When trying to open an UART instance, I got the following:

 java.security.AccessControlException: access denied ("java.util.PropertyPermission" "jdk.dio.uart.inputTimeout" "read")

The problem is:

UARTImpl.java, constructor is:

    UARTImpl(DeviceDescriptor<UART> dscr, int mode)
                                throws DeviceNotFoundException, InvalidDeviceConfigException, UnsupportedAccessModeException{
...
        inputTimeout = Configuration.getNonNegativeIntProperty("jdk.dio.uart.inputTimeout", 2000);
...
}

============

And this call boils to the following one:

    public static int getIntProperty(String key, int def) {
        String value = System.getProperty(key);
        if (value != null) {
            try {
                return Integer.valueOf(value).intValue();
            } catch (NumberFormatException e) {
            }
        }
        return def;
    }
=========================

Having this code running in limited application security context
(only declared permissions by the specification are granted to the application,
and AllPermission is granted to dio classes), we observe a missing doPrigilegedBlock()
to call System.getProperty() in.