From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [regression] nf_iterate(), BUG: unable to handle kernel NULL pointer dereference Date: Thu, 24 Jul 2008 21:35:32 +0200 Message-ID: <20080724193532.GC1694@elte.hu> References: <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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Pekka Enberg , Patrick McHardy , 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 To: Andrew Morton Return-path: Received: from mx3.mail.elte.hu ([157.181.1.138]:46442 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750930AbYGXThB (ORCPT ); Thu, 24 Jul 2008 15:37:01 -0400 Content-Disposition: inline In-Reply-To: <20080724115127.6cfbb616.akpm@linux-foundation.org> Sender: netdev-owner@vger.kernel.org List-ID: * 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? not that i know of. I'll do some re-tests tomorrow to make sure. Ingo