Prevent a crash in ExternalIVR when the 'S' command is sent first.

If the first command sent from an ExternalIVR client is an 'S' command, we were
blindly removing the first element from the play list and deferencing it, even
if it was NULL.  This corrects that and also locks appropriately in one place.

(issue ASTERISK-17889)
Reported by: Chris Maciejewski
........

Merged revisions 362586 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@362587 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/apps/app_externalivr.c b/apps/app_externalivr.c
index 03ef884c875c04ba4e4dcab2b17b3ea15785d012..6cbfbd1377ec7e7fe514b3aacb80b01a2b41fe6e 100644 (file)
--- a/apps/app_externalivr.c
+++ b/apps/app_externalivr.c
@@ -683,13 +683,14 @@ static int eivr_comm(struct ast_channel *chan, struct ivr_localuser *u,
                        if (f->frametype == AST_FRAME_DTMF) {
                                send_eivr_event(eivr_events, f->subclass.integer, NULL, chan);
                                if (u->option_autoclear) {
+                                       AST_LIST_LOCK(&u->playlist);
                                        if (!u->abort_current_sound && !u->playing_silence) {
                                                /* send interrupted file as T data */
-                                               entry = AST_LIST_REMOVE_HEAD(&u->playlist, list);
-                                               send_eivr_event(eivr_events, 'T', entry->filename, chan);
-                                               ast_free(entry);
+                                               if ((entry = AST_LIST_REMOVE_HEAD(&u->playlist, list))) {
+                                                       send_eivr_event(eivr_events, 'T', entry->filename, chan);
+                                                       ast_free(entry);
+                                               }
                                        }
-                                       AST_LIST_LOCK(&u->playlist);
                                        while ((entry = AST_LIST_REMOVE_HEAD(&u->playlist, list))) {
                                                send_eivr_event(eivr_events, 'D', entry->filename, chan);
                                                ast_free(entry);
@@ -768,9 +769,10 @@ static int eivr_comm(struct ast_channel *chan, struct ivr_localuser *u,
                                        AST_LIST_LOCK(&u->playlist);
                                        if (!u->abort_current_sound && !u->playing_silence) {
                                                /* send interrupted file as T data */
-                                               entry = AST_LIST_REMOVE_HEAD(&u->playlist, list);
-                                               send_eivr_event(eivr_events, 'T', entry->filename, chan);
-                                               ast_free(entry);
+                                               if ((entry = AST_LIST_REMOVE_HEAD(&u->playlist, list))) {
+                                                       send_eivr_event(eivr_events, 'T', entry->filename, chan);
+                                                       ast_free(entry);
+                                               }
                                        }
                                        while ((entry = AST_LIST_REMOVE_HEAD(&u->playlist, list))) {
                                                send_eivr_event(eivr_events, 'D', entry->filename, chan);