Re: [PATCH v2 29/39] x86/cet/shstk: Support wrss for userspace

Kees Cook
2022-10-04T04:37:16Z

On Mon, Oct 03, 2022 at 04:00:36PM -0700, Andy Lutomirski wrote:
> On 10/3/22 15:28, Kees Cook wrote:
> > On Thu, Sep 29, 2022 at 03:29:26PM -0700, Rick Edgecombe wrote:
> > > For the current shadow stack implementation, shadow stacks contents easily
> > > be arbitrarily provisioned with data.
> >
> > I can't parse this sentence.
> >
> > > This property helps apps protect
> > > themselves better, but also restricts any potential apps that may want to
> > > do exotic things at the expense of a little security.
> >
> > Is anything using this right now? Wouldn't thing be safer without WRSS?
> > (Why can't we skip this patch?)
> >
>
> So that people don't write programs that need either (shstk off) or (shstk
> on and WRSS on) and crash or otherwise fail on kernels that support shstk
> but don't support WRSS, perhaps?

Right, yes. I meant more "what programs currently need WRSS to operate
under shstk? (And what is it that they are doing that needs it?)"

All is see currently is compiler self-tests and emulators using it?
https://codesearch.debian.net/search?q=%5Cb%28wrss%7CWRSS%29%5Cb&literal=0&perpkg=1

--
Kees Cook