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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,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 5B52AC433DB for ; Fri, 12 Mar 2021 02:40:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2735064F8E for ; Fri, 12 Mar 2021 02:40:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231241AbhCLCjh (ORCPT ); Thu, 11 Mar 2021 21:39:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229636AbhCLCj0 (ORCPT ); Thu, 11 Mar 2021 21:39:26 -0500 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1541FC061760 for ; Thu, 11 Mar 2021 18:39:26 -0800 (PST) Received: by mail-pl1-x630.google.com with SMTP id z5so11225433plg.3 for ; Thu, 11 Mar 2021 18:39:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=djQZd3ysyoSutQHrswnBnuimUYSb59dZwog3T2MV0T0=; b=mLI4wibQX2QDrTDp0g3oVwAnp8g8JH2ZHX3coY+tloIS7hQDHaHg7O3U0tqNyPkaXm 8rDqn7xBBo4XHsB+a2U3CBHCbqJ61M0ldpB/4IwR6Z3ug6eLs539FiVfed3DGaRV2ZTJ k+65bJQ0eM8Sc9pNW/ZbuOFd1znR6iQPephC8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=djQZd3ysyoSutQHrswnBnuimUYSb59dZwog3T2MV0T0=; b=o5TiOa5Eq9gDyvhwUzGXkGcQw2pCnpp2YhIo/RrkvppkEWiNQUfwy+P0RS/BEyij7L KqHry91fiXqbubF1JfRn7n2HDtbaV5mmeXoVPjwJSC0olRhFxJP9YrrLiH89YR1kIoqS CfMn+iIvSEI8ZB+0wSdQAIkh6xjY1e3AP4ZaAKjQRwvLhsRWh40T2+HdVg3Ou7+SKyj1 mgy+yRU7DRO+sFtymUOw6UCAH0uRvcq4NC3bHZb83iFfsBTnCXC5KfccJ04tyMSHuIpI 2Fc8Hlp69TpKzVEsQhk60E16+ny+Q/6OnnIEkWpUcQTP7e46JGRc7RVCvLVGRD0EqIZo w4hQ== X-Gm-Message-State: AOAM530y7ljYBQF+Ku4GFCORHZy/LjJwyYEbBIoCGIO/o3HblBHgsFKJ Gnrbu8g2plYrivnvmlPUiZBBYQ== X-Google-Smtp-Source: ABdhPJyXid/WhlRRi3IuEn/gj018RDIJnIysnt+MQKHLqWW7jwLJATluPmfQx4YLScgrHSTI05ABow== X-Received: by 2002:a17:902:344:b029:e4:a7ab:2e55 with SMTP id 62-20020a1709020344b02900e4a7ab2e55mr11594605pld.63.1615516765493; Thu, 11 Mar 2021 18:39:25 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id k127sm3858828pfd.63.2021.03.11.18.39.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Mar 2021 18:39:24 -0800 (PST) Date: Thu, 11 Mar 2021 18:39:23 -0800 From: Kees Cook To: Sami Tolvanen Cc: Nathan Chancellor , Nick Desaulniers , Masahiro Yamada , Will Deacon , Jessica Yu , Arnd Bergmann , Tejun Heo , bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/17] module: cfi: ensure __cfi_check alignment Message-ID: <202103111837.813997B4@keescook> References: <20210312004919.669614-1-samitolvanen@google.com> <20210312004919.669614-5-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210312004919.669614-5-samitolvanen@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Mar 11, 2021 at 04:49:06PM -0800, Sami Tolvanen wrote: > CONFIG_CFI_CLANG_SHADOW assumes the __cfi_check() function is page > aligned and at the beginning of the .text section. While Clang would > normally align the function correctly, it fails to do so for modules > with no executable code. > > This change ensures the correct __cfi_check() location and > alignment. It also discards the .eh_frame section, which Clang can > generate with certain sanitizers, such as CFI. > > Link: https://bugs.llvm.org/show_bug.cgi?id=46293 > Signed-off-by: Sami Tolvanen > --- > scripts/module.lds.S | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/scripts/module.lds.S b/scripts/module.lds.S > index 168cd27e6122..552ddb084f76 100644 > --- a/scripts/module.lds.S > +++ b/scripts/module.lds.S > @@ -3,10 +3,13 @@ > * Archs are free to supply their own linker scripts. ld will > * combine them automatically. > */ > +#include > + > SECTIONS { > /DISCARD/ : { > *(.discard) > *(.discard.*) > + *(.eh_frame) > } > > __ksymtab 0 : { *(SORT(___ksymtab+*)) } > @@ -40,7 +43,16 @@ SECTIONS { > *(.rodata..L*) > } > > - .text : { *(.text .text.[0-9a-zA-Z_]*) } > +#ifdef CONFIG_CFI_CLANG > + /* > + * With CFI_CLANG, ensure __cfi_check is at the beginning of the > + * .text section, and that the section is aligned to page size. > + */ > + .text : ALIGN(PAGE_SIZE) { > + *(.text.__cfi_check) > + *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) > + } > +#endif Whoops, I think this reverts to the default .text declaration when CONFIG_CFI_CLANG is unset. I think the only thing that needs the ifdef is the ALIGN, yes? Perhaps something like this? #ifdef CONFIG_CFI_CLANG # define ALIGN_CFI ALIGN(PAGE_SIZE) #else # define ALIGN_CFI #endif .text : ALIGN_CFI { *(.text.__cfi_check) *(.text .text.[0-9a-zA-Z_]* .text..L.cfi*) } -Kees > } > > /* bring in arch-specific sections */ > -- > 2.31.0.rc2.261.g7f71774620-goog > -- Kees Cook