linux-kernel - Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and ARCH_SET

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Date:   Wed, 10 Jan 2018 15:45:06 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Andy Lutomirski <luto@...nel.org>, Willy Tarreau <w@....eu>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH v2 2/6] x86/arch_prctl: add ARCH_GET_NOPTI and
 ARCH_SET_NOPTI to enable/disable PTI

On Wed, Jan 10, 2018 at 08:25:08AM +0100, Ingo Molnar wrote:
> We could taint the kernel and warn prominently in the syslog when PTI is disabled 
> globally on the boot line though, if running on affected CPUs.
> 
> Something like:
> 
>  "x86/intel: Page Table Isolation (PTI) is disabled globally. This allows unprivileged, untrusted code to exploit the Meltdown CPU bug to read kernel data."
> 

I think we should warn in the per-mm disabling case too. Not the same
text but a similar blurb about the trusted process becoming a high-value
target.

-- 
Regards/Gruss,
    Boris.

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