features: Fix channel datastore access.

Found as a result of the testsuite tests/callparking test crashing.

Several calls to ast_get_chan_featuremap_config() and
ast_get_chan_features_xfer_config() did not lock the channel before
calling so the channel's datastore list was accessed without the lock's
protection.  Apparently another thread deleted a datastore on the
channel's list while the crashing thread was walking the list.  Crash at
0xdeaddead due to MALLOC_DEBUG's memory filler value as a result.

* Add missing channel locks to calls that were not already protected
as the doxygen for those calls indicates.

Change-Id: Id273b3d305cc616406c353cbc841b2b7655efaa1

main/bridge_channel.c

@@ -1543,8 +1543,13 @@ static void testsuite_notify_feature_success(struct ast_channel *chan, const cha
 {
 #ifdef TEST_FRAMEWORK
 	char *feature = "unknown";
-	struct ast_featuremap_config *featuremap = ast_get_chan_featuremap_config(chan);
-	struct ast_features_xfer_config *xfer = ast_get_chan_features_xfer_config(chan);
+	struct ast_featuremap_config *featuremap;
+	struct ast_features_xfer_config *xfer;
+
+	ast_channel_lock(chan);
+	featuremap = ast_get_chan_featuremap_config(chan);
+	xfer = ast_get_chan_features_xfer_config(chan);
+	ast_channel_unlock(chan);
 
 	if (featuremap) {
 		if (!strcmp(dtmf, featuremap->blindxfer)) {

main/features.c

@@ -766,8 +766,8 @@ static int action_bridge(struct mansession *s, const struct message *m)
 		astman_send_error(s, m, buf);
 		return 0;
 	}
-	xfer_cfg_a = ast_get_chan_features_xfer_config(chana);
 	ast_channel_lock(chana);
+	xfer_cfg_a = ast_get_chan_features_xfer_config(chana);
 	chana_exten = ast_strdupa(ast_channel_exten(chana));
 	chana_context = ast_strdupa(ast_channel_context(chana));
 	chana_priority = ast_channel_priority(chana);
@@ -782,8 +782,8 @@ static int action_bridge(struct mansession *s, const struct message *m)
 		astman_send_error(s, m, buf);
 		return 0;
 	}
-	xfer_cfg_b = ast_get_chan_features_xfer_config(chanb);
 	ast_channel_lock(chanb);
+	xfer_cfg_b = ast_get_chan_features_xfer_config(chanb);
 	chanb_exten = ast_strdupa(ast_channel_exten(chanb));
 	chanb_context = ast_strdupa(ast_channel_context(chanb));
 	chanb_priority = ast_channel_priority(chanb);
@@ -1097,7 +1097,9 @@ static int bridge_exec(struct ast_channel *chan, const char *data)
 		goto done;
 	}
 
+	ast_channel_lock(current_dest_chan);
 	xfer_cfg = ast_get_chan_features_xfer_config(current_dest_chan);
+	ast_channel_unlock(current_dest_chan);
 	bridge_add_failed = ast_bridge_add_channel(bridge, current_dest_chan, peer_features,
 		ast_test_flag(&opts, BRIDGE_OPT_PLAYTONE),
 		xfer_cfg ? xfer_cfg->xfersound : NULL);