Bluetooth: Check for valid HCI UART driver flags

Providing unknown or invalid flags to the HCI UART driver should
result in an error. So check which flags are valid and otherwise
return an error.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index e00f8f5..a49ee1b4 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -477,6 +477,21 @@
 	return 0;
 }
 
+static int hci_uart_set_flags(struct hci_uart *hu, unsigned long flags)
+{
+	unsigned long valid_flags = BIT(HCI_UART_RAW_DEVICE) |
+				    BIT(HCI_UART_RESET_ON_INIT) |
+				    BIT(HCI_UART_CREATE_AMP) |
+				    BIT(HCI_UART_INIT_PENDING);
+
+	if ((flags & ~valid_flags))
+		return -EINVAL;
+
+	hu->hdev_flags = flags;
+
+	return 0;
+}
+
 /* hci_uart_tty_ioctl()
  *
  *    Process IOCTL system call for the tty device.
@@ -527,7 +542,9 @@
 	case HCIUARTSETFLAGS:
 		if (test_bit(HCI_UART_PROTO_SET, &hu->flags))
 			return -EBUSY;
-		hu->hdev_flags = arg;
+		err = hci_uart_set_flags(hu, arg);
+		if (err)
+			return err;
 		break;
 
 	case HCIUARTGETFLAGS: