From patchwork Tue Mar 24 20:32:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 11456461 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A93341731 for ; Tue, 24 Mar 2020 20:33:19 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 13C0D20836 for ; Tue, 24 Mar 2020 20:33:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="RCCVIU1g" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 13C0D20836 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18197-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 18005 invoked by uid 550); 24 Mar 2020 20:32:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 17834 invoked from network); 24 Mar 2020 20:32:53 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=xoyjnNIvkg+j3q/lUm3mcx/meHvti0L2223SyWgmbLU=; b=RCCVIU1gaUOt7SSOHOlSQWbk/wc0LVSYDRbdbvf7vkkrVHHkcc9wzrGS12OmXt54kW 5eS34P5AROrJupwvYUnpBnA0SF51uAHA8is60V059MtkeksLPUZ0uD4HhT+sfHelhrx7 6p/n0PbpIF84rBwBLyiZ4/znqUhgn9YMLGiuY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=xoyjnNIvkg+j3q/lUm3mcx/meHvti0L2223SyWgmbLU=; b=m8TUmPTxMJatuVLfuozxrCufQEcV33nBnzbQo1Gyk+PZ2c1cCGQthZqxrBZRDEWxhq X4sLnnGMlikPimcIPEJHhWtpC8sQ8d6SLpIGrrgZnFzfTDm9Mo0F64Ziua4MAS7PF1G6 TGq/MHZmAD4pGcTBFmaVO4OxEwqNdwN09gA/CivbtHf9HqxP7gAQvCklMg7clcWXA6ry 1B4NfsAF+tJuYOWRRqCgcu+7iFrk12bC4tYASJMoFOKKSH/ATTBZN+RwOQAKYPpLxBw5 4VbHeYERq8fO3kkQBe+ITRYENg4/APLUgTBRviERpHvqj/WPQtI+34INYeHvAmzb742/ nF3w== X-Gm-Message-State: ANhLgQ1CsDnUy0EfNNq3GJaQpDidaQs8RmzKaskpM0k79uJzq24rcEvl Bz825TbFvcnogqLxBakJYvUJTw== X-Google-Smtp-Source: ADFU+vsamiDb3vxQG8SScPpA98WBrw9+0joaymji73ZXk2ZhJ8zsjRiNpylOVu8a2158RuDNslMFDQ== X-Received: by 2002:a17:902:82c5:: with SMTP id u5mr12381681plz.254.1585081960653; Tue, 24 Mar 2020 13:32:40 -0700 (PDT) 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 , Ard Biesheuvel , Jann Horn , "Perla, Enrico" , kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 0/5] Optionally randomize kernel stack offset each syscall Date: Tue, 24 Mar 2020 13:32:26 -0700 Message-Id: <20200324203231.64324-1-keescook@chromium.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 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. -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 v2: - move to per-cpu rdtsc() saved on syscall exit - add static branches for zero-cost dynamic enabling - Kconfig just selects the default state of static branch - __builtin_alloca() produces ugly asm without -fno-stack-clash-protection - made arch agnostic rfc: https://lore.kernel.org/kernel-hardening/20190329081358.30497-1-elena.reshetova@intel.com/ 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 | 19 +++++++++++++++ arch/arm64/Kconfig | 1 + arch/arm64/kernel/syscall.c | 10 ++++++++ arch/x86/Kconfig | 1 + arch/x86/entry/common.c | 12 +++++++++- 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 ++-------- 11 files changed, 136 insertions(+), 23 deletions(-) create mode 100644 include/linux/randomize_kstack.h