From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752501AbeDEJvr (ORCPT ); Thu, 5 Apr 2018 05:51:47 -0400 Received: from gateway34.websitewelcome.com ([192.185.149.77]:29804 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752460AbeDEJvj (ORCPT ); Thu, 5 Apr 2018 05:51:39 -0400 Subject: Re: [PATCH v2] Bluetooth: Remove VLA usage in aes_cmac To: Marcel Holtmann Cc: Johan Hedberg , "David S. Miller" , Bluez mailing list , Network Development , linux-kernel@vger.kernel.org References: <20180321010527.GA16616@embeddedor.com> <3BD15121-532A-45E2-B62E-1008C0289500@holtmann.org> <2af25866-4e8a-7f9c-9298-e45abfab20c7@embeddedor.com> <347FC7F5-4BB3-4477-9EF1-BAAA98F1D107@holtmann.org> From: "Gustavo A. R. Silva" Message-ID: Date: Thu, 5 Apr 2018 04:51:36 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <347FC7F5-4BB3-4477-9EF1-BAAA98F1D107@holtmann.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.145.54.187 X-Source-L: No X-Exim-ID: 1f41YQ-003IPA-EU X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.71]) [189.145.54.187]:54592 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 6 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/05/2018 03:46 AM, Marcel Holtmann wrote: >> By the way, what is you opinion on replacing crypto_shash_descsize(ctx) with PAGE_SIZE / 8 in SHASH_DESC_ON_STACK? >> >> Does it work for you? > > isn’t that just waste? > Agree. > The macro itself is this. > > #define SHASH_DESC_ON_STACK(shash, ctx) \ > char __##shash##_desc[sizeof(struct shash_desc) + \ > crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \ > struct shash_desc *shash = (struct shash_desc *)__##shash##_desc > > For AES-CMAC, we could always do this with a manual macro that gives us the right size. However that is error prone if any internals change. I think what has to happened that crypto_shash_decsize becomes something the compiler can evaluate at compile time. > Yeah. That would imply an analysis of the algorithm each of the callers use. In the case of AES-CMAC, what is the maximum digest size? I tried to find a fixed-length value for AES-CMAC but I didn't get any output with git grep -n _DIGEST_SIZE | grep AES Thanks -- Gustavo