Re: [FFmpeg-devel] [PATCH 1/7] avcodec/bonk: Use unsigned in predictor_calc_error() to avoid undefined overflows

[Paul B Mahol <onemda@gmail.com>]

On 11/6/22, Michael Niedermayer <michael@niedermayer.cc> wrote:
> Fixes: signed integer overflow: 22 * -2107998208 cannot be represented in
> type 'int'
> Fixes:
> 51363/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_BONK_fuzzer-5660734784143360
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/bonk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavcodec/bonk.c b/libavcodec/bonk.c
> index 1695229dbd..9e8892e4db 100644
> --- a/libavcodec/bonk.c
> +++ b/libavcodec/bonk.c
> @@ -278,7 +278,7 @@ static int predictor_calc_error(int *k, int *state, int
> order, int error)
>          *state_ptr = &(state[order-2]);
>
>      for (i = order-2; i >= 0; i--, k_ptr--, state_ptr--) {
> -        int k_value = *k_ptr, state_value = *state_ptr;
> +        unsigned k_value = *k_ptr, state_value = *state_ptr;
>
>          x -= shift_down(k_value * state_value, LATTICE_SHIFT);
>          state_ptr[1] = state_value + shift_down(k_value * x,
> LATTICE_SHIFT);
> --
> 2.17.1
>

probably fine.

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