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Subject: Re: [PATCH 1/2] crypto: s5p - deal gracefully with bogus input
 sizes
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        linux-crypto@vger.kernel.org
Cc:     herbert@gondor.apana.org.au, Krzysztof Kozlowski <krzk@kernel.org>,
        Vladimir Zapolskiy <vz@mleia.com>,
        linux-samsung-soc@vger.kernel.org
From:   Kamil Konieczny <k.konieczny@partner.samsung.com>
Message-ID: <e0eec29e-d869-0d58-75d9-1e2118b649ef@partner.samsung.com>
Date:   Tue, 20 Aug 2019 11:51:15 +0200
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References: <20190819142226.1703-1-ard.biesheuvel@linaro.org>
        <CGME20190819142411epcas2p2237fe8748123416a55680322244c4717@epcas2p2.samsung.com>
        <20190819142226.1703-2-ard.biesheuvel@linaro.org>
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On 19.08.2019 16:22, Ard Biesheuvel wrote:
> The s5p skcipher driver returns -EINVAL for zero length inputs, which
> deviates from the behavior of the generic ECB template, and causes fuzz
> tests to fail. In cases where the input is not a multiple of the AES
> block size (and the chaining mode is not CTR), it prints an error to
> the kernel log, which is a thing we usually try to avoid in response
> to situations that can be triggered by unprivileged users.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/crypto/s5p-sss.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/crypto/s5p-sss.c b/drivers/crypto/s5p-sss.c
> index 9ef25230c199..ef90c58edb1f 100644
> --- a/drivers/crypto/s5p-sss.c
> +++ b/drivers/crypto/s5p-sss.c
> @@ -2056,9 +2056,12 @@ static int s5p_aes_crypt(struct ablkcipher_request *req, unsigned long mode)
>  	struct s5p_aes_ctx *ctx = crypto_ablkcipher_ctx(tfm);
>  	struct s5p_aes_dev *dev = ctx->dev;
>  
> +	if (!req->nbytes)
> +		return 0;
> +
>  	if (!IS_ALIGNED(req->nbytes, AES_BLOCK_SIZE) &&
>  			((mode & FLAGS_AES_MODE_MASK) != FLAGS_AES_CTR)) {
> -		dev_err(dev->dev, "request size is not exact amount of AES blocks\n");
> +		dev_dbg(dev->dev, "request size is not exact amount of AES blocks\n");
>  		return -EINVAL;
>  	}

Acked-by: Kamil Konieczny <k.konieczny@partner.samsung.com>

-- 
Best regards,
Kamil Konieczny
Samsung R&D Institute Poland