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Date:   Mon, 6 Jul 2020 19:42:30 +0200
From:   Corentin Labbe <clabbe.montjoie@gmail.com>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-crypto@vger.kernel.org,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Maxime Ripard <mripard@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Ayush Sawal <ayush.sawal@chelsio.com>,
        Vinay Kumar Yadav <vinay.yadav@chelsio.com>,
        Rohit Maheshwari <rohitm@chelsio.com>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Jamie Iles <jamie@jamieiles.com>,
        Eric Biggers <ebiggers@google.com>,
        Tero Kristo <t-kristo@ti.com>,
        Matthias Brugger <matthias.bgg@gmail.com>
Subject: Re: [PATCH v3 02/13] crypto: amlogic-gxl - permit async skcipher as
 fallback
Message-ID: <20200706174230.GB29043@Red>
References: <20200630121907.24274-1-ardb@kernel.org>
 <20200630121907.24274-3-ardb@kernel.org>
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On Tue, Jun 30, 2020 at 02:18:56PM +0200, Ard Biesheuvel wrote:
> Even though the amlogic-gxl driver implements asynchronous versions of
> ecb(aes) and cbc(aes), the fallbacks it allocates are required to be
> synchronous. Given that SIMD based software implementations are usually
> asynchronous as well, even though they rarely complete asynchronously
> (this typically only happens in cases where the request was made from
> softirq context, while SIMD was already in use in the task context that
> it interrupted), these implementations are disregarded, and either the
> generic C version or another table based version implemented in assembler
> is selected instead.
> 
> Since falling back to synchronous AES is not only a performance issue,
> but potentially a security issue as well (due to the fact that table
> based AES is not time invariant), let's fix this, by allocating an
> ordinary skcipher as the fallback, and invoke it with the completion
> routine that was given to the outer request.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  drivers/crypto/amlogic/amlogic-gxl-cipher.c | 27 ++++++++++----------
>  drivers/crypto/amlogic/amlogic-gxl.h        |  3 ++-
>  2 files changed, 15 insertions(+), 15 deletions(-)
> 

Tested-by: Corentin Labbe <clabbe@baylibre.com>