[FFmpeg-devel] [PATCH 4/4] avcodec/photocd: Use ff_set_dimensions()

Michael Niedermayer michael at niedermayer.cc
Sat Oct 10 14:00:14 EEST 2020


On Mon, Sep 21, 2020 at 12:28:37AM +0200, Paul B Mahol wrote:
> On Sun, Sep 20, 2020 at 10:26:08PM +0200, Michael Niedermayer wrote:
> > Fixes: out of memory
> > Fixes: 25588/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PHOTOCD_fuzzer-6612945080156160
> > 
> > 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/photocd.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libavcodec/photocd.c b/libavcodec/photocd.c
> > index 057c9d33d4..07f10e28b7 100644
> > --- a/libavcodec/photocd.c
> > +++ b/libavcodec/photocd.c
> > @@ -324,8 +324,9 @@ static int photocd_decode_frame(AVCodecContext *avctx, void *data,
> >      else
> >          s->resolution = av_clip(4 - s->lowres, 0, 4);
> >  
> > -    avctx->width  = img_info[s->resolution].width;
> > -    avctx->height = img_info[s->resolution].height;
> > +    ret = ff_set_dimensions(avctx, img_info[s->resolution].width, img_info[s->resolution].height);
> > +    if (ret < 0)
> > +        return ret;
> >  
> >      if ((ret = ff_thread_get_buffer(avctx, &frame, 0)) < 0)
> >          return ret;
> 
> Why is this needed at all, dimensions are alway static and completely allocable.

ff_set_dimensions() sets more than width and height, for example 
it also sets coded_width and coded_height. And it checks dimension validity and
compliance to the users requirements.
There are multiple things here the previous code failed to do and which could
cause problems.

I would suggest to simply always use ff_set_dimensions().

Thanks


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

During times of universal deceit, telling the truth becomes a
revolutionary act. -- George Orwell
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