[FFmpeg-devel] [PATCH 2/4] avformat/rpl: Use 64bit in bitrate computation and check it

[Michael Niedermayer]

On Tue, Apr 27, 2021 at 09:31:56PM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: signed integer overflow: 777777776 * 4 cannot be represented in type 'int'
> > Fixes: 29102/clusterfuzz-testcase-minimized-ffmpeg_dem_RPL_fuzzer-6726188921913344
> > 
> > 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/rpl.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libavformat/rpl.c b/libavformat/rpl.c
> > index b98488c7b1..558e5718ba 100644
> > --- a/libavformat/rpl.c
> > +++ b/libavformat/rpl.c
> > @@ -207,8 +207,10 @@ static int rpl_read_header(AVFormatContext *s)
> >              ast->codecpar->bits_per_coded_sample = 4;
> >  
> >          ast->codecpar->bit_rate = ast->codecpar->sample_rate *
> > -                                  ast->codecpar->bits_per_coded_sample *
> > -                                  ast->codecpar->channels;
> > +                                  (int64_t)ast->codecpar->bits_per_coded_sample;
> > +        if (ast->codecpar->bit_rate > INT64_MAX / ast->codecpar->channels)
> > +            return AVERROR_INVALIDDATA;
> > +        ast->codecpar->bit_rate *= ast->codecpar->channels;
> >  
> >          ast->codecpar->codec_id = AV_CODEC_ID_NONE;
> >          switch (audio_format) {
> > 
> read_line_and_int() can return zero and so you must not divide by
> channels. (Something like __builtin_smulll_overflow() might be
> advantageous here.)

hmm, i saw bits_per_coded_sample cant be 0 and wanted to use that
but clearly i didnt, fascinating.
will switch channels out with bits_per_coded_sample

thx

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

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