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Date: Wed, 28 Mar 2018 13:13:48 -0700
From: Kees Cook <keescook@...omium.org>
To: Alexander Popov <alex.popov@...ux.com>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>, Ingo Molnar <mingo@...nel.org>,
Andy 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>, "H . 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>,
Masami Hiramatsu <mhiramat@...nel.org>, Nicholas Piggin <npiggin@...il.com>,
Al Viro <viro@...iv.linux.org.uk>, "David S . Miller" <davem@...emloft.net>,
Ding Tianhong <dingtianhong@...wei.com>, David Woodhouse <dwmw@...zon.co.uk>,
Josh Poimboeuf <jpoimboe@...hat.com>, Steven Rostedt <rostedt@...dmis.org>,
Dominik Brodowski <linux@...inikbrodowski.net>, Juergen 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>, X86 ML <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v10 0/6] Introduce the STACKLEAK feature and a test
for it
On Wed, Mar 28, 2018 at 12:57 PM, Alexander Popov <alex.popov@...ux.com> wrote:
> This is the 10th version of the patch series introducing STACKLEAK to the
> mainline kernel. The previous version raised a fervent discussion[0].
> The assembly code introduced by v9 irritated the reviewers.
Thanks for persisting!
> I've found the way to bypass the obstacles[1] of the C implementation.
> So I dare come once again. Let me ask you to look at this code without
> preconception.
The assembly changes are now very minimal; thanks for reworking this.
I hope this addresses both Dave Hansen and Linus's (similar)
objections.
> 1. reduces the information that can be revealed through kernel stack leak bugs.
> The idea of erasing the thread stack at the end of syscalls is similar to
> CONFIG_PAGE_POISONING and memzero_explicit() in kernel crypto, which all
> comply with FDP_RIP.2 (Full Residual Information Protection) of the
> Common Criteria standard.
Agreed: I continue to believe this is meaningful even if just for
reducing the lifetime of sensitive data on the stack.
-Kees
--
Kees Cook
Pixel Security
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