netdev - Re: Oops in nf_nat_core.c:find_appropriate

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Message-ID: <484AA276.9090407@trash.net>
Date:	Sat, 07 Jun 2008 17:00:06 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Chuck Ebbert <cebbert@...hat.com>
CC:	Netdev <netdev@...r.kernel.org>,
	Netfilter Development Mailinglist 
	<netfilter-devel@...r.kernel.org>
Subject: Re: Oops in nf_nat_core.c:find_appropriate_src(), kernel 2.6.25.4

Chuck Ebbert wrote:
> Reported at https://bugzilla.redhat.com/show_bug.cgi?id=449315
> 
> In find_appropriate_src():
> 
>         hlist_for_each_entry_rcu(nat, n, &bysource[h], bysource) {
>                 ct = nat->ct;
>                 if (same_src(ct, tuple)) {
> 
> Dereference of ct in same_src() causes the oops. This only seems to
> happen on heavily loaded firewall machines. Kernel 2.6.24.7 works.
> 
> The reporter identifies commit 4d354c5782dc352cec187845d17eedc2c2bfcf67
> ("[NETFILTER]: nf_nat: use RCU for bysource hash") as a possible cause
> of the problem.

We have a similar looking report, but that one also affects 2.6.24:

http://bugzilla.kernel.org/show_bug.cgi?id=10875

Anyways, does this patch help? When reallocating storage
for a conntrack, it is replaced in the list before assigning
the nat->ct pointer.


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