linux-kernel - Re: [PATCH] crypto: sun4i-ss: erase key after use

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Message-ID: <20190915201648.GA1704@sol.localdomain>
Date:   Sun, 15 Sep 2019 13:16:48 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Corentin Labbe <clabbe.montjoie@...il.com>
Cc:     davem@...emloft.net, herbert@...dor.apana.org.au,
        mripard@...nel.org, wens@...e.org,
        linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] crypto: sun4i-ss: erase key after use

On Sun, Sep 15, 2019 at 08:35:36PM +0200, Corentin Labbe wrote:
> When a TFM is unregistered, the sun4i-ss driver does not clean the key used,
> leaking it in memory.
> This patch adds this absent key cleaning.
> 
> Fixes: 6298e948215f ("crypto: sunxi-ss - Add Allwinner Security System crypto accelerator")
> Cc: <stable@...r.kernel.org> # 4.3+
> Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
> ---
>  drivers/crypto/sunxi-ss/sun4i-ss-cipher.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c b/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c
> index fa4b1b47822e..60d99370a4ec 100644
> --- a/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss-cipher.c
> @@ -503,6 +503,8 @@ int sun4i_ss_cipher_init(struct crypto_tfm *tfm)
>  void sun4i_ss_cipher_exit(struct crypto_tfm *tfm)
>  {
>  	struct sun4i_tfm_ctx *op = crypto_tfm_ctx(tfm);
> +
> +	memzero_explicit(op->key, op->keylen);
>  	crypto_free_sync_skcipher(op->fallback_tfm);
>  }
>  
> -- 
> 2.21.0
> 

It's already zeroed by the kzfree() in crypto_destroy_tfm().

- Eric