From patchwork Tue Apr 23 19:49:25 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 10913701 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 B6BE11390 for ; Tue, 23 Apr 2019 19:50:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A60B22853A for ; Tue, 23 Apr 2019 19:50:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 964622862D; Tue, 23 Apr 2019 19:50:12 +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 B4ED22853A for ; Tue, 23 Apr 2019 19:50:11 +0000 (UTC) Received: (qmail 13675 invoked by uid 550); 23 Apr 2019 19:49:46 -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 13570 invoked from network); 23 Apr 2019 19:49:44 -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=c1yvrTp26kS5NawWcZJOQE+ZT11RXDj4zCYzH5JQkb4=; b=gBarm0KyqlLBbUD5hPMVInIA8uyoBUU1s9w2XhxSa/TdXy16ac3S9zPTiwpec0Xjxh k2iBIMrLqWyOdZQO+VJ42jdLCmpOKyo2RFhUC/3BwQP8xCGDY8M5Cj2Qr/GejGmlSTGx /z6ix2Imuf0FkqRjO5mbUmWJ6wVb5RlU8tdLU= 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=c1yvrTp26kS5NawWcZJOQE+ZT11RXDj4zCYzH5JQkb4=; b=M1rcrnrMyEFR5AgjMKn2RSQuB+q0GxKs48T+mLSam6VmTVDQmXPZbo7eHIjYIV5h2p Fu9SI51jJMB/kI+qDQhX+lgMtNI8tRAwM3T5NFma5pQmeJvAj7bzF7EN21e+ZpVDF6D3 cXS44kQVgxogffFGDiSz97h4sYJgR6Hh6fFeGwHvhkw+wQ/H90UlWhsDd/jPVhvF0qmO 4B3hWT5D3dZg8GI+mt9Ky4U4s/cAhmEDYu7wz0AkX3DcME67xzEgHEEsCXtQxxaZbP+1 W8ZwDItosUKQtR/X+M/2CWXioagNxB2S+uoSrm4aXv1a516Arvg+cbKICKAemmgZsTB6 NHyw== X-Gm-Message-State: APjAAAWJtqtvrkBgq8oD6sYKc9eXkbrCZxcWe66M5XfifBv0vvvaeNkw H5tgKR+7HltY3p78d51es49UTA== X-Google-Smtp-Source: APXvYqzZKSGP0Gr7+//KabyT7/cEXmI45ZXQ8jFT1mTgjiC3sDJ9jp6sUQnfstuFJi2ylQJ0ftTsgg== X-Received: by 2002:a63:1d45:: with SMTP id d5mr9916626pgm.184.1556048972642; Tue, 23 Apr 2019 12:49:32 -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 , linux-security-module , Linux Kbuild mailing list , Linux Kernel Mailing List Subject: [PATCH v3 3/3] security: Implement Clang's stack initialization Date: Tue, 23 Apr 2019 12:49:25 -0700 Message-Id: <20190423194925.32151-4-keescook@chromium.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190423194925.32151-1-keescook@chromium.org> References: <20190423194925.32151-1-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 --- Makefile | 5 +++++ security/Kconfig.hardening | 14 ++++++++++++++ 2 files changed, 19 insertions(+) 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 a96d4a43ca65..0a1d4ca314f4 100644 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -18,9 +18,13 @@ 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" default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS + default INIT_STACK_ALL if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT default INIT_STACK_NONE help This option enables initialization of stack variables at @@ -76,6 +80,16 @@ 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