[FFmpeg-devel] [PATCH 2/2] avcodec/wavpack: Prevent frame format from being wrong

[Anton Khirnov]

Quoting Michael Niedermayer (2020-03-20 21:50:18)
> On Fri, Mar 20, 2020 at 10:18:49AM +0100, Anton Khirnov wrote:
> > Quoting Michael Niedermayer (2020-03-20 01:03:36)
> > > Fixes: out of array access
> > > Fixes: 21193/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WAVPACK_fuzzer-5125168956702720
> > > 
> > > 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/wavpack.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/libavcodec/wavpack.c b/libavcodec/wavpack.c
> > > index b27262b94e..e9c870e41e 100644
> > > --- a/libavcodec/wavpack.c
> > > +++ b/libavcodec/wavpack.c
> > > @@ -1488,6 +1488,7 @@ static int wavpack_decode_block(AVCodecContext *avctx, int block_no,
> > >  
> > >          /* get output buffer */
> > >          wc->curr_frame.f->nb_samples = s->samples;
> > > +        wc->curr_frame.f->format     = avctx->sample_fmt;
> > 
> > How does this have any effect? curr_frame.f should now be clean and get
> > initialized from avctx->sample_fmt.
> 
> IIRC
> The format changes between frames, so the struct is still set to the one
> from the previous frame and that overrides the use of the avctx value
> 
> setting it to NONE (here or somewhere else) should work too.

ff_thread_release_buffer() is called on that frame immediately before,
which should reset it to defaults (setting format to FMT_NONE).

-- 
Anton Khirnov