[FFmpeg-devel] [PATCH] avcodec/notchlc: Check available space for luma block code

[Paul B Mahol]

On Sun, Sep 13, 2020 at 03:53:18PM +0200, Michael Niedermayer wrote:
> On Sun, Sep 13, 2020 at 12:39:34AM +0200, Paul B Mahol wrote:
> > On Sat, Sep 12, 2020 at 06:43:30PM +0200, Michael Niedermayer wrote:
> > > Fixes: Timeout (too long -> 2sec)
> > > Fixes: 25439/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_NOTCHLC_fuzzer-5688211127664640
> > > 
> > > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  libavcodec/notchlc.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/libavcodec/notchlc.c b/libavcodec/notchlc.c
> > > index 3f7079da70..e7e69b0c21 100644
> > > --- a/libavcodec/notchlc.c
> > > +++ b/libavcodec/notchlc.c
> > > @@ -229,6 +229,9 @@ static int decode_blocks(AVCodecContext *avctx, AVFrame *p, ThreadFrame *frame,
> > >      bytestream2_seek(&rgb, s->y_data_row_offsets, SEEK_SET);
> > >      bytestream2_seek(gb, s->y_control_data_offset, SEEK_SET);
> > >  
> > > +    if ((avctx->height + 3) / 4 * ((avctx->width + 3) / 4) * 4 > bytestream2_get_bytes_left(gb))
> > > +        return AVERROR_INVALIDDATA;
> > > +
> > >      dsty = (uint16_t *)p->data[0];
> > >      dsta = (uint16_t *)p->data[3];
> > >      ylinesize = p->linesize[0] / 2;
> > > -- 
> > > 2.17.1
> > 
> > Is this correct at all?
> 
> Its the amount that is read from gb in the next loop just below the added 
> check

There is also alpha handling code. Also I dislike completely this reverse style, bytestream2.. should be first.

With that fixed and actually tested that it does not break decoding it should be fine.

> 
> thx
> 
> > 
> > If you do not like timeouts than get smaller samples or reduce dimensions of accepted files.
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> 
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 
> There will always be a question for which you do not know the correct answer.



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