Re: [PATCH 8/9] x86: kvm_hv_set_msr(): use __put_user() instead of 32bit __clear_user()

From: Al Viro
Date: Sat May 30 2020 - 15:19:49 EST

On Sat, May 30, 2020 at 11:52:44AM -0700, Linus Torvalds wrote:

> And I don't understand why you mention set_fs() vs access_ok(). None
> of this code has anything that messes with set_fs(). The access_ok()
> is garbage and shouldn't exist, and those user accesses should all use
> the checking versions and the double underscores are wrong.
> I have no idea why you think the double underscores could _possibly_
> be worth defending.

I do not. What I'm saying is that this just might be a beast different
from *both* __... and the normal ones. I'm not saying that this
__put_user() (or __clear_user(), etc.) is the right primitive here.
If anything, it's closer to the situation for (x86) copy_stack_trace().