linux-kernel - Re: [RFC PATCH 0/2] crypto: caam - fix cts(cbc(aes)) with CAAM driver

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Date:   Fri, 16 Jun 2017 15:59:41 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Horia Geantă <horia.geanta@....com>
Cc:     David Gstir <david@...ma-star.at>,
        Dan Douglass <dan.douglass@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Radu Solea <radu.solea@....com>,
        "richard@...ma-star.at" <richard@...ma-star.at>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 0/2] crypto: caam - fix cts(cbc(aes)) with CAAM driver

On Fri, Jun 16, 2017 at 07:57:00AM +0000, Horia Geantă wrote:
>
> Commit 0605c41cc53ca ("crypto: cts - Convert to skcipher") appends
> CRYPTO_TFM_REQ_MAY_BACKLOG to the original crypto request flags for the
> last block - when calling cts_cbc_encrypt().
> Is it really needed?

Yes, because at this point we cannot tell the sender to back off.

> For cts(cbc(aes)) with cbc(aes) offloaded in HW, i.e. running in async
> mode, we get the below stack for CAAM driver.
> Driver is told that it can sleep (CRYPTO_TFM_REQ_MAY_BACKLOG flag), so
> it uses GFP_KERNEL to allocate memory. However, this is incorrect, since
> driver runs in atomic context (softirq).

This is wrong.  Whether you can sleep or not is determined by
MAY_SLEEP, not MAY_BACKLOG.  MAY_BACKLOG only indicates that this
request must be queued, even if the queue is full.

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