From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 21 May 2007 11:45:07 +0200 From: Nick Piggin 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> Sender: owner-linux-mm@kvack.org Return-Path: 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 List-ID: 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, 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