[FFmpeg-devel] [PATCH 3/5] avcodec/decode: Check progress before dereferencing

[Michael Niedermayer]

On Sat, Apr 27, 2024 at 01:13:54PM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: NULL pointer dereference
> > Fixes: 68192/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP8_fuzzer-6180311026171904
> > 
> > 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/decode.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> > index d031b1ca176..a6131941f43 100644
> > --- a/libavcodec/decode.c
> > +++ b/libavcodec/decode.c
> > @@ -1744,6 +1744,8 @@ void ff_progress_frame_report(ProgressFrame *f, int n)
> >  
> >  void ff_progress_frame_await(const ProgressFrame *f, int n)
> >  {
> > +    if (!f->progress)
> > +        return;
> >      ff_thread_progress_await(&f->progress->progress, n);
> >  }
> >  
> 
> Can I get the sample? I see two places in VP8 where the VP8Frame
> pointers are set before the actual frame inside it is properly allocated.
> 
> (Actually, it was intended for this API to not support waiting on
> non-existent frames (i.e. let the caller check for this; in most
> instances, it is already guaranteed that the frame one waits one exists,
> so this is unnecessary for them).)

did you receive the sample i sent you in april ?

any update on this ?
its still crashing without this patch

Running: 68192/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP8_fuzzer-6180311026171904
libavcodec/decode.c:1766:44: runtime error: member access within null pointer of type 'struct ProgressInternal'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior libavcodec/decode.c:1766:44 in
libavcodec/threadprogress.c:72:36: runtime error: member access within null pointer of type 'ThreadProgress' (aka 'struct ThreadProgress')
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior libavcodec/threadprogress.c:72:36 in

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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