matroskadec: fix NULL pointer dereference in webm_dash_manifest_read_header

The code assumes that s->streams[0] is valid.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>
(cherry picked from commit ff100c9dd97d2f1f456ff38b192edf84f9744738)
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index f3d701fe4d..3c7ab1c9c5 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -3749,6 +3749,11 @@ static int webm_dash_manifest_read_header(AVFormatContext *s)
         av_log(s, AV_LOG_ERROR, "Failed to read file headers\n");
         return -1;
     }
+    if (!s->nb_streams) {
+        matroska_read_close(s);
+        av_log(s, AV_LOG_ERROR, "No streams found\n");
+        return AVERROR_INVALIDDATA;
+    }
 
     if (!matroska->is_live) {
         buf = av_asprintf("%g", matroska->duration);