From nobody Fri Dec 19 18:41:37 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91881ECAAA1 for ; Mon, 24 Oct 2022 16:11:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233723AbiJXQLf (ORCPT ); Mon, 24 Oct 2022 12:11:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39322 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233931AbiJXQFM (ORCPT ); Mon, 24 Oct 2022 12:05:12 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00C4732B9E; Mon, 24 Oct 2022 07:57:49 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4CB57B81649; Mon, 24 Oct 2022 12:19:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BB55C433D6; Mon, 24 Oct 2022 12:19:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666613974; bh=s4PXUvrWJNB2JneVuy9c+iXwcUUBogwyTXM3UHtjRok=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ENRieYn5gjnLy2gkDBvHv0QCNvizhUdIBOD9HIH5vlJOlW+CuGCnIEx/idGNykN2j AKKHutCK8bHNnRnnZCEsO+lcpczm1AVkoOUtZcn6+aX9evS97+JwEv4fiR99hG870S i4rvlaaoRBkrMImnD2y6D1aNNqADgT7Y4tefpGSE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Masahiro Yamada , llvm@lists.linux.dev, Will Deacon , Nick Desaulniers , Nathan Chancellor , Kees Cook Subject: [PATCH 5.10 054/390] hardening: Avoid harmless Clang option under CONFIG_INIT_STACK_ALL_ZERO Date: Mon, 24 Oct 2022 13:27:31 +0200 Message-Id: <20221024113024.928307739@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221024113022.510008560@linuxfoundation.org> References: <20221024113022.510008560@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Kees Cook commit f02003c860d921171be4a27e2893766eb3bc6871 upstream. Currently under Clang, CC_HAS_AUTO_VAR_INIT_ZERO requires an extra -enable flag compared to CC_HAS_AUTO_VAR_INIT_PATTERN. GCC 12[1] will not, and will happily ignore the Clang-specific flag. However, its presence on the command-line is both cumbersome and confusing. Due to GCC's tolerant behavior, though, we can continue to use a single Kconfig cc-option test for the feature on both compilers, but then drop the Clang-specific option in the Makefile. In other words, this patch does not change anything other than making the compiler command line shorter once GCC supports -ftrivial-auto-var-init=3Dz= ero. [1] https://gcc.gnu.org/git/?p=3Dgcc.git;a=3Dcommitdiff;h=3Da25e0b5e6ac8a77= a71c229e0a7b744603365b0e9 Cc: Greg Kroah-Hartman Cc: Masahiro Yamada Cc: llvm@lists.linux.dev Fixes: dcb7c0b9461c ("hardening: Clarify Kconfig text for auto-var-init") Suggested-by: Will Deacon Link: https://lore.kernel.org/lkml/20210914102837.6172-1-will@kernel.org/ Reviewed-by: Nick Desaulniers Reviewed-by: Nathan Chancellor Acked-by: Will Deacon Signed-off-by: Kees Cook Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman --- Makefile | 6 +++--- security/Kconfig.hardening | 5 ++++- 2 files changed, 7 insertions(+), 4 deletions(-) --- a/Makefile +++ b/Makefile @@ -816,12 +816,12 @@ endif =20 # Initialize all stack variables with a zero value. ifdef CONFIG_INIT_STACK_ALL_ZERO -# Future support for zero initialization is still being debated, see -# https://bugs.llvm.org/show_bug.cgi?id=3D45497. These flags are subject t= o being -# renamed or dropped. KBUILD_CFLAGS +=3D -ftrivial-auto-var-init=3Dzero +ifdef CONFIG_CC_IS_CLANG +# https://bugs.llvm.org/show_bug.cgi?id=3D45497 KBUILD_CFLAGS +=3D -enable-trivial-auto-var-init-zero-knowing-it-will-be-r= emoved-from-clang endif +endif =20 DEBUG_CFLAGS :=3D =20 --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -23,13 +23,16 @@ config CC_HAS_AUTO_VAR_INIT_PATTERN def_bool $(cc-option,-ftrivial-auto-var-init=3Dpattern) =20 config CC_HAS_AUTO_VAR_INIT_ZERO + # GCC ignores the -enable flag, so we can test for the feature with + # a single invocation using the flag, but drop it as appropriate in + # the Makefile, depending on the presence of Clang. def_bool $(cc-option,-ftrivial-auto-var-init=3Dzero -enable-trivial-auto-= var-init-zero-knowing-it-will-be-removed-from-clang) =20 choice prompt "Initialize kernel stack variables at function entry" default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PA= TTERN - default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_PATTERN + default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_ZERO default INIT_STACK_NONE help This option enables initialization of stack variables at