[FFmpeg-devel] [PATCH 02/13] avformat/mxfdec: Check run_in to fit in int and be valid
Tomas Härdin
tjoppen at acc.umu.se
Tue Sep 20 14:20:00 EEST 2022
tis 2022-09-20 klockan 13:07 +0200 skrev Tomas Härdin:
> sön 2022-09-18 klockan 19:13 +0200 skrev Michael Niedermayer:
> > Fixes: signed integer overflow: 9223372036854775807 - -2146905566
> > cannot be represented in type 'long'
> > Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_MXF_fuzzer-
> > 6570996594769920
> >
> > 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/mxfdec.c | 6 +++++-
> > 1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> > index e63e803aa56..da81fea3bc1 100644
> > --- a/libavformat/mxfdec.c
> > +++ b/libavformat/mxfdec.c
> > @@ -3681,6 +3681,7 @@ static int mxf_read_header(AVFormatContext
> > *s)
> > KLVPacket klv;
> > int64_t essence_offset = 0;
> > int ret;
> > + int64_t run_in;
> >
> > mxf->last_forward_tell = INT64_MAX;
> >
> > @@ -3690,7 +3691,10 @@ static int mxf_read_header(AVFormatContext
> > *s)
> > }
> > avio_seek(s->pb, -14, SEEK_CUR);
> > mxf->fc = s;
> > - mxf->run_in = avio_tell(s->pb);
> > + run_in = avio_tell(s->pb);
> > + if (run_in < 0 || run_in != (int)run_in)
>
> run_in > INT_MAX is more clear
>
> It strikes me that run_in is also used in lots of places in the
> demuxer
> without checking for overflow
I went and checked S377m and the run-in sequence "shall be less than
65536 bytes long". Both the 2004 and 2009 version of the spec agree on
this. So we should reject run_in >= 65536, and mxf_probe() should be
similarly adjusted.
/Tomas
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