netdev - Re: Oops with latest (netfilter) nf-next tree, when unloading iptable

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Date:	Fri, 14 Sep 2012 15:15:47 +0200 (MEST)
From:	Patrick McHardy <kaber@...sh.net>
To:	Pablo Neira Ayuso <pablo@...monks.org>
cc:	Florian Westphal <fw@...len.de>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	netfilter-devel <netfilter-devel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, yongjun_wei@...ndmicro.com.cn
Subject: Re: Oops with latest (netfilter) nf-next tree, when unloading
 iptable_nat

On Fri, 14 Sep 2012, Pablo Neira Ayuso wrote:

> On Wed, Sep 12, 2012 at 11:36:27PM +0200, Florian Westphal wrote:
>> Jesper Dangaard Brouer <brouer@...hat.com> wrote:
>>
>> [ CC'd Patrick ]
>>
>>> I'm hitting this general protection fault, when unloading iptables_nat.
>>> [  524.591067] Pid: 5842, comm: modprobe Not tainted 3.6.0-rc3-pablo-nf-next+ #1 Red Hat KVM
>>> [  524.591067] RIP: 0010:[<ffffffffa002c2fd>]  [<ffffffffa002c2fd>] nf_nat_proto_clean+0x6d/0xc0 [nf_nat]
>>> [  524.591067] RSP: 0018:ffff880073203e18  EFLAGS: 00010246
>>> [  524.591067] RAX: 0000000000000000 RBX: ffff880077dff2c8 RCX: ffff8800797fab70
>>> [  524.591067] RDX: dead000000200200 RSI: ffff880073203e88 RDI: ffffffffa002f208
>>> [  524.591067] RBP: ffff880073203e28 R08: ffff880073202000 R09: 0000000000000000
>>> [  524.591067] R10: dead000000200200 R11: dead000000100100 R12: ffffffff81c6dc00
>>>  list corruption?   ^^^^^^^^^^^^^^^^      ^^^^^^^^^^^^^^^^
>>
>> Yep, looks like it.
>>
>>> [  524.591067]  [<ffffffffa002c290>] ? nf_nat_net_exit+0x50/0x50 [nf_nat]
>>> [  524.591067]  [<ffffffff815614e3>] nf_ct_iterate_cleanup+0xc3/0x170
>>> [  524.591067]  [<ffffffffa002c54a>] nf_nat_l3proto_unregister+0x8a/0x100 [nf_nat]
>>> [  524.591067]  [<ffffffff812a0303>] ? compat_prepare_timeout+0x13/0xb0
>>> [  524.591067]  [<ffffffffa0035848>] nf_nat_l3proto_ipv4_exit+0x10/0x23 [nf_nat_ipv4]
>>
>> On module removal nf_nat_ipv4 calls nf_iterate_cleanup which invokes
>> nf_nat_proto_clean() for each conntrack.  That will then call
>> hlist_del_rcu(&nat->bysource) using eachs conntracks nat ext area.
>>
>> Problem is that nf_nat_proto_clean() is called multiple times for the same
>> conntrack:
>> a) nf_ct_iterate_cleanup() returns each ct twice (origin, reply)
>> b) we call it both for l3 and for l4 protocol ids
>>
>> We barf in hlist_del_rcu the 2nd time because ->pprev is poisoned.
>>
>> This was introduced with the ipv6 nat patches.
>>
>> --- a/net/netfilter/nf_nat_core.c
>> +++ b/net/netfilter/nf_nat_core.c
>> @@ -487,7 +487,7 @@ static int nf_nat_proto_clean(struct nf_conn *i, void *data)
>>
>>         if (clean->hash) {
>>                 spin_lock_bh(&nf_nat_lock);
>> -               hlist_del_rcu(&nat->bysource);
>> +               hlist_del_init_rcu(&nat->bysource);
>>                 spin_unlock_bh(&nf_nat_lock);
>>         } else {
>>
>> Would probably avoid it.  I guess it would be nicer to only call this
>> once for each ct.
>>
>> Patrick, any other idea?
>
> I already discussed this with Florian (I've been having problems with
> two out of three of my email accounts this week... so I couldn't reply
> to this email in the mailing list).
>
> We can add nf_nat_iterate_cleanup that can iterate over the NAT
> hashtable to replace current usage of nf_ct_iterate_cleanup.

Lets just bail out when IPS_SRC_NAT_DONE is not set, that should also fix
it. Could you try this patch please?
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