Re: [FFmpeg-devel] [PATCH 4/4] avcodec/evc_ps: Check num_ref_pic_list_in_sps

[James Almer <jamrial@gmail.com>]

On 7/26/2023 8:59 PM, Michael Niedermayer wrote:
> Fixes: out of array write
> Fixes: 60798/clusterfuzz-testcase-minimized-ffmpeg_BSF_EVC_FRAME_MERGE_fuzzer-4633529766772736
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavcodec/evc_ps.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/libavcodec/evc_ps.c b/libavcodec/evc_ps.c
> index 04ee6a45e6..64384a392c 100644
> --- a/libavcodec/evc_ps.c
> +++ b/libavcodec/evc_ps.c
> @@ -243,11 +243,20 @@ int ff_evc_parse_sps(GetBitContext *gb, EVCParamSets *ps)
>           sps->rpl1_same_as_rpl0_flag = get_bits1(gb);
>           sps->num_ref_pic_list_in_sps[0] = get_ue_golomb(gb);
>   
> +        if ((unsigned)sps->num_ref_pic_list_in_sps[0] >= EVC_MAX_NUM_RPLS) {

EVC_MAX_NUM_RPLS should be 64, not 32 as it's currently defined. So 
change that too and it LGTM.

> +            ret = AVERROR_INVALIDDATA;
> +            goto fail;
> +        }
> +
>           for (int i = 0; i < sps->num_ref_pic_list_in_sps[0]; ++i)
>               ref_pic_list_struct(gb, &sps->rpls[0][i]);
>   
>           if (!sps->rpl1_same_as_rpl0_flag) {
>               sps->num_ref_pic_list_in_sps[1] = get_ue_golomb(gb);
> +            if ((unsigned)sps->num_ref_pic_list_in_sps[1] >= EVC_MAX_NUM_RPLS) {
> +                ret = AVERROR_INVALIDDATA;
> +                goto fail;
> +            }
>               for (int i = 0; i < sps->num_ref_pic_list_in_sps[1]; ++i)
>                   ref_pic_list_struct(gb, &sps->rpls[1][i]);
>           }
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