Re: [PATCH v3 36/37] x86/cet/shstk: Add ARCH_CET_UNLOCK

Peter Zijlstra
2022-11-15T21:21:55Z

On Tue, Nov 15, 2022 at 01:00:40PM -0800, Dave Hansen wrote:
> On 11/15/22 12:57, Peter Zijlstra wrote:
> > On Tue, Nov 15, 2022 at 08:01:12PM +0000, Edgecombe, Rick P wrote:
> >>>> + if (task != current) {
> >>>> + if (option == ARCH_CET_UNLOCK &&
> >>>> IS_ENABLED(CONFIG_CHECKPOINT_RESTORE)) {
> >>> Why make this conditional on CRIU at all?
> >> Kees asked for it, I think he was worried about attackers using it to
> >> unlock and disable shadow stack. So wanted to lock it down to the
> >> maximum.
> > Well, distros will all have this stuff enabled no? So not much
> > protection in practise.
>
> Yeah, that's true for the distros.
>
> But, I would imagine that our more paranoid friends like the ChromeOS
> folks might appreciate this.

ptrace can modify text, I'm not sure what if anything we're protecting
against.