netfilter: ctnetlink: fix scheduling while atomic

Caused by call to request_module() while holding nf_conntrack_lock.
Reported-and-tested-by: Kövesdi György <kgy@teledigit.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/nf_conntrack_netlink.c

@@ -831,13 +831,16 @@ ctnetlink_parse_nat_setup(struct nf_conn *ct,
 	if (!parse_nat_setup) {
 #ifdef CONFIG_MODULES
 		rcu_read_unlock();
+		spin_unlock_bh(&nf_conntrack_lock);
 		nfnl_unlock();
 		if (request_module("nf-nat-ipv4") < 0) {
 			nfnl_lock();
+			spin_lock_bh(&nf_conntrack_lock);
 			rcu_read_lock();
 			return -EOPNOTSUPP;
 		}
 		nfnl_lock();
+		spin_lock_bh(&nf_conntrack_lock);
 		rcu_read_lock();
 		if (nfnetlink_parse_nat_setup_hook)
 			return -EAGAIN;