From patchwork Thu Jan 31 19:24:30 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Garnier X-Patchwork-Id: 10791369 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E7C6A1390 for ; Thu, 31 Jan 2019 19:46:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DBF6A3102E for ; Thu, 31 Jan 2019 19:46:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CB1A531793; Thu, 31 Jan 2019 19:46:28 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 5A59F3102E for ; Thu, 31 Jan 2019 19:46:27 +0000 (UTC) Received: (qmail 15734 invoked by uid 550); 31 Jan 2019 19:44:14 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Delivered-To: moderator for kernel-hardening@lists.openwall.com Received: (qmail 21671 invoked from network); 31 Jan 2019 19:29:39 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=9s0Jc+lgI+C1BSYL5mSt9awnQxS0L/t2p2g0lX4vn1Q=; b=cRyQFI2WCS8FjD1FVnnc6pGqW7DxKqoEtMnP1mmIEFR3MaERnlX0Puu/0PhnlM+XnV wj1Zu9JymVQIG0BQbr/QSfDksLbnH6IbwmpUkPyB4Rr9K9zCZS+DRK1IqDVDc/dEwJvJ jtlmFRtnCcDFprijI1AGoinebjPLceATP7Zis= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=9s0Jc+lgI+C1BSYL5mSt9awnQxS0L/t2p2g0lX4vn1Q=; b=r+5DZZcEvDZB8uuzojCPxcD2xOrWs4tWpmirzoaMoDi/G80xas4lnyBqD56Z/e/IUl GyfhO7McgM9fG0gtdP5e9tvLIjUmOfWldaUNbfsgBDFr6r9Oy6kfNeo6/NAbBECQlmWE iiRm8bzU4Bv+Sz/sQaA+XZ7SNO6+9+V1wNwr+TgUG5Aqp0FrE4tmife5Z/YFPL0QU+ik zlTuRHcZgvBU/BMyAQSUv/EieN4cd8wyxQR1+mI+iqpGMmXqeBdMgsSj5c76nJzhwQGF 8WM/7avOZfUd6ljmMOkHRcS1iYMr0hzXcMdAm3gHM3qEVk5DX6DwNMncKa5LpehEgzmw OX7A== X-Gm-Message-State: AJcUukd6GayX8b6aK3BbOoNff50EYfIVkCvhAGggpLz3QujIJBYn1tVa v9oeAp1aSKyEX3K8jKzl8qEOPu1/gw0= X-Google-Smtp-Source: ALg8bN7y05ZWZkA8E4kxBIiqovexlhMvMxOCDxhr2UjvxJYUcSVRfW/5iY2KzYWPpZcaTG1skj0GFQ== X-Received: by 2002:a62:3c1:: with SMTP id 184mr36365576pfd.56.1548962967192; Thu, 31 Jan 2019 11:29:27 -0800 (PST) From: Thomas Garnier To: kernel-hardening@lists.openwall.com Cc: kristen@linux.intel.com, Thomas Garnier , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Thomas Garnier , Joerg Roedel , Andy Lutomirski , Francis Deslauriers , Ard Biesheuvel , "H.J. Lu" , "Peter Zijlstra (Intel)" , linux-kernel@vger.kernel.org Subject: [PATCH v6 23/27] x86/modules: Adapt module loading for PIE support Date: Thu, 31 Jan 2019 11:24:30 -0800 Message-Id: <20190131192533.34130-24-thgarnie@chromium.org> X-Mailer: git-send-email 2.20.1.495.gaa96b0ce6b-goog In-Reply-To: <20190131192533.34130-1-thgarnie@chromium.org> References: <20190131192533.34130-1-thgarnie@chromium.org> MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP Adapt module loading to support PIE relocations. Generate dynamic GOT if a symbol requires it but no entry exists in the kernel GOT. Position Independent Executable (PIE) support will allow to extend the KASLR randomization range below 0xffffffff80000000. Signed-off-by: Thomas Garnier --- arch/x86/Makefile | 4 + arch/x86/include/asm/module.h | 11 ++ arch/x86/include/asm/sections.h | 4 + arch/x86/kernel/module.c | 181 +++++++++++++++++++++++++++++++- arch/x86/kernel/module.lds | 3 + 5 files changed, 198 insertions(+), 5 deletions(-) create mode 100644 arch/x86/kernel/module.lds diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 65d6d9a1dd22..5e9c1b02cf87 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -129,8 +129,12 @@ else KBUILD_CFLAGS += $(cflags-y) KBUILD_CFLAGS += -mno-red-zone +ifdef CONFIG_X86_PIE + KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/x86/kernel/module.lds +else KBUILD_CFLAGS += -mcmodel=kernel endif +endif ifdef CONFIG_X86_GLOBAL_STACKPROTECTOR ifeq ($(call cc-option, -mstack-protector-guard=global),) diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h index 7948a17febb4..68ff05e14288 100644 --- a/arch/x86/include/asm/module.h +++ b/arch/x86/include/asm/module.h @@ -5,12 +5,23 @@ #include #include +#ifdef CONFIG_X86_PIE +struct mod_got_sec { + struct elf64_shdr *got; + int got_num_entries; + int got_max_entries; +}; +#endif + struct mod_arch_specific { #ifdef CONFIG_UNWINDER_ORC unsigned int num_orcs; int *orc_unwind_ip; struct orc_entry *orc_unwind; #endif +#ifdef CONFIG_X86_PIE + struct mod_got_sec core; +#endif }; #ifdef CONFIG_X86_64 diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h index 8ea1cfdbeabc..d4468309d743 100644 --- a/arch/x86/include/asm/sections.h +++ b/arch/x86/include/asm/sections.h @@ -13,4 +13,8 @@ extern char __end_rodata_aligned[]; extern char __end_rodata_hpage_align[]; #endif +#if defined(CONFIG_X86_PIE) +extern char __start_got[], __end_got[]; +#endif + #endif /* _ASM_X86_SECTIONS_H */ diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c index b052e883dd8c..f0d3ed92049e 100644 --- a/arch/x86/kernel/module.c +++ b/arch/x86/kernel/module.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include @@ -77,6 +78,173 @@ static unsigned long int get_module_load_offset(void) } #endif +#ifdef CONFIG_X86_PIE +static u64 find_got_kernel_entry(Elf64_Sym *sym, const Elf64_Rela *rela) +{ + u64 *pos; + + for (pos = (u64 *)__start_got; pos < (u64 *)__end_got; pos++) { + if (*pos == sym->st_value) + return (u64)pos + rela->r_addend; + } + + return 0; +} + +static u64 module_emit_got_entry(struct module *mod, void *loc, + const Elf64_Rela *rela, Elf64_Sym *sym) +{ + struct mod_got_sec *gotsec = &mod->arch.core; + u64 *got = (u64 *)gotsec->got->sh_addr; + int i = gotsec->got_num_entries; + u64 ret; + + /* Check if we can use the kernel GOT */ + ret = find_got_kernel_entry(sym, rela); + if (ret) + return ret; + + got[i] = sym->st_value; + + /* + * Check if the entry we just created is a duplicate. Given that the + * relocations are sorted, this will be the last entry we allocated. + * (if one exists). + */ + if (i > 0 && got[i] == got[i - 2]) { + ret = (u64)&got[i - 1]; + } else { + gotsec->got_num_entries++; + BUG_ON(gotsec->got_num_entries > gotsec->got_max_entries); + ret = (u64)&got[i]; + } + + return ret + rela->r_addend; +} + +#define cmp_3way(a, b) ((a) < (b) ? -1 : (a) > (b)) + +static int cmp_rela(const void *a, const void *b) +{ + const Elf64_Rela *x = a, *y = b; + int i; + + /* sort by type, symbol index and addend */ + i = cmp_3way(ELF64_R_TYPE(x->r_info), ELF64_R_TYPE(y->r_info)); + if (i == 0) + i = cmp_3way(ELF64_R_SYM(x->r_info), ELF64_R_SYM(y->r_info)); + if (i == 0) + i = cmp_3way(x->r_addend, y->r_addend); + return i; +} + +static bool duplicate_rel(const Elf64_Rela *rela, int num) +{ + /* + * Entries are sorted by type, symbol index and addend. That means + * that, if a duplicate entry exists, it must be in the preceding + * slot. + */ + return num > 0 && cmp_rela(rela + num, rela + num - 1) == 0; +} + +static unsigned int count_gots(Elf64_Sym *syms, Elf64_Rela *rela, int num) +{ + unsigned int ret = 0; + Elf64_Sym *s; + int i; + + for (i = 0; i < num; i++) { + switch (ELF64_R_TYPE(rela[i].r_info)) { + case R_X86_64_GOTPCREL: + s = syms + ELF64_R_SYM(rela[i].r_info); + + /* + * Use the