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=unavailable 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 BD08BC433E9 for ; Fri, 12 Mar 2021 02:41:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9839564F91 for ; Fri, 12 Mar 2021 02:41:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231559AbhCLCkm (ORCPT ); Thu, 11 Mar 2021 21:40:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231368AbhCLCkZ (ORCPT ); Thu, 11 Mar 2021 21:40:25 -0500 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32950C061574 for ; Thu, 11 Mar 2021 18:40:25 -0800 (PST) Received: by mail-pl1-x62f.google.com with SMTP id j6so11212175plx.6 for ; Thu, 11 Mar 2021 18:40:25 -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=KiZc8nN5pryJpzXUOJy7bJ2ujYQabS0eWCsV+Q2Fjh8=; b=DZqCKeDaA8I99V3+1mZBQymMEqo9f9/pBg9BgWDPK7N3AjBq1yFa1+GBW1jFNRLRd3 hKf7PNNHeLvoSgyG2ej4hi9xWPV/EzF7hsH79qSSrH3lKG0yD73RGYWaGFHYY5cSqb26 TiBly3t+H94MBcwBova2NHIfs+27cLe25uxBQ= 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=KiZc8nN5pryJpzXUOJy7bJ2ujYQabS0eWCsV+Q2Fjh8=; b=X00xKH92iNNk0DJw6djiElVag2a9yhgPEHZ/PZl8G7vLeDEY9wyRmqYmTvenio5QKD RVDpHP/xgERs5aYP8OYcA0zMKbDeUzmATnjXVN680zH544dTWMxs0z5V5HDMUZENJWCV Tp1zFFH6cPyZuX6aJAgUgFZRxJAJmvbQ1PJ8BvS/Euv4CHlncRXqgCYDEBugfloFg+JZ Fzlh2IBLmScUoE/Z+eAMsu2d1F0LwTE9+S25j28QaklthNLDBhA9zKRNNOk3rTzrMTs+ XKdP83teG+i+aRd4e9AiICeZkW7eek+fvhcaq3Z8f/cOrJ9kiJ3o2YgVRbQdHZ2kjHQI NDeA== X-Gm-Message-State: AOAM530929FlJRpg+SQAhI0YAwTe0kVT9jhfnnXclVQ7jOxsQgMTk6CH Y+yyFrfIpeRxVEg0UKz7LJ6yYQ== X-Google-Smtp-Source: ABdhPJz/EQDfMcfGqOziqYaQrc/zqH66k4oqcRejrkalla+YmWjVV7VvtiUOnYrWNhEhKA7Nrnvn7A== X-Received: by 2002:a17:903:102:b029:e5:fc29:de83 with SMTP id y2-20020a1709030102b02900e5fc29de83mr11286686plc.31.1615516824770; Thu, 11 Mar 2021 18:40:24 -0800 (PST) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id z2sm3590568pfc.8.2021.03.11.18.40.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Mar 2021 18:40:24 -0800 (PST) Date: Thu, 11 Mar 2021 18:40:23 -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 02/17] cfi: add __cficanonical Message-ID: <202103111839.81B67E6@keescook> References: <20210312004919.669614-1-samitolvanen@google.com> <20210312004919.669614-3-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210312004919.669614-3-samitolvanen@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, Mar 11, 2021 at 04:49:04PM -0800, Sami Tolvanen wrote: > With CONFIG_CFI_CLANG, the compiler replaces a function address taken > in C code with the address of a local jump table entry, which passes > runtime indirect call checks. However, the compiler won't replace > addresses taken in assembly code, which will result in a CFI failure > if we later jump to such an address in instrumented C code. The code > generated for the non-canonical jump table looks this: > > : /* In C, &noncanonical points here */ > jmp noncanonical > ... > : /* function body */ > ... > > This change adds the __cficanonical attribute, which tells the > compiler to use a canonical jump table for the function instead. This > means the compiler will rename the actual function to .cfi > and points the original symbol to the jump table entry instead: > > : /* jump table entry */ > jmp canonical.cfi > ... > : /* function body */ > ... > > As a result, the address taken in assembly, or other non-instrumented > code always points to the jump table and therefore, can be used for > indirect calls in instrumented code without tripping CFI checks. Thanks for this changelog! Having the explicit examples helps keep this clear. Reviewed-by: Kees Cook -Kees > > Signed-off-by: Sami Tolvanen > --- > include/linux/compiler-clang.h | 1 + > include/linux/compiler_types.h | 4 ++++ > include/linux/init.h | 4 ++-- > include/linux/pci.h | 4 ++-- > 4 files changed, 9 insertions(+), 4 deletions(-) > > diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h > index 1ff22bdad992..c275f23ce023 100644 > --- a/include/linux/compiler-clang.h > +++ b/include/linux/compiler-clang.h > @@ -57,3 +57,4 @@ > #endif > > #define __nocfi __attribute__((__no_sanitize__("cfi"))) > +#define __cficanonical __attribute__((__cfi_canonical_jump_table__)) > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > index 796935a37e37..d29bda7f6ebd 100644 > --- a/include/linux/compiler_types.h > +++ b/include/linux/compiler_types.h > @@ -246,6 +246,10 @@ struct ftrace_likely_data { > # define __nocfi > #endif > > +#ifndef __cficanonical > +# define __cficanonical > +#endif > + > #ifndef asm_volatile_goto > #define asm_volatile_goto(x...) asm goto(x) > #endif > diff --git a/include/linux/init.h b/include/linux/init.h > index b3ea15348fbd..045ad1650ed1 100644 > --- a/include/linux/init.h > +++ b/include/linux/init.h > @@ -220,8 +220,8 @@ extern bool initcall_debug; > __initcall_name(initstub, __iid, id) > > #define __define_initcall_stub(__stub, fn) \ > - int __init __stub(void); \ > - int __init __stub(void) \ > + int __init __cficanonical __stub(void); \ > + int __init __cficanonical __stub(void) \ > { \ > return fn(); \ > } \ > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 86c799c97b77..39684b72db91 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -1944,8 +1944,8 @@ enum pci_fixup_pass { > #ifdef CONFIG_LTO_CLANG > #define __DECLARE_PCI_FIXUP_SECTION(sec, name, vendor, device, class, \ > class_shift, hook, stub) \ > - void stub(struct pci_dev *dev); \ > - void stub(struct pci_dev *dev) \ > + void __cficanonical stub(struct pci_dev *dev); \ > + void __cficanonical stub(struct pci_dev *dev) \ > { \ > hook(dev); \ > } \ > -- > 2.31.0.rc2.261.g7f71774620-goog > -- Kees Cook