linux-kernel - Re: [PATCH] netfilter: nf_conntrack: release conntrack from rcu callback

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Date:	Tue, 7 Jan 2014 14:39:14 +0400
From:	Andrey Wagin <avagin@...il.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, vvs@...nvz.org,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	"David S. Miller" <davem@...emloft.net>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: [PATCH] netfilter: nf_conntrack: release conntrack from rcu callback

Hi Florian,

2014/1/7 Florian Westphal <fw@...len.de>:
> Andrew Vagin <avagin@...il.com> wrote:

>> >                 ct = nf_ct_tuplehash_to_ctrack(h);
>> >                 if (unlikely(nf_ct_is_dying(ct) ||
>> >                              !atomic_inc_not_zero(&ct->ct_general.use)))
>> >                     // which means we should hit this path (0 ref).
>> >                         h = NULL;
>> >                 else {
>> >                     // otherwise, it cannot go away from under us, since
>> >                     // we own a reference now.
>> >                         if (unlikely(!nf_ct_tuple_equal(tuple, &h->tuple) ||
>> >                                      nf_ct_zone(ct) != zone)) {
>
> Perhaps this needs additional !nf_ct_is_confirmed()?

Yes, it think it must help. Thank you for the comments. I resent this patch:
[PATCH] netfilter: nf_conntrack: fix RCU race in nf_conntrack_find_get

>
> It would cover your case (found a recycled element that has been put on
> the unconfirmed list (refcnt already set to 1, ct->tuple is set) on another cpu,
> extensions possibly not yet fully initialised), and the same tuple).
>
> Regards,
> Florian

Thanks,
Andrey
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