Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932651Ab1CDVKm (ORCPT ); Fri, 4 Mar 2011 16:10:42 -0500 Received: from mx1.vsecurity.com ([209.67.252.12]:62671 "EHLO mx1.vsecurity.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932516Ab1CDVKh (ORCPT ); Fri, 4 Mar 2011 16:10:37 -0500 Subject: Re: [PATCH] Make /proc/slabinfo 0400 From: Dan Rosenberg To: Pekka Enberg Cc: Matt Mackall , Linus Torvalds , Dave Hansen , Theodore Tso , cl@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton In-Reply-To: References: <1299174652.2071.12.camel@dan> <1299185882.3062.233.camel@calx> <1299186986.2071.90.camel@dan> <1299188667.3062.259.camel@calx> <1299191400.2071.203.camel@dan> <2DD7330B-2FED-4E58-A76D-93794A877A00@mit.edu> <1299260164.8493.4071.camel@nimitz> <1299262495.3062.298.camel@calx> <1299271041.2071.1398.camel@dan> Content-Type: text/plain; charset="UTF-8" Date: Fri, 04 Mar 2011 16:10:34 -0500 Message-ID: <1299273034.2071.1417.camel@dan> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1320 Lines: 24 On Fri, 2011-03-04 at 22:58 +0200, Pekka Enberg wrote: > On Fri, Mar 4, 2011 at 10:37 PM, Dan Rosenberg wrote: > > This patch makes these techniques more difficult by making it hard to > > know whether the last attacker-allocated object resides before a free or > > allocated object. Especially with vulnerabilities that only allow one > > attempt at exploitation before recovery is needed to avoid trashing too > > much heap state and causing a crash, this could go a long way. I'd > > still argue in favor of removing the ability to know how many objects > > are used in a given slab, since randomizing objects doesn't help if you > > know every object is allocated. > > So if the attacker knows every object is allocated, how does that help > if we're randomizing the initial freelist? If you know you've got a slab completely full of your objects, then it doesn't matter that they happened to be allocated in a random fashion - they're still all allocated, and by freeing one of them and reallocating, you'll still be next to your target. -- 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/