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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 664F1C35247 for ; Wed, 5 Feb 2020 22:40:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40F89214AF for ; Wed, 5 Feb 2020 22:40:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727653AbgBEWkC (ORCPT ); Wed, 5 Feb 2020 17:40:02 -0500 Received: from mga02.intel.com ([134.134.136.20]:60116 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727542AbgBEWjj (ORCPT ); Wed, 5 Feb 2020 17:39:39 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Feb 2020 14:39:38 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,407,1574150400"; d="scan'208";a="225092467" Received: from unknown (HELO localhost.jf.intel.com) ([10.54.75.26]) by fmsmga007.fm.intel.com with ESMTP; 05 Feb 2020 14:39:38 -0800 From: Kristen Carlson Accardi To: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, arjan@linux.intel.com, keescook@chromium.org Cc: rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, Kristen Carlson Accardi Subject: [RFC PATCH 10/11] module: Reorder functions Date: Wed, 5 Feb 2020 14:39:49 -0800 Message-Id: <20200205223950.1212394-11-kristen@linux.intel.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200205223950.1212394-1-kristen@linux.intel.com> References: <20200205223950.1212394-1-kristen@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a module has functions split out into separate text sections (i.e. compiled with the -ffunction-sections flag), reorder the functions to provide some code diversification to modules. Signed-off-by: Kristen Carlson Accardi --- kernel/module.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) diff --git a/kernel/module.c b/kernel/module.c index b56f3224b161..231563e95e61 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -53,6 +53,8 @@ #include #include #include +#include +#include #include #include "module-internal.h" @@ -3245,6 +3247,87 @@ static int find_module_sections(struct module *mod, struct load_info *info) return 0; } +/* + * shuffle_text_list() + * Use a Fisher Yates algorithm to shuffle a list of text sections. + */ +static void shuffle_text_list(Elf_Shdr **list, int size) +{ + int i; + unsigned int j; + Elf_Shdr *temp; + + for (i = size - 1; i > 0; i--) { + /* + * TBD - seed. We need to be able to use a known + * seed so that we can non-randomly randomize for + * debugging. + */ + + // pick a random index from 0 to i + get_random_bytes(&j, sizeof(j)); + j = j % (i + 1); + + temp = list[i]; + list[i] = list[j]; + list[j] = temp; + } +} + +/* + * randomize_text() + * Look through the core section looking for executable code sections. + * Store sections in an array and then shuffle the sections + * to reorder the functions. + */ +static void randomize_text(struct module *mod, struct load_info *info) +{ + int i; + int num_text_sections = 0; + Elf_Shdr **text_list; + int size = 0; + int max_sections = info->hdr->e_shnum; + unsigned int sec = find_sec(info, ".text"); + + if (!IS_ENABLED(CONFIG_FG_KASLR) || !kaslr_enabled()) + return; + + if (sec == 0) + return; + + text_list = kmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL); + if (text_list == NULL) + return; + + for (i = 0; i < max_sections; i++) { + Elf_Shdr *shdr = &info->sechdrs[i]; + const char *sname = info->secstrings + shdr->sh_name; + + if (!(shdr->sh_flags & SHF_ALLOC) || + !(shdr->sh_flags & SHF_EXECINSTR) || + strstarts(sname, ".init")) + continue; + + text_list[num_text_sections] = shdr; + num_text_sections++; + } + + shuffle_text_list(text_list, num_text_sections); + + for (i = 0; i < num_text_sections; i++) { + Elf_Shdr *shdr = text_list[i]; + unsigned int infosec; + const char *sname; + + sname = info->secstrings + shdr->sh_name; + infosec = shdr->sh_info; + + shdr->sh_entsize = get_offset(mod, &size, shdr, infosec); + } + + kfree(text_list); +} + static int move_module(struct module *mod, struct load_info *info) { int i; @@ -3282,6 +3365,8 @@ static int move_module(struct module *mod, struct load_info *info) } else mod->init_layout.base = NULL; + randomize_text(mod, info); + /* Transfer each section which specifies SHF_ALLOC */ pr_debug("final section addresses:\n"); for (i = 0; i < info->hdr->e_shnum; i++) { -- 2.24.1