Bluetooth: SMP: Fix setting unknown auth_req bits

When sending a pairing request or response we should not just blindly
copy the value that the remote device sent. Instead we should at least
make sure to mask out any unknown bits. This is particularly critical
from the upcoming LE Secure Connections feature perspective as
incorrectly indicating support for it (by copying the remote value)
would cause a failure to pair with devices that support it.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Cc: stable@kernel.org
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

net/bluetooth/smp.c

@@ -32,6 +32,8 @@
 
 #define SMP_TIMEOUT	msecs_to_jiffies(30000)
 
+#define AUTH_REQ_MASK   0x07
+
 static inline void swap128(u8 src[16], u8 dst[16])
 {
 	int i;
@@ -230,7 +232,7 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 		req->max_key_size = SMP_MAX_ENC_KEY_SIZE;
 		req->init_key_dist = 0;
 		req->resp_key_dist = dist_keys;
-		req->auth_req = authreq;
+		req->auth_req = (authreq & AUTH_REQ_MASK);
 		return;
 	}
 
@@ -239,7 +241,7 @@ static void build_pairing_cmd(struct l2cap_conn *conn,
 	rsp->max_key_size = SMP_MAX_ENC_KEY_SIZE;
 	rsp->init_key_dist = 0;
 	rsp->resp_key_dist = req->resp_key_dist & dist_keys;
-	rsp->auth_req = authreq;
+	rsp->auth_req = (authreq & AUTH_REQ_MASK);
 }
 
 static u8 check_enc_key_size(struct l2cap_conn *conn, __u8 max_key_size)