Re: [FFmpeg-devel] [PATCH 2/4] avcodec/evc_parse: Check num_remaining_tiles_in_slice_minus1

[Dawid Kozinski/Multimedia (PLT) /SRPOL/Staff Engineer/Samsung Electronics]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of
> Michael Niedermayer
> Sent: czwartek, 5 października 2023 00:59
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Subject: [FFmpeg-devel] [PATCH 2/4] avcodec/evc_parse: Check
> num_remaining_tiles_in_slice_minus1
> 
> Fixes: out of array access
> Fixes: 62467/clusterfuzz-testcase-minimized-
> ffmpeg_BSF_EVC_FRAME_MERGE_fuzzer-6092990982258688
> 
> Found-by: continuous fuzzing process
> https://protect2.fireeye.com/v1/url?k=10fdc12a-701f5c77-10fc4a65-
> 000babd9f1ba-c93ee30773aca891&q=1&e=409cddd0-bda7-445c-b76b-
> 1caf069ec3f8&u=https%3A%2F%2Fgithub.com%2Fgoogle%2Foss-
> fuzz%2Ftree%2Fmaster%2Fprojects%2Fffmpeg
> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc>
> ---
>  libavcodec/evc_parse.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/evc_parse.c b/libavcodec/evc_parse.c index
> bd3a4416f2d..5ab33166cf3 100644
> --- a/libavcodec/evc_parse.c
> +++ b/libavcodec/evc_parse.c
> @@ -58,8 +58,12 @@ int ff_evc_parse_slice_header(GetBitContext *gb,
> EVCParserSliceHeader *sh,
>          if (!sh->arbitrary_slice_flag)
>              sh->last_tile_id = get_bits(gb, pps->tile_id_len_minus1 + 1);
>          else {
> -            sh->num_remaining_tiles_in_slice_minus1 =
get_ue_golomb_long(gb);
> -            num_tiles_in_slice = sh->num_remaining_tiles_in_slice_minus1
+ 2;
> +            unsigned num_remaining_tiles_in_slice_minus1 =
> get_ue_golomb_long(gb);
> +            if (num_remaining_tiles_in_slice_minus1 > EVC_MAX_TILE_ROWS *
> EVC_MAX_TILE_COLUMNS - 2)
> +                return AVERROR_INVALIDDATA;
> +
> +            num_tiles_in_slice = num_remaining_tiles_in_slice_minus1 + 2;
> +            sh->num_remaining_tiles_in_slice_minus1 =
> + num_remaining_tiles_in_slice_minus1;
>              for (int i = 0; i < num_tiles_in_slice - 1; ++i)
>                  sh->delta_tile_id_minus1[i] = get_ue_golomb_long(gb);
>          }
> --
> 2.17.1
> 

Reviewed and tested. It can be merged.

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