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

[James Almer]

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.

> +
>          sps->poc_cycle_length                 = get_ue_golomb(gb);
>  
>          if ((unsigned)sps->poc_cycle_length >=
>