From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754624AbdDDP7C (ORCPT ); Tue, 4 Apr 2017 11:59:02 -0400 Received: from mx2.suse.de ([195.135.220.15]:48122 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753455AbdDDP7B (ORCPT ); Tue, 4 Apr 2017 11:59:01 -0400 Date: Tue, 4 Apr 2017 17:58:56 +0200 From: Michal Hocko To: Kees Cook Cc: Christoph Lameter , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , Linux-MM , LKML Subject: Re: [PATCH] mm: Add additional consistency check Message-ID: <20170404155856.GP15132@dhcp22.suse.cz> References: <20170331164028.GA118828@beast> <20170404113022.GC15490@dhcp22.suse.cz> <20170404151600.GN15132@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Michal Hocko SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 608106B039F for ; Tue, 4 Apr 2017 11:59:02 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id t189so2553280wmt.9 for ; Tue, 04 Apr 2017 08:59:02 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j1si4629773wrc.285.2017.04.04.08.59.00 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 04 Apr 2017 08:59:01 -0700 (PDT) Date: Tue, 4 Apr 2017 17:58:56 +0200 From: Michal Hocko Subject: Re: [PATCH] mm: Add additional consistency check Message-ID: <20170404155856.GP15132@dhcp22.suse.cz> References: <20170331164028.GA118828@beast> <20170404113022.GC15490@dhcp22.suse.cz> <20170404151600.GN15132@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Kees Cook Cc: Christoph Lameter , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , Linux-MM , LKML 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. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org