From patchwork Thu Dec 23 00:22:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexander Lobakin X-Patchwork-Id: 12697681 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D9A80C4332F for ; Thu, 23 Dec 2021 00:26:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232103AbhLWA0f (ORCPT ); Wed, 22 Dec 2021 19:26:35 -0500 Received: from mga09.intel.com ([134.134.136.24]:53166 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345757AbhLWAYC (ORCPT ); Wed, 22 Dec 2021 19:24:02 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1640219042; x=1671755042; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=+KrOqIqb4aeQ6x0G1EHmcHniPYRjIzt9aPk8YuSf44w=; b=UmzSkarp70lbdny1BCH/IXH1WJ2gz2gDlj7yFWGO4w4MDmVUaMWT5H0K 6vE84T+303rLuEt1zi2ndrBGn+gw/te5BrLOwcB7y88tS3Sjfc5SFg8qX ZJdqL9JH1hrMtILIvHkxDmonTLd3LoPL5FyYz4TPrEluYnz9rClkUGB2D RDybQ/H9XoQkw/YZqS6wD920xpLGwsjPYcA94EH4UFUvkX4aziDQk362h Dhbz7N+hnFpBjUst2URYOgPrptDHVLTRuva5kaBVadmk/bXkq5n5MATeq ggW8WcdGAQPTEawosQOHL9uwP6nN2Js6+UY94scf156F9B2r8EZM40kEC w==; X-IronPort-AV: E=McAfee;i="6200,9189,10206"; a="240533510" X-IronPort-AV: E=Sophos;i="5.88,228,1635231600"; d="scan'208";a="240533510" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Dec 2021 16:23:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.88,228,1635231600"; d="scan'208";a="521881976" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by orsmga008.jf.intel.com with ESMTP; 22 Dec 2021 16:23:33 -0800 Received: from newjersey.igk.intel.com (newjersey.igk.intel.com [10.102.20.203]) by irvmail001.ir.intel.com (8.14.3/8.13.6/MailSET/Hub) with ESMTP id 1BN0N79H032467; Thu, 23 Dec 2021 00:23:31 GMT From: Alexander Lobakin To: linux-hardening@vger.kernel.org, x86@kernel.org Cc: Alexander Lobakin , Jesse Brandeburg , Kristen Carlson Accardi , Kees Cook , Miklos Szeredi , Ard Biesheuvel , Tony Luck , Bruce Schlobohm , Jessica Yu , kernel test robot , Miroslav Benes , Evgenii Shatokhin , Jonathan Corbet , Masahiro Yamada , Michal Marek , Nick Desaulniers , Herbert Xu , "David S. Miller" , Thomas Gleixner , Will Deacon , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Arnd Bergmann , Josh Poimboeuf , Nathan Chancellor , Masami Hiramatsu , Marios Pomonis , Sami Tolvanen , "H.J. Lu" , Nicolas Pitre , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org, live-patching@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH v9 12/15] module: Reorder functions Date: Thu, 23 Dec 2021 01:22:06 +0100 Message-Id: <20211223002209.1092165-13-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211223002209.1092165-1-alexandr.lobakin@intel.com> References: <20211223002209.1092165-1-alexandr.lobakin@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org From: Kristen Carlson Accardi Introduce a new config option to allow modules to be re-ordered by function. This option can be enabled independently of the kernel text KASLR or FG_KASLR settings so that it can be used by architectures that do not support either of these features. This option will be selected by default if CONFIG_FG_KASLR is selected. 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. alobakin: Make it work with ClangCFI -- in such builds, .text section must always come first and be page-aligned. Exclude it from the shuffle list and leave as it is. Make this feature depend on `-z unique-symbol` as well, due to the very same reasons. Traditionally, use common shuffle_array() from . Signed-off-by: Kristen Carlson Accardi Reviewed-by: Kees Cook Acked-by: Ard Biesheuvel Tested-by: Ard Biesheuvel Reviewed-by: Tony Luck Tested-by: Tony Luck Acked-by: Jessica Yu Tested-by: Jessica Yu Reported-by: kernel test robot # swap.cocci Co-developed-by: Alexander Lobakin Signed-off-by: Alexander Lobakin --- Makefile | 6 +++- include/linux/linkage.h | 1 + init/Kconfig | 14 ++++++++ kernel/module.c | 73 +++++++++++++++++++++++++++++++++++++++-- 4 files changed, 91 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 3346269341d4..74d270c77d96 100644 --- a/Makefile +++ b/Makefile @@ -900,7 +900,7 @@ export SECSUBST_AFLAGS endif # Same for modules. LD DCE doesn't work for them, thus not checking for it -ifneq ($(CONFIG_LTO_CLANG),) +ifneq ($(CONFIG_MODULE_FG_KASLR)$(CONFIG_LTO_CLANG),) KBUILD_AFLAGS_MODULE += -Wa,--sectname-subst KBUILD_CFLAGS_MODULE += -Wa,--sectname-subst endif @@ -909,6 +909,10 @@ endif # CONFIG_HAVE_ASM_FUNCTION_SECTIONS # ClangLTO implies `-ffunction-sections -fdata-sections`, no need # to specify them manually and trigger a pointless full rebuild ifndef CONFIG_LTO_CLANG +ifdef CONFIG_MODULE_FG_KASLR +KBUILD_CFLAGS_MODULE += -ffunction-sections +endif + ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_FG_KASLR),) KBUILD_CFLAGS_KERNEL += -ffunction-sections endif diff --git a/include/linux/linkage.h b/include/linux/linkage.h index f3c96fb6a534..deb26069278a 100644 --- a/include/linux/linkage.h +++ b/include/linux/linkage.h @@ -80,6 +80,7 @@ #if defined(CONFIG_HAVE_ASM_FUNCTION_SECTIONS) && \ ((defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) && !defined(MODULE)) || \ (defined(CONFIG_FG_KASLR) && !defined(MODULE)) || \ + (defined(CONFIG_MODULE_FG_KASLR) && defined(MODULE)) || \ (defined(CONFIG_LTO_CLANG))) #define SYM_PUSH_SECTION(name) \ diff --git a/init/Kconfig b/init/Kconfig index 381b063b4925..38c82e21efd7 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2376,6 +2376,20 @@ config UNUSED_KSYMS_WHITELIST one per line. The path can be absolute, or relative to the kernel source tree. +config MODULE_FG_KASLR + bool "Module Function Granular Layout Randomization" + depends on $(cc-option,-ffunction-sections) + depends on LD_HAS_Z_UNIQUE_SYMBOL || !LIVEPATCH + default FG_KASLR + depends on BROKEN + help + This option randomizes the module text section by reordering the text + section by function at module load time. In order to use this + feature, the module must have been compiled with the + -ffunction-sections compiler flag. + + If unsure, say N. + endif # MODULES config MODULES_TREE_LOOKUP diff --git a/kernel/module.c b/kernel/module.c index 84a9141a5e15..802e1098eaf4 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -57,6 +57,7 @@ #include #include #include +#include #include #include "module-internal.h" @@ -1527,7 +1528,7 @@ static void free_sect_attrs(struct module_sect_attrs *sect_attrs) for (section = 0; section < sect_attrs->nsections; section++) kfree(sect_attrs->attrs[section].battr.attr.name); - kfree(sect_attrs); + kvfree(sect_attrs); } static void add_sect_attrs(struct module *mod, const struct load_info *info) @@ -1544,7 +1545,7 @@ static void add_sect_attrs(struct module *mod, const struct load_info *info) size[0] = ALIGN(struct_size(sect_attrs, attrs, nloaded), sizeof(sect_attrs->grp.bin_attrs[0])); size[1] = (nloaded + 1) * sizeof(sect_attrs->grp.bin_attrs[0]); - sect_attrs = kzalloc(size[0] + size[1], GFP_KERNEL); + sect_attrs = kvzalloc(size[0] + size[1], GFP_KERNEL); if (sect_attrs == NULL) return; @@ -2416,6 +2417,71 @@ static bool module_init_layout_section(const char *sname) return module_init_section(sname); } +/* + * 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 max_sections = info->hdr->e_shnum; + int num_text_sections = 0; + Elf_Shdr **text_list; + int i, size; + + text_list = kvmalloc_array(max_sections, sizeof(*text_list), GFP_KERNEL); + if (!text_list) + 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) || + (shdr->sh_flags & ARCH_SHF_SMALL) || + module_init_layout_section(sname)) + continue; + + /* + * With CONFIG_CFI_CLANG, .text with __cfi_check() must come + * before any other text sections, and be aligned to PAGE_SIZE. + * Don't include it in the shuffle list. + */ + if (IS_ENABLED(CONFIG_CFI_CLANG) && !strcmp(sname, ".text")) + continue; + + if (!num_text_sections) + size = shdr->sh_entsize; + + text_list[num_text_sections] = shdr; + num_text_sections++; + } + + if (!num_text_sections) + goto exit; + + shuffle_array(text_list, num_text_sections); + + for (i = 0; i < num_text_sections; i++) { + Elf_Shdr *shdr = text_list[i]; + + /* + * get_offset has a section index for it's last + * argument, that is only used by arch_mod_section_prepend(), + * which is only defined by parisc. Since this type + * of randomization isn't supported on parisc, we can + * safely pass in zero as the last argument, as it is + * ignored. + */ + shdr->sh_entsize = get_offset(mod, &size, shdr, 0); + } + +exit: + kvfree(text_list); +} + /* * Lay out the SHF_ALLOC sections in a way not dissimilar to how ld * might -- code, read-only data, read-write data, small data. Tally @@ -2510,6 +2576,9 @@ static void layout_sections(struct module *mod, struct load_info *info) break; } } + + if (IS_ENABLED(CONFIG_MODULE_FG_KASLR)) + randomize_text(mod, info); } static void set_license(struct module *mod, const char *license)