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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id t12sm3441876pga.85.2021.03.09.13.43.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Mar 2021 13:43:11 -0800 (PST) From: Kees Cook To: Thomas Gleixner Cc: Kees Cook , Elena Reshetova , x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Alexander Popov , Ard Biesheuvel , Jann Horn , kernel-hardening@lists.openwall.com, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka , David Hildenbrand , Mike Rapoport , Andrew Morton , Jonathan Corbet , Randy Dunlap Subject: [PATCH v5 0/7] Optionally randomize kernel stack offset each syscall Date: Tue, 9 Mar 2021 13:42:54 -0800 Message-Id: <20210309214301.678739-1-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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