[FFmpeg-cvslog] avformat/matroskadec: Check subtitle stream before dereferencing

[Michael Niedermayer]

ffmpeg | branch: release/2.8 | Michael Niedermayer <michael at niedermayer.cc> | Tue Nov 17 18:19:01 2015 +0100| [b70f7d20e1140983bf986ca240f2d868074a8585] | committer: Michael Niedermayer

avformat/matroskadec: Check subtitle stream before dereferencing

Unrecognized streams are not allocated
Fixes: flicker-1.color1.vp91447030769.08.webm

Found-by: Chris Cunningham <chcunningham at google.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit a5034b324cad4c29d47ef285a30b0705e6eb0384)

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b70f7d20e1140983bf986ca240f2d868074a8585
---

 libavformat/matroskadec.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 43ad9af..3449a29 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -3088,6 +3088,7 @@ static int matroska_read_seek(AVFormatContext *s, int stream_index,
         tracks[i].audio.buf_timecode   = AV_NOPTS_VALUE;
         tracks[i].end_timecode         = 0;
         if (tracks[i].type == MATROSKA_TRACK_TYPE_SUBTITLE &&
+            tracks[i].stream &&
             tracks[i].stream->discard != AVDISCARD_ALL) {
             index_sub = av_index_search_timestamp(
                 tracks[i].stream, st->index_entries[index].timestamp,