Re: [FFmpeg-devel] [PATCH] avcodec/hevc_ps: add proper bound checks around cm_ref_layer_id in colour_mapping_table.

[James Almer <jamrial@gmail.com>]

On 5/17/2023 2:28 PM, Michael Niedermayer wrote:
> From: Clement Lecigne <clecigne@google.com>
> 
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavcodec/hevc_ps.c | 17 +++++++++++++----
>   1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/hevc_ps.c b/libavcodec/hevc_ps.c
> index a55bced0f7..313ebef151 100644
> --- a/libavcodec/hevc_ps.c
> +++ b/libavcodec/hevc_ps.c
> @@ -1374,9 +1374,14 @@ static void colour_mapping_octants(GetBitContext *gb, HEVCPPS *pps, int inp_dept
>           }
>   }
>   
> -static void colour_mapping_table(GetBitContext *gb, HEVCPPS *pps)
> +static int colour_mapping_table(GetBitContext *gb, AVCodecContext *avctx, HEVCPPS *pps)
>   {
> -    pps->num_cm_ref_layers_minus1 = get_ue_golomb_long(gb);
> +    pps->num_cm_ref_layers_minus1 = get_ue_golomb(gb);
> +    if (pps->num_cm_ref_layers_minus1 >= 63U) {
> +        av_log(avctx, AV_LOG_ERROR,
> +               "num_cm_ref_layers_minus1 shall be in the range [0, 63].\n");

The spec in section F.7.4.3.3.5 says 0..61, no 0..63.

I'll amend this (and update the array in the struct while at it) and push.

> +        return AVERROR_INVALIDDATA;
> +    }
>       for (int i = 0; i <= pps->num_cm_ref_layers_minus1; i++)
>           pps->cm_ref_layer_id[i] = get_bits(gb, 6);
>   
> @@ -1397,6 +1402,7 @@ static void colour_mapping_table(GetBitContext *gb, HEVCPPS *pps)
>       }
>   
>       colour_mapping_octants(gb, pps, 0, 0, 0, 0, 1 << pps->cm_octant_depth);
> +    return 0;
>   }
>   
>   static int pps_multilayer_extension(GetBitContext *gb, AVCodecContext *avctx,
> @@ -1439,8 +1445,11 @@ static int pps_multilayer_extension(GetBitContext *gb, AVCodecContext *avctx,
>       }
>   
>       pps->colour_mapping_enabled_flag = get_bits1(gb);
> -    if (pps->colour_mapping_enabled_flag)
> -        colour_mapping_table(gb, pps);
> +    if (pps->colour_mapping_enabled_flag) {
> +        int ret = colour_mapping_table(gb, avctx, pps);
> +        if (ret < 0)
> +            return ret;
> +    }
>   
>       return 0;
>   }
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