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

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Message-ID: <7fcc8361-7928-3e56-686b-9382bef9107e@nxp.com>
Date:   Fri, 21 Aug 2020 15:02:48 +0300
From:   Horia Geantă <horia.geanta@....com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     "Andrei Botila (OSS)" <andrei.botila@....nxp.com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        "David S. Miller" <davem@...emloft.net>,
        "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 8/21/2020 6:47 AM, Herbert Xu wrote:
> On Tue, Aug 11, 2020 at 05:30:41PM +0300, Horia Geantă wrote:
>>
>>> +		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.
> 
> Why? The generic should always be there as otherwise you won't
> even pass the self-test.  If we're OOM then we should error out
> ASAP.
> 
self-tests don't check the cases where a fallback is needed,
so in theory things could go well for a misconfigured kernel
(where a fallback is not available).

But I agree, if driver is updated to select CRYPTO_XTS
then it's probably better to return an error here.

Thanks,
Horia