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Message-ID: <5726d16d-23f3-7d55-d488-e4e0ce262edf@redhat.com>
Date: Mon, 14 May 2018 11:55:34 -0700
From: Laura Abbott <labbott@...hat.com>
To: Alexander Popov <alex.popov@...ux.com>,
kernel-hardening@...ts.openwall.com, Kees Cook <keescook@...omium.org>,
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>, 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>,
Linus Torvalds <torvalds@...ux-foundation.org>,
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@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v11 0/6] Introduce the STACKLEAK feature and a test for it
On 04/06/2018 07:22 AM, Alexander Popov wrote:
> This is the 11th version of the patch series introducing STACKLEAK to the
> mainline kernel. The 9th version raised a fervent discussion[0].
> The assembly code introduced by that version irritated the reviewers.
>
> I've found the way to bypass the obstacles[1] of the C implementation.
> So I dare come again. Let me ask you to look at this code without
> preconception.
>
> Motivation
> ==========
>
> STACKLEAK (initially developed by PaX Team):
>
> 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.
>
> 2. blocks some uninitialized stack variable attacks (e.g. CVE-2017-17712,
> CVE-2010-2963). That kind of bugs should be killed by improving C compilers
> in future, which might take a long time.
>
> 3. blocks stack depth overflow caused by alloca (aka Stack Clash attack).
> That is orthogonal to the mainline kernel VLA cleanup and protects
> un-upstreamed code.
>
> Performance impact
> ==================
>
> Hardware: Intel Core i7-4770, 16 GB RAM
>
> Test #1: building the Linux kernel on a single core
> 0.91% slowdown
>
> Test #2: hackbench -s 4096 -l 2000 -g 15 -f 25 -P
> 4.2% slowdown
>
> So the STACKLEAK description in Kconfig includes:
> "The tradeoff is the performance impact: on a single CPU system kernel
> compilation sees a 1% slowdown, other systems and workloads may vary and you are
> advised to test this feature on your expected workload before deploying it".
>
> Links
> =====
>
> [0] http://www.openwall.com/lists/kernel-hardening/2018/03/03/7
> [1] http://www.openwall.com/lists/kernel-hardening/2018/03/21/4
>
>
> Alexander Popov (6):
> gcc-plugins: Clean up the cgraph_create_edge* macros
> x86/entry: Add STACKLEAK erasing the kernel stack at the end of
> syscalls
> gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack
> lkdtm: Add a test for STACKLEAK
> fs/proc: Show STACKLEAK metrics in the /proc file system
> doc: self-protection: Add information about STACKLEAK feature
>
> Documentation/security/self-protection.rst | 23 +-
> Documentation/x86/x86_64/mm.txt | 2 +
> arch/Kconfig | 53 ++++
> arch/x86/Kconfig | 1 +
> arch/x86/entry/Makefile | 3 +
> arch/x86/entry/calling.h | 14 +
> arch/x86/entry/entry_32.S | 7 +
> arch/x86/entry/entry_64.S | 3 +
> arch/x86/entry/entry_64_compat.S | 5 +
> arch/x86/entry/erase.c | 58 ++++
> arch/x86/include/asm/processor.h | 7 +
> arch/x86/kernel/dumpstack.c | 19 ++
> arch/x86/kernel/process_32.c | 8 +
> arch/x86/kernel/process_64.c | 8 +
> drivers/misc/Makefile | 3 +
> drivers/misc/lkdtm.h | 4 +
> drivers/misc/lkdtm_core.c | 2 +
> drivers/misc/lkdtm_stackleak.c | 141 +++++++++
> fs/proc/base.c | 18 ++
> include/linux/compiler.h | 4 +
> mm/util.c | 33 ++
> scripts/Makefile.gcc-plugins | 3 +
> scripts/gcc-plugins/gcc-common.h | 26 +-
> scripts/gcc-plugins/stackleak_plugin.c | 470 +++++++++++++++++++++++++++++
> 24 files changed, 896 insertions(+), 19 deletions(-)
> create mode 100644 arch/x86/entry/erase.c
> create mode 100644 drivers/misc/lkdtm_stackleak.c
> create mode 100644 scripts/gcc-plugins/stackleak_plugin.c
>
As a point of reference, this series mitigates the leak
fixed by https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0a0b98734479aa5b3c671d5190e86273372cab95
Thanks,
Laura
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