Re: [FFmpeg-devel] [PATCH 4/4] avcodec/vqcdec: Check for end of input in decode_vectors()

[Michael Niedermayer <michael@niedermayer.cc>]

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On Sat, Nov 19, 2022 at 10:03:08AM +1100, Peter Ross wrote:
> On Fri, Nov 18, 2022 at 10:09:18PM +0100, Michael Niedermayer wrote:
> > Fixes: Timeout
> > Fixes: 52695/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VQC_fuzzer-4882310386548736
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavcodec/vqcdec.c | 14 ++++++++++----
> >  1 file changed, 10 insertions(+), 4 deletions(-)
> > 
> > diff --git a/libavcodec/vqcdec.c b/libavcodec/vqcdec.c
> > index 5d1a03158c..18cd99462e 100644
> > --- a/libavcodec/vqcdec.c
> > +++ b/libavcodec/vqcdec.c
> > @@ -137,7 +137,7 @@ static void seed_codebooks(VqcContext * s, const int * seed)
> >      }
> >  }
> >  
> > -static void decode_vectors(VqcContext * s, const uint8_t * buf, int size, int width, int height)
> > +static int decode_vectors(VqcContext * s, const uint8_t * buf, int size, int width, int height)
> >  {
> >      GetBitContext gb;
> >      uint8_t * vectors = s->vectors;
> > @@ -155,9 +155,11 @@ static void decode_vectors(VqcContext * s, const uint8_t * buf, int size, int wi
> >          *dst++ = get_bits(&gb, 8);
> >  
> >          while (show_bits(&gb, 2) != 2) {
> > -
> >              if (dst >= vectors_end - 1)
> > -                return;
> > +                return 0;
> > +
> > +            if (get_bits_left(&gb) < 4)
> > +                return AVERROR_INVALIDDATA;
> >  
> >              if (!show_bits(&gb, 4)) {
> >                  *dst++ = 0;
> > @@ -182,6 +184,8 @@ static void decode_vectors(VqcContext * s, const uint8_t * buf, int size, int wi
> >          skip_bits(&gb, 2);
> >          vectors += 32;
> >      }
> > +
> > +    return 0;
> >  }
> >  
> >  static void load_coeffs(VqcContext * s, const uint8_t * v, int width, int coeff_width)
> > @@ -392,7 +396,9 @@ static int vqc_decode_frame(AVCodecContext *avctx, AVFrame * rframe,
> >          avpriv_request_sample(avctx, "gamma=0x%x, contrast=0x%x\n", gamma, contrast);
> >  
> >      seed_codebooks(s, seed);
> > -    decode_vectors(s, buf + 7, avpkt->size - 7, avctx->width, avctx->height);
> > +    ret = decode_vectors(s, buf + 7, avpkt->size - 7, avctx->width, avctx->height);
> > +    if (ret < 0)
> > +        return ret;
> >      decode_frame(s, avctx->width, avctx->height);
> 
> please apply

will apply

thx

[...]

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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Avoid a single point of failure, be that a person or equipment.

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