Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761338AbXEUJW4 (ORCPT ); Mon, 21 May 2007 05:22:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760665AbXEUJWr (ORCPT ); Mon, 21 May 2007 05:22:47 -0400 Received: from embla.aitel.hist.no ([158.38.50.22]:51736 "HELO embla.aitel.hist.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755727AbXEUJWr (ORCPT ); Mon, 21 May 2007 05:22:47 -0400 Message-ID: <4651629B.2050505@aitel.hist.no> Date: Mon, 21 May 2007 11:12:59 +0200 From: Helge Hafting User-Agent: Icedove 1.5.0.10 (X11/20070329) MIME-Version: 1.0 To: Andrew Morton CC: William Lee Irwin III , Nick Piggin , Christoph Lameter , Linux Kernel Mailing List , Linux Memory Management List , linux-arch@vger.kernel.org Subject: Re: [rfc] increase struct page size?! References: <20070518040854.GA15654@wotan.suse.de> <20070519012530.GB15569@wotan.suse.de> <20070519181501.GC19966@holomorphy.com> <20070519150934.bdabc9b5.akpm@linux-foundation.org> In-Reply-To: <20070519150934.bdabc9b5.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 881 Lines: 23 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? Helge Hafting - 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/