[FFmpeg-devel] [PATCH 1/2] avcodec/vp9: Check in decode_tiles() if there is data remaining

Ronald S. Bultje rsbultje at gmail.com
Tue Aug 7 04:50:57 EEST 2018


Hi,

On Mon, Aug 6, 2018 at 3:00 PM, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> On Tue, Aug 07, 2018 at 01:05:51AM +0800, Ronald S. Bultje wrote:
> > Hi,
> >
> > On Sun, Aug 5, 2018, 9:17 AM Michael Niedermayer <michael at niedermayer.cc
> >
> > wrote:
> >
> > > Fixes: Timeout
> > > Fixes:
> > > 9330/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_
> VP9_fuzzer-5707345857347584
> > >
> > > Found-by: continuous fuzzing process
> > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > > Signed-off-by
> > > <https://github.com/google/oss-fuzz/tree/master/projects/
> ffmpegSigned-off-by>:
> > > Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  libavcodec/vp9.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/libavcodec/vp9.c b/libavcodec/vp9.c
> > > index b1178c9c0c..4ca51ec108 100644
> > > --- a/libavcodec/vp9.c
> > > +++ b/libavcodec/vp9.c
> > > @@ -1302,6 +1302,9 @@ static int decode_tiles(AVCodecContext *avctx,
> > >                          memset(lflvl_ptr->mask, 0,
> > > sizeof(lflvl_ptr->mask));
> > >                      }
> > >
> > > +                    if (td->c->end <= td->c->buffer && td->c->bits >=
> 0) {
> > > +                        return AVERROR_INVALIDDATA;
> > > +                    }
> > >                      if (s->pass == 2) {
> > >                          decode_sb_mem(td, row, col, lflvl_ptr,
> > >                                        yoff2, uvoff2, BL_64X64);
> > >
> >
> > I don't think this matches spec. Implementations could use this to store
> > auxiliary data.
>
> This checks, or rather is intended to check for a premature end of the
> input.
> Am i missing something? because a premature end of input seems not to lead
> to more (auxiliary or other) data in the input.


Hm, I misread it, sorry about that, my bad. Please ignore my first review.

Is end == buffer && bits == 0 something that can happen on valid input if
things just align properly? Otherwise looks OK.

Ronald


More information about the ffmpeg-devel mailing list