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 00360C43217 for ; Thu, 2 Dec 2021 22:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349923AbhLBWhl (ORCPT ); Thu, 2 Dec 2021 17:37:41 -0500 Received: from mga18.intel.com ([134.134.136.126]:48270 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349556AbhLBWg7 (ORCPT ); Thu, 2 Dec 2021 17:36:59 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10186"; a="223730467" X-IronPort-AV: E=Sophos;i="5.87,282,1631602800"; d="scan'208";a="223730467" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Dec 2021 14:33:19 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.87,282,1631602800"; d="scan'208";a="513054743" Received: from irvmail001.ir.intel.com ([10.43.11.63]) by fmsmga007.fm.intel.com with ESMTP; 02 Dec 2021 14:33:11 -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 1B2MWmYc028552; Thu, 2 Dec 2021 22:33:09 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 , 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 v8 11/14] module: Reorder functions Date: Thu, 2 Dec 2021 23:32:11 +0100 Message-Id: <20211202223214.72888-12-alexandr.lobakin@intel.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211202223214.72888-1-alexandr.lobakin@intel.com> References: <20211202223214.72888-1-alexandr.lobakin@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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. 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 [ alobakin: make it work with ClangCFI ] Signed-off-by: Alexander Lobakin --- Makefile | 4 ++ init/Kconfig | 12 ++++++ kernel/kallsyms.c | 4 +- kernel/livepatch/core.c | 3 +- kernel/module.c | 91 ++++++++++++++++++++++++++++++++++++++++- 5 files changed, 109 insertions(+), 5 deletions(-) diff --git a/Makefile b/Makefile index a4d2eac5f81f..649c309d10e2 100644 --- a/Makefile +++ b/Makefile @@ -885,6 +885,10 @@ endif # 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/init/Kconfig b/init/Kconfig index 8baeaef382c9..1f7e57d323bb 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2360,6 +2360,18 @@ 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" + 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/kallsyms.c b/kernel/kallsyms.c index ff9d8b651966..4ff14a94d1bd 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -861,7 +861,7 @@ static int __kallsyms_open(struct inode *inode, struct file *file) * When function granular kaslr is enabled, we need to print out the symbols * at random so we don't reveal the new layout. */ -#ifdef CONFIG_FG_KASLR +#if defined(CONFIG_FG_KASLR) || defined(CONFIG_MODULE_FG_KASLR) static int update_random_pos(struct kallsyms_shuffled_iter *s_iter, loff_t pos, loff_t *new_pos) { @@ -1005,7 +1005,7 @@ static int kallsyms_random_open(struct inode *inode, struct file *file) #define kallsyms_open kallsyms_random_open #else #define kallsyms_open __kallsyms_open -#endif /* !CONFIG_FG_KASLR */ +#endif /* !CONFIG_FG_KASLR && !CONFIG_MODULE_FG_KASLR */ #ifdef CONFIG_KGDB_KDB const char *kdb_walk_kallsyms(loff_t *pos) diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 10ea75111057..8a5240b5eb5e 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -174,7 +174,8 @@ static int klp_find_object_symbol(const char *objname, const char *name, * to resolve symbols when there are duplicates using the previous * symbol position (i.e. sympos != 0). */ - if (IS_ENABLED(CONFIG_FG_KASLR) && sympos) { + if ((IS_ENABLED(CONFIG_FG_KASLR) || IS_ENABLED(CONFIG_MODULE_FG_KASLR)) && + sympos) { pr_err("FG-KASLR is enabled, specifying symbol position %lu for symbol '%s' in object '%s' does not work\n", sympos, name, objname ? objname : "vmlinux"); goto out_err; diff --git a/kernel/module.c b/kernel/module.c index 84a9141a5e15..48d5919d09dd 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 +2417,89 @@ static bool module_init_layout_section(const char *sname) return module_init_section(sname); } +/* + * 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) +{ + u32 i, j; + + for (i = size - 1; i > 0; i--) { + /* + * pick a random index from 0 to i + */ + j = get_random_u32() % (i + 1); + + swap(list[i], list[j]); + } +} + +/* + * 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_text_list(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 +2594,9 @@ 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) -- 2.33.1