Bluetooth: Fix check for connection encryption

commit e694788d upstream.

The conn->link_key variable tracks the type of link key in use. It is
set whenever we respond to a link key request as well as when we get a
link key notification event.

These two events do not however always guarantee that encryption is
enabled: getting a link key request and responding to it may only mean
that the remote side has requested authentication but not encryption. On
the other hand, the encrypt change event is a certain guarantee that
encryption is enabled. The real encryption state is already tracked in
the conn->link_mode variable through the HCI_LM_ENCRYPT bit.

This patch fixes a check for encryption in the hci_conn_auth function to
use the proper conn->link_mode value and thereby eliminates the chance
of a false positive result.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/bluetooth/hci_conn.c

@@ -617,7 +617,7 @@ static int hci_conn_auth(struct hci_conn *conn, __u8 sec_level, __u8 auth_type)
 		/* If we're already encrypted set the REAUTH_PEND flag,
 		 * otherwise set the ENCRYPT_PEND.
 		 */
-		if (conn->key_type != 0xff)
+		if (conn->link_mode & HCI_LM_ENCRYPT)
 			set_bit(HCI_CONN_REAUTH_PEND, &conn->pend);
 		else
 			set_bit(HCI_CONN_ENCRYPT_PEND, &conn->pend);