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=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 618D3C4332F for ; Fri, 3 Sep 2021 06:49:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 431B36101A for ; Fri, 3 Sep 2021 06:49:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1347254AbhICGu5 (ORCPT ); Fri, 3 Sep 2021 02:50:57 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41237 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343902AbhICGu4 (ORCPT ); Fri, 3 Sep 2021 02:50:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630651796; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=paUDlp7iEJb3RmqcU7PhOx7PiOju1z7RQq4LXUKqpHE=; b=Wl2F0BDdaQ12yfbz0HYMUiKNulF9ud2YK/62UZmNOQGwgeuxz+Y1S9mpCOQQrd8wDPN4rQ WpE7BHn53la8r9wK68tr+GMvmA9Xi/vBsCE/PzFvGg537ibsQ/Wqu7uyvJgnI2ApryJEap Vu0hBouYnb79qRgzUzB3sC3LQ9WK5pY= Received: from mail-qt1-f197.google.com (mail-qt1-f197.google.com [209.85.160.197]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-473-ksOSiQe5OsOlf_ecfQQXoA-1; Fri, 03 Sep 2021 02:49:55 -0400 X-MC-Unique: ksOSiQe5OsOlf_ecfQQXoA-1 Received: by mail-qt1-f197.google.com with SMTP id b15-20020a05622a020f00b0029e28300d94so4515327qtx.16 for ; Thu, 02 Sep 2021 23:49:55 -0700 (PDT) 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=paUDlp7iEJb3RmqcU7PhOx7PiOju1z7RQq4LXUKqpHE=; b=B+YsVYTrQ5SREDkF5iMmYrRjwh+IyTStcJhAMqRtlah6115lXrm2aXPCsevWyAPNdo 4hvNc22xsHFiWx2kdvBN8KhBuOmXNwdNMiQ9MFcXbQhowUkNOLVT/qe7uhJscGV/sMy+ lb5AwHbL+lVu9NYEyl6umrtDqrz9G19KmjmenUuXC5d01ZCskq1LROu1QBbiWoZh9LxA FKARoFFgbc/3SuSdUd7MG7bNAtrJlbGrd1/8D8F0YfybJ9b4ArwR41/WCOhZx6qy+/2i UN2/zHsTDIWE8+Qc1yb0CdLaUDaxdgImdQmOc2VWLm+ZbMVBVh/z8v7Br6qo1XNb68dh oqWw== X-Gm-Message-State: AOAM533KZ3Xihk1sQmGz6vYOklVdXQbHJs9ysyFnmVBaHpetHPSScfWu 6t4v4VNH9Mecy2to0k35A+Ou3D+hPQMtdd8HFHotK1pWrFavgydLoBpECLvk+D9HyFzBgVndLL3 KUU3eESe9eZGIKPtWxFWKnRxMeNU9 X-Received: by 2002:a0c:ab4e:: with SMTP id i14mr2154156qvb.28.1630651795053; Thu, 02 Sep 2021 23:49:55 -0700 (PDT) X-Google-Smtp-Source: ABdhPJykW/paz3da/9QXzOhKwMVDERXVXg3CeWKjwGEs1zXPNM88Zu07JB2eia/5zQd1pdOOdeRrmg== X-Received: by 2002:a0c:ab4e:: with SMTP id i14mr2154141qvb.28.1630651794814; Thu, 02 Sep 2021 23:49:54 -0700 (PDT) Received: from treble ([2600:1700:6e32:6c00::d]) by smtp.gmail.com with ESMTPSA id b1sm2565223qtj.76.2021.09.02.23.49.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Sep 2021 23:49:54 -0700 (PDT) Date: Thu, 2 Sep 2021 23:49:51 -0700 From: Josh Poimboeuf To: Kees Cook Cc: Arnd Bergmann , Jessica Yu , Peter Zijlstra , linux-arch@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Alexander Egorenkov , Sven Schnelle , Ilya Leoshkevich , "Steven Rostedt (VMware)" , Ingo Molnar , Sami Tolvanen , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH 3/4] module: Use a list of strings for ro_after_init sections Message-ID: <20210903064951.to4dhiu7zua7s6dn@treble> References: <20210901233757.2571878-1-keescook@chromium.org> <20210901233757.2571878-4-keescook@chromium.org> MIME-Version: 1.0 In-Reply-To: <20210901233757.2571878-4-keescook@chromium.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jpoimboe@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, Sep 01, 2021 at 04:37:56PM -0700, Kees Cook wrote: > Instead of open-coding the section names, use a list for the sections that > need to be marked read-only after init. Unfortunately, it seems we can't > do normal section merging with scripts/module.lds.S as ld.bfd doesn't > correctly update symbol tables. For more details, see commit 6a3193cdd5e5 > ("kbuild: lto: Merge module sections if and only if CONFIG_LTO_CLANG > is enabled"). I'm missing what this has to do with section merging. Can you connect the dots here, i.e. what sections would we want to merge and how would that help here? Instead of hard-coding section names in module.c, I'm wondering if we can do something like the following to set SHF_RO_AFTER_INIT when first creating the sections. Completely untested... diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h index 0449b125d27f..d4ff34c6199c 100644 --- a/arch/x86/include/asm/jump_label.h +++ b/arch/x86/include/asm/jump_label.h @@ -13,7 +13,7 @@ #include #define JUMP_TABLE_ENTRY \ - ".pushsection __jump_table, \"aw\" \n\t" \ + ".pushsection __jump_table, \"0x00200003\" \n\t"\ _ASM_ALIGN "\n\t" \ ".long 1b - . \n\t" \ ".long %l[l_yes] - . \n\t" \ diff --git a/kernel/module.c b/kernel/module.c index 40ec9a030eec..1dda33c9ae49 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3549,15 +3549,6 @@ static struct module *layout_and_allocate(struct load_info *info, int flags) * Note: ro_after_init sections also have SHF_{WRITE,ALLOC} set. */ ndx = find_sec(info, ".data..ro_after_init"); - if (ndx) - info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT; - /* - * Mark the __jump_table section as ro_after_init as well: these data - * structures are never modified, with the exception of entries that - * refer to code in the __init section, which are annotated as such - * at module load time. - */ - ndx = find_sec(info, "__jump_table"); if (ndx) info->sechdrs[ndx].sh_flags |= SHF_RO_AFTER_INIT; diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e5947fbb9e7a..b25ca38179ea 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -20,6 +20,9 @@ #include #include +/* cribbed from include/uapi/linux/elf.h */ +#define SHF_RO_AFTER_INIT 0x00200000 + struct alternative { struct list_head list; struct instruction *insn; @@ -466,7 +469,8 @@ static int create_static_call_sections(struct objtool_file *file) list_for_each_entry(insn, &file->static_call_list, call_node) idx++; - sec = elf_create_section(file->elf, ".static_call_sites", SHF_WRITE, + sec = elf_create_section(file->elf, ".static_call_sites", + SHF_WRITE | SHF_RO_AFTER_INIT, sizeof(struct static_call_site), idx); if (!sec) return -1;