Re: [FFmpeg-devel] [PATCH 3/3] avcodec/osq: avoid undefined negation

From: James Almer <jamrial@gmail.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH 3/3] avcodec/osq: avoid undefined negation
Date: Tue, 4 Feb 2025 00:16:59 -0300
Message-ID: <6c48d727-739d-45c6-a043-cde0d0829efc@gmail.com> (raw)
In-Reply-To: <20250204025845.2059863-3-michael@niedermayer.cc>

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On 2/3/2025 11:58 PM, Michael Niedermayer wrote:
> Fixes: negation of -2147483648 cannot be represented in type 'int32_t' (aka 'int'); cast to an unsigned type to negate this value to itself
> Fixes: 390646659/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_OSQ_fuzzer-5040277374435328
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>   libavcodec/osq.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/osq.c b/libavcodec/osq.c
> index 83b4a9d618d..5c7826778dc 100644
> --- a/libavcodec/osq.c
> +++ b/libavcodec/osq.c
> @@ -190,7 +190,7 @@ static uint32_t get_urice(GetBitContext *gb, int k)
>   
>   static int32_t get_srice(GetBitContext *gb, int x)
>   {
> -    int32_t y = get_urice(gb, x);
> +    uint32_t y = get_urice(gb, x);
>       return get_bits1(gb) ? -y : y;

Does -y here work as intended now that y is unsigned?

>   }
>   

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