From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756969AbeBPBD2 (ORCPT ); Thu, 15 Feb 2018 20:03:28 -0500 Received: from mail-ua0-f195.google.com ([209.85.217.195]:39946 "EHLO mail-ua0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756953AbeBPBD0 (ORCPT ); Thu, 15 Feb 2018 20:03:26 -0500 X-Google-Smtp-Source: AH8x226PXT3X9syo6L3CjPgl07wRIxzzSVlrVYVbyJIlbzaUrAaOLpyL/dVYkq9SuHINsWSD/JddH+nT3PLBd/lW4Hg= MIME-Version: 1.0 In-Reply-To: <20180216001317.GG30522@ZenIV.linux.org.uk> References: <20180214063033.GA15579@avx2> <20180214081935.GA17157@avx2> <20180215190713.GF30522@ZenIV.linux.org.uk> <20180215214113.GA27190@avx2> <20180216001317.GG30522@ZenIV.linux.org.uk> From: Kees Cook Date: Thu, 15 Feb 2018 17:03:25 -0800 X-Google-Sender-Auth: yZGBASN2shrL-TwddJg-fWDWHGQ Message-ID: Subject: Re: [PATCH -mm 1/3] proc: randomize "struct pde_opener" To: Al Viro Cc: Alexey Dobriyan , Andrew Morton , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 15, 2018 at 4:13 PM, Al Viro wrote: > Guess what happens to cache footprint of dcache lookups if the bunch in the > beginning gets spread over the entire thing? Right... And that's besides the > outright miscompiles. Mentioned in private communication, but just for posterity: GCC_PLUGIN_RANDSTRUCT_PERFORMANCE exists specifically to address those kinds of performance concerns. As to removing the markings: please don't. Instead, you'd mentioned wanting to add a TAINT flag for this, and I think that sounds entirely reasonable. We have TAINT flags for considerably less insane things. :) I can send that patch. -Kees -- Kees Cook Pixel Security