On Tue, Jan 09, 2018 at 01:04:20PM +0000, David Woodhouse wrote: > On Mon, 2018-01-08 at 19:27 -0800, Andy Lutomirski wrote: > > > > > > If SMEP is not active, speculation can go anywhere, including to a user > > > controlled gadget which can reload any registers it needs, including > > > with immediate constants. > > > > I thought that, even on pre-SMEP hardware, the CPU wouldn't > > speculatively execute from NX pages. And PTI marks user memory NX > > in kernel mode. > > Hm, now that could be useful. > > Do *all* the KPTI backports (some of which are reimplementations rather > than strictly backports) mark user memory NX?
That doesn't really matter for upstream though; but see here: https://lkml.kernel.org/r/[email protected]
