linux-kernel - Re: [PATCH] crypto: hisilicon: use kfree

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Message-ID: <aDER6cD9S5HcbV2W@gondor.apana.org.au>
Date: Sat, 24 May 2025 08:25:13 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Zilin Guan <zilin@....edu.cn>
Cc: qianweili@...wei.com, wangzhou1@...ilicon.com, davem@...emloft.net,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	jianhao.xu@....edu.cn
Subject: Re: [PATCH] crypto: hisilicon: use kfree_sensitive() for pool cleanup

On Fri, May 23, 2025 at 01:30:57PM +0000, Zilin Guan wrote:
> The error path of hisi_acc_create_sgl_pool() already calls
> kfree_sensitive() to wipe sensitive data before freeing the pool.
> However, hisi_acc_free_sgl_pool() currently uses plain kfree(), which
> may leave secrets behind in memory and undo the protection applied
> during creation.
> 
> This patch replaces kfree() with kfree_sensitive() in
> hisi_acc_free_sgl_pool(), ensuring that all SGL pool deallocations
> securely clear their contents.
> 
> Signed-off-by: Zilin Guan <zilin@....edu.cn>
> ---
>  drivers/crypto/hisilicon/sgl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/crypto/hisilicon/sgl.c b/drivers/crypto/hisilicon/sgl.c
> index c974f95cd126..6a88a2056708 100644
> --- a/drivers/crypto/hisilicon/sgl.c
> +++ b/drivers/crypto/hisilicon/sgl.c
> @@ -151,7 +151,7 @@ void hisi_acc_free_sgl_pool(struct device *dev, struct hisi_acc_sgl_pool *pool)
>  		dma_free_coherent(dev, block[i].size, block[i].sgl,
>  				  block[i].sgl_dma);
>  
> -	kfree(pool);
> +	kfree_sensitive(pool);
>  }
>  EXPORT_SYMBOL_GPL(hisi_acc_free_sgl_pool);

What's in the pool? If it's just pointers then that is not sensitive
information.

You should only use kfree_sensitive if plaintext or private keys are
present.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt