to mount a new instance, and it is not already mounted. But we can * access the host's, so as a final fallback bind-mount it to the destination, as most likely * we are inside a user manager in an unprivileged user namespace. */ r = mount_nofollow_verbose(LOG_DEBUG, bind_source, entry_path, /* fstype = */ NULL, MS_BIND|MS_REC, /* opts = */ NULL); if (r < 0) return r; return 1; } else if (r < 0) return r; /* OK. We have a new mount instance. Let's clear an existing mount and its submounts. */ r = umount_recursive(entry_path, /* flags = */ 0); if (r < 0) log_debug_errno(r, "Failed to unmount directories below '%s', ignoring: %m", entry_path); /* Then, move the new mount instance. */ r = mount_nofollow_verbose(LOG_DEBUG, temporary_mount, entry_path, /* fstype = */ NULL, MS_MOVE, /* opts = */ NULL); if (r < 0) return r; /* We mounted a new instance now. Let's bind mount the children over now. This matters for nspawn * where a bunch of files are overmounted, in particular the boot id. */ (void) bind_mount_submounts(bind_source, entry_path); return 1; } static int mount_private_sysfs(const MountEntry *m, const NamespaceParameters *p) { assert(m); assert(p); return mount_private_apivfs("sysfs", mount_entry_path(m), "/sys", /* opts = */ NULL, p->runtime_scope); } static int mount_procfs(const MountEntry *m, const NamespaceParameters *p) { _cleanup_free_ char *opts = NULL; assert(m); assert(p); if (p->protect_proc != PROTECT_PROC_DEFAULT || p->proc_subset != PROC_SUBSET_ALL) { /* Starting with kernel 5.8 procfs' hidepid= logic is truly per-instance (previously it * pretended to be per-instance but actually was per-namespace), hence let's make use of it * if requested. To make sure this logic succeeds only on kernels where hidepid= is * per-instance, we'll exclusively use the textual value for hidepid=, since support was * added in the same commit: if it's supported it is thus also per-instance. */ const char *hpv = p->protect_proc == PROTECT_PROC_DEFAULT ? "off" : protect_proc_to_string(p->protect_proc); /* hidepid= support was added in 5.8, so we can use fsconfig()/fsopen() (which were added in * 5.2) to check if hidepid= is supported. This avoids a noisy dmesg log by the kernel when * trying to use hidepid= on systems where it isn't supported. The same applies for subset=. * fsopen()/fsconfig() was also backported on some distros which allows us to detect * hidepid=/subset= support in even more scenarios. */ if (mount_option_supported("proc", "hidepid", hpv) != 0) { opts = strjoin("hidepid=", hpv); if (!opts) return -ENOMEM; } if (p->proc_subset == PROC_SUBSET_PID && mount_option_supported("proc", "subset", "pid") != 0) if (!strextend_with_separator(&opts, ",", "subset=pid")) return -ENOMEM; } /* Mount a new instance, so that we get the one that matches our user namespace, if we are running in * one. i.e we don't reuse existing mounts here under any condition, we want a new instance owned by * our user namespace and with our hidepid= settings applied. Hence, let's get rid of everything * mounted on /proc/ first. */ return mount_private_apivfs("proc", mount_entry_path(m), "/proc", opts, p->runtime_scope); } static int mount_tmpfs(const MountEntry *m) { const char *entry_path, *inner_path; int r; assert(m); entry_path = mount_entry_path(m); inner_path = mount_entry_unprefixed_path(m); /* First, get rid of everything that is below if there is anything. Then, overmount with our new * tmpfs */ (void) mkdir_p_label(entry_path, 0755); (void) umount_recursive(entry_path, 0); r = mount_nofollow_verbose(LOG_DEBUG, "tmpfs", entry_path, "tmpfs", m->flags, mount_entry_options(m)); if (r < 0) return r; r = label_fix_full(AT_FDCWD, entry_path, inner_path, 0); if (r < 0) return log_debug_errno(r, "Failed to fix label of '%s' as '%s': %m", entry_path, inner_path); return 1; } static int mount_run(const MountEntry *m) { int r; assert(m); r = path_is_mount_point(mount_entry_path(m)); if (r < 0 && r != -ENOENT) return log_debug_errno(r, "Unable to determine whether /run is already mounted: %m"); if (r > 0) /* make this a NOP if /run is already a mount point */ return 0; return mount_tmpfs(m); } static int mount_mqueuefs(const MountEntry *m) { int r; const char *entry_path; assert(m); entry_path = mount_entry_path(m); (void) mkdir_p_label(entry_path, 0755); (void) umount_recursive(entry_path, 0); r = mount_nofollow_verbose(LOG_DEBUG, "mqueue", entry_path, "mqueue", m->flags, mount_entry_options(m)); if (r < 0) return r; return 1; } static int mount_image( const MountEntry *m, const char *root_directory, const ImagePolicy *image_policy) { _cleanup_free_ char *host_os_release_id = NULL, *host_os_release_version_id = NULL, *host_os_release_sysext_level = NULL, *host_os_release_confext_level = NULL, *extension_name = NULL; int r; assert(m); r = path_extract_filename(mount_entry_source(m), &extension_name); if (r < 0) return log_debug_errno(r, "Failed to extract extension name from %s: %m", mount_entry_source(m)); if (m->mode == MOUNT_EXTENSION_IMAGE) { r = parse_os_release( empty_to_root(root_directory), "ID", &host_os_release_id, "VERSION_ID", &host_os_release_version_id, image_class_info[IMAGE_SYSEXT].level_env, &host_os_release_sysext_level, image_class_info[IMAGE_CONFEXT].level_env, &host_os_release_confext_level, NULL); if (r < 0) return log_debug_errno(r, "Failed to acquire 'os-release' data of OS tree '%s': %m", empty_to_root(root_directory)); if (isempty(host_os_release_id)) return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "'ID' field not found or empty in 'os-release' data of OS tree '%s'.", empty_to_root(root_directory)); } r = verity_dissect_and_mount( /* src_fd= */ -1, mount_entry_source(m), mount_entry_path(m), m->image_options_const, image_policy, host_os_release_id, host_os_release_version_id, host_os_release_sysext_level, host_os_release_confext_level, /* required_sysext_scope= */ NULL, /* ret_image= */ NULL); if (r == -ENOENT && m->ignore) return 0; if (r == -ESTALE && host_os_release_id) return log_error_errno(r, // FIXME: this should not be logged ad LOG_ERR, as it will result in duplicate logging. "Failed to mount image %s, extension-release metadata does not match the lower layer's: ID=%s%s%s%s%s%s%s", mount_entry_source(m), host_os_release_id, host_os_release_version_id ? " VERSION_ID=" : "", strempty(host_os_release_version_id), host_os_release_sysext_level ? image_class_info[IMAGE_SYSEXT].level_env_print : "", strempty(host_os_release_sysext_level), host_os_release_confext_level ? image_class_info[IMAGE_CONFEXT].level_env_print : "", strempty(host_os_release_confext_level)); if (r < 0) return log_debug_errno(r, "Failed to mount image %s on %s: %m", mount_entry_source(m), mount_entry_path(m)); return 1; } static int mount_overlay(const MountEntry *m) { _cleanup_free_ char *options = NULL, *layers = NULL; int r; assert(m); /* Extension hierarchies are optional (e.g.: confext might not have /opt) so check if they actually * exist in an image before attempting to create an overlay with them, otherwise the mount will * fail. We can't check before this, as the images will not be mounted until now. */ /* Note that lowerdir= parameters are in 'reverse' order, so the top-most directory in the overlay * comes first in the list. */ STRV_FOREACH_BACKWARDS(o, m->overlay_layers) { _cleanup_free_ char *escaped = NULL; r = is_dir(*o, /* follow= */ false); if (r <= 0) { if (r != -ENOENT) log_debug_errno(r, "Failed to check whether overlay layer source path '%s' exists, ignoring: %m", *o); continue; } escaped = shell_escape(*o, ",:"); if (!escaped) return log_oom_debug(); if (!strextend_with_separator(&layers, ":", escaped)) return log_oom_debug(); } if (!layers) { log_debug("None of the overlays specified in '%s' exist at the source, skipping.", mount_entry_options(m)); return 0; /* Only the root is set? Then there's nothing to overlay */ } options = strjoin("lowerdir=", layers, ":", mount_entry_path(m)); /* The root goes in last */ if (!options) return log_oom_debug(); (void) mkdir_p_label(mount_entry_path(m), 0755); r = mount_nofollow_verbose(LOG_DEBUG, "overlay", mount_entry_path(m), "overlay", MS_RDONLY, options); if (r == -ENOENT && m->ignore) return 0; if (r < 0) return r; return 1; } static int follow_symlink( const char *root_directory, MountEntry *m) { _cleanup_free_ char *target = NULL; int r; assert(m); /* Let's chase symlinks, but only one step at a time. That's because depending where the symlink points we * might need to change the order in which we mount stuff. Hence: let's normalize piecemeal, and do one step at * a time by specifying CHASE_STEP. This function returns 0 if we resolved one step, and > 0 if we reached the * end and already have a fully normalized name. */ r = chase(mount_entry_path(m), root_directory, CHASE_STEP|CHASE_NONEXISTENT, &target, NULL); if (r < 0) return log_debug_errno(r, "Failed to chase symlinks '%s': %m", mount_entry_path(m)); if (r > 0) /* Reached the end, nothing more to resolve */ return 1; if (m->n_followed >= CHASE_MAX) /* put a boundary on things */ return log_debug_errno(SYNTHETIC_ERRNO(ELOOP), "Symlink loop on '%s'.", mount_entry_path(m)); log_debug("Followed mount entry path symlink %s %s %s.", mount_entry_path(m), special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), target); mount_entry_consume_prefix(m, TAKE_PTR(target)); m->n_followed++; return 0; } static int apply_one_mount( const char *root_directory, MountEntry *m, const NamespaceParameters *p) { _cleanup_free_ char *inaccessible = NULL; bool rbind = true, make = false; const char *what; int r; /* Return 1 when the mount should be post-processed (remounted r/o, etc.), 0 otherwise. In most * cases post-processing is the right thing, the typical exception is when the mount is gracefully * skipped. */ assert(m); assert(p); log_debug("Applying namespace mount on %s", mount_entry_path(m)); switch (m->mode) { case MOUNT_INACCESSIBLE: { _cleanup_free_ char *runtime_dir = NULL; struct stat target; /* First, get rid of everything that is below if there * is anything... Then, overmount it with an * inaccessible path. */ (void) umount_recursive(mount_entry_path(m), 0); if (lstat(mount_entry_path(m), &target) < 0) { if (errno == ENOENT && m->ignore) return 0; return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", mount_entry_path(m)); } /* We don't pass the literal runtime scope through here but one based purely on our UID. This * means that the root user's --user services will use the host's inaccessible inodes rather * then root's private ones. This is preferable since it means device nodes that are * overmounted to make them inaccessible will be overmounted with a device node, rather than * an AF_UNIX socket inode. */ runtime_dir = settle_runtime_dir(geteuid() == 0 ? RUNTIME_SCOPE_SYSTEM : RUNTIME_SCOPE_USER); if (!runtime_dir) return log_oom_debug(); r = mode_to_inaccessible_node(runtime_dir, target.st_mode, &inaccessible); if (r < 0) return log_debug_errno(SYNTHETIC_ERRNO(ELOOP), "File type not supported for inaccessible mounts. Note that symlinks are not allowed."); what = inaccessible; break; } case MOUNT_READ_ONLY: case MOUNT_READ_WRITE: case MOUNT_READ_WRITE_IMPLICIT: case MOUNT_EXEC: case MOUNT_NOEXEC: r = path_is_mount_point_full(mount_entry_path(m), root_directory, /* flags = */ 0); if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", mount_entry_path(m)); if (r > 0) /* Nothing to do here, it is already a mount. We just later toggle the MS_RDONLY * and MS_NOEXEC bits for the mount point if needed. */ return 1; /* This isn't a mount point yet, let's make it one. */ what = mount_entry_path(m); break; case MOUNT_EXTENSION_DIRECTORY: { _cleanup_free_ char *host_os_release_id = NULL, *host_os_release_version_id = NULL, *host_os_release_level = NULL, *extension_name = NULL; _cleanup_strv_free_ char **extension_release = NULL; ImageClass class = IMAGE_SYSEXT; r = path_extract_filename(mount_entry_source(m), &extension_name); if (r < 0) return log_debug_errno(r, "Failed to extract extension name from %s: %m", mount_entry_source(m)); r = load_extension_release_pairs( mount_entry_source(m), IMAGE_SYSEXT, extension_name, /* relax_extension_release_check= */ false, &extension_release); if (r == -ENOENT) { r = load_extension_release_pairs( mount_entry_source(m), IMAGE_CONFEXT, extension_name, /* relax_extension_release_check= */ false, &extension_release); if (r >= 0) class = IMAGE_CONFEXT; } if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to acquire 'extension-release' data