From patchwork Thu Apr 11 18:01:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 10896583 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9B8F91515 for ; Thu, 11 Apr 2019 18:02:08 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8D56528D22 for ; Thu, 11 Apr 2019 18:02:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7D8AC28D84; Thu, 11 Apr 2019 18:02:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 9FB0A28D22 for ; Thu, 11 Apr 2019 18:02:07 +0000 (UTC) Received: (qmail 11861 invoked by uid 550); 11 Apr 2019 18:01:44 -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 11725 invoked from network); 11 Apr 2019 18:01:42 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=3B85ofSIlvxDsMd0QSuvExy6zf6XDf2ci7ySZr6BosA=; b=FJxJDmdUpMx20MRWcPf82L+CMoP0+IfWGeSShTYRZwimBL6DOa2bzUzhOyN5iEpEtS eSnQtl/o+Go4aEZMdTcjevr2Nmu2tJ/8HRqkSin2ytgPLG8H4v0C86nFIoDN8cz+i87h XeXSbBS7IEYhvq1nFhKV5ZJdGKJM+Tt5ix2lc= 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:in-reply-to :references; bh=3B85ofSIlvxDsMd0QSuvExy6zf6XDf2ci7ySZr6BosA=; b=N4qpp1B9NOabAthGJ4h05ffBqyiEiHPNPhfYRO5HWZMnuJKzWM6E7QQzJCApfsnqP4 JveWMTQi/n2uGPB71NLyQ12Y+ZxGv/vHYkWiZLVzPQD7ebozJykMd3vcQVcuX9CCpgS2 q+p7hJrY/taVMK4IzEbaxb/N7BtgDuiMG1KnSJe2lyQlTH4UHalH3Awhbv4DG+LYQvnp gqzn6zsy8tQDeRhMLqrYNqSAv+TeKDAasm6PA8dP5PdU3BVqeMab8zQP1/pnJ8tbwf3w PaZUUFsExWoaaQwmgXACVKsfdjaVGOfuVm/ONgqL6F3tOTFUKl6sai/JYCKSXWKt74+8 nizQ== X-Gm-Message-State: APjAAAUbVPbZ+WfzkLC9+5lhNLgsqiLdqOVAExZGUkSn6EJIzXYs43P6 AoaideeCAgPoriC7hmE3blLq+Q== X-Google-Smtp-Source: APXvYqzrgSW9n/rdk1KPTN6pGC6tzHDVoxfPJiuwlJuazwnH8VkZvPgrN08LGboEC+mzZV3GQdJpBA== X-Received: by 2002:a63:4e5b:: with SMTP id o27mr48786170pgl.204.1555005686906; Thu, 11 Apr 2019 11:01:26 -0700 (PDT) From: Kees Cook To: Alexander Potapenko Cc: Kees Cook , Masahiro Yamada , James Morris , Alexander Popov , Nick Desaulniers , Kostya Serebryany , Dmitry Vyukov , Sandeep Patil , Laura Abbott , Randy Dunlap , Michal Marek , Emese Revfy , "Serge E. Hallyn" , kernel-hardening@lists.openwall.com, linux-security-module@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 3/3] security: Implement Clang's stack initialization Date: Thu, 11 Apr 2019 11:01:17 -0700 Message-Id: <20190411180117.27704-4-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190411180117.27704-1-keescook@chromium.org> References: <20190411180117.27704-1-keescook@chromium.org> X-Virus-Scanned: ClamAV using ClamSMTP CONFIG_INIT_STACK_ALL turns on stack initialization based on -ftrivial-auto-var-init in Clang builds, which has greater coverage than CONFIG_GCC_PLUGINS_STRUCTLEAK_BYREF_ALL. -ftrivial-auto-var-init Clang option provides trivial initializers for uninitialized local variables, variable fields and padding. It has three possible values: pattern - uninitialized locals are filled with a fixed pattern (mostly 0xAA on 64-bit platforms, see https://reviews.llvm.org/D54604 for more details, but 0x000000AA for 32-bit pointers) likely to cause crashes when uninitialized value is used; zero (it's still debated whether this flag makes it to the official Clang release) - uninitialized locals are filled with zeroes; uninitialized (default) - uninitialized locals are left intact. This patch uses only the "pattern" mode when CONFIG_INIT_STACK_ALL is enabled. Developers have the possibility to opt-out of this feature on a per-variable basis by using __attribute__((uninitialized)), but such use should be well justified in comments. Co-developed-by: Alexander Potapenko Signed-off-by: Alexander Potapenko Signed-off-by: Kees Cook Tested-by: Alexander Potapenko --- Makefile | 5 +++++ security/Kconfig.hardening | 15 ++++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index c0a34064c574..a7d9c6cd0267 100644 --- a/Makefile +++ b/Makefile @@ -745,6 +745,11 @@ KBUILD_CFLAGS += -fomit-frame-pointer endif endif +# Initialize all stack variables with a pattern, if desired. +ifdef CONFIG_INIT_STACK_ALL +KBUILD_CFLAGS += -ftrivial-auto-var-init=pattern +endif + DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments) ifdef CONFIG_DEBUG_INFO diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening index 3dd7a28c3822..5dd61770d3f0 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -18,9 +18,12 @@ config GCC_PLUGIN_STRUCTLEAK menu "Memory initialization" +config CC_HAS_AUTO_VAR_INIT + def_bool $(cc-option,-ftrivial-auto-var-init=pattern) + choice prompt "Initialize kernel stack variables at function entry" - depends on GCC_PLUGINS + depends on CC_HAS_AUTO_VAR_INIT || GCC_PLUGINS default INIT_STACK_NONE help This option enables initialization of stack variables at @@ -76,6 +79,16 @@ choice of uninitialized stack variable exploits and information exposures. + config INIT_STACK_ALL + bool "0xAA-init everything on the stack (strongest)" + depends on CC_HAS_AUTO_VAR_INIT + help + Initializes everything on the stack with a 0xAA + pattern. This is intended to eliminate all classes + of uninitialized stack variable exploits and information + exposures, even variables that were warned to have been + left uninitialized. + endchoice config GCC_PLUGIN_STRUCTLEAK_VERBOSE