From patchwork Thu May 21 16:56:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563493 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3176C739 for ; Thu, 21 May 2020 16:57:35 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 97C68208DB for ; Thu, 21 May 2020 16:57:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97C68208DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18836-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 30626 invoked by uid 550); 21 May 2020 16:57:20 -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 Received: (qmail 30594 invoked from network); 21 May 2020 16:57:19 -0000 IronPort-SDR: drmsxYWQKShNNGIBjoocFceIkCTm/Xgzo5vsbDXQOoYRP1rlZvGyhmykNdkopwBE0JHlc9m5Xj D0d6F3579zIg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: aV3JFVvbrYZYbuv7t7Jyrk0/2sjsLErzP4zOHapmIGIX67EvDCFdYOJl51/67vJttU5gLr7E1I /Ec0D7WIPZhw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094669" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, Josh Poimboeuf , Peter Zijlstra Cc: arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi Subject: [PATCH v2 1/9] objtool: Do not assume order of parent/child functions Date: Thu, 21 May 2020 09:56:32 -0700 Message-Id: <20200521165641.15940-2-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 If a .cold function is examined prior to it's parent, the link to the parent/child function can be overwritten when the parent is examined. Only update pfunc and cfunc if they were previously nil to prevent this from happening. Signed-off-by: Kristen Carlson Accardi Acked-by: Josh Poimboeuf --- tools/objtool/elf.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index c4857fa3f1d1..b998c853a1f0 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -408,7 +408,13 @@ static int read_symbols(struct elf *elf) size_t pnamelen; if (sym->type != STT_FUNC) continue; - sym->pfunc = sym->cfunc = sym; + + if (sym->pfunc == NULL) + sym->pfunc = sym; + + if (sym->cfunc == NULL) + sym->cfunc = sym; + coldstr = strstr(sym->name, ".cold"); if (!coldstr) continue; From patchwork Thu May 21 16:56:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563495 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id ED145739 for ; Thu, 21 May 2020 16:57:43 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 36AA6207F7 for ; Thu, 21 May 2020 16:57:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 36AA6207F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18837-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 30703 invoked by uid 550); 21 May 2020 16:57:22 -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 Received: (qmail 30625 invoked from network); 21 May 2020 16:57:20 -0000 IronPort-SDR: RZh2HNoKFwTRvl/9q0nkEEkpQ9RfNK3O09YYA6amefqitWSLa6CbabC/zkybasysetCuLDoaUJ gt29jNuRvsSA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: TeipsK/N9HFpFReQGpALhDkmQ7gbrf5yJhKh+2sZ8PgWZ6NiphMk8urCwhS9X04rZD18VqS5Cs cQRRsz8zTzQA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094697" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, "H. Peter Anvin" Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck Subject: [PATCH v2 2/9] x86: tools/relocs: Support >64K section headers Date: Thu, 21 May 2020 09:56:33 -0700 Message-Id: <20200521165641.15940-3-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 While the relocs tool already supports finding the total number of section headers if vmlinux exceeds 64K sections, it fails to read the extended symbol table to get section header indexes for symbols, causing incorrect symbol table indexes to be used when there are > 64K symbols. Parse the elf file to read the extended symbol table info, and then replace all direct references to st_shndx with calls to sym_index(), which will determine whether the value can be read directly or whether the value should be pulled out of the extended table. Signed-off-by: Kristen Carlson Accardi Reviewed-by: Kees Cook Reviewed-by: Tony Luck Tested-by: Tony Luck --- arch/x86/tools/relocs.c | 104 ++++++++++++++++++++++++++++++---------- 1 file changed, 78 insertions(+), 26 deletions(-) diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index ce7188cbdae5..a00dc133f109 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -14,6 +14,10 @@ static Elf_Ehdr ehdr; static unsigned long shnum; static unsigned int shstrndx; +static unsigned int shsymtabndx; +static unsigned int shxsymtabndx; + +static int sym_index(Elf_Sym *sym); struct relocs { uint32_t *offset; @@ -32,6 +36,7 @@ struct section { Elf_Shdr shdr; struct section *link; Elf_Sym *symtab; + Elf32_Word *xsymtab; Elf_Rel *reltab; char *strtab; }; @@ -265,7 +270,7 @@ static const char *sym_name(const char *sym_strtab, Elf_Sym *sym) name = sym_strtab + sym->st_name; } else { - name = sec_name(sym->st_shndx); + name = sec_name(sym_index(sym)); } return name; } @@ -335,6 +340,23 @@ static uint64_t elf64_to_cpu(uint64_t val) #define elf_xword_to_cpu(x) elf32_to_cpu(x) #endif +static int sym_index(Elf_Sym *sym) +{ + Elf_Sym *symtab = secs[shsymtabndx].symtab; + Elf32_Word *xsymtab = secs[shxsymtabndx].xsymtab; + unsigned long offset; + int index; + + if (sym->st_shndx != SHN_XINDEX) + return sym->st_shndx; + + /* calculate offset of sym from head of table. */ + offset = (unsigned long) sym - (unsigned long) symtab; + index = offset/sizeof(*sym); + + return elf32_to_cpu(xsymtab[index]); +} + static void read_ehdr(FILE *fp) { if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1) { @@ -468,31 +490,60 @@ static void read_strtabs(FILE *fp) static void read_symtabs(FILE *fp) { int i,j; + for (i = 0; i < shnum; i++) { struct section *sec = &secs[i]; - if (sec->shdr.sh_type != SHT_SYMTAB) { + int num_syms; + + switch (sec->shdr.sh_type) { + case SHT_SYMTAB_SHNDX: + sec->xsymtab = malloc(sec->shdr.sh_size); + if (!sec->xsymtab) { + die("malloc of %d bytes for xsymtab failed\n", + sec->shdr.sh_size); + } + if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + sec->shdr.sh_offset, strerror(errno)); + } + if (fread(sec->xsymtab, 1, sec->shdr.sh_size, fp) + != sec->shdr.sh_size) { + die("Cannot read extended symbol table: %s\n", + strerror(errno)); + } + shxsymtabndx = i; + continue; + + case SHT_SYMTAB: + num_syms = sec->shdr.sh_size/sizeof(Elf_Sym); + + sec->symtab = malloc(sec->shdr.sh_size); + if (!sec->symtab) { + die("malloc of %d bytes for symtab failed\n", + sec->shdr.sh_size); + } + if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { + die("Seek to %d failed: %s\n", + sec->shdr.sh_offset, strerror(errno)); + } + if (fread(sec->symtab, 1, sec->shdr.sh_size, fp) + != sec->shdr.sh_size) { + die("Cannot read symbol table: %s\n", + strerror(errno)); + } + for (j = 0; j < num_syms; j++) { + Elf_Sym *sym = &sec->symtab[j]; + + sym->st_name = elf_word_to_cpu(sym->st_name); + sym->st_value = elf_addr_to_cpu(sym->st_value); + sym->st_size = elf_xword_to_cpu(sym->st_size); + sym->st_shndx = elf_half_to_cpu(sym->st_shndx); + } + shsymtabndx = i; + continue; + + default: continue; - } - sec->symtab = malloc(sec->shdr.sh_size); - if (!sec->symtab) { - die("malloc of %d bytes for symtab failed\n", - sec->shdr.sh_size); - } - if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { - die("Seek to %d failed: %s\n", - sec->shdr.sh_offset, strerror(errno)); - } - if (fread(sec->symtab, 1, sec->shdr.sh_size, fp) - != sec->shdr.sh_size) { - die("Cannot read symbol table: %s\n", - strerror(errno)); - } - for (j = 0; j < sec->shdr.sh_size/sizeof(Elf_Sym); j++) { - Elf_Sym *sym = &sec->symtab[j]; - sym->st_name = elf_word_to_cpu(sym->st_name); - sym->st_value = elf_addr_to_cpu(sym->st_value); - sym->st_size = elf_xword_to_cpu(sym->st_size); - sym->st_shndx = elf_half_to_cpu(sym->st_shndx); } } } @@ -759,13 +810,14 @@ static void percpu_init(void) */ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname) { - return (sym->st_shndx == per_cpu_shndx) && + int shndx = sym_index(sym); + + return (shndx == per_cpu_shndx) && strcmp(symname, "__init_begin") && strcmp(symname, "__per_cpu_load") && strncmp(symname, "init_per_cpu_", 13); } - static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { @@ -1088,7 +1140,7 @@ static int do_reloc_info(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, sec_name(sec->shdr.sh_info), rel_type(ELF_R_TYPE(rel->r_info)), symname, - sec_name(sym->st_shndx)); + sec_name(sym_index(sym))); return 0; } From patchwork Thu May 21 16:56:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563497 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 81596739 for ; Thu, 21 May 2020 16:57:53 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id E9B2020826 for ; Thu, 21 May 2020 16:57:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9B2020826 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18838-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 31867 invoked by uid 550); 21 May 2020 16:57:23 -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 Received: (qmail 30670 invoked from network); 21 May 2020 16:57:21 -0000 IronPort-SDR: CrkyXUper19LZTGmGSvSNvqu5Gtrw0SwLxvQtr0eob/czYny2pKC0MK2BiQ0SMWh9+kgDkxhKx lN/VB1ydpiIA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: KgL5+3LiB678fkrVbNIM5wWyFQbpKLy3nifdCghODahi4pxKbFaFjODkotTb+qwuLsUR/0jd9P SfCtZjOQgyxg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094705" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, "H. Peter Anvin" Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi Subject: [PATCH v2 3/9] x86/boot: Allow a "silent" kaslr random byte fetch Date: Thu, 21 May 2020 09:56:34 -0700 Message-Id: <20200521165641.15940-4-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 From: Kees Cook Under earlyprintk, each RNG call produces a debug report line. When shuffling hundreds of functions, this is not useful information (each line is identical and tells us nothing new). Instead, allow for a NULL "purpose" to suppress the debug reporting. Signed-off-by: Kees Cook Signed-off-by: Kristen Carlson Accardi --- arch/x86/lib/kaslr.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/x86/lib/kaslr.c b/arch/x86/lib/kaslr.c index a53665116458..2b3eb8c948a3 100644 --- a/arch/x86/lib/kaslr.c +++ b/arch/x86/lib/kaslr.c @@ -56,11 +56,14 @@ unsigned long kaslr_get_random_long(const char *purpose) unsigned long raw, random = get_boot_seed(); bool use_i8254 = true; - debug_putstr(purpose); - debug_putstr(" KASLR using"); + if (purpose) { + debug_putstr(purpose); + debug_putstr(" KASLR using"); + } if (has_cpuflag(X86_FEATURE_RDRAND)) { - debug_putstr(" RDRAND"); + if (purpose) + debug_putstr(" RDRAND"); if (rdrand_long(&raw)) { random ^= raw; use_i8254 = false; @@ -68,7 +71,8 @@ unsigned long kaslr_get_random_long(const char *purpose) } if (has_cpuflag(X86_FEATURE_TSC)) { - debug_putstr(" RDTSC"); + if (purpose) + debug_putstr(" RDTSC"); raw = rdtsc(); random ^= raw; @@ -76,7 +80,8 @@ unsigned long kaslr_get_random_long(const char *purpose) } if (use_i8254) { - debug_putstr(" i8254"); + if (purpose) + debug_putstr(" i8254"); random ^= i8254(); } @@ -86,7 +91,8 @@ unsigned long kaslr_get_random_long(const char *purpose) : "a" (random), "rm" (mix_const)); random += raw; - debug_putstr("...\n"); + if (purpose) + debug_putstr("...\n"); return random; } From patchwork Thu May 21 16:56:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563499 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 816BE739 for ; Thu, 21 May 2020 16:58:03 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id E8E34207F7 for ; Thu, 21 May 2020 16:58:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8E34207F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18839-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 31939 invoked by uid 550); 21 May 2020 16:57:25 -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 Received: (qmail 31874 invoked from network); 21 May 2020 16:57:23 -0000 IronPort-SDR: ICl9AWQXTosAmAMBbZ1c7AZuO7e4WqWxUiigiRtLvSc6dlHZITZGSftx+ESqmgrosSk2S41kYn Mj8QJeSPD5jg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: Zw0HlnVb2QXZFYtGqKuEgUBIy0YtUb+Hn9kY1fGHVDXq6bxN8QeBgr2Texd/QYSXXUu4PHMexH gZE6NC5W2mFQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094725" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, Masahiro Yamada , Michal Marek , x86@kernel.org, "H. Peter Anvin" Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck , linux-kbuild@vger.kernel.org Subject: [PATCH v2 4/9] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Date: Thu, 21 May 2020 09:56:35 -0700 Message-Id: <20200521165641.15940-5-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 Allow user to select CONFIG_FG_KASLR if dependencies are met. Change the make file to build with -ffunction-sections if CONFIG_FG_KASLR Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck Reviewed-by: Kees Cook --- Makefile | 4 ++++ arch/x86/Kconfig | 13 +++++++++++++ 2 files changed, 17 