linux-kernel - Re: [PATCH 00/13] Virtually mapped stacks with guard pages (x86, core)

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Message-Id: <20160616060538.GA3923@osiris>
Date:	Thu, 16 Jun 2016 08:05:38 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	x86@...nel.org, Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 00/13] Virtually mapped stacks with guard pages (x86,
 core)

On Wed, Jun 15, 2016 at 05:28:22PM -0700, Andy Lutomirski wrote:
> Since the dawn of time, a kernel stack overflow has been a real PITA
> to debug, has caused nondeterministic crashes some time after the
> actual overflow, and has generally been easy to exploit for root.
> 
> With this series, arches can enable HAVE_ARCH_VMAP_STACK.  Arches
> that enable it (just x86 for now) get virtually mapped stacks with
> guard pages.  This causes reliable faults when the stack overflows.
> 
> If the arch implements it well, we get a nice OOPS on stack overflow
> (as opposed to panicing directly or otherwise exploding badly).  On
> x86, the OOPS is nice, has a usable call trace, and the overflowing
> task is killed cleanly.

Do you have numbers which reflect the performance impact of this change?