Revert "Bluetooth: Align minimum encryption key size for LE and BR/EDR connections"

BugLink: https://bugs.launchpad.net/bugs/1833698

This reverts commit 07e38998 which is
commit d5bb334a upstream.

Lots of people have reported issues with this patch, and as there does
not seem to be a fix going into Linus's kernel tree any time soon,
revert the commit in the stable trees so as to get people's machines
working properly again.
Reported-by: Vasily Khoruzhick <anarsoul@gmail.com>
Reported-by: Hans de Goede <hdegoede@redhat.com>
Cc: Jeremy Cline <jeremy@jcline.org>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit b528880e linux-5.1.y)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

include/net/bluetooth/hci_core.h

@@ -174,9 +174,6 @@ struct adv_info {
 
 #define HCI_MAX_SHORT_NAME_LENGTH	10
 
-/* Min encryption key size to match with SMP */
-#define HCI_MIN_ENC_KEY_SIZE		7
-
 /* Default LE RPA expiry time, 15 minutes */
 #define HCI_DEFAULT_RPA_TIMEOUT		(15 * 60)
 

net/bluetooth/hci_conn.c

@@ -1177,14 +1177,6 @@ int hci_conn_check_link_mode(struct hci_conn *conn)
 	    !test_bit(HCI_CONN_ENCRYPT, &conn->flags))
 		return 0;
 
-	/* The minimum encryption key size needs to be enforced by the
-	 * host stack before establishing any L2CAP connections. The
-	 * specification in theory allows a minimum of 1, but to align
-	 * BR/EDR and LE transports, a minimum of 7 is chosen.
-	 */
-	if (conn->enc_key_size < HCI_MIN_ENC_KEY_SIZE)
-		return 0;
-
 	return 1;
 }