insertions(+) diff --git a/Makefile b/Makefile index 04f5662ae61a..28e515baa824 100644 --- a/Makefile +++ b/Makefile @@ -862,6 +862,10 @@ ifdef CONFIG_LIVEPATCH KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone) endif +ifdef CONFIG_FG_KASLR +KBUILD_CFLAGS += -ffunction-sections +endif + # arch Makefile may override CC so keep this after arch Makefile is included NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 2d3f963fd6f1..50e83ea57d70 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2183,6 +2183,19 @@ config RANDOMIZE_BASE If unsure, say Y. +config FG_KASLR + bool "Function Granular Kernel Address Space Layout Randomization" + depends on $(cc-option, -ffunction-sections) + depends on RANDOMIZE_BASE && X86_64 + help + This option improves the randomness of the kernel text + over basic Kernel Address Space Layout Randomization (KASLR) + by reordering the kernel text at boot time. This feature + uses information generated at compile time to re-layout the + kernel text section at boot time at function level granularity. + + If unsure, say N. + # Relocation on x86 needs some additional build support config X86_NEED_RELOCS def_bool y From patchwork Thu May 21 16:56:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563501 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E76E4739 for ; Thu, 21 May 2020 16:58:14 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 5B93B2083E for ; Thu, 21 May 2020 16:58:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B93B2083E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18840-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 32068 invoked by uid 550); 21 May 2020 16:57:26 -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 Received: (qmail 31902 invoked from network); 21 May 2020 16:57:24 -0000 IronPort-SDR: MsBlfdLLA5wvX0f4nZYu2GoDN3dofnTZ/eBd5XFiiNTftCkHnnp3KgYAizAaWwES0konGDtEMw ItnZje8guHhg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: 9SfFdTDsfAhfALwEknMLqp3h+TL9Dg7I6I5yl5HH9puVrI4kq6G9/gJCimlW63xkeR0vPBBGXK i9FqhpFLOFAw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094735" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, "H. Peter Anvin" , Arnd Bergmann Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck , linux-arch@vger.kernel.org Subject: [PATCH v2 5/9] x86: Make sure _etext includes function sections Date: Thu, 21 May 2020 09:56:36 -0700 Message-Id: <20200521165641.15940-6-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 When using -ffunction-sections to place each function in it's own text section so it can be randomized at load time, the linker considers these .text.* sections "orphaned sections", and will place them after the first similar section (.text). In order to accurately represent the end of the text section and the orphaned sections, _etext must be moved so that it is after both .text and .text.* The text size must also be calculated to include .text AND .text.* Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck --- arch/x86/kernel/vmlinux.lds.S | 18 +++++++++++++++++- include/asm-generic/vmlinux.lds.h | 2 +- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 1bf7e312361f..044f7528a2f0 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -147,8 +147,24 @@ SECTIONS #endif } :text =0xcccc - /* End of text section, which should occupy whole number of pages */ +#ifdef CONFIG_FG_KASLR + /* + * -ffunction-sections creates .text.* sections, which are considered + * "orphan sections" and added after the first similar section (.text). + * Adding this ALIGN statement causes the address of _etext + * to be below that of all the .text.* orphaned sections + */ + . = ALIGN(PAGE_SIZE); +#endif _etext = .; + + /* + * the size of the .text section is used to calculate the address + * range for orc lookups. If we just use SIZEOF(.text), we will + * miss all the .text.* sections. Calculate the size using _etext + * and _stext and save the value for later. + */ + text_size = _etext - _stext; . = ALIGN(PAGE_SIZE); X86_ALIGN_RODATA_BEGIN diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 71e387a5fe90..f5baee74854c 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -813,7 +813,7 @@ . = ALIGN(4); \ .orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \ orc_lookup = .; \ - . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \ + . += (((text_size + LOOKUP_BLOCK_SIZE - 1) / \ LOOKUP_BLOCK_SIZE) + 1) * 4; \ orc_lookup_end = .; \ } From patchwork Thu May 21 16:56:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563503 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 7728C739 for ; Thu, 21 May 2020 16:58:27 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id B3400207F7 for ; Thu, 21 May 2020 16:58:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B3400207F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18841-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 32121 invoked by uid 550); 21 May 2020 16:57:27 -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 Received: (qmail 31949 invoked from network); 21 May 2020 16:57:25 -0000 IronPort-SDR: x2F5Ib1W1YzJy6ozXXOgdwjes1+IZeZXV+517Lpouk7sP6SEuDHIlWopFIZCpY+kpA8KzU9XVe yyqbHGNRmyUQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: njCmB4gTQK2dXMgbbspYYmVit8ug7SUj50qxN2fydRgyxBuD1iCtuub5OK15JFfabU7bfQ1djv BPXbA74Drzfg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094746" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, "H. Peter Anvin" Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck Subject: [PATCH v2 6/9] x86/tools: Add relative relocs for randomized functions Date: Thu, 21 May 2020 09:56:37 -0700 Message-Id: <20200521165641.15940-7-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 When reordering functions, the relative offsets for relocs that are either in the randomized sections, or refer to the randomized sections will need to be adjusted. Add code to detect whether a reloc satisifies these cases, and if so, add them to the appropriate reloc list. Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck Reviewed-by: Kees Cook --- arch/x86/boot/compressed/Makefile | 7 +++- arch/x86/tools/relocs.c | 55 ++++++++++++++++++++++++------- arch/x86/tools/relocs.h | 4 +-- arch/x86/tools/relocs_common.c | 15 ++++++--- 4 files changed, 62 insertions(+), 19 deletions(-) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 5f7c262bcc99..3a5a004498de 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -117,6 +117,11 @@ $(obj)/vmlinux: $(vmlinux-objs-y) FORCE $(call if_changed,check-and-link-vmlinux) OBJCOPYFLAGS_vmlinux.bin := -R .comment -S + +ifdef CONFIG_FG_KASLR + RELOCS_ARGS += --fg-kaslr +endif + $(obj)/vmlinux.bin: vmlinux FORCE $(call if_changed,objcopy) @@ -124,7 +129,7 @@ targets += $(patsubst $(obj)/%,%,$(vmlinux-objs-y)) vmlinux.bin.all vmlinux.relo CMD_RELOCS = arch/x86/tools/relocs quiet_cmd_relocs = RELOCS $@ - cmd_relocs = $(CMD_RELOCS) $< > $@;$(CMD_RELOCS) --abs-relocs $< + cmd_relocs = $(CMD_RELOCS) $(RELOCS_ARGS) $< > $@;$(CMD_RELOCS) $(RELOCS_ARGS) --abs-relocs $< $(obj)/vmlinux.relocs: vmlinux FORCE $(call if_changed,relocs) diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c index a00dc133f109..bf51ff1854ff 100644 --- a/arch/x86/tools/relocs.c +++ b/arch/x86/tools/relocs.c @@ -42,6 +42,8 @@ struct section { }; static struct section *secs; +static int fg_kaslr; + static const char * const sym_regex_kernel[S_NSYMTYPES] = { /* * Following symbols have been audited. There values are constant and do @@ -351,8 +353,8 @@ static int sym_index(Elf_Sym *sym) return sym->st_shndx; /* calculate offset of sym from head of table. */ - offset = (unsigned long) sym - (unsigned long) symtab; - index = offset/sizeof(*sym); + offset = (unsigned long)sym - (unsigned long)symtab; + index = offset / sizeof(*sym); return elf32_to_cpu(xsymtab[index]); } @@ -500,22 +502,22 @@ static void read_symtabs(FILE *fp) sec->xsymtab = malloc(sec->shdr.sh_size); if (!sec->xsymtab) { die("malloc of %d bytes for xsymtab failed\n", - sec->shdr.sh_size); + sec->shdr.sh_size); } if (fseek(fp, sec->shdr.sh_offset, SEEK_SET) < 0) { die("Seek to %d failed: %s\n", - sec->shdr.sh_offset, strerror(errno)); + sec->shdr.sh_offset, strerror(errno)); } if (fread(sec->xsymtab, 1, sec->shdr.sh_size, fp) - != sec->shdr.sh_size) { + != sec->shdr.sh_size) { die("Cannot read extended symbol table: %s\n", - strerror(errno)); + strerror(errno)); } shxsymtabndx = i; continue; case SHT_SYMTAB: - num_syms = sec->shdr.sh_size/sizeof(Elf_Sym); + num_syms = sec->shdr.sh_size / sizeof(Elf_Sym); sec->symtab = malloc(sec->shdr.sh_size); if (!sec->symtab) { @@ -818,6 +820,32 @@ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname) strncmp(symname, "init_per_cpu_", 13); } +static int is_function_section(struct section *sec) +{ + const char *name; + + if (!fg_kaslr) + return 0; + + name = sec_name(sec->shdr.sh_info); + + return(!strncmp(name, ".text.", 6)); +} + +static int is_randomized_sym(ElfW(Sym) *sym) +{ + const char *name; + + if (!fg_kaslr) + return 0; + + if (sym->st_shndx > shnum) + return 0; + + name = sec_name(sym_index(sym)); + return(!strncmp(name, ".text.", 6)); +} + static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, const char *symname) { @@ -842,13 +870,17 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym, case R_X86_64_PC32: case R_X86_64_PLT32: /* - * PC relative relocations don't need to be adjusted unless - * referencing a percpu symbol. + * we need to keep pc relative relocations for sections which + * might be randomized, and for the percpu section. + * We also need to keep relocations for any offset which might + * reference an address in a section which has been randomized. * * NB: R_X86_64_PLT32 can be treated as R_X86_64_PC32. */ - if (is_percpu_sym(sym, symname)) + if (is_function_section(sec) || is_randomized_sym(sym) || + is_percpu_sym(sym, symname)) add_reloc(&relocs32neg, offset); + break; case R_X86_64_PC64: @@ -1158,8 +1190,9 @@ static void print_reloc_info(void) void process(FILE *fp, int use_real_mode, int as_text, int show_absolute_syms, int show_absolute_relocs, - int show_reloc_info) + int show_reloc_info, int fgkaslr) { + fg_kaslr = fgkaslr; regex_init(use_real_mode); read_ehdr(fp); read_shdrs(fp); diff --git a/arch/x86/tools/relocs.h b/arch/x86/tools/relocs.h index 43c83c0fd22c..05504052c846 100644 --- a/arch/x86/tools/relocs.h +++ b/arch/x86/tools/relocs.h @@ -31,8 +31,8 @@ enum symtype { void process_32(FILE *fp, int use_real_mode, int as_text, int show_absolute_syms, int show_absolute_relocs, - int show_reloc_info); + int show_reloc_info, int fg_kaslr); void process_64(FILE *fp, int use_real_mode, int as_text, int show_absolute_syms, int show_absolute_relocs, - int show_reloc_info); + int show_reloc_info, int fg_kaslr); #endif /* RELOCS_H */ diff --git a/arch/x86/tools/relocs_common.c b/arch/x86/tools/relocs_common.c index 6634352a20bc..1407db72367a 100644 --- a/arch/x86/tools/relocs_common.c +++ b/arch/x86/tools/relocs_common.c @@ -12,14 +12,14 @@ void die(char *fmt, ...) static void usage(void) { - die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode]" \ - " vmlinux\n"); + die("relocs [--abs-syms|--abs-relocs|--reloc-info|--text|--realmode|" \ + "--fg-kaslr] vmlinux\n"); } int main(int argc, char **argv) { int show_absolute_syms, show_absolute_relocs, show_reloc_info; - int as_text, use_real_mode; + int as_text, use_real_mode, fg_kaslr; const char *fname; FILE *fp; int i; @@ -30,6 +30,7 @@ int main(int argc, char **argv) show_reloc_info = 0; as_text = 0; use_real_mode = 0; + fg_kaslr = 0; fname = NULL; for (i = 1; i < argc; i++) { char *arg = argv[i]; @@ -54,6 +55,10 @@ int main(int argc, char **argv) use_real_mode = 1; continue; } + if (strcmp(arg, "--fg-kaslr") == 0) { + fg_kaslr = 1; + continue; + } } else if (!fname) { fname = arg; @@ -75,11 +80,11 @@ int main(int argc, char **argv) if (e_ident[EI_CLASS] == ELFCLASS64) process_64(fp, use_real_mode, as_text, show_absolute_syms, show_absolute_relocs, - show_reloc_info); + show_reloc_info, fg_kaslr); else process_32(fp, use_real_mode, as_text, show_absolute_syms, show_absolute_relocs, - show_reloc_info); + show_reloc_info, fg_kaslr); fclose(fp); return 0; } From patchwork Thu May 21 16:56:38 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563505 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8A8DA912 for ; Thu, 21 May 2020 16:58:41 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 4909C207F7 for ; Thu, 21 May 2020 16:58:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4909C207F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18842-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 1677 invoked by uid 550); 21 May 2020 16:57:43 -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 Received: (qmail 1565 invoked from network); 21 May 2020 16:57:42 -0000 IronPort-SDR: 7lar1xbe/HMi/Ijik3RhHG+SPad9xipBl+4iigZWeuMvMFBsxpiXL5LBeHB7zCMBn+fLZ1Jue6 GbpFR8VWRj1Q== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: oIIsplNzl/tmzT9GO7STmR/YnAM0/4go22Zm8D/7z7bt3L+IuJX0B47DPGf7M7/I2j82kG8GAO lyL8Tuef+SYA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094772" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, Jonathan Corbet , x86@kernel.org, "H. Peter Anvin" Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck , linux-doc@vger.kernel.org Subject: [PATCH v2 7/9] x86: Add support for function granular KASLR Date: Thu, 21 May 2020 09:56:38 -0700 Message-Id: <20200521165641.15940-8-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 At boot time, find all the function sections that have separate .text sections, shuffle them, and then copy them to new locations. Adjust any relocations accordingly. Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck --- Documentation/security/fgkaslr.rst | 155 +++++ Documentation/security/index.rst | 1 + arch/x86/boot/compressed/Makefile | 3 + arch/x86/boot/compressed/fgkaslr.c | 823 +++++++++++++++++++++++ arch/x86/boot/compressed/kaslr.c | 4 - arch/x86/boot/compressed/misc.c | 109 ++- arch/x86/boot/compressed/misc.h | 34 + arch/x86/boot/compressed/utils.c | 12 + arch/x86/boot/compressed/vmlinux.symbols | 17 + arch/x86/include/asm/boot.h | 15 +- include/uapi/linux/elf.h | 1 + 11 files changed, 1159 insertions(+), 15 deletions(-) create mode 100644 Documentation/security/fgkaslr.rst create mode 100644 arch/x86/boot/compressed/fgkaslr.c create mode 100644 arch/x86/boot/compressed/utils.c create mode 100644 arch/x86/boot/compressed/vmlinux.symbols diff --git a/Documentation/security/fgkaslr.rst b/Documentation/security/fgkaslr.rst new file mode 100644 index 000000000000..94939c62c50d --- /dev/null +++ b/Documentation/security/fgkaslr.rst @@ -0,0 +1,155 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================================================== +Function Granular Kernel Address Space Layout Randomization (fgkaslr) +===================================================================== + +:Date: 6 April 2020 +:Author: Kristen Accardi + +Kernel Address Space Layout Randomization (KASLR) was merged into the kernel +with the objective of increasing the difficulty of code reuse attacks. Code +reuse attacks reused existing code snippets to get around existing memory +protections. They exploit software bugs which expose addresses of useful code +snippets to control the flow of execution for their own nefarious purposes. +KASLR as it was originally implemented moves the entire kernel code text as a +unit at boot time in order to make addresses less predictable. The order of the +code within the segment is unchanged - only the base address is shifted. There +are a few shortcomings to this algorithm. + +1. Low Entropy - there are only so many locations the kernel can fit in. This + means an attacker could guess without too much trouble. +2. Knowledge of a single address can reveal the offset of the base address, + exposing all other locations for a published/known kernel image. +3. Info leaks abound. + +Finer grained ASLR has been proposed as a way to make ASLR more resistant +to info leaks. It is not a new concept at all, and there are many variations +possible. Function reordering is an implementation of finer grained ASLR +which randomizes the layout of an address space on a function level +granularity. The term "fgkaslr" is used in this document to refer to the +technique of function reordering when used with KASLR, as well as finer grained +KASLR in general. + +The objective of this patch set is to improve a technology that is already +merged into the kernel (KASLR). This code will not prevent all code reuse +attacks, and should be considered as one of several tools that can be used. + +Implementation Details +====================== + +The over-arching objective of the fgkaslr implementation is incremental +improvement over the existing KASLR algorithm. It is designed to work with +the existing solution, and there are two main area where code changes occur: +Build time, and Load time. + +Build time +---------- + +GCC has had an option to place functions into individual .text sections +for many years now (-ffunction-sections). This option is used to implement +function reordering at load time. The final compiled vmlinux retains all the +section headers, which can be used to help find the address ranges of each +function. Using this information and an expanded table of relocation addresses, +individual text sections can be shuffled immediately after decompression. +Some data tables inside the kernel that have assumptions about order +require sorting after the update. In order to modify these tables, +a few key symbols from the objcopy symbol stripping process are preserved +for use after shuffling the text segments. + +Load time +--------- + +The boot kernel was modified to parse the vmlinux elf file after +decompression to check for symbols for modifying data tables, and to +look for any .text.* sections to randomize. The sections are then shuffled, +and tables are updated or resorted. The existing code which updated relocation +addresses was modified to account for not just a fixed delta from the load +address, but the offset that the function section was moved to. This requires +inspection of each address to see if it was impacted by a randomization. + +In order to hide the new layout, symbols reported through /proc/kallsyms will +be sorted by name alphabetically rather than by address. + +Performance Impact +================== + +There are two areas where function reordering can impact performance: boot +time latency, and run time performance. + +Boot time latency +----------------- + +This implementation of finer grained KASLR impacts the boot time of the kernel +in several places. It requires additional parsing of the kernel ELF file to +obtain the section headers of the sections to be randomized. It calls the +random number generator for each section to be randomized to determine that +section's new memory location. It copies the decompressed kernel into a new +area of memory to avoid corruption when laying out the newly randomized +sections. It increases the number of relocations the kernel has to perform at +boot time vs. standard KASLR, and it also requires a lookup on each address +that needs to be relocated to see if it was in a randomized section and needs +to be adjusted