Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758532AbXEUJpV (ORCPT ); Mon, 21 May 2007 05:45:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754970AbXEUJpK (ORCPT ); Mon, 21 May 2007 05:45:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:60409 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754934AbXEUJpI (ORCPT ); Mon, 21 May 2007 05:45:08 -0400 Date: Mon, 21 May 2007 11:45:07 +0200 From: Nick Piggin To: Helge Hafting Cc: Andrew Morton , William Lee Irwin III , Christoph Lameter , Linux Kernel Mailing List , Linux Memory Management List , linux-arch@vger.kernel.org Subject: Re: [rfc] increase struct page size?! Message-ID: <20070521094507.GB19642@wotan.suse.de> References: <20070518040854.GA15654@wotan.suse.de> <20070519012530.GB15569@wotan.suse.de> <20070519181501.GC19966@holomorphy.com> <20070519150934.bdabc9b5.akpm@linux-foundation.org> <4651629B.2050505@aitel.hist.no> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4651629B.2050505@aitel.hist.no> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 996 Lines: 26 On Mon, May 21, 2007 at 11:12:59AM +0200, Helge Hafting wrote: > Andrew Morton wrote: > >On Sat, 19 May 2007 11:15:01 -0700 William Lee Irwin III > > wrote: > > > > > >>Much the same holds for the atomic_t's; 32 + PAGE_SHIFT is > >>44 bits or more, about as much as is possible, and one reference per > >>page per page is not even feasible. Full-length atomic_t's are just > >>not necessary. > >> > > > >You can overflow a page's refcount by mapping it 4G times. That requires > >32GB of pagetable memory. It's quite feasible with remap_file_pages(). > > > But do anybody ever need to do that? > Such an attack is easily thwarted by refusing to map it more > than, say 3G times? That still allows you to DoS the page. - 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/