Merged revisions 67715 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.2

........
r67715 | russell | 2007-06-06 11:40:51 -0500 (Wed, 06 Jun 2007) | 5 lines

We have some bug reports showing crashes due to a double free of a channel.
Add a sanity check to ast_channel_free() to make sure we don't go on trying
to free a channel that wasn't found in the channel list.
(issue #8850, and others...)

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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@67716 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/linkedlists.h

@@ -729,8 +729,10 @@ struct {								\
   used to link entries of this list together.
   \warning The removed entry is \b not freed nor modified in any way.
  */
-#define AST_LIST_REMOVE(head, elm, field) do {			        \
+#define AST_LIST_REMOVE(head, elm, field) ({			        \
+	__typeof(elm) __res = NULL; \
 	if ((head)->first == (elm)) {					\
+		__res = (head)->first;                      \
 		(head)->first = (elm)->field.next;			\
 		if ((head)->last == (elm))			\
 			(head)->last = NULL;			\
@@ -739,13 +741,15 @@ struct {								\
 		while (curelm && (curelm->field.next != (elm)))			\
 			curelm = curelm->field.next;			\
 		if (curelm) { \
+			__res = curelm; \
 			curelm->field.next = (elm)->field.next;			\
 			if ((head)->last == (elm))				\
 				(head)->last = curelm;				\
 		} \
 	}								\
-        (elm)->field.next = NULL;                                       \
-} while (0)
+	(elm)->field.next = NULL;                                       \
+	(__res); \
+})
 
 #define AST_RWLIST_REMOVE AST_LIST_REMOVE
 

main/channel.c

@@ -1176,7 +1176,10 @@ void ast_channel_free(struct ast_channel *chan)
 	headp=&chan->varshead;
 	
 	AST_LIST_LOCK(&channels);
-	AST_LIST_REMOVE(&channels, chan, chan_list);
+	if (!AST_LIST_REMOVE(&channels, chan, chan_list)) {
+		AST_LIST_UNLOCK(&channels);
+		ast_log(LOG_ERROR, "Unable to find channel in list to free. Assuming it has already been done.\n");
+	}
 	/* Lock and unlock the channel just to be sure nobody
 	   has it locked still */
 	ast_channel_lock(chan);