From patchwork Mon Apr 8 17:04:17 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Potapenko X-Patchwork-Id: 10889905 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 8DFB817E1 for ; Mon, 8 Apr 2019 17:04:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 78294283B0 for ; Mon, 8 Apr 2019 17:04:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 6C29A28708; Mon, 8 Apr 2019 17:04:32 +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=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 77D1C283B0 for ; Mon, 8 Apr 2019 17:04:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728982AbfDHRE3 (ORCPT ); Mon, 8 Apr 2019 13:04:29 -0400 Received: from mail-yw1-f73.google.com ([209.85.161.73]:44191 "EHLO mail-yw1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728905AbfDHRE3 (ORCPT ); Mon, 8 Apr 2019 13:04:29 -0400 Received: by mail-yw1-f73.google.com with SMTP id l203so10970632ywb.11 for ; Mon, 08 Apr 2019 10:04:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=Qe2VE7lyZVupjMwRpQ+dHdBGYyLN/Bj/tqxvBGnY3Yw=; b=HOJKpGb/cbGJXi9w+tc4PVhynYzKaHAHM8Aeh+hoEteVLQpORr//ykK9jWUCFRr/0e Ueb5XWofRFOLcKmixicUTYM+DVFolNrzQG46BVUhDCYyUbS/lRMCNqvGaEF9ybBo0lRF 55uQFJD7KdtjNmhrne3sR9tjA3eTIhYUar+UXP+ubs2l8k7Fnk9NFbaDsDYvvMTMbRed oL73zSOUKgzMwJqFp2heeAVPpJtgoxi6Cq9qyl2U12TNLI5MjB/MN2oq1PF57b6+wlO4 MFaxQu7CAPQuHrc3tHrUVS+eUbhFsGpArU41lbOMoFBeNXeJyvSqvi09u3bUGOE3ECCc 0YMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=Qe2VE7lyZVupjMwRpQ+dHdBGYyLN/Bj/tqxvBGnY3Yw=; b=mex36Hy6Sakow3VnnCQAcHr4VVHT6QSifTgexrAHSlpBiWmoBY61QBD0f6D7m9QAs2 v0fexmiLgiwhJPcNNUSwz0JTtKIOM9HdrvGq9bMwlKp6TZFAdn55kU7/SrQSdNTqnEj7 GHowKYQu8P3bsfFodpFg7P9xkQMXiJHviYcmS+Y8d0EJl9347lljhKj7SM89T8iBn6IY wVCGuG7mpIgrU3RTYL3e6HioRZ671az9we5p+dqgf1jWDlvoAXO8gE3cEDzhsw41qq3O zhaadPa4wIsRK4O9gHAdA0zkUWwJrrEOVHSwV6W1mVmIPkUet2zmovpFCfDQebnRDIFL wb/w== X-Gm-Message-State: APjAAAUL10uVleKTRfuwPH3NqyelGNYVVohncLvon6XrwcFEqSj/1AEv pOHQve1OZiQYjAOF1c4eKBU5To6X6sM= X-Google-Smtp-Source: APXvYqx345bwZUW1qENJgcBZ9oGUG7SYOQw1bKVYzKDoYZOkLS4SVmnezDgvGpTFShw+2uQ5NRuaTqIxQBY= X-Received: by 2002:a81:3ac7:: with SMTP id h190mr2106812ywa.5.1554743068175; Mon, 08 Apr 2019 10:04:28 -0700 (PDT) Date: Mon, 8 Apr 2019 19:04:17 +0200 In-Reply-To: <20190408170418.148554-1-glider@google.com> Message-Id: <20190408170418.148554-2-glider@google.com> Mime-Version: 1.0 References: <20190408170418.148554-1-glider@google.com> X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH v3 1/2] initmem: introduce CONFIG_INIT_ALL_MEMORY and CONFIG_INIT_ALL_STACK From: Alexander Potapenko To: yamada.masahiro@socionext.com, jmorris@namei.org, serge@hallyn.com Cc: linux-security-module@vger.kernel.org, linux-kbuild@vger.kernel.org, ndesaulniers@google.com, kcc@google.com, dvyukov@google.com, keescook@chromium.org, sspatil@android.com, kernel-hardening@lists.openwall.com Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP CONFIG_INIT_ALL_MEMORY is going to be an umbrella config for options that force heap and stack initialization. The rationale behind doing so is to reduce the severity of bugs caused by using uninitialized memory. CONFIG_INIT_ALL_STACK turns on stack initialization based on -ftrivial-auto-var-init in Clang builds and on -fplugin-arg-structleak_plugin-byref-all in GCC builds. -ftrivial-auto-var-init is a Clang flag that 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) 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. The proposed config builds the kernel with -ftrivial-auto-var-init=pattern. Developers have the possibility to opt-out of this feature