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Message-Id: <1522267032-6603-1-git-send-email-alex.popov@linux.com>
Date: Wed, 28 Mar 2018 22:57:06 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: 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>,
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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>,
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"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
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Boris Lukashev <blukashev@...pervictus.com>,
x86@...nel.org,
linux-kernel@...r.kernel.org,
alex.popov@...ux.com
Subject: [PATCH RFC v10 0/6] Introduce the STACKLEAK feature and a test for it
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.
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.
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/entry_32.S | 11 +
arch/x86/entry/entry_64.S | 11 +
arch/x86/entry/entry_64_compat.S | 11 +
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 +++++++++++++++++++++++++++++
23 files changed, 900 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
--
2.7.4
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