[FFmpeg-devel] [PATCH] avcodec/h264_ps: Check offset_for_non_ref_pic and offset_for_top_to_bottom_field

[Michael Niedermayer]

On Sat, May 11, 2019 at 03:35:26PM -0300, James Almer wrote:
> On 5/11/2019 2:59 PM, Michael Niedermayer wrote:
> > Fixes: signed integer overflow: -2147483648 + -1 cannot be represented in type 'int'
> > Fixes: 14444/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_H264_fuzzer-5675880333967360
> > 
> > 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_ps.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/libavcodec/h264_ps.c b/libavcodec/h264_ps.c
> > index 7c92c68b38..e38cf2a533 100644
> > --- a/libavcodec/h264_ps.c
> > +++ b/libavcodec/h264_ps.c
> > @@ -451,6 +451,15 @@ int ff_h264_decode_seq_parameter_set(GetBitContext *gb, AVCodecContext *avctx,
> >          sps->delta_pic_order_always_zero_flag = get_bits1(gb);
> >          sps->offset_for_non_ref_pic           = get_se_golomb_long(gb);
> >          sps->offset_for_top_to_bottom_field   = get_se_golomb_long(gb);
> > +
> > +        if (   sps->offset_for_non_ref_pic         == INT32_MIN
> > +            || sps->offset_for_top_to_bottom_field == INT32_MIN
> > +        ) {
> > +            av_log(avctx, AV_LOG_ERROR,
> > +                   "offset_for_non_ref_pic or offset_for_top_to_bottom_field underflow\n");
> > +            goto fail;
> > +        }
> 
> The valid range is INT32_MIN + 1 to INT32_MAX, so it should be good. But
> maybe the error message should instead say it's out of range?
> 
> Fwiw, there's another get_se_golomb_long() call right below these, with
> the same range constrains.

will fix all cases togteher and use suggested error message

Thanks

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

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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