net/rds: Check laddr_check before calling it

In rds_bind(), laddr_check is called without checking if it is NULL or
not. And rs_transport should be reset if rds_add_bound() fails.

Fixes: c5c1a030a7db ("net/rds: An rds_sock is added too early to the hash table")
Reported-by: [e-mail]
Signed-off-by: Ka-Cheong Poon <[e-mail]>
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/rds/bind.c

···
 	 */
 	if (rs->rs_transport) {
 		trans = rs->rs_transport;
-		if (trans->laddr_check(sock_net(sock->sk),
+		if (!trans->laddr_check ||
+		    trans->laddr_check(sock_net(sock->sk),
 				       binding_addr, scope_id) != 0) {
 			ret = -ENOPROTOOPT;
 			goto out;
···
 
 	sock_set_flag(sk, SOCK_RCU_FREE);
 	ret = rds_add_bound(rs, binding_addr, &port, scope_id);
+	if (ret)
+		rs->rs_transport = NULL;
 
 out:
 	release_sock(sk);