res_pjsip_t38: Make t38_reinvite_response_cb tolerant of NULL channel

t38_reinvite_response_cb can get called by res_pjsip_session's
session_inv_on_tsx_state_changed in situations where session->channel
is NULL.  If it is, the ast_log warning segfaults because it tries
to get the channel name from a NULL channel.

* Check session->channel and print "unknown channel" when it's NULL.

ASTERISK-27236
Reported by: Ross Beer

Change-Id: I4326e288d36327f6c79ab52226d54905cdc87dc7

diff --git a/res/res_pjsip_t38.c b/res/res_pjsip_t38.c
index 27eff424a886082cb6fe892b5eb0a3d84053d18b..ce914a1e8a602970a8db2089d5cad8893e95c63a 100644 (file)
--- a/res/res_pjsip_t38.c
+++ b/res/res_pjsip_t38.c
@@ -302,9 +302,9 @@ static int t38_reinvite_response_cb(struct ast_sip_session *session, pjsip_rx_da
        }
 
        state = t38_state_get_or_alloc(session);
-       if (!state) {
+       if (!session->channel || !state) {
                ast_log(LOG_WARNING, "Received response to T.38 re-invite on '%s' but state unavailable\n",
-                       ast_channel_name(session->channel));
+                       session->channel ? ast_channel_name(session->channel) : "unknown channel");
                return 0;
        }