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Date: Tue, 9 Mar 2021 13:42:54 -0800
From: Kees Cook <keescook@...omium.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Kees Cook <keescook@...omium.org>,
Elena Reshetova <elena.reshetova@...el.com>,
x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Potapenko <glider@...gle.com>,
Alexander Popov <alex.popov@...ux.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Jann Horn <jannh@...gle.com>,
kernel-hardening@...ts.openwall.com,
linux-hardening@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Vlastimil Babka <vbabka@...e.cz>,
David Hildenbrand <david@...hat.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jonathan Corbet <corbet@....net>,
Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH v5 0/7] Optionally randomize kernel stack offset each syscall
v5:
- rebase to v5.12-rc2
- clean up static branch issues introduced since v4 series
- adjust comments (Mark Rutland)
- update kernel-parameters.txt (Randy Dunlap)
v4: https://lore.kernel.org/lkml/20200622193146.2985288-1-keescook@chromium.org/
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 earlier
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 the latest 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].
At the very least, the first three patches should land ASAP, the first
is a minor bug fix for v5.11. The next two are optimizations for static
branch usage that Peter already Acked.
If I can get an Ack from an arm64 maintainer, I think this could all
land via -tip to make merging easiest.
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 (7):
mm: Restore init_on_* static branch defaults
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
lkdtm: Add REPORT_STACK for checking stack offsets
.../admin-guide/kernel-parameters.txt | 11 +++++
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 | 3 ++
arch/x86/include/asm/entry-common.h | 8 ++++
drivers/misc/lkdtm/bugs.c | 17 ++++++++
drivers/misc/lkdtm/core.c | 1 +
drivers/misc/lkdtm/lkdtm.h | 1 +
include/linux/jump_label.h | 19 +++++++++
include/linux/mm.h | 10 +++--
include/linux/randomize_kstack.h | 42 +++++++++++++++++++
init/main.c | 23 ++++++++++
mm/page_alloc.c | 4 +-
17 files changed, 177 insertions(+), 6 deletions(-)
create mode 100644 include/linux/randomize_kstack.h
--
2.25.1
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