[FFmpeg-cvslog] avcodec/mpeg4videodec: Check bps (VOL header) before VOP for studio profile

[Michael Niedermayer]

ffmpeg | branch: release/4.0 | Michael Niedermayer <michael at niedermayer.cc> | Sun Apr 29 20:28:46 2018 +0200| [b367c23da125b5f27b734310b357098d8a2906dc] | committer: Michael Niedermayer

avcodec/mpeg4videodec: Check bps (VOL header) before VOP for studio profile

Fixes: runtime error: shift exponent -1 is negative
Fixes: 7486/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-4977380939530240

Fixes: runtime error: index 36 out of bounds for type 'const uint8_t [32]'
Fixes: 7566/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-6536620682510336

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit b3a18511cc93082ebecce0861bc15d7f548492e0)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b367c23da125b5f27b734310b357098d8a2906dc
---

 libavcodec/mpeg4videodec.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 9ee2f37c69..561ee2fa33 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -3219,9 +3219,13 @@ end:
         s->low_delay = 1;
     s->avctx->has_b_frames = !s->low_delay;
 
-    if (s->studio_profile)
+    if (s->studio_profile) {
+        if (!s->avctx->bits_per_raw_sample) {
+            av_log(s->avctx, AV_LOG_ERROR, "Missing VOL header\n");
+            return AVERROR_INVALIDDATA;
+        }
         return decode_studio_vop_header(ctx, gb);
-    else
+    } else
         return decode_vop_header(ctx, gb);
 }