openrc-run: fix rc_parallel race in svc_exec

svc_exec waits until SIGCHLD comes in to close its input, but in
rc_parallel case the SIGCHLD might be unrelated.

Checking the proper pid is found in signal handler and only signaling
signal_pipe the status code directly avoids this problem.

src/fstabinfo/fstabinfo.c

@@ -23,6 +23,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <stdbool.h>
+#include <spawn.h>
 
 /* Yay for linux and its non liking of POSIX functions.
    Okay, we could use getfsent but the man page says use getmntent instead
@@ -63,6 +64,8 @@
 #include "_usage.h"
 #include "helpers.h"
 
+extern char **environ;
+
 const char *applet = NULL;
 const char *extraopts = NULL;
 const char getoptstring[] = "MRbmop:t:" getoptstring_COMMON;
@@ -112,7 +115,7 @@ do_mount(struct ENT *ent, bool remount)
 {
 	char *argv[10];
 	pid_t pid;
-	int status;
+	int status, err;
 
 	argv[0] = UNCONST("mount");
 	argv[1] = UNCONST("-o");
@@ -137,23 +140,14 @@ do_mount(struct ENT *ent, bool remount)
 		argv[8] = NULL;
 #endif
 	}
-	switch (pid = vfork()) {
+	err = posix_spawnp(&pid, argv[0], NULL, NULL, argv, environ);
-	case -1:
+	if (err)
-		eerrorx("%s: vfork: %s", applet, strerror(errno));
+		eerrorx("%s: posix_spawnp: %s", applet, strerror(err));
-		/* NOTREACHED */
+	while (waitpid(pid, &status, 0) < 0 && errno == EINTR);
-	case 0:
+	if (WIFEXITED(status))
-		execvp(argv[0], argv);
+		return WEXITSTATUS(status);
-		eerror("%s: execvp: %s", applet, strerror(errno));
+	else
-		_exit(EXIT_FAILURE);
+		return -1;
-		/* NOTREACHED */
-	default:
-		waitpid(pid, &status, 0);
-		if (WIFEXITED(status))
-			return WEXITSTATUS(status);
-		else
-			return -1;
-		/* NOTREACHED */
-	}
 }
 
 #define OUTPUT_FILE      (1 << 1)

src/libeinfo/einfo.h

@@ -69,22 +69,22 @@ void elog(int, const char * EINFO_RESTRICT, ...) EINFO_PRINTF(2, 3);
  * The x suffix means function will exit() returning failure.
  */
 /*@{*/
-int einfon(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int einfon(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int ewarnn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int ewarnn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int eerrorn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int eerrorn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int einfo(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int einfo(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int ewarn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int ewarn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-void ewarnx(const char * __EINFO_RESTRICT, ...) EINFO_XPRINTF(1, 2);
+void ewarnx(const char * EINFO_RESTRICT, ...) EINFO_XPRINTF(1, 2);
-int eerror(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int eerror(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-void eerrorx(const char * __EINFO_RESTRICT, ...) EINFO_XPRINTF(1, 2);
+void eerrorx(const char * EINFO_RESTRICT, ...) EINFO_XPRINTF(1, 2);
 
-int einfovn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int einfovn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int ewarnvn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int ewarnvn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int ebeginvn(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int ebeginvn(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int eendvn(int, const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(2, 3);
+int eendvn(int, const char * EINFO_RESTRICT, ...) EINFO_PRINTF(2, 3);
-int ewendvn(int, const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(2, 3);
+int ewendvn(int, const char * EINFO_RESTRICT, ...) EINFO_PRINTF(2, 3);
-int einfov(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int einfov(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
-int ewarnv(const char * __EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
+int ewarnv(const char * EINFO_RESTRICT, ...) EINFO_PRINTF(1, 2);
 /*@}*/
 
 /*! @ingroup ebegin

src/openrc-run/openrc-run.c

@@ -107,7 +107,8 @@ static RC_STRINGLIST *deptypes_mwua;	/* need+want+use+after deps for stopping */
 static void
 handle_signal(int sig)
 {
-	int serrno = errno;
+	int serrno = errno, status;
+	pid_t pid;
 	const char *signame = NULL;
 	struct winsize ws;
 
@@ -117,12 +118,13 @@ handle_signal(int sig)
 		break;
 
 	case SIGCHLD:
-		if (signal_pipe[1] > -1) {
+		while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
-			if (write(signal_pipe[1], &sig, sizeof(sig)) == -1)
+			if (signal_pipe[1] > -1 && pid == service_pid) {
-				eerror("%s: send: %s",
+				if (write(signal_pipe[1], &status, sizeof(status)) == -1)
-				    service, strerror(errno));
+					eerror("%s: send: %s",
-		} else
+					    service, strerror(errno));
-			rc_waitpid(-1);
+			}
+		}
 		break;
 
 	case SIGWINCH:
@@ -438,6 +440,7 @@ svc_exec(const char *arg1, const char *arg2)
 			if (errno != EINTR) {
 				eerror("%s: poll: %s",
 				    service, strerror(errno));
+				ret = -1;
 				break;
 			}
 		}
@@ -448,9 +451,20 @@ svc_exec(const char *arg1, const char *arg2)
 				write_prefix(buffer, bytes, &prefixed);
 			}
 
