On Thu, Aug 30, 2018 at 7:58 PM Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> wrote: > > On Thu, 2018-08-30 at 10:33 -0700, Dave Hansen wrote: > > 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. > > > > A task could go beyond the bottom of its shadow stack by doing either > 'ret' or 'incssp'. If it is the 'ret' case, the token prevents it. > If it is the 'incssp' case, a guard page cannot prevent it entirely, > right? I mean the other direction, on "call".
