netdev - Re: Netfilter: kernel panic with REDIRECT target. (2.6.23 and 2.6.23.8)

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Date:	Tue, 20 Nov 2007 04:09:58 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	johnpol@....mipt.ru
Cc:	david@...olicited.net, kaber@...sh.net, ismail@...dus.org.tr,
	netdev@...r.kernel.org
Subject: Re: Netfilter: kernel panic with REDIRECT target. (2.6.23 and
 2.6.23.8)

From: Evgeniy Polyakov <johnpol@....mipt.ru>
Date: Tue, 20 Nov 2007 14:55:20 +0300

> > >> Ok, let's try it hard way.
> > >> Please check attached patch and tell if it helped (it will produce
> > >> some debug though).
> > >
> > > With both patches applied - one Patrick showed and this one.
> > >   
> > Now works, with this in dmesg
> > 
> > conntrack: ea94159c, new: ead4d7c4, old: ead4d7d0, ct: 00000000.
> 
> David (Miller :), please apply attached patch, which also needed to fix
> netfilter connection tracking bug.
> When connection tracking entry (nf_conn) is about to copy itself it can
> have some of its extension users (like nat) as being already freed and
> thus not required to be copied.
> Frankly saying, it can be not the correct fix, but from code observation
> and test, perfomed by David <david@...olicited.net> it is.
> 
> Actually looking at this function I suspect it was copied from
> nf_nat_setup_info() and thus bug was introduced.
> 
> Signed-off-by: Evgeniy Polyakov <johnpol@....mipt.ru>

Evgeniy, thanks for figuring this out.

I think it is fair to let Patrick take a quick look at this
before it is applied (and Linus is away until next week
anyways so there is no rush :-)

I suspect this error might live elsewhere too, so perhaps a good
audit should be done for this kind of thing as well so we can
kill all such gremlins now.

Thanks again.

> diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c
> index 70e7997..86b465b 100644
> --- a/net/ipv4/netfilter/nf_nat_core.c
> +++ b/net/ipv4/netfilter/nf_nat_core.c
> @@ -607,13 +607,10 @@ static void nf_nat_move_storage(struct nf_conn *conntrack, void *old)
>  	struct nf_conn_nat *new_nat = nf_ct_ext_find(conntrack, NF_CT_EXT_NAT);
>  	struct nf_conn_nat *old_nat = (struct nf_conn_nat *)old;
>  	struct nf_conn *ct = old_nat->ct;
> -	unsigned int srchash;
>  
> -	if (!(ct->status & IPS_NAT_DONE_MASK))
> +	if (!ct || !(ct->status & IPS_NAT_DONE_MASK))
>  		return;
>  
> -	srchash = hash_by_src(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
> -
>  	write_lock_bh(&nf_nat_lock);
>  	hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
>  	new_nat->ct = ct;
> 
> -- 
> 	Evgeniy Polyakov
-
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