-			/* Only SIGCHLD signals come down this pipe */
+			/* signal_pipe receives service_pid's exit status */
-			if (fd[0].revents & (POLLIN | POLLHUP))
+			if (fd[0].revents & (POLLIN | POLLHUP)) {
+				if ((s = read(signal_pipe[0], &ret, sizeof(ret))) != sizeof(ret)) {
+					eerror("%s: receive failed: %s", service,
+						s < 0 ? strerror(errno) : "short read");
+					ret = -1;
+					break;
+				}
+				ret = WEXITSTATUS(ret);
+				if (ret != 0 && errno == ECHILD)
+					/* killall5 -9 could cause this */
+					ret = 0;
 				break;
+			}
 		}
 	}
 
@@ -473,11 +487,6 @@ svc_exec(const char *arg1, const char *arg2)
 		master_tty = -1;
 	}
 
-	ret = rc_waitpid(service_pid);
-	ret = WEXITSTATUS(ret);
-	if (ret != 0 && errno == ECHILD)
-		/* killall5 -9 could cause this */
-		ret = 0;
 	service_pid = 0;
 
 	return ret;
@@ -612,7 +621,7 @@ svc_start_check(void)
 	}
 
 	if (exclusive_fd == -1)
-		exclusive_fd = svc_lock(applet);
+		exclusive_fd = svc_lock(applet, !deps);
 	if (exclusive_fd == -1) {
 		if (errno == EACCES)
 			eerrorx("%s: superuser access required", applet);
@@ -864,7 +873,7 @@ svc_stop_check(RC_SERVICE *state)
 		exit(EXIT_FAILURE);
 
 	if (exclusive_fd == -1)
-		exclusive_fd = svc_lock(applet);
+		exclusive_fd = svc_lock(applet, !deps);
 	if (exclusive_fd == -1) {
 		if (errno == EACCES)
 			eerrorx("%s: superuser access required", applet);
@@ -1041,26 +1050,6 @@ svc_stop(void)
 static void
 svc_restart(void)
 {
-	/* This is hairy and a better way needs to be found I think!
-	 * The issue is this - openvpn need net and dns. net can restart
-	 * dns via resolvconf, so you could have openvpn trying to restart
-	 * dnsmasq which in turn is waiting on net which in turn is waiting
-	 * on dnsmasq.
-	 * The work around is for resolvconf to restart its services with
-	 * --nodeps which means just that.
-	 * The downside is that there is a small window when our status is
-	 * invalid.
-	 * One workaround would be to introduce a new status,
-	 * or status locking. */
-	if (!deps) {
-		RC_SERVICE state = rc_service_state(service);
-		if (state & RC_SERVICE_STARTED || state & RC_SERVICE_INACTIVE)
-			svc_exec("stop", "start");
-		else
-			svc_exec("start", NULL);
-		return;
-	}
-
 	if (!(rc_service_state(service) & RC_SERVICE_STOPPED)) {
 		get_started_services();
 		svc_stop();

src/openrc/rc.c

@@ -87,6 +87,7 @@ static RC_HOOK hook_out;
 struct termios *termios_orig = NULL;
 
 RC_PIDLIST service_pids;
+RC_PIDLIST free_these_pids;
 
 static void
 clean_failed(void)
@@ -116,8 +117,7 @@ clean_failed(void)
 static void
 cleanup(void)
 {
-	RC_PID *p1 = LIST_FIRST(&service_pids);
+	RC_PID *p, *tmp;
-	RC_PID *p2;
 
 	if (!rc_in_logger && !rc_in_plugin &&
 	    applet && (strcmp(applet, "rc") == 0 || strcmp(applet, "openrc") == 0))
@@ -139,10 +139,13 @@ cleanup(void)
 		rc_logger_close();
 	}
 
-	while (p1) {
+	LIST_FOREACH_SAFE(p, &service_pids, entries, tmp) {
-		p2 = LIST_NEXT(p1, entries);
+		LIST_REMOVE(p, entries);
-		free(p1);
+		free(p);
-		p1 = p2;
+	}
+	LIST_FOREACH_SAFE(p, &free_these_pids, entries, tmp) {
+		LIST_REMOVE(p, entries);
+		free(p);
 	}
 
 	rc_stringlist_free(main_hotplugged_services);
@@ -344,22 +347,46 @@ static char *get_krunlevel(void)
 static void
 add_pid(pid_t pid)
 {
+	sigset_t sset, old;
 	RC_PID *p = xmalloc(sizeof(*p));
 	p->pid = pid;
+
+	/* this list will be accessed inside the SIGCHLD signal handler.
+	 * so we need to ensure that the SIGCHLD handler doesn't get invoked
+	 * while the list is at an inconsistent state.
+	 */
+	sigemptyset(&sset);
+	sigaddset(&sset, SIGCHLD);
+	sigprocmask(SIG_SETMASK, &sset, &old);
 	LIST_INSERT_HEAD(&service_pids, p, entries);
+	sigprocmask(SIG_SETMASK, &old, NULL);
 }
 
 static void
-remove_pid(pid_t pid)
+remove_pid(pid_t pid, bool inside_signal)
 {
-	RC_PID *p;
+	sigset_t sset, old;
+	RC_PID *p, *tmp;
 
