Bluetooth: Prevent double register of suspend

Suspend notifier should only be registered and unregistered once per
hdev. Simplify this by only registering during driver registration and
simply exiting early when HCI_USER_CHANNEL is set.
Reported-by: syzbot <syzkaller@googlegroups.com>
Fixes: 359ee4f8 (Bluetooth: Unregister suspend with userchannel)
Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/hci_core.c

@@ -2406,6 +2406,10 @@ static int hci_suspend_notifier(struct notifier_block *nb, unsigned long action,
 		container_of(nb, struct hci_dev, suspend_notifier);
 	int ret = 0;
 
+	/* Userspace has full control of this device. Do nothing. */
+	if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL))
+		return NOTIFY_DONE;
+
 	if (action == PM_SUSPEND_PREPARE)
 		ret = hci_suspend_dev(hdev);
 	else if (action == PM_POST_SUSPEND)

net/bluetooth/hci_sock.c

@@ -887,7 +887,6 @@ static int hci_sock_release(struct socket *sock)
 			 */
 			hci_dev_do_close(hdev);
 			hci_dev_clear_flag(hdev, HCI_USER_CHANNEL);
-			hci_register_suspend_notifier(hdev);
 			mgmt_index_added(hdev);
 		}
 
@@ -1216,7 +1215,6 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
 		}
 
 		mgmt_index_removed(hdev);
-		hci_unregister_suspend_notifier(hdev);
 
 		err = hci_dev_open(hdev->id);
 		if (err) {
@@ -1231,7 +1229,6 @@ static int hci_sock_bind(struct socket *sock, struct sockaddr *addr,
 				err = 0;
 			} else {
 				hci_dev_clear_flag(hdev, HCI_USER_CHANNEL);
-				hci_register_suspend_notifier(hdev);
 				mgmt_index_added(hdev);
 				hci_dev_put(hdev);
 				goto done;