linux-kernel - Re: Soft lockup on shutdown in nf_ct_iterate

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Date:	Sun, 25 Feb 2007 20:03:36 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Martin Josefsson <gandalf@...g.westbo.se>
CC:	Chuck Ebbert <cebbert@...hat.com>,
	netfilter-devel@...ts.netfilter.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Soft lockup on shutdown in nf_ct_iterate_cleanup()

Martin Josefsson wrote:
> What about this case:
> 
> 1. Conntrack entry is created and placed on the unconfirmed list
> 2. The event cache bumps the refcount of the conntrack entry
> 3. module removal of ip_conntrack unregisters all hooks
> 4. packet is dropped by an iptables rule
> 5. packet is freed but we still have a refcount on the conntrack entry
> 
> Now there's no way to get that refcount to decrease as that only happens
> when the event cache receives another packet or the current packet makes
> it through the stack as you wrote above. And neither of this will happen
> since we unregistered the hooks providing the packets and dropped the
> packet.

The event cache is flushed on conntrack module unload after the hooks
have been unregistered, which should release all references.
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