/* SPDX-License-Identifier: GPL-2.0-or-later */ #include #include #include #include #include "blockdev-util.h" #include "btrfs-util.h" #include "device-util.h" #include "fd-util.h" #include "fdset.h" #include "main-func.h" #include "parse-util.h" #include "path-util.h" #include "pretty-print.h" #include "process-util.h" #include "signal-util.h" #include "sort-util.h" #include "strv.h" #include "time-util.h" #include "udevadm.h" static usec_t arg_timeout_usec = USEC_INFINITY; static char **arg_devices = NULL; static char **arg_backing = NULL; static char **arg_cmdline = NULL; static bool arg_print = false; STATIC_DESTRUCTOR_REGISTER(arg_devices, strv_freep); STATIC_DESTRUCTOR_REGISTER(arg_backing, strv_freep); STATIC_DESTRUCTOR_REGISTER(arg_cmdline, strv_freep); static int help(void) { _cleanup_free_ char *link = NULL; int r; r = terminal_urlify_man("udevadm", "8", &link); if (r < 0) return log_oom(); printf("%s [OPTIONS...] COMMAND\n" "%s [OPTIONS...] --print\n" "\n%sLock a block device and run a command.%s\n\n" " -h --help Print this message\n" " -V --version Print version of the program\n" " -d --device=DEVICE Block device to lock\n" " -b --backing=FILE File whose backing block device to lock\n" " -t --timeout=SECS Block at most the specified time waiting for lock\n" " -p --print Only show which block device the lock would be taken on\n" "\nSee the %s for details.\n", program_invocation_short_name, program_invocation_short_name, ansi_highlight(), ansi_normal(), link); return 0; } static int parse_argv(int argc, char *argv[]) { static const struct option options[] = { { "help", no_argument, NULL, 'h' }, { "version", no_argument, NULL, 'V' }, { "device", required_argument, NULL, 'd' }, { "backing", required_argument, NULL, 'b' }, { "timeout", required_argument, NULL, 't' }, { "print", no_argument, NULL, 'p' }, {} }; int c, r; assert(argc >= 0); assert(argv); while ((c = getopt_long(argc, argv, arg_print ? "hVd:b:t:p" : "+hVd:b:t:p", options, NULL)) >= 0) switch (c) { case 'h': return help(); case 'V': return print_version(); case 'd': case 'b': { _cleanup_free_ char *s = NULL; char ***l = c == 'd' ? &arg_devices : &arg_backing; r = path_make_absolute_cwd(optarg, &s); if (r < 0) return log_error_errno(r, "Failed to make path '%s' absolute: %m", optarg); path_simplify(s); if (strv_consume(l, TAKE_PTR(s)) < 0) return log_oom(); strv_uniq(*l); break; } case 't': r = parse_sec(optarg, &arg_timeout_usec); if (r < 0) return log_error_errno(r, "Failed to parse --timeout= parameter: %s", optarg); break; case 'p': arg_print = true; break; case '?': return -EINVAL; default: assert_not_reached(); } if (arg_print) { if (optind != argc) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No arguments expected"); } else { if (optind + 1 > argc) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Too few arguments, command to execute."); arg_cmdline = strv_copy(argv + optind); if (!arg_cmdline) return log_oom(); } if (strv_isempty(arg_devices) && strv_isempty(arg_backing)) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No devices to lock specified, refusing."); return 1; } static int find_devno( dev_t **devnos, size_t *n_devnos, const char *device, bool backing) { dev_t devt; int r; assert(devnos); assert(n_devnos); assert(*devnos || *n_devnos == 0); assert(device); r = path_get_whole_disk(device, backing, &devt); if (r < 0) return log_error_errno(r, "Failed to find whole block device for '%s': %m", device); if (typesafe_bsearch(&devt, *devnos, *n_devnos, devt_compare_func)) { log_debug("Device %u:%u already listed for locking, ignoring.", major(devt), minor(devt)); return 0; } if (!GREEDY_REALLOC(*devnos, *n_devnos + 1)) return log_oom(); (*devnos)[(*n_devnos)++] = devt; /* Immediately sort again, to ensure the binary search above will work for the next device we add */ typesafe_qsort(*devnos, *n_devnos, devt_compare_func); return 1; } static int lock_device( const char *path, dev_t devno, usec_t deadline) { _cleanup_close_ int fd = -1; struct stat st; int r; fd = open(path, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY); if (fd < 0) return log_error_errno(errno, "Failed to open '%s': %m", path); if (fstat(fd, &st) < 0) return log_error_errno(errno, "Failed to stat '%s': %m", path); /* Extra safety: check that the device still refers to what we think it refers to */ if (!S_ISBLK(st.st_mode) || st.st_rdev != devno) return log_error_errno(SYNTHETIC_ERRNO(ENXIO), "Path '%s' no longer refers to specified block device %u:%u: %m", path, major(devno), minor(devno)); if (flock(fd, LOCK_EX|LOCK_NB) < 0) { if (errno != EAGAIN) return log_error_errno(errno, "Failed to lock device '%s': %m", path); if (deadline == 0) return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Device '%s' is currently locked.", path); if (deadline == USEC_INFINITY) { log_info("Device '%s' is currently locked, waiting%s", path, special_glyph(SPECIAL_GLYPH_ELLIPSIS)); if (flock(fd, LOCK_EX) < 0) return log_error_errno(errno, "Failed to lock device '%s': %m", path); } else { _cleanup_(sigkill_waitp) pid_t flock_pid = 0; /* flock() doesn't support a time-out. Let's fake one then. The traditional way to do * this is via alarm()/setitimer()/timer_create(), but that's racy, given that the * SIGALRM might already fire between the alarm() and the flock() in which case the * flock() is never cancelled and we lock up (this is a short time window, but with * short timeouts on a loaded machine we might run into it, who knows?). Let's * instead do the lock out-of-process: fork off a child that does the locking, and * that we'll wait on and kill if it takes too long. */ log_info("Device '%s' is currently locked, waiting %s%s", path, FORMAT_TIMESPAN(usec_sub_unsigned(deadline, now(CLOCK_MONOTONIC)), 0), special_glyph(SPECIAL_GLYPH_ELLIPSIS)); BLOCK_SIGNALS(SIGCHLD); r = safe_fork("(timed-flock)", FORK_DEATHSIG|FORK_LOG, &flock_pid); if (r < 0) return r; if (r == 0) { /* Child */ if (flock(fd, LOCK_EX) < 0) { log_error_errno(errno, "Failed to lock device '%s': %m", path); _exit(EXIT_FAILURE); } _exit(EXIT_SUCCESS); } for (;;) { siginfo_t si; sigset_t ss; usec_t n; assert(sigemptyset(&ss) >= 0); assert(sigaddset(&ss, SIGCHLD) >= 0); n = now(CLOCK_MONOTONIC); if (n >= deadline) return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Timeout reached."); r = sigtimedwait(&ss, NULL, TIMESPEC_STORE(deadline - n)); if (r < 0) { if (errno != EAGAIN) return log_error_errno(errno, "Failed to wait for SIGCHLD: %m"); return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Timeout reached."); } assert(r == SIGCHLD); zero(si); if (waitid(P_PID, flock_pid, &si, WEXITED|WNOHANG|WNOWAIT) < 0) return log_error_errno(errno, "Failed to wait for child: %m"); if (si.si_pid != 0) { assert(si.si_pid == flock_pid); if (si.si_code != CLD_EXITED || si.si_status != EXIT_SUCCESS) return log_error_errno(SYNTHETIC_ERRNO(EPROTO), "Unexpected exit status of file lock child."); break; } log_debug("Got SIGCHLD for other child, continuing."); } } } log_debug("Successfully locked %s (%u:%u)%s", path, major(devno), minor(devno), special_glyph(SPECIAL_GLYPH_ELLIPSIS)); return TAKE_FD(fd); } int lock_main(int argc, char *argv[], void *userdata) { _cleanup_(fdset_freep) FDSet *fds = NULL; _cleanup_free_ dev_t *devnos = NULL; size_t n_devnos = 0; usec_t deadline; pid_t pid; int r; r = parse_argv(argc, argv); if (r <= 0) return r; STRV_FOREACH(i, arg_devices) { r = find_devno(&devnos, &n_devnos, *i, /* backing= */ false); if (r < 0) return r; } STRV_FOREACH(i, arg_backing) { r = find_devno(&devnos, &n_devnos, *i, /* backing= */ true); if (r < 0) return r; } assert(n_devnos > 0); fds = fdset_new(); if (!fds) return log_oom(); if (IN_SET(arg_timeout_usec, 0, USEC_INFINITY)) deadline = arg_timeout_usec; else deadline = usec_add(now(CLOCK_MONOTONIC), arg_timeout_usec); for (size_t i = 0; i < n_devnos; i++) { _cleanup_free_ char *node = NULL; r = devname_from_devnum(S_IFBLK, devnos[i], &node); if (r < 0) return log_error_errno(r, "Failed to format block device path: %m"); if (arg_print) printf("%s\n", node); else { _cleanup_close_ int fd = -1; fd = lock_device(node, devnos[i], deadline); if (fd < 0) return fd; r = fdset_put(fds, fd); if (r < 0) return log_oom(); TAKE_FD(fd); } } if (arg_print) return EXIT_SUCCESS; /* Ignore SIGINT and allow the forked process to receive it */ (void) ignore_signals(SIGINT); r = safe_fork("(lock)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_CLOSE_ALL_FDS|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pid); if (r < 0) return r; if (r == 0) { /* Child */ execvp(arg_cmdline[0], arg_cmdline); log_open(); log_error_errno(errno, "Failed to execute %s: %m", arg_cmdline[0]); _exit(EXIT_FAILURE); } return wait_for_terminate_and_check(arg_cmdline[0], pid, 0); }