From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765034AbXLOANg (ORCPT ); Fri, 14 Dec 2007 19:13:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752070AbXLOAN2 (ORCPT ); Fri, 14 Dec 2007 19:13:28 -0500 Received: from emailhub.stusta.mhn.de ([141.84.69.5]:48854 "EHLO mailhub.stusta.mhn.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753813AbXLOAN2 (ORCPT ); Fri, 14 Dec 2007 19:13:28 -0500 Date: Sat, 15 Dec 2007 01:13:31 +0100 From: Adrian Bunk To: Hugh Dickins Cc: Chuck Ebbert , Linus Torvalds , Andrew Morton , Willy Tarreau , stable@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tmpfs: restore missing clear_highpage Message-ID: <20071215001331.GC5403@stusta.de> References: <475F24A7.3020106@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 12, 2007 at 05:01:51AM +0000, Hugh Dickins wrote: > On Tue, 11 Dec 2007, Chuck Ebbert wrote: > > On 11/28/2007 01:55 PM, Hugh Dickins wrote: > > > tmpfs was misconverted to __GFP_ZERO in 2.6.11. There's an unusual case in > > > which shmem_getpage receives the page from its caller instead of allocating. > > > We must cover this case by clear_highpage before SetPageUptodate, as before. > > > > > > Signed-off-by: Hugh Dickins > > > --- > > > > What are the symptoms of the bug this fixes? > > I've not seen it in practice, just noticed it while working on that > area in the code. What's the polite way of describing these things > in public? It's a vulnerability which might allow an attacker to > access data from inside the kernel which should have been zeroed - > in very limited circumstances I'd prefer not to have to devise and > announce. > > It would also be wrong data, so could for example crash any program > rightly relying on uninitialized static data to be zeroed - in the > unlikely event that its data was coming via this route (in most setups > it never can do, perhaps I'd conclude that's true of all setups). It > has escaped notice for nearly three years, so it's not a commonplace. > > Further discussion offline if you like! Can we get or is there already a CVE number? > Hugh cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed