DO NOT APPLY: x86-64, espfix: Don't leak bits 31:16 of %esp returning to 16-bit stack

[Greg KH]

On Tue, Jul 15, 2014 at 04:56:36PM -0700, Andrew Lutomirski wrote:
> On Tue, Jul 15, 2014 at 4:52 PM, Greg KH <greg at kroah.com> wrote:
> > On Tue, Jul 15, 2014 at 04:21:46PM -0700, Andrew Lutomirski wrote:
> >> On Tue, Jul 15, 2014 at 2:28 PM, Kamal Mostafa <kamal at canonical.com> wrote:
> >> > 3.13.11.5 -stable review patch.  If anyone has any objections, please let me know.
> >> >
> >> > ------------------
> >> >
> >> > From: "H. Peter Anvin" <hpa at linux.intel.com>
> >> >
> >> > commit 3891a04aafd668686239349ea58f3314ea2af86b upstream.
> >>
> >> Do not apply to any -stable release yet.  This causes nasty regressions on Xen.
> >
> > I thought you all found the Xen-regression-fix patch a few hours ago,
> > right?
> 
> That patch is insufficient: Xen guests still fail to initialize
> espfix64 correctly on SMP.  It's currently unclear that espfix64 can
> work at all on Xen -- it's may be rather fundamentally incompatible
> with the Xen hypercall IRET mechanism.  So it might need to be
> disabled entirely on Xen (and maybe Xen will fix the info leak in the
> hypervisor).

Ok, I'll pospone these all until the next round of stable releases next
week, Linus's tree should be fixed by then.

thanks,

greg k-h