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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 496DBC433DF for ; Tue, 11 Aug 2020 16:01:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0801C20774 for ; Tue, 11 Aug 2020 16:01:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597161703; bh=NL5JPcBD4J0heqlmpMus4+OlKKnHgMlLWggf1hazt1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=YFRGycsHs1779aMulRkkg3oocWiU2F8KLBjzm5oFTwV9e/L/L91B5gHzPFVvwYkeS n3EK5UIzPegsqKRS9eOjho2ENaYafn3QgajgMkPiQKKD+PDUwRwt414py6OdCtVSxk Xm9LvnANI0RifDPVD9OPCE0dzfg1qyv7UsF7mCPE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729070AbgHKQBl (ORCPT ); Tue, 11 Aug 2020 12:01:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:55276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729045AbgHKQBk (ORCPT ); Tue, 11 Aug 2020 12:01:40 -0400 Received: from linux-8ccs (p57a236d4.dip0.t-ipconnect.de [87.162.54.212]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 172CF206B5; Tue, 11 Aug 2020 16:01:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597161699; bh=NL5JPcBD4J0heqlmpMus4+OlKKnHgMlLWggf1hazt1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dvjZthd1QBr9r/BmnZaKjeFiPW/or+Xe6DbVIATO8yweiy5jb52nknbeorZqjq8J2 2IM2FlZ9P/hLoipDyKJqg1yjMO+t1v6bfmPz5+sU+08+ydJR3qnFcWhlrt1gcKcmM6 YO6d9HvlsAY7+2ap+v6ktLl6W4lOLYiPXfYK5ssY= Date: Tue, 11 Aug 2020 18:01:35 +0200 From: Jessica Yu To: Mauro Carvalho Chehab Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, Thomas Gleixner , keescook@chromium.org, Josh Poimboeuf , Miroslav Benes , Mark Rutland , Ard Biesheuvel Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX Message-ID: <20200811160134.GA13652@linux-8ccs> References: <20200403171303.GK20760@hirez.programming.kicks-ass.net> <20200808101222.5103093e@coco.lan> <20200810092523.GA8612@linux-8ccs> <20200810150647.GB8612@linux-8ccs> <20200811163427.6edbf343@coco.lan> <20200811145524.GE2674@hirez.programming.kicks-ass.net> <20200811172738.2d632a09@coco.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200811172738.2d632a09@coco.lan> X-OS: Linux linux-8ccs 5.8.0-rc6-lp150.12.61-default+ x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Mauro Carvalho Chehab [11/08/20 17:27 +0200]: >Em Tue, 11 Aug 2020 16:55:24 +0200 >peterz@infradead.org escreveu: > >> On Tue, Aug 11, 2020 at 04:34:27PM +0200, Mauro Carvalho Chehab wrote: >> > [33] .plt PROGBITS 0000000000000340 00035c80 >> > 0000000000000001 0000000000000000 WAX 0 0 1 >> > [34] .init.plt NOBITS 0000000000000341 00035c81 >> > 0000000000000001 0000000000000000 WA 0 0 1 >> > [35] .text.ftrace[...] PROGBITS 0000000000000342 00035c81 >> > 0000000000000001 0000000000000000 WAX 0 0 1 >> >> .plt and .text.ftrace_tramplines are buggered. >> >> arch/arm64/kernel/module.lds even marks then as NOLOAD. > >Hmm... Shouldn't the code at module_enforce_rwx_sections() or at >load_module() ignore such sections instead of just rejecting probing >all modules? > >I mean, if the existing toolchain is not capable of excluding >those sections, either the STRICT_MODULE_RWX hardening should be >disabled, if a broken toolchain is detected or some runtime code >should handle such sections on a different way. Hi Mauro, thanks for providing the readelf output. The sections marked 'WAX' are indeed the reason why the module loader is rejecting them. Interesting, my cross-compiled modules do not have the executable flag - [38] .plt NOBITS 0000000000000340 00038fc0 0000000000000001 0000000000000000 WA 0 0 1 [39] .init.plt NOBITS 0000000000000341 00038fc0 0000000000000001 0000000000000000 WA 0 0 1 [40] .text.ftrace_tram NOBITS 0000000000000342 00038fc0 0000000000000001 0000000000000000 WA 0 0 1 ld version: GNU ld (GNU Binutils) 2.34 Copyright (C) 2020 Free Software Foundation, Inc. This program is free software; you may redistribute it under the terms of the GNU General Public License version 3 or (at your option) a later version. And gcc: aarch64-linux-gcc (GCC) 9.3.0 Copyright (C) 2019 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. I'm a bit confused about what NOLOAD actually implies in this context. From the ld documentation - "The `(NOLOAD)' directive will mark a section to not be loaded at run time." But these sections are marked SHF_ALLOC and are referenced to in the module plt code. Or does it just tell the linker to not initialize it? Adding Ard to CC, I'm sure he'd know more about the section flag specifics. Jessica