 int devmem_is_allowed(unsigned long pagenr)
 {
	if (pagenr < 256)
		return 1;
	if (iomem_is_exclusive(pagenr << PAGE_SHIFT))
 		return 0;
	if (!page_is_ram(pagenr))
		return 1;
	return 0;
 }

The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.