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Date: Thu, 12 Jul 2018 14:32:57 -0700
From: Kees Cook <keescook@...omium.org>
To: Alexander Popov <alex.popov@...ux.com>
Cc: Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>, Pax Team <pageexec@...email.hu>, 
	Brad Spengler <spender@...ecurity.net>, Andrew Lutomirski <luto@...nel.org>, 
	Tycho Andersen <tycho@...ho.ws>, Laura Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, 
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, Borislav Petkov <bp@...en8.de>, 
	Richard Sandiford <richard.sandiford@....com>, Thomas Gleixner <tglx@...utronix.de>, 
	Peter Anvin <hpa@...or.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, 
	"Dmitry V. Levin" <ldv@...linux.org>, Emese Revfy <re.emese@...il.com>, Jonathan Corbet <corbet@....net>, 
	Andrey Ryabinin <aryabinin@...tuozzo.com>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Thomas Garnier <thgarnie@...gle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Alexei Starovoitov <ast@...nel.org>, Josef Bacik <jbacik@...com>, 
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	Al Viro <viro@...iv.linux.org.uk>, David Miller <davem@...emloft.net>, 
	dingtianhong <dingtianhong@...wei.com>, David Woodhouse <dwmw@...zon.co.uk>, 
	Josh Poimboeuf <jpoimboe@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Dominik Brodowski <linux@...inikbrodowski.net>, Jürgen Groß <jgross@...e.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Dan Williams <dan.j.williams@...el.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Mathias Krause <minipli@...glemail.com>, 
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>, Kyle Huey <me@...ehuey.com>, 
	Dmitry Safonov <dsafonov@...tuozzo.com>, Will Deacon <will.deacon@....com>, 
	Arnd Bergmann <arnd@...db.de>, Florian Weimer <fweimer@...hat.com>, 
	Boris Lukashev <blukashev@...pervictus.com>, Andrey Konovalov <andreyknvl@...gle.com>, 
	"the arch/x86 maintainers" <x86@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v14 0/6] Introduce the STACKLEAK feature and a test for it

On Thu, Jul 12, 2018 at 2:22 PM, Alexander Popov <alex.popov@...ux.com> wrote:
> On 12.07.2018 23:50, Ingo Molnar wrote:
>> Let's make sure informed users have an easy runtime way out
>> from the worst of the overhead that doesn't involve "recompile your distro
>> kernel". Also, make it easier to measure and fingerpoint the overhead...
>
> Would you like the following solution?
>
> I'll create the CONFIG_STACKLEAK_RUNTIME_DISABLE config option, which would be
> similar to CONFIG_SECURITY_SELINUX_DISABLE. That option will provide a sysctl
> switch disabling stackleak_erase(), which provides the most of performance penalty.

I don't think CONFIG/sysctl is the way to go. I'd recommend making it
a boot arg and using a static key, similar to what's happening to
hardened_usercopy:

https://patchwork.kernel.org/patch/10505059/

-Kees

-- 
Kees Cook
Pixel Security

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