ife: error out when nla attributes are empty

act_ife at least requires TCA_IFE_PARMS, so we have to bail out
when there is no attribute passed in.

Reported-by: syzbot+fbb5b288c9cb6a2eeac4@syzkaller.appspotmail.com
Fixes: ef6980b ("introduce IFE action")
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: congwang

net/sched/act_ife.c

@@ -481,6 +481,11 @@ static int tcf_ife_init(struct net *net, struct nlattr *nla,
 	int ret = 0;
 	int err;
 
+	if (!nla) {
+		NL_SET_ERR_MSG_MOD(extack, "IFE requires attributes to be passed");
+		return -EINVAL;
+	}
+
 	err = nla_parse_nested_deprecated(tb, TCA_IFE_MAX, nla, ife_policy,
 					  NULL);
 	if (err < 0)