Re: [PATCH nf v3] netfilter: nft_bitwise: fix dst corruption in same register shifts

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi Fernando,

On Thu, Apr 23, 2026 at 05:54:53PM +0200, Fernando Fernandez Mancera wrote:
[...]
> @@ -201,6 +206,11 @@ static int nft_bitwise_init_shift(struct nft_bitwise *priv,
>  		return -EINVAL;
>  	}
>  
> +	if (priv->sreg != priv->dreg &&
> +	    priv->dreg < priv->sreg + n &&
> +	    priv->sreg < priv->dreg + n)

Is this enough? Just to make sure we are on the same page.

NFT_REG_1
NFT_REG_2
NFT_REG_3
NFT_REG_4

have a size of 128 bytes.

Then, NFT_REG32_00, NFT_REG32_01, NFT_REG32_02 and NFT_REG32_03
basically overlap with NFT_REG_1. They split the 128 bytes of
NFT_REG_1 in 4 registers of 32 bytes.

Is this check above enough to deal with the partial overlaps?

Thanks!

> +		return -EINVAL;
> +
>  	return 0;
>  }
>  
> -- 
> 2.53.0
> 
>