[FFmpeg-devel] [PATCH 3/4] avcodec/bonk: Check unquant for overflow

[Paul B Mahol]

On 11/5/22, Michael Niedermayer <michael at niedermayer.cc> wrote:
> Fixes: signed integer overflow: -2889074 * 2048 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 at niedermayer.cc>
> ---
>  libavcodec/bonk.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/bonk.c b/libavcodec/bonk.c
> index 471e09fe14..1695229dbd 100644
> --- a/libavcodec/bonk.c
> +++ b/libavcodec/bonk.c
> @@ -363,12 +363,17 @@ static int bonk_decode(AVCodecContext *avctx, AVFrame
> *frame,
>              return ret;
>
>          for (int i = 0; i < samples_per_packet; i++) {
> +            int64_t t64;
>              for (int j = 0; j < s->down_sampling - 1; j++) {
>                  sample[0] = predictor_calc_error(s->k, state, s->n_taps,
> 0);
>                  sample++;
>              }
>
> -            sample[0] = predictor_calc_error(s->k, state, s->n_taps,
> s->input_samples[i] * quant);
> +            t64 = s->input_samples[i] * (int64_t)quant;
> +            if ((int32_t)t64 != t64)
> +                return AVERROR_INVALIDDATA;
> +
> +            sample[0] = predictor_calc_error(s->k, state, s->n_taps, t64);
>              sample++;
>          }
>

NAK, using int64_t and thus slowing things down.

> --
> 2.17.1
>
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