From: Stephan Mueller Subject: Re: [PATCH v7 1/2] crypto: AF_ALG: add AEAD support Date: Mon, 05 Jan 2015 11:46:50 +0100 Message-ID: <6798882.ly1QjqTYep@tachyon.chronox.de> References: <6964260.mNa1jtPz7Z@tachyon.chronox.de> <1609020.xcc11L81HZ@tachyon.chronox.de> <20150105103159.GA24878@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Daniel Borkmann , 'Quentin Gouchet' , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-crypto-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ABI/API To: Herbert Xu Return-path: In-Reply-To: <20150105103159.GA24878-lOAM2aK0SrRLBo1qDEOMRrpzq4S04n8Q@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-crypto.vger.kernel.org Am Montag, 5. Januar 2015, 21:31:59 schrieb Herbert Xu: Hi Herbert, > On Fri, Jan 02, 2015 at 03:41:33PM +0100, Stephan Mueller wrote: > > + if (!con.aead_assoclen) > > + return -EINVAL; > > AD being zero should be fine. Ok, removed. > > > + /* aead_recvmsg limits the maximum AD size to one page */ > > + if (con.aead_assoclen > PAGE_SIZE) > > + return -E2BIG; > > I don't see any need to limit the size of the AD. 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. > > Cheers, -- Ciao Stephan