[FFmpeg-devel] [PATCH 1/2] avformat/mvdec: Fix integer overflow with billions of channels

[Michael Niedermayer]

On Tue, Jun 23, 2020 at 05:22:53AM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: signed integer overflow: 1394614304 * 2 cannot be represented in type 'int'
> > Fixes: 23491/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5697377020411904
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavformat/mvdec.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
> > index 64166a84b1..fa87384c6b 100644
> > --- a/libavformat/mvdec.c
> > +++ b/libavformat/mvdec.c
> > @@ -355,7 +355,7 @@ static int mv_read_header(AVFormatContext *avctx)
> >              avio_skip(pb, 8);
> >              av_add_index_entry(ast, pos, timestamp, asize, 0, AVINDEX_KEYFRAME);
> >              av_add_index_entry(vst, pos + asize, i, vsize, 0, AVINDEX_KEYFRAME);
> > -            timestamp += asize / (ast->codecpar->channels * 2);
> > +            timestamp += asize / (ast->codecpar->channels * 2LL);
> >          }
> >      } else if (!version && avio_rb16(pb) == 3) {
> >          avio_skip(pb, 4);
> > 
> You could avoid using 64 the 64 bit intermediate by multiplying with 2U
> or by using asize / ast->codecpar->channels / 2.
> 
> Whatever you prefer should also be applied to read_index.

will apply to both

thanks

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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