Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Mon, 16 Jul 2018 10:24:26 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>
Cc: 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>,
 Masami Hiramatsu <mhiramat@...nel.org>, Nick Piggin <npiggin@...il.com>,
 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 16.07.2018 01:44, Ingo Molnar wrote:
> 
> * Kees Cook <keescook@...omium.org> wrote:
> 
>> 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:
> 
> Why no sysctl? It's a PITA to reboot systems just to turn a stupid knob off.
> 
> Also, it's _much_ easier to measure performance impact when there's a sysctl.

Yes, you are right.

But I looked carefully and now see the troubles which sysctl would bring us.
Each 'task_struct' has 'lowest_stack', which must be initialized before enabling
STACKLEAK. So runtime enabling via sysctl is not plain and may bring race
conditions.

On the other hand, a boot param + static key that can only disable STACKLEAK
during __init are much more robust. I'm preparing the patch and performance
measurements.

Best regards,
Alexander

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.