Bluetooth: serialize calls to sco_sock_{set,clear}_timer

Currently, calls to sco_sock_set_timer are made under the locked
socket, but this does not apply to all calls to sco_sock_clear_timer.

Both sco_sock_{set,clear}_timer should be serialized by lock_sock to
prevent unexpected concurrent clearing/setting of timers.

Additionally, since sco_pi(sk)->conn is only cleared under the locked
socket, this change allows us to avoid races between
sco_sock_clear_timer and the call to kfree(conn) in sco_conn_del.
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/sco.c

@@ -453,8 +453,8 @@ static void __sco_sock_close(struct sock *sk)
 /* Must be called on unlocked socket. */
 static void sco_sock_close(struct sock *sk)
 {
-	sco_sock_clear_timer(sk);
 	lock_sock(sk);
+	sco_sock_clear_timer(sk);
 	__sco_sock_close(sk);
 	release_sock(sk);
 	sco_sock_kill(sk);
@@ -1104,8 +1104,8 @@ static void sco_conn_ready(struct sco_conn *conn)
 	BT_DBG("conn %p", conn);
 
 	if (sk) {
-		sco_sock_clear_timer(sk);
 		lock_sock(sk);
+		sco_sock_clear_timer(sk);
 		sk->sk_state = BT_CONNECTED;
 		sk->sk_state_change(sk);
 		release_sock(sk);