netdev - Re: Oops in nf_nat_core.c:find_appropriate

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Message-ID: <4850FD48.8050309@trash.net>
Date:	Thu, 12 Jun 2008 12:41:12 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	paulmck@...ux.vnet.ibm.com
CC:	Chuck Ebbert <cebbert@...hat.com>, Krzysztof Oledzki <ole@....pl>,
	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

Paul E. McKenney wrote:
> On Tue, Jun 10, 2008 at 11:02:59AM +0200, Patrick McHardy wrote:
>> Possibly fixes https://bugzilla.redhat.com/show_bug.cgi?id=449315
>> and/or http://bugzilla.kernel.org/show_bug.cgi?id=10875
> 
> One question and one nit below.
> 
>> @@ -570,8 +569,8 @@ static void nf_nat_move_storage(void *new, void *old)
>>  		return;
>>
>>  	spin_lock_bh(&nf_nat_lock);
>> -	hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
>>  	new_nat->ct = ct;
>> +	hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
> 
> The intent is to ensure that new_nat->ct is initialized before any
> readers can find new_nat, right?  If so, OK.

Correct. Its relying on the smb_wmb() in hlist_replace_rcu(),
but that seems OK.

>> diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
>> index bcc19fa..8a3f8b3 100644
>> --- a/net/netfilter/nf_conntrack_extend.c
>> +++ b/net/netfilter/nf_conntrack_extend.c
>> @@ -59,12 +59,19 @@ nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
>>  	if (!*ext)
>>  		return NULL;
>>
>> +	INIT_RCU_HEAD(&(*ext)->rcu);
> 
> Nit: the above is unnecessary.

I think its good style to use explicit initializers without
making assumptions about what exactly they do.

Thanks for the review.

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