Re: [PATCH v4 3/4] x86/uaccess: Use pointer masking to limit uaccess speculation

[Christoph Hellwig]

On Thu, May 06, 2021 at 08:36:08AM +0000, David Laight wrote:
> 	uaddr = access_ok(uaddr, size)

access_ok as a public API is not interesting.  There are very few
valid uses cases for ever calling access_ok outside the usual
uaccess helper.  So leave access_ok alone, there is not point in
touching all the callers except for removing most of them.  If OTOH
we can micro-optimize get_user and put_user by using a different
variant of access_ok that seems fair game and actually useful.