Re: [FFmpeg-devel] [PATCH 1/2] avformat/matroskadec: Fix infinite loop with bz decompression

[Michael Niedermayer <michael@niedermayer.cc>]

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On Fri, Feb 04, 2022 at 04:07:10PM +0100, Michael Niedermayer wrote:
> On Fri, Feb 04, 2022 at 04:29:18AM +0100, Andreas Rheinhardt wrote:
> > Michael Niedermayer:
> > > Fixes: Infinite loop
> > > Fixes: 43932/clusterfuzz-testcase-minimized-ffmpeg_dem_MATROSKA_fuzzer-6175167573786624
> > > 
> > > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > > ---
> > >  libavformat/matroskadec.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> > > index d165f6ab90..5a9acfb247 100644
> > > --- a/libavformat/matroskadec.c
> > > +++ b/libavformat/matroskadec.c
> > > @@ -1742,7 +1742,7 @@ static int matroska_decode_buffer(uint8_t **buf, int *buf_size,
> > >      case MATROSKA_TRACK_ENCODING_COMP_BZLIB:
> > >      {
> > >          bz_stream bzstream = { 0 };
> > > -        if (BZ2_bzDecompressInit(&bzstream, 0, 0) != BZ_OK)
> > > +        if (!pkt_size || BZ2_bzDecompressInit(&bzstream, 0, 0) != BZ_OK)
> > >              return -1;
> > >          bzstream.next_in  = data;
> > >          bzstream.avail_in = isize;
> > 
> > I see nothing in the zlib-API manual that would preclude this from
> > happening with zlib, too, so it should be checked there, too.
> > LGTM apart from that.
> 
> It didnt happen with the same case when i just routed it to the zlib
> instead of bz case. But i didnt look what happened exactly

will apply with the check for zlib too, it feels like a good idea even when
it seems not needed

thx

[...]

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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The day soldiers stop bringing you their problems is the day you have stopped 
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you do not care. Either case is a failure of leadership. - Colin Powell

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