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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C10FC28B2B for ; Fri, 19 Aug 2022 17:48:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354782AbiHSRs0 (ORCPT ); Fri, 19 Aug 2022 13:48:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59532 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351375AbiHSRr5 (ORCPT ); Fri, 19 Aug 2022 13:47:57 -0400 Received: from mail-lj1-x22c.google.com (mail-lj1-x22c.google.com [IPv6:2a00:1450:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 47FC210B513 for ; Fri, 19 Aug 2022 10:15:06 -0700 (PDT) Received: by mail-lj1-x22c.google.com with SMTP id by6so5074142ljb.11 for ; Fri, 19 Aug 2022 10:15:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc; bh=JAXhCl3E9jd9ApnOWZBAjKRPaL6FpmdOdGj2ig44w3U=; b=YTvX3/p+STgYcKJuwODn8Uc2Aou3SxtXuHaCCf7vVsR3gKxBrq7ZAMDSwSiCbB4VOw frem9BQfTK15GIHNFl7F7raHe34pjYsm1E8g01nDz+2/OVBD3wTKZKiCWkNs/7bALyz0 bOiDvwn8NCVcAJiAf3RbfLshZ9IbeZ1rh0baIar/vssInLWH64yottw/7dBYcphX8V34 4EdLdkSZdpcZH79nWgSM441h/ciz/UmRA6ABKwmbvFF/Ohf7mxyVmdjraKmXcVUkHuQ8 xcqJ7JPRusqrN7kUR223Yrc0yypsAxBh+WsQJpZAwvCdMBg9E/HfQU6pU3Y4S+HfNbM9 Q+ew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc; bh=JAXhCl3E9jd9ApnOWZBAjKRPaL6FpmdOdGj2ig44w3U=; b=YiJGbbErQDL2mJJH2oaQl1hkfqgSEPvJ/Um16mu5Ez2CQ0lKiHVfdKUbxBxHSwlDvz B7/syiXdS7rhjfadQlAYYSXkU8jRgE58KwG7dpTznegyo9Ly2ViSSdo2kX0GK/Fs4Xoa SJjzI4eDWnVOV5qccwXcIeOppukYeZ3bWZhouURNU38TtLdFxa+thpJwlgUG8JHC9WP3 6mZMMuQ0b+YRdD+ilUOTccE5tvQ+0KfxYGdXGZFSHyovhVU9PlJZkVhhMNR8V/QWhxl/ uXU9x42iBpnF+5XifeX+zvjXFIWoeqHfbmnCE9MaLnAOSfZHTCaoVos41p5Bh2iA1SMc O1vg== X-Gm-Message-State: ACgBeo341YECEiQHILiSQr4uP7e4DyvF7IqbjBgIItHnZIVTMcK/k+aW keQBqIjIkZWf4qyLPa5rGVFkiPqcxsOs2WnnyUteNg== X-Google-Smtp-Source: AA6agR7GKpemeJnJ8VnG9PjjkIm1ieSXlIFGKo/VPqH7oed8eOn1lSRe+2EBvu50VsAbVa33qJMy+FeN/vfsCpCuvg8= X-Received: by 2002:a2e:a910:0:b0:261:b408:1169 with SMTP id j16-20020a2ea910000000b00261b4081169mr2289309ljq.360.1660929304284; Fri, 19 Aug 2022 10:15:04 -0700 (PDT) MIME-Version: 1.0 References: <20220819153829.135562864@linuxfoundation.org> <20220819153829.220984987@linuxfoundation.org> In-Reply-To: <20220819153829.220984987@linuxfoundation.org> From: Nick Desaulniers Date: Fri, 19 Aug 2022 10:14:51 -0700 Message-ID: Subject: Re: [PATCH 5.10 001/545] Makefile: link with -z noexecstack --no-warn-rwx-segments To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Fangrui Song , Linus Torvalds , Jens Axboe Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 19, 2022 at 8:46 AM Greg Kroah-Hartman wrote: > > From: Nick Desaulniers > > commit 0d362be5b14200b77ecc2127936a5ff82fbffe41 upstream. > > Users of GNU ld (BFD) from binutils 2.39+ will observe multiple > instances of a new warning when linking kernels in the form: > > ld: warning: vmlinux: missing .note.GNU-stack section implies executable stack > ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker > ld: warning: vmlinux has a LOAD segment with RWX permissions > > Generally, we would like to avoid the stack being executable. Because > there could be a need for the stack to be executable, assembler sources > have to opt-in to this security feature via explicit creation of the > .note.GNU-stack feature (which compilers create by default) or command > line flag --noexecstack. Or we can simply tell the linker the > production of such sections is irrelevant and to link the stack as > --noexecstack. > > LLVM's LLD linker defaults to -z noexecstack, so this flag isn't > strictly necessary when linking with LLD, only BFD, but it doesn't hurt > to be explicit here for all linkers IMO. --no-warn-rwx-segments is > currently BFD specific and only available in the current latest release, > so it's wrapped in an ld-option check. > > While the kernel makes extensive usage of ELF sections, it doesn't use > permissions from ELF segments. > > Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/ > Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 > Link: https://github.com/llvm/llvm-project/issues/57009 > Reported-and-tested-by: Jens Axboe > Suggested-by: Fangrui Song > Signed-off-by: Nick Desaulniers > Signed-off-by: Linus Torvalds > Signed-off-by: Greg Kroah-Hartman > --- > Makefile | 5 +++++ > 1 file changed, 5 insertions(+) > > --- a/Makefile > +++ b/Makefile > @@ -983,6 +983,11 @@ KBUILD_CFLAGS += $(KCFLAGS) > KBUILD_LDFLAGS_MODULE += --build-id=sha1 > LDFLAGS_vmlinux += --build-id=sha1 > > +KBUILD_LDFLAGS += -z noexecstack > +ifeq ($(CONFIG_LD_IS_BFD),y) > +KBUILD_LDFLAGS += $(call ld-option,--no-warn-rwx-segments) > +endif 5.10.y is missing CONFIG_LD_IS_BFD. Specifically commit 02aff8592204 ("kbuild: check the minimum linker version in Kconfig") which first landed in v5.12-rc1. I'd recommend simply dropping the `ifeq` guards; the ld-option guard will still work. Otherwise GNU BFD 2.39 users will observe linker warnings related to rwx-segments. Greg, do you mind dropping this patch and I'll supply a v2, or is it too late and I should send a patch on top? > + > ifeq ($(CONFIG_STRIP_ASM_SYMS),y) > LDFLAGS_vmlinux += $(call ld-option, -X,) > endif > > -- Thanks, ~Nick Desaulniers