From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 2E3B76B00D1 for ; Wed, 3 Jun 2009 11:39:38 -0400 (EDT) Date: Wed, 3 Jun 2009 08:38:47 -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: Message-ID: References: <20090530192829.GK6535@oblivion.subreption.com> <20090530230022.GO6535@oblivion.subreption.com> <20090531022158.GA9033@oblivion.subreption.com> <20090602203405.GC6701@oblivion.subreption.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: "Larry H." , linux-mm@kvack.org, Alan Cox , Rik van Riel , linux-kernel@vger.kernel.org, pageexec@freemail.hu List-ID: 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, 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