of extension tree %s: %m", mount_entry_source(m)); r = parse_os_release( empty_to_root(root_directory), "ID", &host_os_release_id, "VERSION_ID", &host_os_release_version_id, image_class_info[class].level_env, &host_os_release_level, NULL); if (r < 0) return log_debug_errno(r, "Failed to acquire 'os-release' data of OS tree '%s': %m", empty_to_root(root_directory)); if (isempty(host_os_release_id)) return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "'ID' field not found or empty in 'os-release' data of OS tree '%s'.", empty_to_root(root_directory)); r = extension_release_validate( extension_name, host_os_release_id, host_os_release_version_id, host_os_release_level, /* host_extension_scope = */ NULL, /* Leave empty, we need to accept both system and portable */ extension_release, class); if (r < 0) return log_debug_errno(r, "Failed to compare directory %s extension-release metadata with the root's os-release: %m", extension_name); if (r == 0) return log_debug_errno(SYNTHETIC_ERRNO(ESTALE), "Directory %s extension-release metadata does not match the root's.", extension_name); _fallthrough_; } case MOUNT_BIND: rbind = false; _fallthrough_; case MOUNT_BIND_RECURSIVE: { _cleanup_free_ char *chased = NULL; /* Since mount() will always follow symlinks we chase the symlinks on our own first. Note * that bind mount source paths are always relative to the host root, hence we pass NULL as * root directory to chase() here. */ r = chase(mount_entry_source(m), NULL, CHASE_TRAIL_SLASH, &chased, NULL); if (r == -ENOENT && m->ignore) { log_debug_errno(r, "Path %s does not exist, ignoring.", mount_entry_source(m)); return 0; } if (r < 0) return log_debug_errno(r, "Failed to follow symlinks on %s: %m", mount_entry_source(m)); log_debug("Followed source symlinks %s %s %s.", mount_entry_source(m), special_glyph(SPECIAL_GLYPH_ARROW_RIGHT), chased); free_and_replace(m->source_malloc, chased); what = mount_entry_source(m); make = true; break; } case MOUNT_EMPTY_DIR: case MOUNT_TMPFS: return mount_tmpfs(m); case MOUNT_PRIVATE_TMP: case MOUNT_PRIVATE_TMP_READ_ONLY: what = mount_entry_source(m); make = true; break; case MOUNT_PRIVATE_DEV: return mount_private_dev(m, p->runtime_scope); case MOUNT_BIND_DEV: return mount_bind_dev(m); case MOUNT_PRIVATE_SYSFS: return mount_private_sysfs(m, p); case MOUNT_BIND_SYSFS: return mount_bind_sysfs(m); case MOUNT_PROCFS: return mount_procfs(m, p); case MOUNT_RUN: return mount_run(m); case MOUNT_MQUEUEFS: return mount_mqueuefs(m); case MOUNT_IMAGE: return mount_image(m, NULL, p->mount_image_policy); case MOUNT_EXTENSION_IMAGE: return mount_image(m, root_directory, p->extension_image_policy); case MOUNT_OVERLAY: return mount_overlay(m); default: assert_not_reached(); } assert(what); r = mount_nofollow_verbose(LOG_DEBUG, what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL); if (r < 0) { bool try_again = false; if (r == -ENOENT && make) { int q; /* Hmm, either the source or the destination are missing. Let's see if we can create the destination, then try again. */ (void) mkdir_parents(mount_entry_path(m), 0755); q = make_mount_point_inode_from_path(what, mount_entry_path(m), 0755); if (q < 0 && q != -EEXIST) // FIXME: this shouldn't be logged at LOG_WARNING, but be bubbled up, and logged there to avoid duplicate logging log_warning_errno(q, "Failed to create destination mount point node '%s', ignoring: %m", mount_entry_path(m)); else try_again = true; } if (try_again) r = mount_nofollow_verbose(LOG_DEBUG, what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL); if (r < 0) return log_error_errno(r, "Failed to mount %s to %s: %m", what, mount_entry_path(m)); // FIXME: this should not be logged here, but be bubbled up, to avoid duplicate logging } log_debug("Successfully mounted %s to %s", what, mount_entry_path(m)); return 1; } static int make_read_only(const MountEntry *m, char **deny_list, FILE *proc_self_mountinfo) { unsigned long new_flags = 0, flags_mask = 0; bool submounts; int r; assert(m); assert(proc_self_mountinfo); if (m->state != MOUNT_APPLIED) return 0; if (mount_entry_read_only(m) || m->mode == MOUNT_PRIVATE_DEV) { new_flags |= MS_RDONLY; flags_mask |= MS_RDONLY; } if (m->nosuid) { new_flags |= MS_NOSUID; flags_mask |= MS_NOSUID; } if (flags_mask == 0) /* No Change? */ return 0; /* We generally apply these changes recursively, except for /dev, and the cases we know there's * nothing further down. Set /dev readonly, but not submounts like /dev/shm. Also, we only set the * per-mount read-only flag. We can't set it on the superblock, if we are inside a user namespace * and running Linux <= 4.17. */ submounts = mount_entry_read_only(m) && !IN_SET(m->mode, MOUNT_EMPTY_DIR, MOUNT_TMPFS); if (submounts) r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, deny_list, proc_self_mountinfo); else r = bind_remount_one_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, proc_self_mountinfo); /* Note that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked * read-only already stays this way. This improves compatibility with container managers, where we * won't attempt to undo read-only mounts already applied. */ if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to re-mount '%s'%s: %m", mount_entry_path(m), submounts ? " and its submounts" : ""); return 0; } static int make_noexec(const MountEntry *m, char **deny_list, FILE *proc_self_mountinfo) { unsigned long new_flags = 0, flags_mask = 0; bool submounts; int r; assert(m); assert(proc_self_mountinfo); if (m->state != MOUNT_APPLIED) return 0; if (mount_entry_noexec(m)) { new_flags |= MS_NOEXEC; flags_mask |= MS_NOEXEC; } else if (mount_entry_exec(m)) { new_flags &= ~MS_NOEXEC; flags_mask |= MS_NOEXEC; } if (flags_mask == 0) /* No Change? */ return 0; submounts = !IN_SET(m->mode, MOUNT_EMPTY_DIR, MOUNT_TMPFS); if (submounts) r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, deny_list, proc_self_mountinfo); else r = bind_remount_one_with_mountinfo(mount_entry_path(m), new_flags, flags_mask, proc_self_mountinfo); if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to re-mount '%s'%s: %m", mount_entry_path(m), submounts ? " and its submounts" : ""); return 0; } static int make_nosuid(const MountEntry *m, FILE *proc_self_mountinfo) { bool