Re: [PATCH v7 24/41] mm: Don't allow write GUPs to shadow stack memory

Borislav Petkov
2023-03-06T13:10:28Z

On Mon, Feb 27, 2023 at 02:29:40PM -0800, Rick Edgecombe wrote:
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
>
> Shadow stack memory is writable only in very specific, controlled ways.
> However, since it is writable, the kernel treats it as such. As a result
^
,

> there remain many ways for userspace to trigger the kernel to write to
> shadow stack's via get_user_pages(, FOLL_WRITE) operations. To make this a

"stacks"

or "to write to a shadow stack via..."

> little less exposed, block writable GUPs for shadow stack VMAs.

GUPs?

I supposed this means "prevent get_user_pages() from pinning pages to
which the corresponding VMA is a shadow stack one."?

Or something like that which is less mm-internal speak...

--
Regards/Gruss,
Boris.