net sched: simple action fix late binding

The process below was broken and is fixed with this patch.

//add a simple action and give it an instance id of 1
sudo tc actions add action simple sdata "foobar" index 1
//create a filter which binds to simple action id 1
sudo tc filter add dev $DEV parent ffff: protocol ip prio 1 u32\
match ip dst 17.0.0.1/32 flowid 1:10 action simple index 1

Message before fix was:
RTNETLINK answers: Invalid argument
We have an error talking to the kernel
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/act_simple.c

@@ -87,7 +87,7 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 	struct tc_defact *parm;
 	struct tcf_defact *d;
 	char *defdata;
-	int ret = 0, err;
+	int ret = 0, err, exists = 0;
 
 	if (nla == NULL)
 		return -EINVAL;
@@ -99,13 +99,21 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 	if (tb[TCA_DEF_PARMS] == NULL)
 		return -EINVAL;
 
-	if (tb[TCA_DEF_DATA] == NULL)
-		return -EINVAL;
 
 	parm = nla_data(tb[TCA_DEF_PARMS]);
+	exists = tcf_hash_check(tn, parm->index, a, bind);
+	if (exists && bind)
+		return 0;
+
+	if (tb[TCA_DEF_DATA] == NULL) {
+		if (exists)
+			tcf_hash_release(a, bind);
+		return -EINVAL;
+	}
+
 	defdata = nla_data(tb[TCA_DEF_DATA]);
 
-	if (!tcf_hash_check(tn, parm->index, a, bind)) {
+	if (!exists) {
 		ret = tcf_hash_create(tn, parm->index, est, a,
 				      sizeof(*d), bind, false);
 		if (ret)
@@ -122,8 +130,6 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 	} else {
 		d = to_defact(a);
 
-		if (bind)
-			return 0;
 		tcf_hash_release(a, bind);
 		if (!ovr)
 			return -EEXIST;