If fourth argument is NULL it should be passed without
using lock_user function which would, in that case, return
EFAULT, and system call supports passing NULL as fourth argument.
Signed-off-by: NLena Djokic <Lena.Djokic@rt-rk.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>