Re: [PATCH] x86/uaccess: instrument copy_from_user_nmi()

[Peter Zijlstra]

On Thu, Oct 27, 2022 at 11:58:35AM -0700, Kees Cook wrote:

> I wandered around attempting to deal with in_nmi(), etc. And in
> the end just drop the attempt to cover it. It's worth noting that
> copy_from_user_nmi() exists on 1 architecture and has exactly 1
> call-site...

Yeah, back when I wrote it, it was a lot more complicated because we
could not reliably take #PF from NMI context; it did manual page-walks,
kmap_atomic()s and mempcy(). That's all fixed now and it's really mostly
a rudiment -- except for these instrumentation issues it seems.