Re: [FFmpeg-devel] [PATCH 3/4] avcodec/h263dec: Sanity check against minimal I/P frame size

[Michael Niedermayer <michael@niedermayer.cc>]

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On Mon, Aug 15, 2022 at 09:04:09PM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: Timeout
> > Fixes: 49718/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEG4_fuzzer-4874987894341632
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/h263dec.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/libavcodec/h263dec.c b/libavcodec/h263dec.c
> > index 8db0eccd89..c03a55a4fd 100644
> > --- a/libavcodec/h263dec.c
> > +++ b/libavcodec/h263dec.c
> > @@ -553,6 +553,8 @@ retry:
> >      avctx->has_b_frames = !s->low_delay;
> >  
> >      if (CONFIG_MPEG4_DECODER && avctx->codec_id == AV_CODEC_ID_MPEG4) {
> > +        if (s->pict_type != AV_PICTURE_TYPE_B && s->mb_num/2 > get_bits_count(&s->gb))
> > +            return AVERROR_INVALIDDATA;
> >          if (ff_mpeg4_workaround_bugs(avctx) == 1)
> >              goto retry;
> >          if (s->studio_profile != (s->idsp.idct == NULL))
> 
> Is it possible that you wanted to use get_bits_left() here?

yes 

thx


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