daemon: if one of the standard fds is missing open it to /dev/null

Signed-off-by: Matthias Lederhofer <matled@gmx.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

daemon.c

@@ -662,6 +662,18 @@ static int service_loop(int socknum, int *socklist)
 	}
 }
 
+/* if any standard file descriptor is missing open it to /dev/null */
+static void sanitize_stdfds(void)
+{
+	int fd = open("/dev/null", O_RDWR, 0);
+	while (fd != -1 && fd < 2)
+		fd = dup(fd);
+	if (fd == -1)
+		die("open /dev/null or dup failed: %s", strerror(errno));
+	if (fd > 2)
+		close(fd);
+}
+
 static int serve(int port)
 {
 	int socknum, *socklist;
@@ -773,5 +785,7 @@ int main(int argc, char **argv)
 		return execute(peer);
 	}
 
+	sanitize_stdfds();
+
 	return serve(port);
 }