kernel GOT when possible, else reserve a + * custom one for this module. + */ + if (!duplicate_rel(rela, i) && + !find_got_kernel_entry(s, rela + i)) + ret++; + break; + } + } + return ret; +} + +/* + * Generate GOT entries for GOTPCREL relocations that do not exists in the + * kernel GOT. Based on arm64 module-plts implementation. + */ +int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, + char *secstrings, struct module *mod) +{ + unsigned long gots = 0; + Elf_Shdr *symtab = NULL; + Elf64_Sym *syms = NULL; + char *strings, *name; + int i; + + /* + * Find the empty .got section so we can expand it to store the PLT + * entries. Record the symtab address as well. + */ + for (i = 0; i < ehdr->e_shnum; i++) { + if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) { + mod->arch.core.got = sechdrs + i; + } else if (sechdrs[i].sh_type == SHT_SYMTAB) { + symtab = sechdrs + i; + syms = (Elf64_Sym *)symtab->sh_addr; + } + } + + if (!mod->arch.core.got) { + pr_err("%s: module GOT section missing\n", mod->name); + return -ENOEXEC; + } + if (!syms) { + pr_err("%s: module symtab section missing\n", mod->name); + return -ENOEXEC; + } + + for (i = 0; i < ehdr->e_shnum; i++) { + Elf64_Rela *rels = (void *)ehdr + sechdrs[i].sh_offset; + int numrels = sechdrs[i].sh_size / sizeof(Elf64_Rela); + + if (sechdrs[i].sh_type != SHT_RELA) + continue; + + /* sort by type, symbol index and addend */ + sort(rels, numrels, sizeof(Elf64_Rela), cmp_rela, NULL); + + gots += count_gots(syms, rels, numrels); + } + + mod->arch.core.got->sh_type = SHT_NOBITS; + mod->arch.core.got->sh_flags = SHF_ALLOC; + mod->arch.core.got->sh_addralign = L1_CACHE_BYTES; + mod->arch.core.got->sh_size = (gots + 1) * sizeof(u64); + mod->arch.core.got_num_entries = 0; + mod->arch.core.got_max_entries = gots; + + /* + * If a _GLOBAL_OFFSET_TABLE_ symbol exists, make it absolute for + * modules to correctly reference it. Similar to s390 implementation. + */ + strings = (void *) ehdr + sechdrs[symtab->sh_link].sh_offset; + for (i = 0; i < symtab->sh_size/sizeof(Elf_Sym); i++) { + if (syms[i].st_shndx != SHN_UNDEF) + continue; + name = strings + syms[i].st_name; + if (!strcmp(name, "_GLOBAL_OFFSET_TABLE_")) { + syms[i].st_shndx = SHN_ABS; + break; + } + } + return 0; +} +#endif + void *module_alloc(unsigned long size) { void *p; @@ -190,16 +358,20 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, if ((s64)val != *(s32 *)loc) goto overflow; break; +#ifdef CONFIG_X86_PIE + case R_X86_64_GOTPCREL: + val = module_emit_got_entry(me, loc, rel + i, sym); + /* fallthrough */ +#endif case R_X86_64_PC32: case R_X86_64_PLT32: if (*(u32 *)loc != 0) goto invalid_relocation; val -= (u64)loc; *(u32 *)loc = val; -#if 0 - if ((s64)val != *(s32 *)loc) + if (IS_ENABLED(CONFIG_X86_PIE) && + (s64)val != *(s32 *)loc) goto overflow; -#endif break; case R_X86_64_PC64: if (*(u64 *)loc != 0) @@ -223,8 +395,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, overflow: pr_err("overflow in relocation type %d val %Lx\n", (int)ELF64_R_TYPE(rel[i].r_info), val); - pr_err("`%s' likely not compiled with -mcmodel=kernel\n", - me->name); + pr_err("`%s' likely too far from the kernel\n", me->name); return -ENOEXEC; } #endif diff --git a/arch/x86/kernel/module.lds b/arch/x86/kernel/module.lds new file mode 100644 index 000000000000..fd6e95a4b454 --- /dev/null +++ b/arch/x86/kernel/module.lds @@ -0,0 +1,3 @@ +SECTIONS { + .got (NOLOAD) : { BYTE(0) } +}