[RFC] Bluetooth: Check key sizes only when Secure Simple Pairing is enabled

[Marcel Holtmann <marcel@holtmann.org>]

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

diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
index 3cf0764d5793..7516cdde3373 100644
--- a/net/bluetooth/hci_conn.c
+++ b/net/bluetooth/hci_conn.c
@@ -1272,8 +1272,13 @@ int hci_conn_check_link_mode(struct hci_conn *conn)
 			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
-- 
2.20.1