submounts; int r; assert(m); assert(proc_self_mountinfo); if (m->state != MOUNT_APPLIED) return 0; submounts = !IN_SET(m->mode, MOUNT_EMPTY_DIR, MOUNT_TMPFS); if (submounts) r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), MS_NOSUID, MS_NOSUID, NULL, proc_self_mountinfo); else r = bind_remount_one_with_mountinfo(mount_entry_path(m), MS_NOSUID, MS_NOSUID, proc_self_mountinfo); if (r == -ENOENT && m->ignore) return 0; if (r < 0) return log_debug_errno(r, "Failed to re-mount '%s'%s: %m", mount_entry_path(m), submounts ? " and its submounts" : ""); return 0; } static bool namespace_parameters_mount_apivfs(const NamespaceParameters *p) { assert(p); /* * ProtectControlGroups= and ProtectKernelTunables= imply MountAPIVFS=, * since to protect the API VFS mounts, they need to be around in the * first place... */ return p->mount_apivfs || p->protect_control_groups || p->protect_kernel_tunables || p->protect_proc != PROTECT_PROC_DEFAULT || p->proc_subset != PROC_SUBSET_ALL; } /* Walk all mount entries and dropping any unused mounts. This affects all * mounts: * - that are implicitly protected by a path that has been rendered inaccessible * - whose immediate parent requests the same protection mode as the mount itself * - that are outside of the relevant root directory * - which are duplicates */ static void drop_unused_mounts(MountList *ml, const char *root_directory) { assert(ml); assert(root_directory); assert(ml->mounts || ml->n_mounts == 0); typesafe_qsort(ml->mounts, ml->n_mounts, mount_path_compare); drop_duplicates(ml); drop_outside_root(ml, root_directory); drop_inaccessible(ml); drop_nop(ml); } static int create_symlinks_from_tuples(const char *root, char **strv_symlinks) { int r; STRV_FOREACH_PAIR(src, dst, strv_symlinks) { _cleanup_free_ char *src_abs = NULL, *dst_abs = NULL; src_abs = path_join(root, *src); dst_abs = path_join(root, *dst); if (!src_abs || !dst_abs) return -ENOMEM; r = mkdir_parents_label(dst_abs, 0755); if (r < 0) return log_debug_errno( r, "Failed to create parent directory for symlink '%s': %m", dst_abs); r = symlink_idempotent(src_abs, dst_abs, true); if (r < 0) return log_debug_errno( r, "Failed to create symlink from '%s' to '%s': %m", src_abs, dst_abs); } return 0; } static void mount_entry_path_debug_string(const char *root, MountEntry *m, char **error_path) { assert(m); /* Create a string suitable for debugging logs, stripping for example the local working directory. * For example, with a BindPaths=/var/bar that does not exist on the host: * * Before: * foo.service: Failed to set up mount namespacing: /run/systemd/unit-root/var/bar: No such file or directory * After: * foo.service: Failed to set up mount namespacing: /var/bar: No such file or directory * * Note that this is an error path, so no OOM check is done on purpose. */ if (!error_path) return; if (!mount_entry_path(m)) { *error_path = NULL; return; } if (root) { const char *e = startswith(mount_entry_path(m), root); if (e) { *error_path = strdup(e); return; } } *error_path = strdup(mount_entry_path(m)); return; } static int apply_mounts( MountList *ml, const char *root, const NamespaceParameters *p, char **error_path) { _cleanup_fclose_ FILE *proc_self_mountinfo = NULL; _cleanup_free_ char **deny_list = NULL; int r; assert(ml); assert(root); assert(p); if (ml->n_mounts == 0) /* Shortcut: nothing to do */ return 0; /* Open /proc/self/mountinfo now as it may become unavailable if we mount anything on top of * /proc. For example, this is the case with the option: 'InaccessiblePaths=/proc'. */ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re"); if (!proc_self_mountinfo) { r = -errno; if (error_path) *error_path = strdup("/proc/self/mountinfo"); return log_debug_errno(r, "Failed to open /proc/self/mountinfo: %m"); } /* First round, establish all mounts we need */ for (;;) { bool again = false; FOREACH_ARRAY(m, ml->mounts, ml->n_mounts) { if (m->state != MOUNT_PENDING) continue; /* ExtensionImages/Directories are first opened in the propagate directory, not in the root_directory */ r = follow_symlink(!IN_SET(m->mode, MOUNT_EXTENSION_IMAGE, MOUNT_EXTENSION_DIRECTORY) ? root : NULL, m); if (r < 0) { mount_entry_path_debug_string(root, m, error_path); return r; } if (r == 0) { /* We hit a symlinked mount point. The entry got rewritten and might * point to a very different place now. Let's normalize the changed * list, and start from the beginning. After all to mount the entry * at the new location we might need some other mounts first */ again = true; break; } /* Returns 1 if the mount should be post-processed, 0 otherwise */ r = apply_one_mount(root, m, p); if (r < 0) { mount_entry_path_debug_string(root, m, error_path); return r; } m->state = r == 0 ? MOUNT_SKIPPED : MOUNT_APPLIED; } if (!again) break; drop_unused_mounts(ml, root); } /* Now that all filesystems have been set up, but before the * read-only switches are flipped, create the exec dirs and other symlinks. * Note that when /var/lib is not empty/tmpfs, these symlinks will already * exist, which means this will be a no-op. */ r = create_symlinks_from_tuples(root, p->symlinks); if (r < 0) return log_debug_errno(r, "Failed to set up symlinks inside mount namespace: %m"); /* Create a deny list we can pass to bind_mount_recursive() */ deny_list = new(char*, ml->n_mounts+1); if (!deny_list) return -ENOMEM; for (size_t j = 0; j < ml->n_mounts; j++) deny_list[j] = (char*) mount_entry_path(ml->mounts+j); deny_list[ml->n_mounts] = NULL; /* Second round, flip the ro bits if necessary. */ FOREACH_ARRAY(m, ml->mounts, ml->n_mounts) { r = make_read_only(m, deny_list, proc_self_mountinfo); if (r < 0) { mount_entry_path_debug_string(root, m, error_path); return r; } } /* Third round, flip the noexec bits with a simplified deny list. */ for (size_t j = 0; j < ml->n_mounts; j++) if (IN_SET((ml->mounts+j)->mode, MOUNT_EXEC, MOUNT_NOEXEC)) deny_list[j] = (char*) mount_entry_path(ml->mounts+j); deny_list[ml->n_mounts] = NULL; FOREACH_ARRAY(m, ml->mounts, ml->n_mounts) { r = make_noexec(m, deny_list, proc_self_mountinfo); if (r < 0) { mount_entry_path_debug_string(root, m, error_path); return r; } } /* Fourth round, flip the nosuid bits without a deny list. */ if (p->mount_nosuid) FOREACH_ARRAY(m, ml->mounts, ml->n_mounts) { r = make_nosuid(m, proc_self_mountinfo); if (r < 0) { mount_entry_path_debug_string(root, m, error_path); return r; } } return 1; } static bool root_read_only( char **read_only_paths, ProtectSystem protect_system) { /* Determine whether the root directory is going to be read-only given the configured settings. */ if (protect_system == PROTECT_SYSTEM_STRICT) return true; if (prefixed_path_strv_contains(read_only_paths, "/")) return true; return false; } static bool home_read_only( char * const *read_only_paths, char * const *inaccessible_paths, char * const *empty_directories, const BindMount *bind_mounts, size_t n_bind_mounts, const TemporaryFileSystem *temporary_filesystems, size_t n_temporary_filesystems, ProtectHome protect_home) { /* Determine whether the /home directory is going to be read-only given the configured settings. Yes, * this is a bit sloppy, since we don't bother checking for cases where / is affected by multiple * settings. */ if (protect_home != PROTECT_HOME_NO) return true; if (prefixed_path_strv_contains(read_only_paths, "/home") || prefixed_path_strv_contains(inaccessible_paths, "/home") || prefixed_path_strv_contains(empty_directories, "/home")) return true; FOREACH_ARRAY(i, temporary_filesystems, n_temporary_filesystems) if (path_equal(i->path, "/home")) return true; /* If /home is overmounted with some dir from the host it's not writable. */ FOREACH_ARRAY(i, bind_mounts, n_bind_mounts) if (path_equal(i->destination, "/home")) return true; return false; } int setup_namespace(const NamespaceParameters *p, char **error_path) { _cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL; _cleanup_(dissected_image_unrefp) DissectedImage *dissected_image = NULL; _cleanup_strv_free_ char **hierarchies = NULL; _cleanup_(mount_list_done) MountList ml = {}; _cleanup_close_ int userns_fd = -EBADF; bool require_prefix = false; const char *root; DissectImageFlags dissect_image_flags = DISSECT_IMAGE_GENERIC_ROOT | DISSECT_IMAGE_REQUIRE_ROOT | DISSECT_IMAGE_DISCARD_ON_LOOP | DISSECT_IMAGE_RELAX_VAR_CHECK | DISSECT_IMAGE_FSCK | DISSECT_IMAGE_USR_NO_ROOT | DISSECT_IMAGE_GROWFS | DISSECT_IMAGE_ADD_PARTITION_DEVICES | DISSECT_IMAGE_PIN_PARTITION_DEVICES | DISSECT_IMAGE_ALLOW_USERSPACE_VERITY; int r; assert(p); /* Make sure that all mknod(), mkdir() calls we do are unaffected by the umask, and the access modes * we configure take effect */ BLOCK_WITH_UMASK(0000); bool setup_propagate = !isempty(p->propagate_dir) && !isempty(p->incoming_dir); unsigned long mount_propagation_flag = p->mount_propagation_flag != 0 ? p->mount_propagation_flag : MS_SHARED; if (p->root_image) { /* Make the whole image read-only if we can determine that we only access it in a read-only fashion. */ if (root_read_only(p->read_only_paths, p->protect_system) && home_read_only(p->read_only_paths, p->inaccessible_paths, p->empty_directories, p->bind_mounts, p->n_bind_mounts, p->temporary_filesystems, p->n_temporary_filesystems, p->protect_home) && strv_isempty(p->read_write_paths)) dissect_image_flags |= DISSECT_IMAGE_READ_ONLY; SET_FLAG(dissect_image_flags, DISSECT_IMAGE_NO_PARTITION_TABLE, p->verity && p->verity->data_path); if (p->runtime_scope == RUNTIME_SCOPE_SYSTEM) { /* In system mode we mount directly */ r = loop_device_make_by_path( p->root_image, FLAGS_SET(dissect_image_flags, DISSECT_IMAGE_DEVICE_READ_ONLY) ? O_RDONLY : -1 /* < 0 means writable if possible, read-only as fallback */, /* sector_size= */ UINT32_MAX, FLAGS_SET(dissect_image_flags, DISSECT_IMAGE_NO_PARTITION_TABLE) ? 0 : LO_FLAGS_PARTSCAN, LOCK_SH, &loop_device); if (r < 0) return log_debug_errno(r, "Failed to create loop device for root image: %m"); r = dissect_loop_device( loop_device, p->verity, p->root_image_options, p->root_image_policy, dissect_image_flags, &dissected_image); if (r < 0) return log_debug_errno(r, "Failed to dissect image: %m"); r = dissected_image_load_verity_sig_partition( dissected_image, loop_device->fd, p->verity); if (r < 0) return r; r = dissected_image_decrypt( dissected_image, NULL, p->verity, dissect_image_flags); if (r < 0) return log_debug_errno(r, "Failed to decrypt dissected image: %m"); } else { userns_fd = namespace_open_by_type(NAMESPACE_USER); if (userns_fd < 0) return log_debug_errno(userns_fd, "Failed to open our own user namespace: %m"); r = mountfsd_mount_image( p->root_image, userns_fd, p->root_image_policy, dissect_image_flags, &dissected_image); if (r < 0) return r; } } if (p->root_directory) root = p->root_directory; else { /* /run/systemd should have been created by PID 1 early on already, but in some cases, like * when running tests (test-execute), it might not have been created yet so let's make sure * we create it if it doesn't already exist. */ (void) mkdir_p_label("/run/systemd", 0755); /* Always create the mount namespace in a temporary directory, instead of operating directly * in the root. The temporary directory prevents any mounts from being potentially obscured * my other mounts we already applied. We use the same mount point for all images, which is * safe, since they all live in their own namespaces after all, and hence won't see each * other. (Note: this directory is also created by PID 1 early on, we create it here for * similar reasons as /run/systemd/ first.) */ root = "/run/systemd/mount-rootfs"; (void) mkdir_label(root, 0555); require_prefix = true; } if (p->n_extension_images > 0 || !strv_isempty(p->extension_directories)) { /* Hierarchy population needs to be done for sysext and confext extension images */ r = parse_env_extension_hierarchies(&hierarchies, "SYSTEMD_SYSEXT_AND_CONFEXT_HIERARCHIES"); if (r < 0) return r; } r = append_access_mounts(&ml, p->read_write_paths, MOUNT_READ_WRITE, require_prefix); if (r < 0) return r; r = append_access_mounts(&ml, p->read_only_paths, MOUNT_READ_ONLY, require_prefix); if (r < 0) return r; r = append_access_mounts(&ml, p->inaccessible_paths, MOUNT_INACCESSIBLE, require_prefix); if (r < 0) return r; r = append_access_mounts(&ml, p->exec_paths, MOUNT_EXEC, require_prefix); if (r < 0) return r; r = append_access_mounts(&ml, p->no_exec_paths, MOUNT_NOEXEC, require_prefix); if (r < 0) return r; r = append_empty_dir_mounts(&ml, p->empty_directories); if (r < 0) return r; r = append_bind_mounts(&ml, p->bind_mounts, p->n_bind_mounts); if (r < 0) return r; r = append_tmpfs_mounts(&ml, p->temporary_filesystems, p->n_temporary_filesystems); if (r < 0) return r; if (p->tmp_dir) { bool ro = streq(p->tmp_dir, RUN_SYSTEMD_EMPTY); MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/tmp", .mode = ro ? MOUNT_PRIVATE_TMP_READ_ONLY : MOUNT_PRIVATE_TMP, .source_const = p->tmp_dir, }; } if (p->var_tmp_dir) { bool ro = streq(p->var_tmp_dir, RUN_SYSTEMD_EMPTY); MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/var/tmp", .mode = ro ? MOUNT_PRIVATE_TMP_READ_ONLY : MOUNT_PRIVATE_TMP, .source_const = p->var_tmp_dir, }; } r = append_mount_images(&ml, p->mount_images, p->n_mount_images); if (r < 0) return r; r = append_extensions(&ml, root, p->extension_dir, hierarchies, p->extension_images, p->n_extension_images, p->extension_directories); if (r < 0) return r; if (p->private_dev) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/dev", .mode = MOUNT_PRIVATE_DEV, .flags = DEV_MOUNT_OPTIONS, }; } /* In case /proc is successfully mounted with pid tree subset only (ProcSubset=pid), the protective mounts to non-pid /proc paths would fail. But the pid only option may have failed gracefully, so let's try the mounts but it's not fatal if they don't succeed. */ bool ignore_protect_proc = p->ignore_protect_paths || p->proc_subset == PROC_SUBSET_PID; if (p->protect_kernel_tunables) { r = append_static_mounts(&ml, protect_kernel_tunables_proc_table, ELEMENTSOF(protect_kernel_tunables_proc_table), ignore_protect_proc); if (r < 0) return r; r = append_static_mounts(&ml, protect_kernel_tunables_sys_table, ELEMENTSOF(protect_kernel_tunables_sys_table), p->ignore_protect_paths); if (r < 0) return r; } if (p->protect_kernel_modules) { r = append_static_mounts(&ml, protect_kernel_modules_table, ELEMENTSOF(protect_kernel_modules_table), p->ignore_protect_paths); if (r < 0) return r; } if (p->protect_kernel_logs) { r = append_static_mounts(&ml, protect_kernel_logs_proc_table, ELEMENTSOF(protect_kernel_logs_proc_table), ignore_protect_proc); if (r < 0) return r; r = append_static_mounts(&ml, protect_kernel_logs_dev_table, ELEMENTSOF(protect_kernel_logs_dev_table), p->ignore_protect_paths); if (r < 0) return r; } if (p->protect_control_groups) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/sys/fs/cgroup", .mode = MOUNT_READ_ONLY, }; } r = append_protect_home(&ml, p->protect_home, p->ignore_protect_paths); if (r < 0) return r; r = append_protect_system(&ml, p->protect_system, false); if (r < 0) return r; if (namespace_parameters_mount_apivfs(p)) { r = append_static_mounts(&ml, apivfs_table, ELEMENTSOF(apivfs_table), p->ignore_protect_paths); if (r < 0) return r; } /* Note, if proc is mounted with subset=pid then neither of the two paths will exist, i.e. they are * implicitly protected by the mount option. */ if (p->protect_hostname) { r = append_static_mounts( &ml, protect_hostname_table, ELEMENTSOF(protect_hostname_table), ignore_protect_proc); if (r < 0) return r; } if (p->private_network) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/sys", .mode = MOUNT_PRIVATE_SYSFS, }; } if (p->private_ipc) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/dev/mqueue", .mode = MOUNT_MQUEUEFS, .flags = MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME, }; } if (p->creds_path) { /* If our service has a credentials store configured, then bind that one in, but hide * everything else. */ MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/run/credentials", .mode = MOUNT_TMPFS, .read_only = true, .options_const = "mode=0755" TMPFS_LIMITS_EMPTY_OR_ALMOST, .flags = MS_NODEV|MS_STRICTATIME|MS_NOSUID|MS_NOEXEC, }; me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = p->creds_path, .mode = MOUNT_BIND, .read_only = true, .source_const = p->creds_path, .ignore = true, }; } else { /* If our service has no credentials store configured, then make the whole credentials tree * inaccessible wholesale. */ MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/run/credentials", .mode = MOUNT_INACCESSIBLE, .ignore = true, }; } if (p->log_namespace) { _cleanup_free_ char *q = NULL; q = strjoin("/run/systemd/journal.", p->log_namespace); if (!q) return log_oom_debug(); MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/run/systemd/journal", .mode = MOUNT_BIND_RECURSIVE, .read_only = true, .source_malloc = TAKE_PTR(q), }; } /* Will be used to add bind mounts at runtime */ if (setup_propagate) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .source_const = p->propagate_dir, .path_const = p->incoming_dir, .mode = MOUNT_BIND, .read_only = true, }; } if (p->notify_socket) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = p->notify_socket, .source_const = p->notify_socket, .mode = MOUNT_BIND, .read_only = true, }; } if (p->host_os_release_stage) { MountEntry *me = mount_list_extend(&ml); if (!me) return log_oom_debug(); *me = (MountEntry) { .path_const = "/run/host/.os-release-stage/", .source_const = p->host_os_release_stage, .mode = MOUNT_BIND, .read_only = true, .ignore = true, /* Live copy, don't hard-fail if it goes missing */ }; } /* Prepend the root directory where that's necessary */ r = prefix_where_needed(&ml, root); if (r < 0) return r; drop_unused_mounts(&ml, root); /* All above is just preparation, figuring out what to do. Let's now actually start doing something. */ if (unshare(CLONE_NEWNS) < 0) { r = log_debug_errno(errno, "Failed to unshare the mount namespace: %m"); if (ERRNO_IS_PRIVILEGE(r) || ERRNO_IS_NOT_SUPPORTED(r)) /* If the kernel doesn't support namespaces, or when there's a MAC or seccomp filter * in place that doesn't allow us to create namespaces (or a missing cap), then * propagate a recognizable error back, which the caller can use to detect this case * (and only this) and optionally continue without namespacing applied. */ return -ENOANO; return r; } /* Create the source directory to allow runtime propagation of mounts */ if (setup_propagate) (void) mkdir_p(p->propagate_dir, 0600); if (p->n_extension_images > 0 || !strv_isempty(p->extension_directories)) /* ExtensionImages/Directories mountpoint directories will be created while parsing the * mounts to create, so have the parent ready */ (void) mkdir_p(p->extension_dir, 