-	LIST_FOREACH(p, &service_pids, entries)
+	/* same rationale for blocking SIGCHLD as add_pid() */
-	    if (p->pid == pid) {
+	sigemptyset(&sset);
-		    LIST_REMOVE(p, entries);
+	sigaddset(&sset, SIGCHLD);
-		    free(p);
+	sigprocmask(SIG_SETMASK, &sset, &old);
-		    return;
+	LIST_FOREACH(p, &service_pids, entries) {
-	    }
+		if (p->pid == pid) {
+			LIST_REMOVE(p, entries);
+			LIST_INSERT_HEAD(&free_these_pids, p, entries);
+			break;
+		}
+	}
+	/* only call free if we're not inside a signal handler */
+	if (!inside_signal) {
+		LIST_FOREACH_SAFE(p, &free_these_pids, entries, tmp) {
+			LIST_REMOVE(p, entries);
+			free(p);
+		}
+	}
+	sigprocmask(SIG_SETMASK, &old, NULL);
 }
 
 static void
@@ -397,7 +424,7 @@ handle_signal(int sig)
 
 		/* Remove that pid from our list */
 		if (pid > 0)
-			remove_pid(pid);
+			remove_pid(pid, true);
 		break;
 
 	case SIGWINCH:
@@ -606,7 +633,7 @@ stop:
 			add_pid(pid);
 			if (!parallel) {
 				rc_waitpid(pid);
-				remove_pid(pid);
+				remove_pid(pid, false);
 			}
 		}
 	}
@@ -672,7 +699,7 @@ do_start_services(const RC_STRINGLIST *start_services, bool parallel)
 			add_pid(pid);
 			if (!parallel) {
 				rc_waitpid(pid);
-				remove_pid(pid);
+				remove_pid(pid, false);
 			}
 		}
 	}
@@ -745,6 +772,7 @@ int main(int argc, char **argv)
 
 	applet = basename_c(argv[0]);
 	LIST_INIT(&service_pids);
+	LIST_INIT(&free_these_pids);
 	atexit(cleanup);
 	if (!applet)
 		eerrorx("arguments required");

src/shared/helpers.h

@@ -21,6 +21,7 @@
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -28,7 +29,7 @@
 
 #define ERRX fprintf (stderr, "out of memory\n"); exit (1)
 
-#define UNCONST(a)		((void *)(unsigned long)(const void *)(a))
+#define UNCONST(a)		((void *)(uintptr_t)(const void *)(a))
 
 #define RC_UNUSED __attribute__((__unused__))
 #define RC_NORETURN __attribute__((__noreturn__))

src/shared/misc.c

@@ -234,7 +234,7 @@ signal_setup_restart(int sig, void (*handler)(int))
 }
 
 int
-svc_lock(const char *applet)
+svc_lock(const char *applet, bool ignore_lock_failure)
 {
 	char *file = NULL;
 	int fd;
@@ -245,6 +245,14 @@ svc_lock(const char *applet)
 	if (fd == -1)
 		return -1;
 	if (flock(fd, LOCK_EX | LOCK_NB) == -1) {
+		if (ignore_lock_failure) {
+			/* Two services with a need b, and b's start()
+			 * calling restart --no-deps on a would cause
+			 * harmless errors: just ignore them.
+			 * See https://github.com/OpenRC/openrc/issues/224
+			 */
+			exit(EXIT_SUCCESS);
+		}
 		eerror("Call to flock failed: %s", strerror(errno));
 		close(fd);
 		return -1;
@@ -274,7 +282,7 @@ exec_service(const char *service, const char *arg)
 	sigset_t old;
 	struct sigaction sa;
 
-	fd = svc_lock(basename_c(service));
+	fd = svc_lock(basename_c(service), false);
 	if (fd == -1)
 		return -1;
 

src/shared/misc.h

@@ -50,7 +50,7 @@ void env_filter(void);
 void env_config(void);
 int signal_setup(int sig, void (*handler)(int));
 int signal_setup_restart(int sig, void (*handler)(int));
-int svc_lock(const char *);
+int svc_lock(const char *, bool);
 int svc_unlock(const char *, int);
 pid_t exec_service(const char *, const char *);