linux-kernel - Re: [PATCH] netfilter: nf_conntrack: fix RCU race in nf_conntrack_find

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Message-ID: <20140109205622.GA29458@breakpoint.cc>
Date:	Thu, 9 Jan 2014 21:56:22 +0100
From:	Florian Westphal <fw@...len.de>
To:	Andrew Vagin <avagin@...allels.com>
Cc:	Florian Westphal <fw@...len.de>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Andrey Vagin <avagin@...nvz.org>,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, netdev@...r.kernel.org,
	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: fix RCU race in
 nf_conntrack_find_get

Andrew Vagin <avagin@...allels.com> wrote:
> Can we allocate conntrack with zero ct_general.use and increment it at
> the first time before inserting the conntrack into the hash table?
> When conntrack is allocated it is attached exclusively to one skb.
> It must be destroyed with skb, if it has not been confirmed, so we
> don't need refcnt on this stage.
> 
> I found only one place, where a reference counter of unconfirmed
> conntract can incremented. It's ctnetlink_dump_table().

What about skb_clone, etc?  They will also increment the refcnt
if a conntrack entry is attached to the skb.
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