[FFmpeg-cvslog] asfdec_o: make sure packet_size is non-zero before seeking

[Andreas Cadhalpun]

ffmpeg | branch: release/2.8 | Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com> | Wed Jan  6 19:03:17 2016 +0100| [4679e543880ae6f316e00f480ca5a79f33eb1dc9] | committer: Andreas Cadhalpun

asfdec_o: make sure packet_size is non-zero before seeking

This fixes infinite loops due to seeking back.

Reviewed-by: Alexandra Hájková <alexandra.khirnova at gmail.com>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>
(cherry picked from commit 3776a72962b0622af17c4aef89a831da2cbaceca)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun at googlemail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=4679e543880ae6f316e00f480ca5a79f33eb1dc9
---

 libavformat/asfdec_o.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavformat/asfdec_o.c b/libavformat/asfdec_o.c
index 798f159..2b3d9e6 100644
--- a/libavformat/asfdec_o.c
+++ b/libavformat/asfdec_o.c
@@ -1287,6 +1287,10 @@ static int asf_read_payload(AVFormatContext *s, AVPacket *pkt)
         }
         if (!asf_pkt) {
             if (asf->packet_offset + asf->packet_size <= asf->data_offset + asf->data_size) {
+                if (!asf->packet_size) {
+                    av_log(s, AV_LOG_ERROR, "Invalid packet size 0.\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 avio_seek(pb, asf->packet_offset + asf->packet_size, SEEK_SET);
                 av_log(s, AV_LOG_WARNING, "Skipping the stream with the invalid stream index %d.\n",
                        asf->stream_index);