Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754645AbYGXS4G (ORCPT ); Thu, 24 Jul 2008 14:56:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752737AbYGXSzw (ORCPT ); Thu, 24 Jul 2008 14:55:52 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:55300 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752610AbYGXSzv (ORCPT ); Thu, 24 Jul 2008 14:55:51 -0400 Subject: Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference From: Pekka Enberg To: Andrew Morton Cc: Patrick McHardy , Ingo Molnar , David Miller , herbert@gondor.apana.org.au, w@1wt.eu, davidn@davidnewall.com, torvalds@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stefanr@s5r6.in-berlin.de, rjw@sisk.pl, ilpo.jarvinen@helsinki.fi, Dave Jones , clip2@gmx.de, vegard.nossum@gmail.com In-Reply-To: <20080724115127.6cfbb616.akpm@linux-foundation.org> References: <20080724060448.GA10203@elte.hu> <20080724.022259.113079007.davem@davemloft.net> <20080724093411.GA12001@elte.hu> <20080724115625.GA23994@elte.hu> <20080724115957.GA25701@elte.hu> <48886FA6.6050908@trash.net> <84144f020807240544q507e1b7cv220d1afbae0ee0f0@mail.gmail.com> <48887A71.5010209@trash.net> <1216905812.5897.6.camel@penberg-laptop> <48888434.3030207@trash.net> <1216906476.12021.4.camel@penberg-laptop> <20080724115127.6cfbb616.akpm@linux-foundation.org> Date: Thu, 24 Jul 2008 21:55:44 +0300 Message-Id: <1216925744.12392.1.camel@penberg-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit X-Mailer: Evolution 2.22.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1793 Lines: 44 On Thu, 2008-07-24 at 11:51 -0700, Andrew Morton wrote: > On Thu, 24 Jul 2008 16:34:36 +0300 Pekka Enberg wrote: > > > > >> Your patch introduced a use-after-free and double-free. > > > >> krealloc() frees the old pointer, but it is still used > > > >> for the ->move operations, then freed again. > > > >> > > > >> To fix this I think we need a __krealloc() that doesn't > > > >> free the old memory, especially since it must not be > > > >> freed immediately because it may still be used in a RCU > > > >> read side (see the last part in the patch attached to > > > >> this mail (based on a kernel without your patch)). > > > > > > > > Agreed. Something like this, perhaps? > > > > > > > > [PATCH] netfilter: fix double-free and use-after free > > > > > > > > As suggested by Patrick McHardy, introduce a __krealloc() that doesn't > > > > free the original buffer to fix a double-free and use-after-free bug > > > > introduced by me in netfilter that uses RCU. > > > > > > > > Reported-by: Patrick McHardy > > > > Signed-off-by: Pekka Enberg > > > > > > Looks good to me, thanks. > > > > Ingo, can you please test this? Andrew, I'm at OLS so can you pick up > > the patch in your tree? > > Sure. Or Patrick can do so and it can be merged via the net tree. > > Ingo, did this patch actually fix something over there? Apparently it didn't but it did fix Dieter's problem: http://lkml.org/lkml/2008/7/24/337 Dieter, can we add a Tested-by tag from you to this patch? -- 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/