Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW

[Dave Hansen]

On 08/30/2018 10:26 AM, Yu-cheng Yu wrote:
> We don't have the guard page now, but there is a shadow stack token
> there, which cannot be used as a return address.

The overall concern is that we could overflow into a page that we did
not intend.  Either another actual shadow stack or something that a page
that the attacker constructed, like the transient scenario Jann described.