by a new offset. Finally, it re-sorts a few data tables that +are required to be sorted by address. + +Booting a test VM on a modern, well appointed system showed an increase in +latency of approximately 1 second. + +Run time +-------- + +The performance impact at run-time of function reordering varies by workload. +Randomly reordering the functions will cause an increase in cache misses +for some workloads. Some workloads perform significantly worse under FGKASLR, +while others stay the same or even improve. In general, it will depend on the +code flow whether or not finer grained KASLR will impact a workload, and how +the underlying code was designed. Because the layout changes per boot, each +time a system is rebooted the performance of a workload may change. + +Image Size +========== + +fgkaslr increases the size of the kernel binary due to the extra section +headers that are included, as well as the extra relocations that need to +be added. You can expect fgkaslr to increase the size of the resulting +vmlinux by about 3%, and the compressed image (bzImage) by 15%. + +Memory Usage +============ + +fgkaslr increases the amount of heap that is required at boot time, +although this extra memory is released when the kernel has finished +decompression. As a result, it may not be appropriate to use this feature +on systems without much memory. + +Building +======== + +To enable fine grained KASLR, you need to have the following config options +set (including all the ones you would use to build normal KASLR) + +``CONFIG_FG_KASLR=y`` + +fgkaslr for the kernel is only supported for the X86_64 architecture. + +Modules +======= + +Modules are randomized similarly to the rest of the kernel by shuffling +the sections at load time prior to moving them into memory. The module must +also have been build with the -ffunction-sections compiler option. + +Although fgkaslr for the kernel is only supported for the X86_64 architecture, +it is possible to use fgkaslr with modules on other architectures. To enable +this feature, select the following config option: + +``CONFIG_MODULE_FG_KASLR`` + +This option is selected automatically for X86_64 when CONFIG_FG_KASLR is set. + +Disabling +========= + +Disabling normal kaslr using the nokaslr command line option also disables +fgkaslr. In addtion, it is possible to disable fgkaslr separately by booting +with fgkaslr=off on the commandline. diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst index fc503dd689a7..5e370c409ad2 100644 --- a/Documentation/security/index.rst +++ b/Documentation/security/index.rst @@ -7,6 +7,7 @@ Security Documentation credentials IMA-templates + fgkaslr keys/index lsm lsm-development diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 3a5a004498de..0ad5a31f1f0a 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -80,10 +80,12 @@ vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/kernel_info.o $(obj)/head_$(BITS).o vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o +vmlinux-objs-$(CONFIG_FG_KASLR) += $(obj)/utils.o ifdef CONFIG_X86_64 vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr_64.o vmlinux-objs-y += $(obj)/mem_encrypt.o vmlinux-objs-y += $(obj)/pgtable_64.o + vmlinux-objs-$(CONFIG_FG_KASLR) += $(obj)/fgkaslr.o endif vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o @@ -120,6 +122,7 @@ OBJCOPYFLAGS_vmlinux.bin := -R .comment -S ifdef CONFIG_FG_KASLR RELOCS_ARGS += --fg-kaslr + OBJCOPYFLAGS += --keep-symbols=$(srctree)/$(src)/vmlinux.symbols endif $(obj)/vmlinux.bin: vmlinux FORCE diff --git a/arch/x86/boot/compressed/fgkaslr.c b/arch/x86/boot/compressed/fgkaslr.c new file mode 100644 index 000000000000..451e807de276 --- /dev/null +++ b/arch/x86/boot/compressed/fgkaslr.c @@ -0,0 +1,823 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fgkaslr.c + * + * This contains the routines needed to reorder the kernel text section + * at boot time. + */ +#include "misc.h" +#include "error.h" +#include "pgtable.h" +#include "../string.h" +#include "../voffset.h" +#include +#include +#include "../../include/asm/extable.h" +#include "../../include/asm/orc_types.h" + +/* + * Longest parameter of 'fgkaslr=' is 'off' right now, plus an extra '\0' + * for termination. + */ +#define MAX_FGKASLR_ARG_LENGTH 4 +int nofgkaslr; + +/* + * Use normal definitions of mem*() from string.c. There are already + * included header files which expect a definition of memset() and by + * the time we define memset macro, it is too late. + */ +#undef memcpy +#undef memset +#define memzero(s, n) memset((s), 0, (n)) +#define memmove memmove + +void *memmove(void *dest, const void *src, size_t n); + +static unsigned long percpu_start; +static unsigned long percpu_end; + +static long kallsyms_names; +static long kallsyms_offsets; +static long kallsyms_num_syms; +static long kallsyms_relative_base; +static long kallsyms_markers; +static long __start___ex_table_addr; +static long __stop___ex_table_addr; +static long _stext; +static long _etext; +static long _sinittext; +static long _einittext; +static long __start_orc_unwind_ip; +static long __stop_orc_unwind_ip; +static long __start_orc_unwind; + +/* addresses in mapped address space */ +static int *base; +static u8 *names; +static unsigned long relative_base; +static unsigned int *markers_addr; + +struct kallsyms_name { + u8 len; + u8 indecis[256]; +}; + +struct kallsyms_name *names_table; + +struct orc_entry *cur_orc_table; +int *cur_orc_ip_table; + +/* + * This is an array of pointers to sections headers for randomized sections + */ +Elf64_Shdr **sections; + +/* + * This is an array of all section headers, randomized or otherwise. + */ +Elf64_Shdr *sechdrs; + +/* + * The number of elements in the randomized section header array (sections) + */ +int sections_size; + +static bool is_text(long addr) +{ + if ((addr >= _stext && addr < _etext) || + (addr >= _sinittext && addr < _einittext)) + return true; + return false; +} + +bool is_percpu_addr(long pc, long offset) +{ + unsigned long ptr; + long address; + + address = pc + offset + 4; + + ptr = (unsigned long)address; + + if (ptr >= percpu_start && ptr < percpu_end) + return true; + + return false; +} + +static int cmp_section_addr(const void *a, const void *b) +{ + unsigned long ptr = (unsigned long)a; + Elf64_Shdr *s = *(Elf64_Shdr **)b; + unsigned long end = s->sh_addr + s->sh_size; + + if (ptr >= s->sh_addr && ptr < end) + return 0; + + if (ptr < s->sh_addr) + return -1; + + return 1; +} + +/* + * Discover if the address is in a randomized section and if so, adjust + * by the saved offset. + */ +Elf64_Shdr *adjust_address(long *address) +{ + Elf64_Shdr **s; + Elf64_Shdr *shdr; + + if (nofgkaslr) + return NULL; + + s = bsearch((const void *)*address, sections, sections_size, sizeof(*s), + cmp_section_addr); + if (s) { + shdr = *s; + *address += shdr->sh_offset; + return shdr; + } + + return NULL; +} + +void adjust_relative_offset(long pc, long *value, Elf64_Shdr *section) +{ + Elf64_Shdr *s; + long address; + + if (nofgkaslr) + return; + + /* + * sometimes we are updating a relative offset that would + * normally be relative to the next instruction (such as a call). + * In this case to calculate the target, you need to add 32bits to + * the pc to get the next instruction value. However, sometimes + * targets are just data that was stored in a table such as ksymtab + * or cpu alternatives. In this case our target is not relative to + * the next instruction. + */ + + /* + * Calculate the address that this offset would call. + */ + if (!is_text(pc)) + address = pc + *value; + else + address = pc + *value + 4; + + /* + * if the address is in section that was randomized, + * we need to adjust the offset. + */ + s = adjust_address(&address); + if (s) + *value += s->sh_offset; + + /* + * If the PC that this offset was calculated for was in a section + * that has been randomized, the value needs to be adjusted by the + * same amount as the randomized section was adjusted from it's original + * location. + */ + if (section) + *value -= section->sh_offset; +} + +static void kallsyms_swp(void *a, void *b, int size) +{ + int idx1, idx2; + int temp; + struct kallsyms_name name_a; + + /* determine our index into the array */ + idx1 = (int *)a - base; + idx2 = (int *)b - base; + temp = base[idx1]; + base[idx1] = base[idx2]; + base[idx2] = temp; + + /* also swap the names table */ + memcpy(&name_a, &names_table[idx1], sizeof(name_a)); + memcpy(&names_table[idx1], &names_table[idx2], + sizeof(struct kallsyms_name)); + memcpy(&names_table[idx2], &name_a, sizeof(struct kallsyms_name)); +} + +static int kallsyms_cmp(const void *a, const void *b) +{ + int addr_a, addr_b; + unsigned long uaddr_a, uaddr_b; + + addr_a = *(int *)a; + addr_b = *(int *)b; + + if (addr_a >= 0) + uaddr_a = addr_a; + if (addr_b >= 0) + uaddr_b = addr_b; + + if (addr_a < 0) + uaddr_a = relative_base - 1 - addr_a; + if (addr_b < 0) + uaddr_b = relative_base - 1 - addr_b; + + if (uaddr_b > uaddr_a) + return -1; + + return 0; +} + +static void deal_with_names(int num_syms) +{ + int num_bytes; + int i, j; + int offset; + + /* we should have num_syms kallsyms_name entries */ + num_bytes = num_syms * sizeof(*names_table); + names_table = malloc(num_syms * sizeof(*names_table)); + if (!names_table) { + debug_putstr("\nbytes requested: "); + debug_puthex(num_bytes); + error("\nunable to allocate space for names table\n"); + } + + /* read all the names entries */ + offset = 0; + for (i = 0; i < num_syms; i++) { + names_table[i].len = names[offset]; + offset++; + for (j = 0; j < names_table[i].len; j++) { + names_table[i].indecis[j] = names[offset]; + offset++; + } + } +} + +static void write_sorted_names(int num_syms) +{ + int i, j; + int offset = 0; + unsigned int *markers; + + /* + * we are going to need to regenerate the markers table, which is a + * table of offsets into the compressed stream every 256 symbols. + * this code copied almost directly from scripts/kallsyms.c + */ + markers = malloc(sizeof(unsigned int) * ((num_syms + 255) / 256)); + if (!markers) { + debug_putstr("\nfailed to allocate heap space of "); + debug_puthex(((num_syms + 255) / 256)); + debug_putstr(" bytes\n"); + error("Unable to allocate space for markers table"); + } + + for (i = 0; i < num_syms; i++) { + if ((i & 0xFF) == 0) + markers[i >> 8] = offset; + + names[offset] = (u8)names_table[i].len; + offset++; + for (j = 0; j < names_table[i].len; j++) { + names[offset] = (u8)names_table[i].indecis[j]; + offset++; + } + } + + /* write new markers table over old one */ + for (i = 0; i < ((num_syms + 255) >> 8); i++) + markers_addr[i] = markers[i]; + + free(markers); + free(names_table); +} + +static void sort_kallsyms(unsigned long map) +{ + int num_syms; + int i; + + debug_putstr("\nRe-sorting kallsyms...\n"); + + num_syms = *(int *)(kallsyms_num_syms + map); + base = (int *)(kallsyms_offsets + map); + relative_base = *(unsigned long *)(kallsyms_relative_base + map); + markers_addr = (unsigned int *)(kallsyms_markers + map); + names = (u8 *)(kallsyms_names + map); + + /* + * the kallsyms table was generated prior to any randomization. + * it is a bunch of offsets from "relative base". In order for + * us to check if a symbol has an address that was in a randomized + * section, we need to reconstruct the address to it's original + * value prior to handle_relocations. + */ + for (i = 0; i < num_syms; i++) { + unsigned long addr; + int new_base; + + /* + * according to kernel/kallsyms.c, positive offsets are absolute + * values and negative offsets are relative to the base. + */ + if (base[i] >= 0) + addr = base[i]; + else + addr = relative_base - 1 - base[i]; + + if (adjust_address(&addr)) { + /* here we need to recalcuate the offset */ + new_base = relative_base - 1 - addr; + base[i] = new_base; + } + } + + /* + * here we need to read in all the kallsyms_names info + * so that we can regenerate it. + */ + deal_with_names(num_syms); + + sort(base, num_syms, sizeof(int), kallsyms_cmp, kallsyms_swp); + + /* write the newly sorted names table over the old one */ + write_sorted_names(num_syms); +} + +#include "../../../../lib/extable.c" + +static inline unsigned long +ex_fixup_handler(const struct exception_table_entry *x) +{ + return ((unsigned long)&x->handler + x->handler); +} + +static inline unsigned long +ex_fixup_addr(const struct exception_table_entry *x) +{ + return ((unsigned long)&x->fixup + x->fixup); +} + +static void update_ex_table(unsigned long map) +{ + struct exception_table_entry *start_ex_table = + (struct exception_table_entry *)(__start___ex_table_addr + map); + struct exception_table_entry *stop_ex_table = + (struct exception_table_entry *)(__stop___ex_table_addr + map); + int num_entries = + (__stop___ex_table_addr - __start___ex_table_addr) / + sizeof(struct exception_table_entry); + int i; + + debug_putstr("\nUpdating