From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932084AbZE3NY7 (ORCPT ); Sat, 30 May 2009 09:24:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758222AbZE3NYw (ORCPT ); Sat, 30 May 2009 09:24:52 -0400 Received: from casper.infradead.org ([85.118.1.10]:35285 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757756AbZE3NYv (ORCPT ); Sat, 30 May 2009 09:24:51 -0400 Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator From: Peter Zijlstra To: pageexec@freemail.hu Cc: "Larry H." , Arjan van de Ven , Alan Cox , Ingo Molnar , Rik van Riel , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar In-Reply-To: <1243689707.6645.134.camel@laptop> 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> Content-Type: text/plain Date: Sat, 30 May 2009 15:24:31 +0200 Message-Id: <1243689871.6645.136.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2009-05-30 at 15:21 +0200, 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? Also, I'm not at all opposed to make crypto code use kzfree(). That code knows it had sensitive data in memory, it can wipe the memory when it frees it -- that makes perfect sense. Wiping everything because we're too 'lazy' to figure out what really matters otoh seems silly. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 6D7C66B00C6 for ; Sat, 30 May 2009 09:24:20 -0400 (EDT) Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator From: Peter Zijlstra In-Reply-To: <1243689707.6645.134.camel@laptop> 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> Content-Type: text/plain Date: Sat, 30 May 2009 15:24:31 +0200 Message-Id: <1243689871.6645.136.camel@laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: pageexec@freemail.hu Cc: "Larry H." , Arjan van de Ven , Alan Cox , Ingo Molnar , Rik van Riel , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar List-ID: On Sat, 2009-05-30 at 15:21 +0200, 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? Also, I'm not at all opposed to make crypto code use kzfree(). That code knows it had sensitive data in memory, it can wipe the memory when it frees it -- that makes perfect sense. Wiping everything because we're too 'lazy' to figure out what really matters otoh seems silly. -- 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