[FFmpeg-devel] [PATCH 1/2] avcodec/dirac_vlc: Fix invalid shift

[Rostislav Pehlivanov]

On 28 July 2017 at 02:22, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> Fixes: runtime error: shift exponent 65 is too large for 64-bit type
> 'residual' (aka 'unsigned long')
> Fixes: 2737/clusterfuzz-testcase-minimized-4968639147016192
>
> 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/dirac_vlc.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/libavcodec/dirac_vlc.c b/libavcodec/dirac_vlc.c
> index 773f720858..f9a6017ec0 100644
> --- a/libavcodec/dirac_vlc.c
> +++ b/libavcodec/dirac_vlc.c
> @@ -96,6 +96,9 @@ int ff_dirac_golomb_read_16bit(DiracGolombLUT *lut_ctx,
> const uint8_t *buf,
>          if ((c_idx + 1) > coeffs)
>              return c_idx;
>
> +        if (res_bits >= RSIZE_BITS)
> +            return 0;
> +
>          if (res_bits && l->sign) {
>              int32_t coeff = 1;
>              APPEND_RESIDUE(res, l->preamble);
> --
> 2.13.0
>
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>

Empty the residue instead of giving up. That's the better solution I think.