From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4651629B.2050505@aitel.hist.no> Date: Mon, 21 May 2007 11:12:59 +0200 From: Helge Hafting MIME-Version: 1.0 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: owner-linux-mm@kvack.org Return-Path: 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 List-ID: 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, 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