linux-kernel - Re: [PATCH RESEND 1/9] crypto: caam/jr - add fallback for XTS with more than 8B IV

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Date:   Tue, 11 Aug 2020 17:30:41 +0300
From:   Horia Geantă <horia.geanta@....com>
To:     "Andrei Botila (OSS)" <andrei.botila@....nxp.com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND 1/9] crypto: caam/jr - add fallback for XTS with
 more than 8B IV

On 8/6/2020 7:36 PM, Andrei Botila (OSS) wrote:
> @@ -3344,12 +3382,30 @@ static int caam_cra_init(struct crypto_skcipher *tfm)
>  	struct caam_skcipher_alg *caam_alg =
>  		container_of(alg, typeof(*caam_alg), skcipher);
>  	struct caam_ctx *ctx = crypto_skcipher_ctx(tfm);
> +	u32 alg_aai = caam_alg->caam.class1_alg_type & OP_ALG_AAI_MASK;
>  
>  	crypto_skcipher_set_reqsize(tfm, sizeof(struct caam_skcipher_req_ctx));
This is being called twice in case of XTS.

>  
>  	ctx->enginectx.op.do_one_request = skcipher_do_one_req;
>  
> -	return caam_init_common(crypto_skcipher_ctx(tfm), &caam_alg->caam,
> +	if (alg_aai == OP_ALG_AAI_XTS) {
> +		const char *tfm_name = crypto_tfm_alg_name(&tfm->base);
> +		struct crypto_skcipher *fallback;
> +
> +		fallback = crypto_alloc_skcipher(tfm_name, 0,
> +						 CRYPTO_ALG_NEED_FALLBACK);
Driver should select CRYPTO_XTS, such that at least the generic
xts implementation is available.

> +		if (IS_ERR(fallback)) {
> +			pr_err("Failed to allocate %s fallback: %ld\n",
> +			       tfm_name, PTR_ERR(fallback));
> +			return PTR_ERR(fallback);
Shouldn't error out so early. It might be that the fallback won't be needed.
Let's postpone this until we're sure fallback is required.

Horia