avcodec/mpeg4videodec: Clear partitioned frame in decode_studio_vop_header()

partitioned_frame is also set/cleared in decode_vop_header()

Fixes: out of array read
Fixes: 9789/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-5638681627983872
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 233b8525ceabd14eec5ffc96e74ccad608d0bd02..f44ee76bd4194630882e6fe26630ae08618439e6 100644 (file)
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -3056,6 +3056,7 @@ static int decode_studio_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb)
     if (get_bits_left(gb) <= 32)
         return 0;
 
+    s->partitioned_frame = 0;
     s->decode_mb = mpeg4_decode_studio_mb;
 
     decode_smpte_tc(ctx, gb);