oggdemux: fix potential crash in SEEKING query handler

Take chain lock when accessing chains. Fall back gracefully
when there's no current chain Hopefully fixes crash when
seeking in Jamendo or Magnatune streams in Amarok.

https://bugzilla.gnome.org/show_bug.cgi?id=675609

diff --git a/ext/ogg/gstoggdemux.c b/ext/ogg/gstoggdemux.c
index 0c1a9bb..cb8c2f7 100644 (file)
--- a/ext/ogg/gstoggdemux.c
+++ b/ext/ogg/gstoggdemux.c
@@ -301,11 +301,23 @@ gst_ogg_pad_src_query (GstPad * pad, GstObject * parent, GstQuery * query)
         gboolean seekable = FALSE;
         gint64 stop = -1;
 
+        GST_CHAIN_LOCK (ogg);
         if (ogg->pullmode) {
           seekable = TRUE;
           stop = ogg->total_time;
         } else if (ogg->push_disable_seeking) {
           seekable = FALSE;
+        } else if (ogg->current_chain == NULL) {
+          GstQuery *squery;
+
+          /* assume we can seek if upstream is seekable in BYTES format */
+          GST_LOG_OBJECT (ogg, "no current chain, check upstream seekability");
+          squery = gst_query_new_seeking (GST_FORMAT_BYTES);
+          if (gst_pad_peer_query (ogg->sinkpad, squery))
+            gst_query_parse_seeking (squery, NULL, &seekable, NULL, NULL);
+          else
+            seekable = FALSE;
+          gst_query_unref (squery);
         } else if (ogg->current_chain->streams->len) {
           gint i;
 
@@ -334,6 +346,7 @@ gst_ogg_pad_src_query (GstPad * pad, GstObject * parent, GstQuery * query)
         }
 
         gst_query_set_seeking (query, GST_FORMAT_TIME, seekable, 0, stop);
+        GST_CHAIN_UNLOCK (ogg);
       } else {
         res = FALSE;
       }