From: Vlad Buslov <vladbu@mellanox.com>
Date: Fri, 10 Aug 2018 20:51:50 +0300
Subject: net: sched: act_tunnel_key: remove dependency on rtnl lock
Patch-mainline: v4.19-rc1
Git-commit: 729e01260989cc06c8a78491b46545793aef323a
References: bsc#1109837

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/act_tunnel_key.c |   25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

--- a/net/sched/act_tunnel_key.c
+++ b/net/sched/act_tunnel_key.c
@@ -204,7 +204,6 @@ static int tunnel_key_init(struct net *n
 {
 	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 *n
 
 	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);
@@ -488,8 +485,10 @@ static int tunnel_key_dump(struct sk_buf
 	};
 	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))
@@ -521,10 +520,12 @@ static int tunnel_key_dump(struct sk_buf
 	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;
 }