net/smc: check variable before dereferencing in smc_close.c

smc->clcsock and smc->clcsock->sk are used before the check if they can
be dereferenced. Fix this by checking the variables first.

Fixes: a60a2b1 ("net/smc: reduce active tcp_listen workers")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_close.c

@@ -208,11 +208,12 @@ int smc_close_active(struct smc_sock *smc)
 		break;
 	case SMC_LISTEN:
 		sk->sk_state = SMC_CLOSED;
-		smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
-		smc->clcsock->sk->sk_user_data = NULL;
 		sk->sk_state_change(sk); /* wake up accept */
-		if (smc->clcsock && smc->clcsock->sk)
+		if (smc->clcsock && smc->clcsock->sk) {
+			smc->clcsock->sk->sk_data_ready = smc->clcsk_data_ready;
+			smc->clcsock->sk->sk_user_data = NULL;
 			rc = kernel_sock_shutdown(smc->clcsock, SHUT_RDWR);
+		}
 		smc_close_cleanup_listen(sk);
 		release_sock(sk);
 		flush_work(&smc->tcp_listen_work);