/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include "sd-daemon.h" #include "bpf-dlopen.h" #if HAVE_VMLINUX_H #include "bpf-link.h" #endif #include "build-path.h" #include "common-signal.h" #include "env-util.h" #include "fd-util.h" #include "fs-util.h" #include "mkdir.h" #include "nsresourced-manager.h" #include "parse-util.h" #include "process-util.h" #include "recurse-dir.h" #include "set.h" #include "signal-util.h" #include "socket-util.h" #include "stat-util.h" #include "stdio-util.h" #include "strv.h" #include "umask-util.h" #include "unaligned.h" #include "user-util.h" #include "userns-registry.h" #include "userns-restrict.h" #define LISTEN_TIMEOUT_USEC (25 * USEC_PER_SEC) static int start_workers(Manager *m, bool explicit_request); static int on_worker_exit(sd_event_source *s, const siginfo_t *si, void *userdata) { Manager *m = ASSERT_PTR(userdata); assert(s); assert_se(!set_remove(m->workers_dynamic, s) != !set_remove(m->workers_fixed, s)); sd_event_source_disable_unref(s); if (si->si_code == CLD_EXITED) { if (si->si_status == EXIT_SUCCESS) log_debug("Worker " PID_FMT " exited successfully.", si->si_pid); else log_warning("Worker " PID_FMT " died with a failure exit status %i, ignoring.", si->si_pid, si->si_status); } else if (si->si_code == CLD_KILLED) log_warning("Worker " PID_FMT " was killed by signal %s, ignoring.", si->si_pid, signal_to_string(si->si_status)); else if (si->si_code == CLD_DUMPED) log_warning("Worker " PID_FMT " dumped core by signal %s, ignoring.", si->si_pid, signal_to_string(si->si_status)); else log_warning("Got unexpected exit code via SIGCHLD, ignoring."); (void) start_workers(m, /* explicit_request= */ false); /* Fill up workers again if we fell below the low watermark */ return 0; } static int on_sigusr2(sd_event_source *s, const struct signalfd_siginfo *si, void *userdata) { Manager *m = ASSERT_PTR(userdata); assert(s); (void) start_workers(m, /* explicit_request=*/ true); /* Workers told us there's more work, let's add one more worker as long as we are below the high watermark */ return 0; } static int on_deferred_start_worker(sd_event_source *s, uint64_t usec, void *userdata) { Manager *m = ASSERT_PTR(userdata); assert(s); m->deferred_start_worker_event_source = sd_event_source_unref(m->deferred_start_worker_event_source); (void) start_workers(m, /* explicit_request=*/ false); return 0; } DEFINE_PRIVATE_HASH_OPS_WITH_KEY_DESTRUCTOR( event_source_hash_ops, sd_event_source, (void (*)(const sd_event_source*, struct siphash*)) trivial_hash_func, (int (*)(const sd_event_source*, const sd_event_source*)) trivial_compare_func, sd_event_source_disable_unref); int manager_new(Manager **ret) { _cleanup_(manager_freep) Manager *m = NULL; int r; m = new(Manager, 1); if (!m) return -ENOMEM; *m = (Manager) { .listen_fd = -EBADF, .worker_ratelimit = { .interval = 2 * USEC_PER_SEC, .burst = 250, }, .registry_fd = -EBADF, }; r = sd_event_new(&m->event); if (r < 0) return r; r = sd_event_set_signal_exit(m->event, true); if (r < 0) return r; r = sd_event_add_signal(m->event, NULL, (SIGRTMIN+18)|SD_EVENT_SIGNAL_PROCMASK, sigrtmin18_handler, NULL); if (r < 0) return r; r = sd_event_add_memory_pressure(m->event, NULL, NULL, NULL); if (r < 0) log_debug_errno(r, "Failed allocate memory pressure event source, ignoring: %m"); r = sd_event_set_watchdog(m->event, true); if (r < 0) log_debug_errno(r, "Failed