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=-7.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 0ABE4C4360F for ; Fri, 5 Apr 2019 11:33:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF4CE2186A for ; Fri, 5 Apr 2019 11:33:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nifty.com header.i=@nifty.com header.b="kfg0em9a" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730788AbfDELdG (ORCPT ); Fri, 5 Apr 2019 07:33:06 -0400 Received: from condef-07.nifty.com ([202.248.20.72]:49092 "EHLO condef-07.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730497AbfDELdG (ORCPT ); Fri, 5 Apr 2019 07:33:06 -0400 X-Greylist: delayed 582 seconds by postgrey-1.27 at vger.kernel.org; Fri, 05 Apr 2019 07:33:04 EDT Received: from conssluserg-01.nifty.com ([10.126.8.80])by condef-07.nifty.com with ESMTP id x35BJDVq008832 for ; Fri, 5 Apr 2019 20:19:13 +0900 Received: from mail-vs1-f43.google.com (mail-vs1-f43.google.com [209.85.217.43]) (authenticated) by conssluserg-01.nifty.com with ESMTP id x35BJ8fE009495; Fri, 5 Apr 2019 20:19:08 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-01.nifty.com x35BJ8fE009495 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1554463149; bh=e0fM4ld4iYjoz/U6adhn4po1aJ4MYA3AvKh4EaHvlVw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=kfg0em9aarvj/KCwAyUflftGznXkikK3HyCSELhl1iu26XsHZyvHc1qwo/deD9iao GYKSpdbLMRI1MmRvLZLBDg1e6ywVZSvGRzSp+XR4MbB7KZa+5mgt1pZcq4YQr3dFU0 aFRH24z+Mqi8svUB8P0drVrkt+fS1Slc/nDOHD6QjGhNe3bI3DrAo8grUsoH79OFd6 68Si9hRWbdQFntSMHZPAz/oMmE8Bmy8tYlZD12W4MJcWuFpW5a/bxiEB+hrPn/Hf14 CXYBvHp4sY3kXrdkZzmeTfY2xlbYIdl9TkgsbJvCicRA/Pc/vbebJ426iHcGPfQxuW PzQaxHXuKtDRQ== X-Nifty-SrcIP: [209.85.217.43] Received: by mail-vs1-f43.google.com with SMTP id n4so3260516vsm.3; Fri, 05 Apr 2019 04:19:08 -0700 (PDT) X-Gm-Message-State: APjAAAWpIUofHppOq2TWaU4g9id9swrdmevHiw9qnGqPGFI0kCoAsgnp 3lXKYQUVIEwuk4t1O5ysqP5cvv8dM5C9glgO7dU= X-Google-Smtp-Source: APXvYqx8PVDLkPDnk1A7Uy0aCsuO44C3RKL5fzo47SmLsL3OB4ExjbZRexpyLxyyTDec5rnxRNY7idCLAMtPUtwpTW4= X-Received: by 2002:a67:c29e:: with SMTP id k30mr7432268vsj.203.1554463147645; Fri, 05 Apr 2019 04:19:07 -0700 (PDT) MIME-Version: 1.0 References: <20190308132701.133598-1-glider@google.com> <20190308132701.133598-2-glider@google.com> In-Reply-To: <20190308132701.133598-2-glider@google.com> From: Masahiro Yamada Date: Fri, 5 Apr 2019 20:18:31 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/2] initmem: introduce CONFIG_INIT_ALL_MEMORY and CONFIG_INIT_ALL_STACK To: Alexander Potapenko Cc: James Morris , "Serge E. Hallyn" , linux-security-module@vger.kernel.org, Linux Kbuild mailing list , Nick Desaulniers , kcc@google.com, Dmitry Vyukov , Kees Cook , sspatil@android.com, Kernel Hardening Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Mar 8, 2019 at 10:27 PM Alexander Potapenko wrote: > > 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-file (by using the INIT_ALL_MEMORY_ Makefile prefix) Do you have a plan to use this per-file prefix? If so, could you elaborate which parts should opt out? > or per-variable > (by using __attribute__((uninitialized))) basis. > > 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 > --- > Makefile | 3 ++- > scripts/Makefile.initmem | 10 ++++++++++ > scripts/Makefile.lib | 6 ++++++ > security/Kconfig | 1 + > security/Kconfig.initmem | 29 +++++++++++++++++++++++++++++ > 5 files changed, 48 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/scripts/Makefile.lib b/scripts/Makefile.lib > index 12b88d09c3a4..53d18fd15c79 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -131,6 +131,12 @@ _c_flags += $(if $(patsubst n%,, \ > $(CFLAGS_UBSAN)) > endif > > +ifeq ($(CONFIG_INIT_ALL_MEMORY),y) > +_c_flags += $(if $(patsubst n%,, \ > + $(INIT_ALL_MEMORY_$(basetarget).o)$(INIT_ALL_MEMORY)y), \ > + $(CFLAGS_INITMEM)) > +endif > + > ifeq ($(CONFIG_KCOV),y) > _c_flags += $(if $(patsubst n%,, \ > $(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INSTRUMENT_ALL)), \ > 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..27aec394365e > --- /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 > + 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). Ugh, the logic is getting complicated. When I enabled INIT_ALL_MEMORY, I saw this: WARNING: unmet direct dependencies detected for GCC_PLUGINS Depends on [n]: HAVE_GCC_PLUGINS [=y] && PLUGIN_HOSTCC [=]!= Selected by [y]: - INIT_ALL_STACK [=y] && INIT_ALL_MEMORY [=y] && (CC_HAS_AUTO_VAR_INIT [=n] || HAVE_GCC_PLUGINS [=y]) && !CC_HAS_AUTO_VAR_INIT [=n] > +endif # INIT_ALL_MEMORY > +endmenu > -- > 2.21.0.360.g471c308f928-goog > -- Best Regards Masahiro Yamada