From: Marcel Holtmann <marcel@holtmann.org>
Subject: [RFC] Bluetooth: Check key sizes only when Secure Simple Pairing is enabled
Date: Wed, 22 May 2019 09:05:40 +0200
Message-id: <20190522070540.48895-1-marcel@holtmann.org>
Patch-mainline: No, RFC
References: bsc#1135556

The encryption is only mandatory to be enforced when both sides are using
Secure Simple Pairing and this means the key size check makes only sense
in that case.

On legacy Bluetooth 2.0 and earlier devices like mice the encryption was
optional and thus causing an issue if the key size check is not bound to
using Secure Simple Pairing.

Fixes: d5bb334a8e17 ("Bluetooth: Align minimum encryption key size for LE and BR/EDR connections")
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 net/bluetooth/hci_conn.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1148,8 +1148,13 @@ int hci_conn_check_link_mode(struct hci_
 			return 0;
 	}
 
-	if (hci_conn_ssp_enabled(conn) &&
-	    !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
+	/* If Secure Simple Pairing is not enabled, then legacy connection
+	 * setup is used and no encryption or key sizes can be enforced.
+	 */
+	if (!hci_conn_ssp_enabled(conn))
+		return 1;
+
+	if (!test_bit(HCI_CONN_ENCRYPT, &conn->flags))
 		return 0;
 
 	/* The minimum encryption key size needs to be enforced by the