to enable watchdog handling, ignoring: %m"); r = sd_event_add_signal(m->event, NULL, SIGUSR2|SD_EVENT_SIGNAL_PROCMASK, on_sigusr2, m); if (r < 0) return r; *ret = TAKE_PTR(m); return 0; } Manager* manager_free(Manager *m) { if (!m) return NULL; set_free(m->workers_fixed); set_free(m->workers_dynamic); m->deferred_start_worker_event_source = sd_event_source_unref(m->deferred_start_worker_event_source); safe_close(m->listen_fd); #if HAVE_VMLINUX_H sd_event_source_disable_unref(m->userns_restrict_bpf_ring_buffer_event_source); bpf_ring_buffer_free(m->userns_restrict_bpf_ring_buffer); userns_restrict_bpf_free(m->userns_restrict_bpf); #endif safe_close(m->registry_fd); sd_event_unref(m->event); return mfree(m); } static size_t manager_current_workers(Manager *m) { assert(m); return set_size(m->workers_fixed) + set_size(m->workers_dynamic); } static int start_one_worker(Manager *m) { _cleanup_(sd_event_source_disable_unrefp) sd_event_source *source = NULL; bool fixed; pid_t pid; int r; assert(m); fixed = set_size(m->workers_fixed) < NSRESOURCE_WORKERS_MIN; r = safe_fork_full( "(sd-worker)", /* stdio_fds= */ NULL, &m->listen_fd, 1, FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|FORK_REOPEN_LOG|FORK_LOG|FORK_CLOSE_ALL_FDS, &pid); if (r < 0) return log_error_errno(r, "Failed to fork new worker child: %m"); if (r == 0) { char pids[DECIMAL_STR_MAX(pid_t)]; /* Child */ if (m->listen_fd == 3) { r = fd_cloexec(3, false); if (r < 0) { log_error_errno(r, "Failed to turn off O_CLOEXEC for fd 3: %m"); _exit(EXIT_FAILURE); } } else { if (dup2(m->listen_fd, 3) < 0) { /* dup2() creates with O_CLOEXEC off */ log_error_errno(errno, "Failed to move listen fd to 3: %m"); _exit(EXIT_FAILURE); } safe_close(m->listen_fd); } xsprintf(pids, PID_FMT, pid); if (setenv("LISTEN_PID", pids, 1) < 0) { log_error_errno(errno, "Failed to set $LISTEN_PID: %m"); _exit(EXIT_FAILURE); } if (setenv("LISTEN_FDS", "1", 1) < 0) { log_error_errno(errno, "Failed to set $LISTEN_FDS: %m"); _exit(EXIT_FAILURE); } if (setenv("NSRESOURCE_FIXED_WORKER", one_zero(fixed), 1) < 0) { log_error_errno(errno, "Failed to set $NSRESOURCE_FIXED_WORKER: %m"); _exit(EXIT_FAILURE); } #if HAVE_VMLINUX_H bool supported = m->userns_restrict_bpf; #else bool supported = false; #endif /* Tell the workers whether to enable the userns API */ if (setenv("NSRESOURCE_API", one_zero(supported), 1) < 0) { log_error_errno(errno, "Failed to set $NSRESOURCE_API: %m"); _exit(EXIT_FAILURE); } r = setenv_systemd_log_level(); if (r < 0) { log_error_errno(r, "Failed to set $SYSTEMD_LOG_LEVEL: %m"); _exit(EXIT_FAILURE); } r = invoke_callout_binary(SYSTEMD_NSRESOURCEWORK_PATH, STRV_MAKE("systemd-nsresourcework", "xxxxxxxxxxxxxxxx")); /* With some extra space rename_process() can make use of */ log_error_errno(r, "Failed start worker process: %m"); _exit(EXIT_FAILURE); } r = sd_event_add_child(m->event, &source, pid, WEXITED, on_worker_exit, m); if (r < 0) return log_error_errno(r, "Failed to watch child " PID_FMT ": %m", pid); r = set_ensure_put( fixed ? &m->workers_fixed : &m->workers_dynamic, &event_source_hash_ops, source); if (r < 0) return log_error_errno(r, "Failed to add child process to set: %m"); TAKE_PTR(source); return 0; } static int start_workers(Manager *m, bool explicit_request) { int r; assert(m); for (;;) { size_t n; n = manager_current_workers(m); if (n >= NSRESOURCE_WORKERS_MIN && (!explicit_request || n >= NSRESOURCE_WORKERS_MAX)) break; if (!ratelimit_below(&m->worker_ratelimit)) { /* If we keep starting workers too often but none sticks, let's fail the whole * daemon, something is wrong */ if (n == 0) { sd_event_exit(m->event, EXIT_FAILURE); return log_error_errno(SYNTHETIC_ERRNO(EUCLEAN), "Worker threads requested too frequently, but worker count is zero, something is wrong."); } /* Otherwise, let's stop spawning more for a while. */ log_warning("Worker threads requested too frequently, not starting new ones for a while."); if (!m->deferred_start_worker_event_source) { r = sd_event_add_time( m->event, &m->deferred_start_worker_event_source, CLOCK_MONOTONIC, ratelimit_end(&m->worker_ratelimit), /* accuracy_usec= */ 0, on_deferred_start_worker, m); if (r < 0) return log_error_errno(r, "Failed to allocate deferred start worker event source: %m"); } break; } r = start_one_worker(m); if (r < 0) return r; explicit_request = false; } return 0; } static void manager_release_userns_bpf(Manager *m, uint64_t inode) { #if HAVE_VMLINUX_H int r; assert(m); if (inode == 0) return; assert(m->userns_restrict_bpf); r = userns_restrict_reset_by_inode(m->userns_restrict_bpf, inode); if (r < 0) return (void) log_warning_errno(r, "Failed to remove namespace inode from BPF map, ignoring: %m"); #endif } static void manager_release_userns_fds(Manager *m, uint64_t inode) { int r; assert(m); assert(inode != 0); r = sd_notifyf(/* unset_environment= */ false, "FDSTOREREMOVE=1\n" "FDNAME=userns-%" PRIu64 "\n", inode); if (r < 0) log_warning_errno(r, "Failed to send fd store removal message, ignoring: %m"); } static void manager_release_userns_by_inode(Manager *m, uint64_t inode) { _cleanup_(userns_info_freep) UserNamespaceInfo *userns_info = NULL; _cleanup_close_ int lock_fd = -EBADF; int r; assert(m); assert(inode != 0); lock_fd = userns_registry_lock(m->registry_fd); if (lock_fd < 0) return (void) log_error_errno(lock_fd, "Failed to lock registry: %m"); r = userns_registry_load_by_userns_inode(m->registry_fd, inode, &userns_info); if (r < 0) log_full_errno(r == -ENOENT ? LOG_DEBUG : LOG_WARNING, r, "Failed to find userns for inode %" PRIu64 ", ignoring: %m", inode); if (userns_info && uid_is_valid(userns_info->start)) log_debug("Removing user namespace mapping %" PRIu64 " for UID " UID_FMT ".", inode, userns_info->start); else log_debug("Removing user namespace mapping %" PRIu64 ".", inode); /* Remove the BPF rules */ manager_release_userns_bpf(m, inode); /* Remove the resources from the fdstore */ manager_release_userns_fds(m, inode); /* And finally remove the resources file from disk */ if (userns_info) { /* Remove the cgroups of this userns */ r = userns_info_remove_cgroups(userns_info); if (r < 0) log_warning_errno(r, "Failed to remove cgroups of user namespace: %m"); r = userns_registry_remove(m->registry_fd, userns_info); if (r < 0) log_warning_errno(r, "Failed to remove user namespace '%s', ignoring.", userns_info->name); } } static int manager_scan_registry(Manager *m, Set **registry_inodes) { _cleanup_free_ DirectoryEntries *de = NULL; int r; assert(m); assert(registry_inodes); assert(m->registry_fd >= 0); r = readdir_all(m->registry_fd, RECURSE_DIR_IGNORE_DOT, &de); if (r < 0) return log_error_errno(r, "Failed to enumerate registry."); for (size_t i = 0; i < de->n_entries; i++) { struct