[PATCH 1/2] mcstrans: defer SIGTERM cleanup to the main loop

sigterm_handler() calls cleanup_exit(), which walks and frees the
translation and color tables and unlinks the socket. None of that is
async-signal-safe; a SIGTERM arriving while the main loop is inside
malloc/free or inside finish_context_translations() during a SIGHUP
reload can deadlock or corrupt the heap.

Set a flag from the handler and let the top of the poll loop call
cleanup_exit() from normal context, matching the existing SIGHUP
restart_daemon pattern. poll() is not restarted (SA_RESTART is not
set) so a signal delivered during the blocking poll returns EINTR and
the loop rechecks the flag. The narrow check then poll window matches
the existing SIGHUP handling.

Signed-off-by: Stephen Smalley <[email protected]>
---
 mcstrans/src/mcstransd.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mcstrans/src/mcstransd.c b/mcstrans/src/mcstransd.c
index 5bdaadb7..3db58a17 100644
--- a/mcstrans/src/mcstransd.c
+++ b/mcstrans/src/mcstransd.c
@@ -58,6 +58,7 @@
 static int sockfd = -1; /* socket we are listening on */
 
 static volatile sig_atomic_t restart_daemon = false;
+static volatile sig_atomic_t terminate = false;
 static void cleanup_exit(int ret) __attribute__((noreturn));
 static void cleanup_exit(int ret)
 {
@@ -407,6 +408,10 @@ static void process_connections(void)
 	ufds[0].revents = 0;
 
 	while (1) {
+		if (terminate) {
+			free(ufds);
+			cleanup_exit(0);
+		}
 		if (restart_daemon) {
 			syslog(LOG_NOTICE, "Reload Translations");
 			finish_context_colors();
@@ -442,11 +447,9 @@ static void process_connections(void)
 	}
 }
 
-static void sigterm_handler(int sig) __attribute__((noreturn));
-
 static void sigterm_handler(int UNUSED(sig))
 {
-	cleanup_exit(0);
+	terminate = true;
 }
 
 static void sighup_handler(int UNUSED(sig))
-- 
2.55.0