on a per-variable basis by using __attribute__((uninitialized)). For GCC builds, CONFIG_INIT_ALL_STACK is simply wired up to CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL. No opt-out is possible at the moment. Signed-off-by: Alexander Potapenko Cc: Masahiro Yamada Cc: James Morris Cc: "Serge E. Hallyn" Cc: Nick Desaulniers Cc: Kostya Serebryany Cc: Dmitry Vyukov Cc: Kees Cook Cc: Sandeep Patil Cc: linux-security-module@vger.kernel.org Cc: linux-kbuild@vger.kernel.org Cc: kernel-hardening@lists.openwall.com --- v2: - addressed Kees Cook's comments: added GCC support v3: addressed Masahiro Yamada's comments: - dropped per-file opt-out mechanism - fixed GCC_PLUGINS dependencies --- Makefile | 3 ++- scripts/Makefile.initmem | 10 ++++++++++ security/Kconfig | 1 + security/Kconfig.initmem | 29 +++++++++++++++++++++++++++++ 4 files changed, 42 insertions(+), 1 deletion(-) create mode 100644 scripts/Makefile.initmem create mode 100644 security/Kconfig.initmem diff --git a/Makefile b/Makefile index f070e0d65186..028ca37878fd 100644 --- a/Makefile +++ b/Makefile @@ -448,7 +448,7 @@ export HOSTCXX KBUILD_HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE -export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN CFLAGS_INITMEM export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL @@ -840,6 +840,7 @@ KBUILD_ARFLAGS := $(call ar-option,D) include scripts/Makefile.kasan include scripts/Makefile.extrawarn include scripts/Makefile.ubsan +include scripts/Makefile.initmem # Add any arch overrides and user supplied CPPFLAGS, AFLAGS and CFLAGS as the # last assignments diff --git a/scripts/Makefile.initmem b/scripts/Makefile.initmem new file mode 100644 index 000000000000..a6253d78fe35 --- /dev/null +++ b/scripts/Makefile.initmem @@ -0,0 +1,10 @@ +ifdef CONFIG_INIT_ALL_STACK + +# Clang's -ftrivial-auto-var-init=pattern flag initializes the +# uninitialized parts of local variables (including fields and padding) +# with a fixed pattern (0xAA in most cases). +ifdef CONFIG_CC_HAS_AUTO_VAR_INIT + CFLAGS_INITMEM := -ftrivial-auto-var-init=pattern +endif + +endif diff --git a/security/Kconfig b/security/Kconfig index e4fe2f3c2c65..cc12a39424dd 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -230,6 +230,7 @@ config STATIC_USERMODEHELPER_PATH If you wish for all usermode helper programs to be disabled, specify an empty string here (i.e. ""). +source "security/Kconfig.initmem" source "security/selinux/Kconfig" source "security/smack/Kconfig" source "security/tomoyo/Kconfig" diff --git a/security/Kconfig.initmem b/security/Kconfig.initmem new file mode 100644 index 000000000000..5e49a55382ad --- /dev/null +++ b/security/Kconfig.initmem @@ -0,0 +1,29 @@ +menu "Initialize all memory" + +config CC_HAS_AUTO_VAR_INIT + def_bool $(cc-option,-ftrivial-auto-var-init=pattern) + +config INIT_ALL_MEMORY + bool "Initialize all memory" + default n + help + Enforce memory initialization to mitigate infoleaks and make + the control-flow bugs depending on uninitialized values more + deterministic. + +if INIT_ALL_MEMORY + +config INIT_ALL_STACK + bool "Initialize all stack" + depends on INIT_ALL_MEMORY + depends on CC_HAS_AUTO_VAR_INIT || (HAVE_GCC_PLUGINS && PLUGIN_HOSTCC != "") + select GCC_PLUGINS if !CC_HAS_AUTO_VAR_INIT + select GCC_PLUGIN_STRUCTLEAK if !CC_HAS_AUTO_VAR_INIT + select GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if !CC_HAS_AUTO_VAR_INIT + default y + help + Initialize uninitialized stack data with a fixed pattern + (0x00 in GCC, 0xAA in Clang). + +endif # INIT_ALL_MEMORY +endmenu