Subject: Re: [PATCH nf-next 3/3] netfilter: replace list_head with single linked list

From: Aaron Conole <[email-masked]>
Date: Mon, 11 Jul 2016 14:56:31 -0400

Thanks for this;  I will send a v2 in the next two days.

-Aaron

Florian Westphal <[email-masked]> writes:

> Aaron Conole <[email-masked]> wrote:
>> --- a/net/netfilter/core.c
>> +++ b/net/netfilter/core
> [..]
>> +#define nf_entry_dereference(e) \
>> +	rcu_dereference_protected(e, lockdep_is_held(&nf_hook_mutex))
>>  
>> -static struct list_head *nf_find_hook_list(struct net *net,
>> -					   const struct nf_hook_ops *reg)
>> +static struct nf_hook_entry *nf_find_hook_list(struct net *net,
>> +					       const struct nf_hook_ops *reg)
>>  {
>> -	struct list_head *hook_list = NULL;
>> +	struct nf_hook_entry *hook_list = NULL;
>>  
>>  	if (reg->pf != NFPROTO_NETDEV)
>> -		hook_list = &net->nf.hooks[reg->pf][reg->hooknum];
>> +		hook_list = rcu_dereference(net->nf.hooks[reg->pf]
>> +					    [reg->hooknum]);
>>  	else if (reg->hooknum == NF_NETDEV_INGRESS) {
>>  #ifdef CONFIG_NETFILTER_INGRESS
>>  		if (reg->dev && dev_net(reg->dev) == net)
>> -			hook_list = &reg->dev->nf_hooks_ingress;
>> +			hook_list =
>> +				rcu_dereference(reg->dev->nf_hooks_ingress);
>
> Both of these should use nf_entry_dereference() to avoid the lockdep
> splat reported by kbuild robot:
>
> net/netfilter/core.c:75 suspicious rcu_dereference_check() usage!
> 2 locks held by swapper/1:
> #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff81c2e567>] rtnl_lock+0x17/0x20
> #1: (nf_hook_mutex){+.+...}, at: [<ffffffff81c58fcb>]
> nf_register_net_hook+0xcb/0x240
>