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

[Florian Westphal]

Aaron Conole <acon...@bytheb.org> 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