From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0CA24C282DD for ; Tue, 23 Apr 2019 19:49:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0FC721850 for ; Tue, 23 Apr 2019 19:49:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="gBarm0Ky" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726935AbfDWTtf (ORCPT ); Tue, 23 Apr 2019 15:49:35 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:34625 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726915AbfDWTtd (ORCPT ); Tue, 23 Apr 2019 15:49:33 -0400 Received: by mail-pg1-f196.google.com with SMTP id v12so8139936pgq.1 for ; Tue, 23 Apr 2019 12:49:33 -0700 (PDT) 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=bjo3kuTIQO9ca5vXoeOg1U3sHgUzXmnNRsiqcgxFeAvH2O/Jw0nkXlZB8Hky0GB/Ns t5t6J19g4ckMeEMDFiFWrQ7tnt12Yo4NIAzHFkRpcK+KQpbhjy/0bShUdbyIsvkcFqpM Lq3FnpeME+ViC50EDP5snZD+YhS8sgfykDTn0feD/XFx+XdPMtxGDw+Bz8rCxz9+XF/Q VheptOzw9GeCEoi/2xkrQIWgAa9TMxKGD/9mgL/sBQMOSlUtz3NoOfW3+++3CkwLv5Eg aoWNzlH7wArhs+SodF/q630ysgfwD58HXNbaXcZwKrXBliXNG5Db5/EDDb4AZ8iP0f7u zKjg== X-Gm-Message-State: APjAAAXF7/BFUGw74LmoM7un9XEtWY1R/yL15ql3erJ43bHCpsoi0CE5 XoZDRaAxroeHfpn52YZJOE7tTA== 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) Received: from www.outflux.net (173-164-112-133-Oregon.hfc.comcastbusiness.net. [173.164.112.133]) by smtp.gmail.com with ESMTPSA id t13sm28351701pgo.14.2019.04.23.12.49.29 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 23 Apr 2019 12:49:30 -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> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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 -- 2.17.1