From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932430AbZE3OK2 (ORCPT ); Sat, 30 May 2009 10:10:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758907AbZE3OKV (ORCPT ); Sat, 30 May 2009 10:10:21 -0400 Received: from mx2.redhat.com ([66.187.237.31]:40434 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758124AbZE3OKV (ORCPT ); Sat, 30 May 2009 10:10:21 -0400 Message-ID: <4A213DF9.2040207@redhat.com> Date: Sat, 30 May 2009 10:08:57 -0400 From: Rik van Riel Organization: Red Hat, Inc User-Agent: Thunderbird 2.0.0.17 (X11/20080915) MIME-Version: 1.0 To: Peter Zijlstra CC: pageexec@freemail.hu, "Larry H." , Arjan van de Ven , Alan Cox , Ingo Molnar , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator References: <20090522073436.GA3612@elte.hu> , <20090530054856.GG29711@oblivion.subreption.com> , <1243679973.6645.131.camel@laptop> <4A211BA8.8585.17B52182@pageexec.freemail.hu> <1243689707.6645.134.camel@laptop> In-Reply-To: <1243689707.6645.134.camel@laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > On Sat, 2009-05-30 at 13:42 +0200, pageexec@freemail.hu wrote: >>> Why waste time on this? >> e.g., when userland executes a syscall, it 'can run kernel code'. if that kernel >> code (note: already exists, isn't provided by the attacker) gives unintended >> kernel memory back to userland, there is a problem. that problem is addressed >> in part by early sanitizing of freed data. > > Right, so the whole point is to minimize the impact of actual bugs, > right? So why not focus on fixing those actual bugs? Can we create tools > to help us find such bugs faster? We use sparse for a lot of static > checking, we create things like lockdep and kmemcheck to dynamically > find trouble. > > Can we instead of working around a problem, fix the actual problem? Do you drive without seatbelts, because the real fix is to stay out of accidents? No software is bug free. Let me repeat that: no software is bug free. This means your security strategy cannot rely on software being bug free. This is why every security strategy is a "belt and suspenders" thing, where: 1) code is audited to remove as many bugs as possible, and 2) the system is configured in such a way that the impact of the remaining bugs is limited For example, if you check your own system you will find that system daemons like bind and httpd run with limited privileges. This is done because, again, no software is bug free and you want to limit the damage that can be done after a bug is exploited. -- All rights reversed.