net: sched: act_tunnel_key: remove dependency on rtnl lock

Use tcf lock to protect tunnel key action struct private data from
concurrent modification in init and dump. Use rcu swap operation to
reassign params pointer under protection of tcf lock. (old params value is
not used by init, so there is no need of standalone rcu dereference step)

Remove rtnl lock assertion that is no longer required.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_tunnel_key.c

@@ -204,7 +204,6 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 {
 	struct tc_action_net *tn = net_generic(net, tunnel_key_net_id);
 	struct nlattr *tb[TCA_TUNNEL_KEY_MAX + 1];
-	struct tcf_tunnel_key_params *params_old;
 	struct tcf_tunnel_key_params *params_new;
 	struct metadata_dst *metadata = NULL;
 	struct tc_tunnel_key *parm;
@@ -346,24 +345,22 @@ static int tunnel_key_init(struct net *net, struct nlattr *nla,
 
 	t = to_tunnel_key(*a);
 
-	ASSERT_RTNL();
 	params_new = kzalloc(sizeof(*params_new), GFP_KERNEL);
 	if (unlikely(!params_new)) {
 		tcf_idr_release(*a, bind);
 		NL_SET_ERR_MSG(extack, "Cannot allocate tunnel key parameters");
 		return -ENOMEM;
 	}
-
-	params_old = rtnl_dereference(t->params);
-
-	t->tcf_action = parm->action;
 	params_new->tcft_action = parm->t_action;
 	params_new->tcft_enc_metadata = metadata;
 
-	rcu_assign_pointer(t->params, params_new);
-
-	if (params_old)
-		kfree_rcu(params_old, rcu);
+	spin_lock(&t->tcf_lock);
+	t->tcf_action = parm->action;
+	rcu_swap_protected(t->params, params_new,
+			   lockdep_is_held(&t->tcf_lock));
+	spin_unlock(&t->tcf_lock);
+	if (params_new)
+		kfree_rcu(params_new, rcu);
 
 	if (ret == ACT_P_CREATED)
 		tcf_idr_insert(tn, *a);
@@ -485,12 +482,13 @@ static int tunnel_key_dump(struct sk_buff *skb, struct tc_action *a,
 		.index    = t->tcf_index,
 		.refcnt   = refcount_read(&t->tcf_refcnt) - ref,
 		.bindcnt  = atomic_read(&t->tcf_bindcnt) - bind,
-		.action   = t->tcf_action,
 	};
 	struct tcf_t tm;
 
-	params = rtnl_dereference(t->params);
-
+	spin_lock(&t->tcf_lock);
+	params = rcu_dereference_protected(t->params,
+					   lockdep_is_held(&t->tcf_lock));
+	opt.action   = t->tcf_action;
 	opt.t_action = params->tcft_action;
 
 	if (nla_put(skb, TCA_TUNNEL_KEY_PARMS, sizeof(opt), &opt))
@@ -522,10 +520,12 @@ static int tunnel_key_dump(struct sk_buff *skb, struct tc_action *a,
 	if (nla_put_64bit(skb, TCA_TUNNEL_KEY_TM, sizeof(tm),
 			  &tm, TCA_TUNNEL_KEY_PAD))
 		goto nla_put_failure;
+	spin_unlock(&t->tcf_lock);
 
 	return skb->len;
 
 nla_put_failure:
+	spin_unlock(&t->tcf_lock);
 	nlmsg_trim(skb, b);
 	return -1;
 }