Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET_NOPTI to enable/disable PTI

[Willy Tarreau]

On Tue, Jan 09, 2018 at 10:29:40PM +0100, Borislav Petkov wrote:
> On Tue, Jan 09, 2018 at 01:26:57PM -0800, Andy Lutomirski wrote:
> > 2.Turning off PTI is, in general, a terrible idea.  It totally breaks
> > any semblance of a security model on a Meltdown-affected CPU.  So I
> > think we should require CAP_SYS_RAWIO *and* that the system is booted
> > with pti=allow_optout or something like that.
> 
> Uhh, I like that.
> 
> Maybe also taint the kernel ...

Requiring a reboot just to fix a performance problem you've discovered
the hard way is not the most friendly way to help users I'm afraid.
However, definitely +1 on tainting!

Willy