From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754285AbdDDPQG (ORCPT ); Tue, 4 Apr 2017 11:16:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:43440 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752454AbdDDPQF (ORCPT ); Tue, 4 Apr 2017 11:16:05 -0400 Date: Tue, 4 Apr 2017 17:16:00 +0200 From: Michal Hocko To: Christoph Lameter Cc: Kees Cook , Andrew Morton , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Add additional consistency check Message-ID: <20170404151600.GN15132@dhcp22.suse.cz> References: <20170331164028.GA118828@beast> <20170404113022.GC15490@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 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? > The main issue that may exist here is the adding of overhead to a critical > code path like kfree(). Yes, nothing is for free. But if the attack space is real then we probably want to sacrifice few cycles (to simply return ASAP without further further processing). This all should be in the changelog ideally with some numbers. I suspect this would be hard to measure in most workloads. -- Michal Hocko SUSE Labs