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 08:31:28 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Willy Tarreau <w@....eu>, Andy Lutomirski <luto@...nel.org>,
        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

* Borislav Petkov <bp@...en8.de> wrote:

> Oh, and you've built the kernel with the option to be able to disable
> PTI so it's not like you haven't seen it already.

In general in many corporate environments requiring kernel reboots or kernel 
rebuilds limits the real-world usability of any kernel feature we offer down to 
"non-existent". Saying "build your own kernel or reboot" is excluding a large 
subset of our real-world users.

Build and boot options are fine for developers and testing. Otherwise _everything_ 
not readily accessible when your distro kernel has booted up is essentially behind 
a usability (and corporate policy) wall so steep that it's essentially 
non-existent to many users.

So either we make this properly sysctl (and/or prctl) controllable, or just don't 
do it at all.

Thanks,

	Ingo