0600); /* Remount / as SLAVE so that nothing now mounted in the namespace * shows up in the parent */ if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to remount '/' as SLAVE: %m"); if (p->root_image) { /* A root image is specified, mount it to the right place */ r = dissected_image_mount( dissected_image, root, /* uid_shift= */ UID_INVALID, /* uid_range= */ UID_INVALID, userns_fd, dissect_image_flags); if (r < 0) return log_debug_errno(r, "Failed to mount root image: %m"); /* Now release the block device lock, so that udevd is free to call BLKRRPART on the device * if it likes. */ if (loop_device) { r = loop_device_flock(loop_device, LOCK_UN); if (r < 0) return log_debug_errno(r, "Failed to release lock on loopback block device: %m"); } r = dissected_image_relinquish(dissected_image); if (r < 0) return log_debug_errno(r, "Failed to relinquish dissected image: %m"); } else if (p->root_directory) { /* A root directory is specified. Turn its directory into bind mount, if it isn't one yet. */ r = path_is_mount_point_full(root, /* root = */ NULL, AT_SYMLINK_FOLLOW); if (r < 0) return log_debug_errno(r, "Failed to detect that %s is a mount point or not: %m", root); if (r == 0) { r = mount_nofollow_verbose(LOG_DEBUG, root, root, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; } } else { /* Let's mount the main root directory to the root directory to use */ r = mount_nofollow_verbose(LOG_DEBUG, "/", root, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; } /* Try to set up the new root directory before mounting anything else there. */ if (p->root_image || p->root_directory) (void) base_filesystem_create(root, UID_INVALID, GID_INVALID); /* Now make the magic happen */ r = apply_mounts(&ml, root, p, error_path); if (r < 0) return r; /* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */ r = mount_switch_root(root, /* mount_propagation_flag = */ 0); if (r == -EINVAL && p->root_directory) { /* If we are using root_directory and we don't have privileges (ie: user manager in a user * namespace) and the root_directory is already a mount point in the parent namespace, * MS_MOVE will fail as we don't have permission to change it (with EINVAL rather than * EPERM). Attempt to bind-mount it over itself (like we do above if it's not already a * mount point) and try again. */ r = mount_nofollow_verbose(LOG_DEBUG, root, root, NULL, MS_BIND|MS_REC, NULL); if (r < 0) return r; r = mount_switch_root(root, /* mount_propagation_flag = */ 0); } if (r < 0) return log_debug_errno(r, "Failed to mount root with MS_MOVE: %m"); /* Remount / as the desired mode. Note that this will not reestablish propagation from our side to * the host, since what's disconnected is disconnected. */ if (mount(NULL, "/", NULL, mount_propagation_flag | MS_REC, NULL) < 0) return log_debug_errno(errno, "Failed to remount '/' with desired mount flags: %m"); /* bind_mount_in_namespace() will MS_MOVE into that directory, and that's only supported for * non-shared mounts. This needs to happen after remounting / or it will fail. */ if (setup_propagate && mount(NULL, p->incoming_dir, NULL, MS_SLAVE, NULL) < 0) return log_debug_errno(errno, "Failed to remount %s with MS_SLAVE: %m", p->incoming_dir); return 0; } void bind_mount_free_many(BindMount *b, size_t n) { assert(b || n == 0); FOREACH_ARRAY(i, b, n) { free(i->source); free(i->destination); } free(b); } int bind_mount_add(BindMount **b, size_t *n, const BindMount *item) { _cleanup_free_ char *s = NULL, *d = NULL; BindMount *c; assert(b); assert(n); assert(item); s = strdup(item->source); if (!s) return -ENOMEM; d = strdup(item->destination); if (!d) return -ENOMEM; c = reallocarray(*b, *n + 1, sizeof(BindMount)); if (!c) return -ENOMEM; *b = c; c[(*n)++] = (BindMount) { .source = TAKE_PTR(s), .destination = TAKE_PTR(d), .read_only = item->read_only, .nosuid = item->nosuid, .recursive = item->recursive, .ignore_enoent = item->ignore_enoent, }; return 0; } MountImage* mount_image_free_many(MountImage *m, size_t *n) { assert(n); assert(m || *n == 0); for (size_t i = 0; i < *n; i++) { free(m[i].source); free(m[i].destination); mount_options_free_all(m[i].mount_options); } free(m); *n = 0; return NULL; } int mount_image_add(MountImage **m, size_t *n, const MountImage *item) { _cleanup_free_ char *s = NULL, *d = NULL; _cleanup_(mount_options_free_allp) MountOptions *options = NULL; MountImage *c; assert(m); assert(n); assert(item); s = strdup(item->source); if (!s) return -ENOMEM; if (item->destination) { d = strdup(item->destination); if (!d) return -ENOMEM; } LIST_FOREACH(mount_options, i, item->mount_options) { _cleanup_(mount_options_free_allp) MountOptions *o = NULL; o = new(MountOptions, 1); if (!o) return -ENOMEM; *o = (MountOptions) { .partition_designator = i->partition_designator, .options = strdup(i->options), }; if (!o->options) return -ENOMEM; LIST_APPEND(mount_options, options, TAKE_PTR(o)); } c = reallocarray(*m, *n + 1, sizeof(MountImage)); if (!c) return -ENOMEM; *m = c; c[(*n)++] = (MountImage) { .source = TAKE_PTR(s), .destination = TAKE_PTR(d), .mount_options = TAKE_PTR(options), .ignore_enoent = item->ignore_enoent, .type = item->type, }; return 0; } void temporary_filesystem_free_many(TemporaryFileSystem *t, size_t n) { assert(t || n == 0); for (size_t i = 0; i < n; i++) { free(t[i].path); free(t[i].options); } free(t); } int temporary_filesystem_add( TemporaryFileSystem **t, size_t *n, const char *path, const char *options) { _cleanup_free_ char *p = NULL, *o = NULL; TemporaryFileSystem *c; assert(t); assert(n); assert(path); p = strdup(path); if (!p) return -ENOMEM; if (!isempty(options)) { o = strdup(options); if (!o) return -ENOMEM; } c = reallocarray(*t, *n + 1, sizeof(TemporaryFileSystem)); if (!c) return -ENOMEM; *t = c; c[(*n)++] = (TemporaryFileSystem) { .path = TAKE_PTR(p), .options = TAKE_PTR(o), }; return 0; } static int make_tmp_prefix(const char *prefix) { _cleanup_free_ char *t = NULL; _cleanup_close_ int fd = -EBADF; int r; /* Don't do anything unless we know the dir is actually missing */ r = access(prefix, F_OK); if (r >= 0) return 0; if (errno != ENOENT) return -errno; WITH_UMASK(000) r = mkdir_parents(prefix, 0755); if (r < 0) return r; r = tempfn_random(prefix, NULL, &t); if (r < 0) return r; /* umask will corrupt this access mode, but that doesn't matter, we need to call chmod() anyway for * the suid bit, below. */ fd = open_mkdir_at(AT_FDCWD, t, O_EXCL|O_CLOEXEC, 0777); if (fd < 0) return fd; r = RET_NERRNO(fchmod(fd, 01777)); if (r < 0) { (void) rmdir(t); return r; } r = RET_NERRNO(rename(t, prefix)); if (r < 0) { (void) rmdir(t); return r == -EEXIST ? 