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From: Kees Cook <keescook@chromium.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>,
	Elena Reshetova <elena.reshetova@intel.com>,
	x86@kernel.org, Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Potapenko <glider@google.com>,
	Alexander Popov <alex.popov@linux.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jann Horn <jannh@google.com>,
	kernel-hardening@lists.openwall.com,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v4 0/5] Optionally randomize kernel stack offset each syscall
Date: Mon, 22 Jun 2020 12:31:41 -0700	[thread overview]
Message-ID: <20200622193146.2985288-1-keescook@chromium.org> (raw)

v4:
- rebase to v5.8-rc2
v3: https://lore.kernel.org/lkml/20200406231606.37619-1-keescook@chromium.org/
v2: https://lore.kernel.org/lkml/20200324203231.64324-1-keescook@chromium.org/
rfc: https://lore.kernel.org/kernel-hardening/20190329081358.30497-1-elena.reshetova@intel.com/

Hi,

This is a continuation and refactoring of Elena's earlier effort to add
kernel stack base offset randomization. In the time since the previous
discussions, two attacks[1][2] were made public that depended on stack
determinism, so we're no longer in the position of "this is a good idea
but we have no examples of attacks". :)

Earlier discussions also devolved into debates on entropy sources, which
is mostly a red herring, given the already low entropy available due
to stack size. Regardless, entropy can be changed/improved separately
from this series as needed.

Earlier discussions also got stuck debating how much syscall overhead
was too much, but this is also a red herring since the feature itself
needs to be selectable at boot with no cost for those that don't want it:
this is solved here with static branches.

So, here is an improved version, made as arch-agnostic as possible,
with usage added for x86 and arm64. It also includes some small static
branch clean ups, and addresses some surprise performance issues due to
the stack canary[3].

Note that for v5.8, this depends on this fix (due to how x86 changed its
stack protector removal for syscall entry):
https://lore.kernel.org/lkml/202006221201.3641ED037E@keescook/

Thanks!

-Kees

[1] https://a13xp0p0v.github.io/2020/02/15/CVE-2019-18683.html
[2] https://repositorio-aberto.up.pt/bitstream/10216/125357/2/374717.pdf
[3] https://lore.kernel.org/lkml/202003281520.A9BFF461@keescook/


Kees Cook (5):
  jump_label: Provide CONFIG-driven build state defaults
  init_on_alloc: Unpessimize default-on builds
  stack: Optionally randomize kernel stack offset each syscall
  x86/entry: Enable random_kstack_offset support
  arm64: entry: Enable random_kstack_offset support

 Makefile                         |  4 ++++
 arch/Kconfig                     | 23 ++++++++++++++++++
 arch/arm64/Kconfig               |  1 +
 arch/arm64/kernel/Makefile       |  5 ++++
 arch/arm64/kernel/syscall.c      | 10 ++++++++
 arch/x86/Kconfig                 |  1 +
 arch/x86/entry/common.c          | 11 +++++++++
 include/linux/jump_label.h       | 19 +++++++++++++++
 include/linux/mm.h               | 18 +++++---------
 include/linux/randomize_kstack.h | 40 ++++++++++++++++++++++++++++++++
 init/main.c                      | 23 ++++++++++++++++++
 mm/page_alloc.c                  | 12 ++--------
 12 files changed, 145 insertions(+), 22 deletions(-)
 create mode 100644 include/linux/randomize_kstack.h

-- 
2.25.1


             reply	other threads:[~2020-06-22 19:32 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-22 19:31 Kees Cook [this message]
2020-06-22 19:31 ` [PATCH v4 1/5] jump_label: Provide CONFIG-driven build state defaults Kees Cook
2020-06-22 19:31 ` [PATCH v4 2/5] init_on_alloc: Unpessimize default-on builds Kees Cook
2020-06-22 19:31 ` [PATCH v4 3/5] stack: Optionally randomize kernel stack offset each syscall Kees Cook
2020-06-22 19:40   ` Randy Dunlap
2020-06-22 21:26     ` Kees Cook
2020-06-22 20:07   ` Jann Horn
2020-06-22 21:30     ` Kees Cook
2020-06-22 21:42       ` Jann Horn
2020-06-22 22:04         ` Kees Cook
2020-06-22 22:56   ` Arvind Sankar
2020-06-22 23:07     ` Kees Cook
2020-06-23  0:05       ` Arvind Sankar
2020-06-23  0:56         ` Kees Cook
2020-06-23 13:42           ` David Laight
2020-06-23 12:38   ` Alexander Popov
2020-06-22 19:31 ` [PATCH v4 4/5] x86/entry: Enable random_kstack_offset support Kees Cook
2020-06-22 19:31 ` [PATCH v4 5/5] arm64: entry: " Kees Cook
2020-06-23  9:40   ` Mark Rutland

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