From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id D89496B009C for ; Wed, 3 Jun 2009 14:45:57 -0400 (EDT) Date: Wed, 3 Jun 2009 11:45:38 -0700 (PDT) From: Linus Torvalds Subject: Re: Security fix for remapping of page 0 (was [PATCH] Change ZERO_SIZE_PTR to point at unmapped space) In-Reply-To: <20090603183939.GC18561@oblivion.subreption.com> Message-ID: References: <20090530230022.GO6535@oblivion.subreption.com> <20090531022158.GA9033@oblivion.subreption.com> <20090602203405.GC6701@oblivion.subreption.com> <20090603182949.5328d411@lxorguk.ukuu.org.uk> <20090603180037.GB18561@oblivion.subreption.com> <20090603183939.GC18561@oblivion.subreption.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Larry H." Cc: Alan Cox , Christoph Lameter , linux-mm@kvack.org, Rik van Riel , linux-kernel@vger.kernel.org, pageexec@freemail.hu List-ID: On Wed, 3 Jun 2009, Larry H. wrote: > > > > The fact, the NULL pointer attack is neither easy nor common. It's > > perfectly reasonable to say "we'll allow mmap at virtual address zero". > > And how could you calibrate if this attack venue isn't easy to take > advantage of? Or not commonly abused? What empirical results led you to this > conclusion? It's not a primary attack vector. You need to have already broken local security to get there - you need to be able to execute code. That means that you've already by-passed all the main security. It's thus by definition less common than attack vectors like buffer overflows that give you that capability in the first place. Linus -- 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