dirent *dentry = de->entries[i]; _cleanup_free_ char *u = NULL; const char *e, *p; uint64_t inode; p = startswith(dentry->d_name, "i"); if (!p) continue; e = endswith(p, ".userns"); if (!e) continue; u = strndup(p, e - p); if (!u) return log_oom(); r = safe_atou64(u, &inode); if (r < 0) { log_warning_errno(r, "Failed to parse userns inode number from '%s', skipping: %m", dentry->d_name); continue; } if (inode > UINT32_MAX) { /* namespace inode numbers are 23bit only right now */ log_warning("userns inode number outside of 32bit range, skipping."); continue; } if (set_ensure_put(registry_inodes, NULL, UINT32_TO_PTR(inode)) < 0) return log_oom(); log_debug("Found user namespace %" PRIu64 " in registry directory", inode); } return 0; } static int manager_make_listen_socket(Manager *m) { static const union sockaddr_union sockaddr = { .un.sun_family = AF_UNIX, .un.sun_path = "/run/systemd/io.systemd.NamespaceResource", }; int r; assert(m); if (m->listen_fd >= 0) return 0; m->listen_fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0); if (m->listen_fd < 0) return log_error_errno(errno, "Failed to bind on socket: %m"); (void) sockaddr_un_unlink(&sockaddr.un); WITH_UMASK(0000) if (bind(m->listen_fd, &sockaddr.sa, SOCKADDR_UN_LEN(sockaddr.un)) < 0) return log_error_errno(errno, "Failed to bind socket: %m"); r = mkdir_p("/run/systemd/userdb", 0755); if (r < 0) return log_error_errno(r, "Failed to create /run/systemd/userdb: %m"); r = symlink_idempotent("../io.systemd.NamespaceResource", "/run/systemd/userdb/io.systemd.NamespaceResource", /* make_relative= */ false); if (r < 0) return log_error_errno(r, "Failed to symlink userdb socket: %m"); if (listen(m->listen_fd, SOMAXCONN) < 0) return log_error_errno(errno, "Failed to listen on socket: %m"); return 1; } static int manager_scan_listen_fds(Manager *m, Set **fdstore_inodes) { _cleanup_strv_free_ char **names = NULL; int n, r; assert(m); assert(fdstore_inodes); n = sd_listen_fds_with_names(/* unset_environment= */ true, &names); if (n < 0) return log_error_errno(n, "Failed to determine number of passed file descriptors: %m"); for (int i = 0; i < n; i++) { _cleanup_close_ int fd = SD_LISTEN_FDS_START + i; /* Take possession */ const char *e; /* If this is a BPF allowlist related fd, just close it, but remember which start UIDs this covers */ e = startswith(names[i], "userns-"); if (e) { uint64_t inode; r = safe_atou64(e, &inode); if (r < 0) { log_warning_errno(r, "Failed to parse UID from fd name '%s', ignoring: %m", e); continue; } if (inode > UINT32_MAX) { log_warning("Inode number outside of 32bit range, ignoring"); continue; } if (set_ensure_put(fdstore_inodes, NULL, UINT32_TO_PTR(inode)) < 0) return log_oom(); continue; } /* We don't check the name for the stream socket, for compatibility with older versions */ r = sd_is_socket(fd, AF_UNIX, SOCK_STREAM, 1); if (r < 0) return log_error_errno(r, "Failed to detect if passed file descriptor is a socket: %m"); if (r > 0) { if (m->listen_fd >= 0) return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ), "Passed more than one AF_UNIX/SOCK_STREAM socket, refusing."); m->listen_fd = TAKE_FD(fd); continue; } log_warning("Closing passed file descriptor %i (%s) we don't recognize.", fd, names[i]); } return 0; } #if HAVE_VMLINUX_H static int ringbuf_event(void *userdata, void *data, size_t size) { Manager *m = ASSERT_PTR(userdata); size_t