net: sched: act_nat: remove dependency on rtnl lock

According to the new locking rule, we have to take tcf_lock for both
->init() and ->dump(), as RTNL will be removed.

Use tcf spinlock to protect private nat action data from concurrent
modification during dump. (nat init already uses tcf spinlock when changing
action state)
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_nat.c

@@ -256,28 +256,31 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 	unsigned char *b = skb_tail_pointer(skb);
 	struct tcf_nat *p = to_tcf_nat(a);
 	struct tc_nat opt = {
-		.old_addr = p->old_addr,
-		.new_addr = p->new_addr,
-		.mask     = p->mask,
-		.flags    = p->flags,
-
 		.index    = p->tcf_index,
-		.action   = p->tcf_action,
 		.refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 		.bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 	};
 	struct tcf_t t;
 
+	spin_lock_bh(&p->tcf_lock);
+	opt.old_addr = p->old_addr;
+	opt.new_addr = p->new_addr;
+	opt.mask = p->mask;
+	opt.flags = p->flags;
+	opt.action = p->tcf_action;
+
 	if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
 
 	tcf_tm_dump(&t, &p->tcf_tm);
 	if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
 		goto nla_put_failure;
+	spin_unlock_bh(&p->tcf_lock);
 
 	return skb->len;
 
 nla_put_failure:
+	spin_unlock_bh(&p->tcf_lock);
 	nlmsg_trim(skb, b);
 	return -1;
 }