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Message-ID: <20180712135944.GB6199@gmail.com> Date: Thu, 12 Jul 2018 15:59:44 +0200 From: Ingo Molnar <mingo@...nel.org> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Alexander Popov <alex.popov@...ux.com>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Kees Cook <keescook@...omium.org>, 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 * Linus Torvalds <torvalds@...ux-foundation.org> wrote: > On Wed, Jul 11, 2018 at 1:37 PM Alexander Popov <alex.popov@...ux.com> wrote: > > > > This is the 14th version of the patch series introducing STACKLEAK > > to the mainline kernel for x86. This version comes with style changes > > according to the feedback from Ingo Molnar and includes Laura Abbott's > > modifications of scripts/Makefile.gcc-plugins. > > As before, I will repeat that I think 1% on a kernel compile (which > has almost no actual kernel footprint) is a huge cost, and other - > more kernel-centric - loads will likely see much worse performance. > > And I still think that this is stupid, and peoples time would be > *much* better spent on plugins that have much lower costs and get > pretty much the same advanytages (ie the whole "just initialize all > automatics to zero" thing or similar). > > But whatever. I'll just continue to tell people not to use silly > config options that have a high cost-to-point ratio. If people *want* > to waste their CPU, that's their problem. So I agree that it's pretty stupid. Since 95%+ of our users just use what the distro configured - so at minimum I'd like to see a runtime patching based way for root to disable it, so that people (who care or who are hurt by it) can turn the check off - which should be the most expensive part causing much of the 1% overhead. Shouldn't be too hard to implement, this is just a checking method called for every system call that does nothing substantial in 99.99999% of the cases. Thanks, Ingo
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