n; if ((size % sizeof(unsigned int)) != 0) /* Not multiples of "unsigned int"? */ return -EIO; n = size / sizeof(unsigned int); for (size_t i = 0; i < n; i++) { const void *d; uint64_t inode; d = (const uint8_t*) data + i * sizeof(unsigned int); inode = unaligned_read_ne32(d); log_debug("Got BPF ring buffer notification that user namespace %" PRIu64 " is now dead.", inode); manager_release_userns_by_inode(m, inode); } return 0; } static int on_ringbuf_io(sd_event_source *s, int fd, uint32_t revents, void *userdata) { Manager *m = ASSERT_PTR(userdata); int r; r = sym_ring_buffer__poll(m->userns_restrict_bpf_ring_buffer, 0); if (r < 0) return log_error_errno(r, "Got failure reading from BPF ring buffer: %m"); return 0; } static int manager_setup_bpf(Manager *m) { int rb_fd = -EBADF, poll_fd = -EBADF, r; assert(m); assert(!m->userns_restrict_bpf); assert(!m->userns_restrict_bpf_ring_buffer); assert(!m->userns_restrict_bpf_ring_buffer_event_source); r = userns_restrict_install(/* pin= */ true, &m->userns_restrict_bpf); if (r < 0) { log_notice_errno(r, "Proceeding with user namespace interfaces disabled."); return 0; } rb_fd = sym_bpf_map__fd(m->userns_restrict_bpf->maps.userns_ringbuf); if (rb_fd < 0) return log_error_errno(rb_fd, "Failed to get fd of ring buffer: %m"); m->userns_restrict_bpf_ring_buffer = sym_ring_buffer__new(rb_fd, ringbuf_event, m, NULL); if (!m->userns_restrict_bpf_ring_buffer) return log_error_errno(errno, "Failed to allocate BPF ring buffer object: %m"); poll_fd = sym_ring_buffer__epoll_fd(m->userns_restrict_bpf_ring_buffer); if (poll_fd < 0) return log_error_errno(poll_fd, "Failed to get poll fd of ring buffer: %m"); r = sd_event_add_io( m->event, &m->userns_restrict_bpf_ring_buffer_event_source, poll_fd, EPOLLIN, on_ringbuf_io, m); if (r < 0) return log_error_errno(r, "Failed to allocate event source for BPF ring buffer: %m"); return 0; } #else static int manager_setup_bpf(Manager *m) { log_notice("Not setting up BPF subsystem, as functionality has been disabled at compile time."); return 0; } #endif int manager_startup(Manager *m) { _cleanup_(set_freep) Set *fdstore_inodes = NULL, *registry_inodes = NULL; void *p; int r; assert(m); assert(m->registry_fd < 0); assert(m->listen_fd < 0); m->registry_fd = userns_registry_open_fd(); if (m->registry_fd < 0) return log_error_errno(m->registry_fd, "Failed to open registry directory: %m"); r = manager_setup_bpf(m); if (r < 0) return r; r = manager_scan_listen_fds(m, &fdstore_inodes); if (r < 0) return r; r = manager_scan_registry(m, ®istry_inodes); if (r < 0) return r; /* If there are resources tied to UIDs not found in the registry, then release them */ SET_FOREACH(p, fdstore_inodes) { uint64_t inode; if (set_contains(registry_inodes, p)) continue; inode = PTR_TO_UINT32(p); log_debug("Found stale fd store entry for user namespace %" PRIu64 ", removing.", inode); manager_release_userns_by_inode(m, inode); } r = manager_make_listen_socket(m); if (r < 0) return r; /* Let's make sure every accept() call on this socket times out after 25s. This allows workers to be * GC'ed on idle */ if (setsockopt(m->listen_fd, SOL_SOCKET, SO_RCVTIMEO, TIMEVAL_STORE(LISTEN_TIMEOUT_USEC), sizeof(struct timeval)) < 0) return log_error_errno(errno, "Failed to se SO_RCVTIMEO: %m"); r = start_workers(m, /* explicit_request= */ false); if (r < 0) return r; return 0; }