Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758530AbZFCPkP (ORCPT ); Wed, 3 Jun 2009 11:40:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756270AbZFCPkD (ORCPT ); Wed, 3 Jun 2009 11:40:03 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:57539 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754734AbZFCPkB (ORCPT ); Wed, 3 Jun 2009 11:40:01 -0400 Date: Wed, 3 Jun 2009 08:38:47 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Christoph Lameter cc: "Larry H." , linux-mm@kvack.org, Alan Cox , Rik van Riel , linux-kernel@vger.kernel.org, pageexec@freemail.hu Subject: Re: Security fix for remapping of page 0 (was [PATCH] Change ZERO_SIZE_PTR to point at unmapped space) In-Reply-To: Message-ID: References: <20090530192829.GK6535@oblivion.subreption.com> <20090530230022.GO6535@oblivion.subreption.com> <20090531022158.GA9033@oblivion.subreption.com> <20090602203405.GC6701@oblivion.subreption.com> User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1084 Lines: 30 On Wed, 3 Jun 2009, Christoph Lameter wrote: > On Wed, 3 Jun 2009, Linus Torvalds wrote: > > > The point being that we do need to support mmap at zero. Not necessarily > > universally, but it can't be some fixed "we don't allow that". > > Hmmm... Depend on some capability? CAP_SYS_PTRACE may be something > remotely related? But as mentioned several times, we do have the system-wide setting in 'mmap_min_addr' (that then can be overridden by CAP_SYS_RAWIO, so in that sense a capability already exists). It defaults to 64kB in at least the x86 defconfig files, but to 0 in the Kconfig defaults. Also, for some reason it has a "depends on SECURITY", which means that if you just default to the old-style unix security you'll lose it. So there are several ways to disable it by mistake. I don't know what distros do. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/