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Message-ID: <4229997.MZP3tP9eGb@tachyon.chronox.de>
Date: Mon, 05 Jan 2015 12:14:24 +0100
From: Stephan Mueller <smueller@...onox.de>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Daniel Borkmann <dborkman@...hat.com>,
'Quentin Gouchet' <quentin.gouchet@...il.com>,
linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
ABI/API <linux-api@...r.kernel.org>
Subject: Re: [PATCH v7 1/2] crypto: AF_ALG: add AEAD support
Am Montag, 5. Januar 2015, 21:51:06 schrieb Herbert Xu:
Hi Herbert,
> On Mon, Jan 05, 2015 at 11:46:50AM +0100, Stephan Mueller wrote:
> > The need for that check lies in aead_recvmsg:
> > /*
> >
> > * first chunk of input is AD -- one scatterlist entry is one
> > page,
> > * and we process only one scatterlist, the maximum size of AD is
> > * one page
> > */
> >
> > sg_init_table(&assoc, 1);
> > sg_set_page(&assoc, sg_page(sg), ctx->aead_assoclen, sg->offset);
> > aead_request_set_assoc(&ctx->aead_req, &assoc,
> > ctx->aead_assoclen);
> >
> > There you see that I only create an sg table with one entry for the AD. If
> > we would allow an arbitrary AD size, I would see the need of a for loop
> > in addition to the one directly beneath this AD scatterlist setting: one
> > for identifying how many sg entries I need to allocate and one for the
> > actual assignment.
> >
> > As I felt that one page should be sufficient for the AD, I wanted to avoid
> > the extra overhead for another for loop.
>
> Please remove the limit as otherwise we would never be able to
> add support for this in a future kernel as appliations won't be
> able to rely on it.
>
> There is no such limit in the kernel interface and we shouldn't
> be adding one here.
One question: are you aware of an existing mechanism to split one scatterlist
into two at a given offset?
>
> Cheers,
--
Ciao
Stephan
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