Re: [FFmpeg-devel] [PATCH] lavfi/perlin: Fix out of bounds stack buffer write

From: Stefano Sabatini <stefasab@gmail.com>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] lavfi/perlin: Fix out of bounds stack buffer write
Date: Sat, 6 Jul 2024 11:26:00 +0200
Message-ID: <ZokNqNoufsJwI5GO@mariano> (raw)
In-Reply-To: <D2F9SW6UXDCW.16Z6454LXC9CP@gmail.com>

On date Tuesday 2024-07-02 20:38:00 +0200, Marvin Scholz wrote:
> An incorrect calculation in ff_perlin_init causes a write to the
> stack array at index 256, which is out of bounds.
> 
> Fixes: CID1608711
> ---
>  libavfilter/perlin.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavfilter/perlin.c b/libavfilter/perlin.c
> index 09bae7ad33..ffad8c1e4e 100644
> --- a/libavfilter/perlin.c
> +++ b/libavfilter/perlin.c
> @@ -129,7 +129,7 @@ int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persiste
>          for (i = 0; i < 256; i++) {
>              unsigned int random_idx = av_lfg_get(&lfg) % (256-i);
>              uint8_t random_val = random_permutations[random_idx];
> -            random_permutations[random_idx] = random_permutations[256-i];
> +            random_permutations[random_idx] = random_permutations[255-i];
>  
>              perlin->permutations[i] = perlin->permutations[i+256] = random_val;
>          }

Looks good, thanks.
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