From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753339AbbAELOd (ORCPT ); Mon, 5 Jan 2015 06:14:33 -0500 Received: from mail.eperm.de ([89.247.134.16]:59381 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753175AbbAELOb (ORCPT ); Mon, 5 Jan 2015 06:14:31 -0500 X-AuthUser: sm@eperm.de From: Stephan Mueller To: Herbert Xu Cc: Daniel Borkmann , "'Quentin Gouchet'" , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, ABI/API Subject: Re: [PATCH v7 1/2] crypto: AF_ALG: add AEAD support Date: Mon, 05 Jan 2015 12:14:24 +0100 Message-ID: <4229997.MZP3tP9eGb@tachyon.chronox.de> User-Agent: KMail/4.14.3 (Linux/3.17.7-300.fc21.x86_64; KDE/4.14.3; x86_64; ; ) In-Reply-To: <20150105105105.GA25517@gondor.apana.org.au> References: <6964260.mNa1jtPz7Z@tachyon.chronox.de> <6798882.ly1QjqTYep@tachyon.chronox.de> <20150105105105.GA25517@gondor.apana.org.au> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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