[FFmpeg-devel] [PATCH 1/6] avcodec/h264_slice: Check input SPS in ff_h264_update_thread_context()

[Michael Niedermayer]

On Tue, Mar 23, 2021 at 12:34:16AM +0100, Michael Niedermayer wrote:
> On Mon, Mar 22, 2021 at 10:12:47PM +0100, Hendrik Leppkes wrote:
> > On Mon, Mar 22, 2021 at 10:05 PM Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> > >
> > > Fixes: crash
> > > Fixes: check_pkt.mp4
> > >
> > > Found-by: Rafael Dutra <rafael.dutra at cispa.de>
> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > ---
> > >  libavcodec/h264_slice.c | 5 ++---
> > >  1 file changed, 2 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
> > > index 14b945756b..910d8b8848 100644
> > > --- a/libavcodec/h264_slice.c
> > > +++ b/libavcodec/h264_slice.c
> > > @@ -304,9 +304,8 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
> > >      if (dst == src)
> > >          return 0;
> > >
> > > -    // We can't fail if SPS isn't set at it breaks current skip_frame code
> > > -    //if (!h1->ps.sps)
> > > -    //    return AVERROR_INVALIDDATA;
> > > +    if (inited && !h1->ps.sps)
> > > +        return AVERROR_INVALIDDATA;
> > >
> > 
> > Any considerations for the removed comment?
> 
> Without the inited, i could reproduce a skip_frame failure, replicating what
> i assumed the comment meant.
> 
> With inited, the next lines would determine if we need to reinit but 
> without h1->ps.sps the current set of checks have a good chance of
> dereferencing a null pointer. So this looks like a clean failure is
> better. And unlikely that was occuring in any use case.
> 
> So i think the comment, at least as written is not correct.

a week passed with no comments, so i intend to apply this as it fixes a
null pointer dereference

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

You can kill me, but you cannot change the truth.
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