Re: [PATCH v2 14/18] lib/test_lockup: fix kernel pointer check for separate address spaces

[Christoph Hellwig <hch@xxxxxx>]

On Wed, Feb 16, 2022 at 02:13:28PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> test_kernel_ptr() uses access_ok() to figure out if a given address
> points to user space instead of kernel space. However on architectures
> that set CONFIG_ALTERNATE_USER_ADDRESS_SPACE, a pointer can be valid
> for both, and the check always fails because access_ok() returns true.
> 
> Make the check for user space pointers conditional on the type of
> address space layout.

What is this code even trying to do?  It looks extremly broken.