When doing a fork() and exec(), two problems existed (Issue 8086):

1) Ignored signals stayed ignored after the exec().
2) Signals could possibly fire between the fork() and exec(), causing Asterisk
signal handlers within the child to execute, which caused nasty race conditions.


git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.2@48374 f38db490-d61c-443f-a65b-d21fe96a405b

2 files changed, 28 insertions, 3 deletions

diff --git a/res/res_agi.c b/res/res_agi.c
index 022cee46e..1d39c6936 100644
--- a/res/res_agi.c
+++ b/res/res_agi.c
@@ -234,7 +234,7 @@ static int launch_script(char *script, char *argv[], int *fds, int *efd, int *op
 	int audio[2];
 	int x;
 	int res;
-	sigset_t signal_set;
+	sigset_t signal_set, old_set;
 	
 	if (!strncasecmp(script, "agi://", 6))
 		return launch_netscript(script, argv, fds, efd, opid);
@@ -276,6 +276,10 @@ static int launch_script(char *script, char *argv[], int *fds, int *efd, int *op
 			return -1;
 		}
 	}
+
+	/* Block SIGHUP during the fork - prevents a race */
+	sigfillset(&signal_set);
+	pthread_sigmask(SIG_BLOCK, &signal_set, &old_set);
 	pid = fork();
 	if (pid < 0) {
 		ast_log(LOG_WARNING, "Failed to fork(): %s\n", strerror(errno));
@@ -293,9 +297,18 @@ static int launch_script(char *script, char *argv[], int *fds, int *efd, int *op
 		} else {
 			close(STDERR_FILENO + 1);
 		}
-		
+
+		/* Before we unblock our signals, return our trapped signals back to the defaults */
+		signal(SIGHUP, SIG_DFL);
+		signal(SIGCHLD, SIG_DFL);
+		signal(SIGINT, SIG_DFL);
+		signal(SIGURG, SIG_DFL);
+		signal(SIGTERM, SIG_DFL);
+		signal(SIGPIPE, SIG_DFL);
+		signal(SIGXFSZ, SIG_DFL);
+
 		/* unblock important signal handlers */
-		if (sigfillset(&signal_set) || pthread_sigmask(SIG_UNBLOCK, &signal_set, NULL)) {
+		if (pthread_sigmask(SIG_UNBLOCK, &signal_set, NULL)) {
 			ast_log(LOG_WARNING, "unable to unblock signals for AGI script: %s\n", strerror(errno));
 			_exit(1);
 		}
@@ -310,6 +323,7 @@ static int launch_script(char *script, char *argv[], int *fds, int *efd, int *op
 		fprintf(stderr, "Failed to execute '%s': %s\n", script, strerror(errno));
 		_exit(1);
 	}
+	pthread_sigmask(SIG_SETMASK, &old_set, NULL);
 	if (option_verbose > 2) 
 		ast_verbose(VERBOSE_PREFIX_3 "Launched AGI Script %s\n", script);
 	fds[0] = toast[0];
diff --git a/res/res_musiconhold.c b/res/res_musiconhold.c
index c7f1fff6a..746fa2d06 100644
--- a/res/res_musiconhold.c
+++ b/res/res_musiconhold.c
@@ -326,6 +326,7 @@ static int spawn_mp3(struct mohclass *class)
 	int argc = 0;
 	DIR *dir = NULL;
 	struct dirent *de;
+	sigset_t signal_set, old_set;
 
 	
 	if (!strcasecmp(class->dir, "nodir")) {
@@ -426,6 +427,11 @@ static int spawn_mp3(struct mohclass *class)
 	if (time(NULL) - class->start < respawn_time) {
 		sleep(respawn_time - (time(NULL) - class->start));
 	}
+
+	/* Block signals during the fork() */
+	sigfillset(&signal_set);
+	pthread_sigmask(SIG_BLOCK, &signal_set, &old_set);
+
 	time(&class->start);
 	class->pid = fork();
 	if (class->pid < 0) {
@@ -440,6 +446,10 @@ static int spawn_mp3(struct mohclass *class)
 		if (option_highpriority)
 			ast_set_priority(0);
 
+		/* Reset ignored signals back to default */
+		signal(SIGPIPE, SIG_DFL);
+		pthread_sigmask(SIG_UNBLOCK, &signal_set, NULL);
+
 		close(fds[0]);
 		/* Stdout goes to pipe */
 		dup2(fds[1], STDOUT_FILENO);
@@ -466,6 +476,7 @@ static int spawn_mp3(struct mohclass *class)
 		_exit(1);
 	} else {
 		/* Parent */
+		pthread_sigmask(SIG_SETMASK, &old_set, NULL);
 		close(fds[1]);
 	}
 	return fds[0];