0 : r; /* it's fine if someone else created the dir by now */ } return 0; } static int setup_one_tmp_dir(const char *id, const char *prefix, char **path, char **tmp_path) { _cleanup_free_ char *x = NULL; _cleanup_free_ char *y = NULL; sd_id128_t boot_id; bool rw = true; int r; assert(id); assert(prefix); assert(path); /* We include the boot id in the directory so that after a * reboot we can easily identify obsolete directories. */ r = sd_id128_get_boot(&boot_id); if (r < 0) return r; x = strjoin(prefix, "/systemd-private-", SD_ID128_TO_STRING(boot_id), "-", id, "-XXXXXX"); if (!x) return -ENOMEM; r = make_tmp_prefix(prefix); if (r < 0) return r; WITH_UMASK(0077) if (!mkdtemp(x)) { if (errno == EROFS || ERRNO_IS_DISK_SPACE(errno)) rw = false; else return -errno; } if (rw) { y = strjoin(x, "/tmp"); if (!y) return -ENOMEM; WITH_UMASK(0000) if (mkdir(y, 0777 | S_ISVTX) < 0) return -errno; r = label_fix_full(AT_FDCWD, y, prefix, 0); if (r < 0) return r; if (tmp_path) *tmp_path = TAKE_PTR(y); } else { /* Trouble: we failed to create the directory. Instead of failing, let's simulate /tmp being * read-only. This way the service will get the EROFS result as if it was writing to the real * file system. */ WITH_UMASK(0000) r = mkdir_p(RUN_SYSTEMD_EMPTY, 0500); if (r < 0) return r; r = free_and_strdup(&x, RUN_SYSTEMD_EMPTY); if (r < 0) return r; } *path = TAKE_PTR(x); return 0; } int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) { _cleanup_(namespace_cleanup_tmpdirp) char *a = NULL; _cleanup_(rmdir_and_freep) char *a_tmp = NULL; char *b; int r; assert(id); assert(tmp_dir); assert(var_tmp_dir); r = setup_one_tmp_dir(id, "/tmp", &a, &a_tmp); if (r < 0) return r; r = setup_one_tmp_dir(id, "/var/tmp", &b, NULL); if (r < 0) return r; a_tmp = mfree(a_tmp); /* avoid rmdir */ *tmp_dir = TAKE_PTR(a); *var_tmp_dir = TAKE_PTR(b); return 0; } int setup_shareable_ns(int ns_storage_socket[static 2], unsigned long nsflag) { _cleanup_close_ int ns = -EBADF; const char *ns_name, *ns_path; int r; assert(ns_storage_socket); assert(ns_storage_socket[0] >= 0); assert(ns_storage_socket[1] >= 0); ns_name = ASSERT_PTR(namespace_single_flag_to_string(nsflag)); /* We use the passed socketpair as a storage buffer for our namespace reference fd. Whatever process * runs this first shall create a new namespace, all others should just join it. To serialize that we * use a file lock on the socket pair. * * It's a bit crazy, but hey, works great! */ r = posix_lock(ns_storage_socket[0], LOCK_EX); if (r < 0) return r; CLEANUP_POSIX_UNLOCK(ns_storage_socket[0]); ns = receive_one_fd(ns_storage_socket[0], MSG_PEEK|MSG_DONTWAIT); if (ns >= 0) { /* Yay, found something, so let's join the namespace */ r = RET_NERRNO(setns(ns, nsflag)); if (r < 0) return r; return 0; } if (ns != -EAGAIN) return ns; /* Nothing stored yet, so let's create a new namespace. */ if (unshare(nsflag) < 0) return -errno; if (nsflag == CLONE_NEWNET) (void) loopback_setup(); ns_path = strjoina("/proc/self/ns/", ns_name); ns = open(ns_path, O_RDONLY|O_CLOEXEC|O_NOCTTY); if (ns < 0) return -errno; r = send_one_fd(ns_storage_socket[1], ns, MSG_DONTWAIT); if (r < 0) return r; return 1; } int open_shareable_ns_path(int ns_storage_socket[static 2], const char *path, unsigned long nsflag) { _cleanup_close_ int ns = -EBADF; int r; assert(ns_storage_socket); assert(ns_storage_socket[0] >= 0); assert(ns_storage_socket[1] >= 0); assert(path); /* If the storage socket doesn't contain a ns fd yet, open one via the file system and store it in * it. This is supposed to be called ahead of time, i.e. before setup_shareable_ns() which will * allocate a new anonymous ns if needed. */ r = posix_lock(ns_storage_socket[0], LOCK_EX); if (r < 0) return r; CLEANUP_POSIX_UNLOCK(ns_storage_socket[0]); ns = receive_one_fd(ns_storage_socket[0], MSG_PEEK|MSG_DONTWAIT); if (ns >= 0) return 0; if (ns != -EAGAIN) return ns; /* Nothing stored yet. Open the file from the file system. */ ns = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC); if (ns < 0) return -errno; r = fd_is_ns(ns, nsflag); if (r == 0) return -EINVAL; if (r < 0 && r != -EUCLEAN) /* EUCLEAN: we don't know */ return r; r = send_one_fd(ns_storage_socket[1], ns, MSG_DONTWAIT); if (r < 0) return r; return 1; } bool ns_type_supported(NamespaceType type) { const char *t, *ns_proc; t = namespace_type_to_string(type); if (!t) /* Don't know how to translate this? Then it's not supported */ return false; ns_proc = strjoina("/proc/self/ns/", t); return access(ns_proc, F_OK) == 0; } static const char *const protect_home_table[_PROTECT_HOME_MAX] = { [PROTECT_HOME_NO] = "no", [PROTECT_HOME_YES] = "yes", [PROTECT_HOME_READ_ONLY] = "read-only", [PROTECT_HOME_TMPFS] = "tmpfs", }; DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(protect_home, ProtectHome, PROTECT_HOME_YES); static const char *const protect_system_table[_PROTECT_SYSTEM_MAX] = { [PROTECT_SYSTEM_NO] = "no", [PROTECT_SYSTEM_YES] = "yes", [PROTECT_SYSTEM_FULL] = "full", [PROTECT_SYSTEM_STRICT] = "strict", }; DEFINE_STRING_TABLE_LOOKUP_WITH_BOOLEAN(protect_system, ProtectSystem, PROTECT_SYSTEM_YES); static const char* const namespace_type_table[] = { [NAMESPACE_MOUNT] = "mnt", [NAMESPACE_CGROUP] = "cgroup", [NAMESPACE_UTS] = "uts", [NAMESPACE_IPC] = "ipc", [NAMESPACE_USER] = "user", [NAMESPACE_PID] = "pid", [NAMESPACE_NET] = "net", [NAMESPACE_TIME] = "time", }; DEFINE_STRING_TABLE_LOOKUP(namespace_type, NamespaceType); static const char* const protect_proc_table[_PROTECT_PROC_MAX] = { [PROTECT_PROC_DEFAULT] = "default", [PROTECT_PROC_NOACCESS] = "noaccess", [PROTECT_PROC_INVISIBLE] = "invisible", [PROTECT_PROC_PTRACEABLE] = "ptraceable", }; DEFINE_STRING_TABLE_LOOKUP(protect_proc, ProtectProc); static const char* const proc_subset_table[_PROC_SUBSET_MAX] = { [PROC_SUBSET_ALL] = "all", [PROC_SUBSET_PID] = "pid", }; DEFINE_STRING_TABLE_LOOKUP(proc_subset, ProcSubset);