The copy_to_user() function returns the number of bytes remaining to be copied, but we want to return -EFAULT if the copy doesn't complete. Fixes: b754ffbbc0ee ("cxl/mem: Add basic IOCTL interface") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Link: https://lore.kernel.org/r/YC+K3kgzqm20zCWY@mwanda Signed-off-by: Dan Williams <dan.j.williams@intel.com>