[FFmpeg-devel] [PATCH 2/2] avcodec/h264_parser: fix nalsize parser

[Michael Niedermayer]

On Mon, Aug 16, 2021 at 11:31:15PM +0200, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: left shift of 16711968 by 8 places cannot be represented in type 'int'
> > Fixes: 36601/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_H264_fuzzer-6581933285965824
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > ---
> >  libavcodec/h264_parser.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
> > index d3c56cc188..22111c62a2 100644
> > --- a/libavcodec/h264_parser.c
> > +++ b/libavcodec/h264_parser.c
> > @@ -86,7 +86,7 @@ static int h264_find_frame_end(H264ParseContext *p, const uint8_t *buf,
> >              int nalsize = 0;
> >              i = next_avc;
> >              for (j = 0; j < p->nal_length_size; j++)
> > -                nalsize = (nalsize << 8) | buf[i++];
> > +                nalsize = ((unsigned)nalsize << 8) | buf[i++];
> >              if (nalsize <= 0 || nalsize > buf_size - i) {
> >                  av_log(logctx, AV_LOG_ERROR, "AVC-parser: nal size %d remaining %d\n", nalsize, buf_size - i);
> >                  return buf_size;
> > 
> Makes me wonder why I never applied this:
> https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200529161755.9904-1-andreas.rheinhardt@gmail.com/
> (Your fix would only fix the undefined behaviour, not the nonsense
> logmessage (with negative sizes) one gets in this scenarion.)

if there was no reason why it wasnt applied then please apply and backport your fix

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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