[FFmpeg-devel] [PATCH 3/3] avformat/rmdec: Check codec_length without overflow

[Michael Niedermayer]

On Mon, Feb 15, 2021 at 09:38:44PM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: signed integer overflow: 2147483647 + 64 cannot be represented in type 'int'
> > Fixes: 30333/clusterfuzz-testcase-minimized-ffmpeg_dem_RM_fuzzer-5175286983426048
> > 
> > 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/rmdec.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
> > index 521b9d0e8c..613fb407df 100644
> > --- a/libavformat/rmdec.c
> > +++ b/libavformat/rmdec.c
> > @@ -223,7 +223,7 @@ static int rm_read_audio_stream_info(AVFormatContext *s, AVIOContext *pb,
> >                  if (version == 5)
> >                      avio_r8(pb);
> >                  codecdata_length = avio_rb32(pb);
> > -                if(codecdata_length + AV_INPUT_BUFFER_PADDING_SIZE <= (unsigned)codecdata_length){
> > +                if(codecdata_length < 0 || codecdata_length > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE){
> >                      av_log(s, AV_LOG_ERROR, "codecdata_length too large\n");
> >                      return -1;
> >                  }
> > 
> The first of these checks can be avoided by making codecdata_length
> unsigned.

will apply unsigned style check

thx

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

Everything should be made as simple as possible, but not simpler.
-- Albert Einstein
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