Bluetooth: Fix encryption key size handling for LTKs

The encryption key size for LTKs is supposed to be applied only at the
moment of encryption. When generating a Link Key (using LE SC) from
the LTK the full non-shortened value should be used. This patch
modifies the code to always keep the full value around and only apply
the key size when passing the value to HCI.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 7b61be7..fcbfa41 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -4955,7 +4955,8 @@
 			goto not_found;
 	}
 
-	memcpy(cp.ltk, ltk->val, sizeof(ltk->val));
+	memcpy(cp.ltk, ltk->val, ltk->enc_size);
+	memset(cp.ltk + ltk->enc_size, 0, sizeof(cp.ltk) - ltk->enc_size);
 	cp.handle = cpu_to_le16(conn->handle);
 
 	conn->pending_sec_level = smp_ltk_sec_level(ltk);