Re: [PATCH v21 06/26] x86/cet: Add control-protection fault handler

[Andy Lutomirski]

On Wed, Feb 24, 2021 at 11:20 AM Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Wed, Feb 24, 2021 at 09:56:13AM -0800, Yu, Yu-cheng wrote:
> > No.  Maybe I am doing too much.  The GP fault sets si_addr to zero, for
> > example.  So maybe do the same here?
>
> No, you're looking at this from the wrong angle. This is going to be
> user-visible and the moment it gets upstream, it is cast in stone.
>
> So the whole use case of what luserspace needs to do or is going to do
> or wants to do on a SEGV_CPERR, needs to be described, agreed upon by
> people etc before it goes out. And thus clarified whether the address
> gets copied out or not.

I vote 0.  The address is in ucontext->gregs[REG_RIP] [0] regardless.
Why do we need to stick a copy somewhere else?

[0] or however it's spelled.  i can never remember.

>
> Thx.
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette