Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754782AbdDDQCw (ORCPT ); Tue, 4 Apr 2017 12:02:52 -0400 Received: from mail-io0-f174.google.com ([209.85.223.174]:34848 "EHLO mail-io0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754444AbdDDQCt (ORCPT ); Tue, 4 Apr 2017 12:02:49 -0400 MIME-Version: 1.0 In-Reply-To: <20170404155856.GP15132@dhcp22.suse.cz> References: <20170331164028.GA118828@beast> <20170404113022.GC15490@dhcp22.suse.cz> <20170404151600.GN15132@dhcp22.suse.cz> <20170404155856.GP15132@dhcp22.suse.cz> From: Kees Cook Date: Tue, 4 Apr 2017 09:02:48 -0700 X-Google-Sender-Auth: 7PmwbyUNwqLaBZ_Dr6iAIZYcGVk Message-ID: Subject: Re: [PATCH] mm: Add additional consistency check To: Michal Hocko Cc: Christoph Lameter , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , Linux-MM , 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 Content-Length: 1354 Lines: 35 On Tue, Apr 4, 2017 at 8:58 AM, Michal Hocko wrote: > On Tue 04-04-17 08:46:02, Kees Cook wrote: >> On Tue, Apr 4, 2017 at 8:16 AM, Michal Hocko wrote: >> > On Tue 04-04-17 10:07:23, Cristopher Lameter wrote: >> >> On Tue, 4 Apr 2017, Michal Hocko wrote: >> >> >> >> > NAK without a proper changelog. Seriously, we do not blindly apply >> >> > changes from other projects without a deep understanding of all >> >> > consequences. >> >> >> >> Functionalitywise this is trivial. A page must be a slab page in order to >> >> be able to determine the slab cache of an object. Its definitely not ok if >> >> the page is not a slab page. >> > >> > Yes, but we do not have to blow the kernel, right? Why cannot we simply >> > leak that memory? >> >> I can put this behind CHECK_DATA_CORRUPTION() instead of BUG(), which >> allows the system builder to choose between WARN and BUG. Some people >> absolutely want the kernel to BUG on data corruption as it could be an >> attack. > > CHECK_DATA_CORRUPTION sounds as better fit to me. This would, however > require to handle the potenial corruption by returning and leaking the > memory. IIUC, that would be the "return s" path? I should likely change the WARN_ON_ONCE there to be CHECK_DATA_CORRUPTION too. I'll add this to my series. -Kees -- Kees Cook Pixel Security