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 3A0CAC32789 for ; Sun, 21 Aug 2022 07:01:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230082AbiHUHAy (ORCPT ); Sun, 21 Aug 2022 03:00:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229725AbiHUHAP (ORCPT ); Sun, 21 Aug 2022 03:00:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7578226130; Sun, 21 Aug 2022 00:00:12 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 104A860CF5; Sun, 21 Aug 2022 07:00:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 16178C433D6; Sun, 21 Aug 2022 07:00:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661065211; bh=Jk+w6RRPYKSTK9pnvnj/GWadQ00NplT6eFMPA3t59qE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wlDPPkfgHLjTZlMv+CIpu39kdkGOM5+vtYAVv+wmOyD+5/WDzDYO9BajZ3o3vRoum utIZOFZVlXbkFNBQ3vz9t6t2qKs4LfvQbG3t4mHAeHe/Mvt0nATCl2aQibA36JaLVd 9gkqFZHw+wdv33316NLq7+1dQ6RMzf4CuKkxxw+0= Date: Sat, 20 Aug 2022 20:09:52 +0200 From: Greg Kroah-Hartman To: Nick Desaulniers Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Fangrui Song , Linus Torvalds , Jens Axboe Subject: Re: [PATCH 5.10 001/545] Makefile: link with -z noexecstack --no-warn-rwx-segments Message-ID: References: <20220819153829.135562864@linuxfoundation.org> <20220819153829.220984987@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 19, 2022 at 10:14:51AM -0700, Nick Desaulniers wrote: > 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? I've fixed it up, thanks! greg k-h