[FFmpeg-devel] [PATCH 1/2] avcodec/mobiclip: check for pmode=2 ax/ay=0

[Paul B Mahol]

On Sat, Sep 12, 2020 at 04:35:54PM +0200, Michael Niedermayer wrote:
> Fixes: out of array access
> Fixes: 25452/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MOBICLIP_fuzzer-5081657055641600
> 
> 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/mobiclip.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/libavcodec/mobiclip.c b/libavcodec/mobiclip.c
> index 13f0edc89d..3ede370bef 100644
> --- a/libavcodec/mobiclip.c
> +++ b/libavcodec/mobiclip.c
> @@ -914,6 +914,9 @@ static int predict_intra(AVCodecContext *avctx, AVFrame *frame, int ax, int ay,
>              int shift = adjust(size, size) == 8 ? 3 : 2;
>              uint8_t *block;
>  
> +            if (ax == 0 && ay == 0)
> +                return -1;
> +

Please clip it instead, FFMAX(ax - 1, 0) above.

I forgot to do it.

>              for (int x = 0; x < size; x++) {
>                  int val = top[x];
>                  arr1[x] = adjust(((bottommost - val) * (1 << shift)) + r6 * (x + 1), size);
> -- 
> 2.17.1
> 
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