[FFmpeg-cvslog] avformat/asfdec_o: Check lang_idx

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Jan 12 21:45:38 2021 +0100| [06e5c791949b63555aa4305df6ce9d2ffa45ec90] | committer: Michael Niedermayer

avformat/asfdec_o: Check lang_idx

Fixes: index 26981 out of bounds for type 'ASFStreamData [128]'
Fixes: 27334/clusterfuzz-testcase-minimized-ffmpeg_dem_ASF_O_fuzzer-6197611002068992

Alternatively the array could be increased in size or the cases not fitting be ignored

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=06e5c791949b63555aa4305df6ce9d2ffa45ec90
---

 libavformat/asfdec_o.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavformat/asfdec_o.c b/libavformat/asfdec_o.c
index 3729adee2f..c1d90360b4 100644
--- a/libavformat/asfdec_o.c
+++ b/libavformat/asfdec_o.c
@@ -854,6 +854,8 @@ static int asf_read_ext_stream_properties(AVFormatContext *s, const GUIDParseTab
     st_num     = avio_rl16(pb);
     st_num    &= ASF_STREAM_NUM;
     lang_idx   = avio_rl16(pb); // Stream Language ID Index
+    if (lang_idx >= ASF_MAX_STREAMS)
+        return AVERROR_INVALIDDATA;
     for (i = 0; i < asf->nb_streams; i++) {
         if (st_num == asf->asf_st[i]->stream_index) {
             st                       = s->streams[asf->asf_st[i]->index];