On Mon, Dec 05, 2022 at 09:51:39AM -0800, Nhat Pham wrote:

> +	if (!access_ok(cstat, sizeof(struct cachestat)))
> +		return -EFAULT;

What for?  You are using copy_to_user() later, right?

> +	f = fdget(fd);
> +	if (f.file) {

It would be easier to read if you inverted the condition here.