netdev - Re: [PATCH nf V2] netfilter: fix oops in nfqueue during netns error unwinding

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Message-ID: <87k2ixo3pn.fsf@x220.int.ebiederm.org>
Date:	Fri, 13 May 2016 19:58:28 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Florian Westphal <fw@...len.de>
Cc:	Pablo Neira Ayuso <pablo@...filter.org>,
	netfilter-devel@...r.kernel.org, dale.4d@...il.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH nf V2] netfilter: fix oops in nfqueue during netns error unwinding

Florian Westphal <fw@...len.de> writes:

> Eric W. Biederman <ebiederm@...ssion.com> wrote:
>> Florian could you test and verify this patch fixes your issues?
>
> Yes, this seems to work.
>
> Pablo, I'm fine with this patch going into -nf/stable but I do not think
> making the pointers per netns is a desireable option in the long term.
>
>> Unlike the other possibilities that have been discussed this also
>> addresses the nf_queue path as well as the nf_queue_hook_drop path.
>
> The nf_queue path should have been fine, no?
>
> Or putting it differently: can we start processing skbs before a netns
> is fully initialized?

The practical case that worries me is what happens when someone does
"rmmod nfnetlink_queue" while the system is running.  It appears to me
that today we could free the per netns data during the rcu grace period
and cause a similar issue in nfnl_queue_pernet.

That looks like it could affect both the nf_queue path and the
nf_queue_nf_hook_drop path.

Eric