Bluetooth: Delay check for conn->smp in smp_conn_security()

There are several actions that smp_conn_security() might make that do
not require a valid SMP context (conn->smp pointer). One of these
actions is to encrypt the link with an existing LTK. If the SMP
context wasn't initialized properly we should still allow the
independent actions to be done, i.e. the check for the context should
only be done at the last possible moment.

Reported-by: Chuck Ebbert <cebbert.lkml@gmail.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org # 4.0+

net/bluetooth/smp.c

@@ -2311,12 +2311,6 @@ int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
 	if (!conn)
 		return 1;
 
-	chan = conn->smp;
-	if (!chan) {
-		BT_ERR("SMP security requested but not available");
-		return 1;
-	}
-
 	if (!hci_dev_test_flag(hcon->hdev, HCI_LE_ENABLED))
 		return 1;
 
@@ -2330,6 +2324,12 @@ int smp_conn_security(struct hci_conn *hcon, __u8 sec_level)
 		if (smp_ltk_encrypt(conn, hcon->pending_sec_level))
 			return 0;
 
+	chan = conn->smp;
+	if (!chan) {
+		BT_ERR("SMP security requested but not available");
+		return 1;
+	}
+
 	l2cap_chan_lock(chan);
 
 	/* If SMP is already in progress ignore this request */