exception table..."); + for (i = 0; i < num_entries; i++) { + unsigned long insn = ex_to_insn(&start_ex_table[i]); + unsigned long fixup = ex_fixup_addr(&start_ex_table[i]); + unsigned long handler = ex_fixup_handler(&start_ex_table[i]); + unsigned long addr; + Elf64_Shdr *s; + + /* check each address to see if it needs adjusting */ + addr = insn - map; + s = adjust_address(&addr); + if (s) + start_ex_table[i].insn += s->sh_offset; + + addr = fixup - map; + s = adjust_address(&addr); + if (s) + start_ex_table[i].fixup += s->sh_offset; + + addr = handler - map; + s = adjust_address(&addr); + if (s) + start_ex_table[i].handler += s->sh_offset; + } +} + +static void sort_ex_table(unsigned long map) +{ + struct exception_table_entry *start_ex_table = + (struct exception_table_entry *)(__start___ex_table_addr + map); + struct exception_table_entry *stop_ex_table = + (struct exception_table_entry *)(__stop___ex_table_addr + map); + + debug_putstr("\nRe-sorting exception table..."); + + sort_extable(start_ex_table, stop_ex_table); +} + +static inline unsigned long orc_ip(const int *ip) +{ + return (unsigned long)ip + *ip; +} + +static void orc_sort_swap(void *_a, void *_b, int size) +{ + struct orc_entry *orc_a, *orc_b; + struct orc_entry orc_tmp; + int *a = _a, *b = _b, tmp; + int delta = _b - _a; + + /* Swap the .orc_unwind_ip entries: */ + tmp = *a; + *a = *b + delta; + *b = tmp - delta; + + /* Swap the corresponding .orc_unwind entries: */ + orc_a = cur_orc_table + (a - cur_orc_ip_table); + orc_b = cur_orc_table + (b - cur_orc_ip_table); + orc_tmp = *orc_a; + *orc_a = *orc_b; + *orc_b = orc_tmp; +} + +static int orc_sort_cmp(const void *_a, const void *_b) +{ + struct orc_entry *orc_a; + const int *a = _a, *b = _b; + unsigned long a_val = orc_ip(a); + unsigned long b_val = orc_ip(b); + + if (a_val > b_val) + return 1; + if (a_val < b_val) + return -1; + + /* + * The "weak" section terminator entries need to always be on the left + * to ensure the lookup code skips them in favor of real entries. + * These terminator entries exist to handle any gaps created by + * whitelisted .o files which didn't get objtool generation. + */ + orc_a = cur_orc_table + (a - cur_orc_ip_table); + return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1; +} + +static void sort_orc_table(unsigned long map) +{ + int num_entries = + (__stop_orc_unwind_ip - __start_orc_unwind_ip) / sizeof(int); + + cur_orc_ip_table = (int *)(__start_orc_unwind_ip + map); + cur_orc_table = (struct orc_entry *)(__start_orc_unwind + map); + + debug_putstr("\nRe-sorting orc tables...\n"); + sort(cur_orc_ip_table, num_entries, sizeof(int), orc_sort_cmp, + orc_sort_swap); +} + +void post_relocations_cleanup(unsigned long map) +{ + if (!nofgkaslr) { + update_ex_table(map); + sort_ex_table(map); + sort_orc_table(map); + } + + /* + * maybe one day free will do something. So, we "free" this memory + * in either case + */ + free(sections); + free(sechdrs); +} + +void pre_relocations_cleanup(unsigned long map) +{ + if (nofgkaslr) + return; + + sort_kallsyms(map); +} + +static void shuffle_sections(int *list, int size) +{ + int i; + unsigned long j; + int temp; + + for (i = size - 1; i > 0; i--) { + j = kaslr_get_random_long(NULL) % (i + 1); + + temp = list[i]; + list[i] = list[j]; + list[j] = temp; + } +} + +static void move_text(int num_sections, char *secstrings, Elf64_Shdr *text, + void *source, void *dest, Elf64_Phdr *phdr) +{ + unsigned long adjusted_addr; + int copy_bytes; + void *stash; + Elf64_Shdr **sorted_sections; + int *index_list; + int i, j; + + memmove(dest, source + text->sh_offset, text->sh_size); + copy_bytes = text->sh_size; + dest += text->sh_size; + adjusted_addr = text->sh_addr + text->sh_size; + + /* + * we leave the sections sorted in their original order + * by s->sh_addr, but shuffle the indexes in a random + * order for copying. + */ + index_list = malloc(sizeof(int) * num_sections); + if (!index_list) + error("Failed to allocate space for index list"); + + for (i = 0; i < num_sections; i++) + index_list[i] = i; + + shuffle_sections(index_list, num_sections); + + /* + * to avoid overwriting earlier sections before they can get + * copied to dest, stash everything into a buffer first. + * this will cause our source address to be off by + * phdr->p_offset though, so we'll adjust s->sh_offset below. + * + * TBD: ideally we'd simply decompress higher up so that our + * copy wasn't in danger of overwriting anything important. + */ + stash = malloc(phdr->p_filesz); + if (!stash) + error("Failed to allocate space for text stash"); + + memcpy(stash, source + phdr->p_offset, phdr->p_filesz); + + /* now we'd walk through the sections. */ + for (j = 0; j < num_sections; j++) { + unsigned long aligned_addr; + Elf64_Shdr *s; + const char *sname; + void *src; + int pad_bytes; + + s = sections[index_list[j]]; + + sname = secstrings + s->sh_name; + + /* align addr for this section */ + aligned_addr = ALIGN(adjusted_addr, s->sh_addralign); + + /* + * copy out of stash, so adjust offset + */ + src = stash + s->sh_offset - phdr->p_offset; + + /* + * Fill any space between sections with int3 + */ + pad_bytes = aligned_addr - adjusted_addr; + memset(dest, 0xcc, pad_bytes); + + dest = (void *)ALIGN((unsigned long)dest, s->sh_addralign); + + memmove(dest, src, s->sh_size); + + dest += s->sh_size; + copy_bytes += s->sh_size + pad_bytes; + adjusted_addr = aligned_addr + s->sh_size; + + /* we can blow away sh_offset for our own uses */ + s->sh_offset = aligned_addr - s->sh_addr; + } + + free(index_list); + + /* + * move remainder of text segment. Ok to just use original source + * here since this area is untouched. + */ + memmove(dest, source + text->sh_offset + copy_bytes, + phdr->p_filesz - copy_bytes); + free(stash); +} + +#define GET_SYM(name) \ + do { \ + if (!name) { \ + if (strcmp(#name, strtab + sym->st_name) == 0) {\ + name = sym->st_value; \ + continue; \ + } \ + } \ + } while (0) + +static void parse_symtab(Elf64_Sym *symtab, char *strtab, long num_syms) +{ + Elf64_Sym *sym; + + if (!symtab || !strtab) + return; + + debug_putstr("\nLooking for symbols... "); + + /* + * walk through the symbol table looking for the symbols + * that we care about. + */ + for (sym = symtab; --num_syms >= 0; sym++) { + if (!sym->st_name) + continue; + + GET_SYM(kallsyms_num_syms); + GET_SYM(kallsyms_offsets); + GET_SYM(kallsyms_relative_base); + GET_SYM(kallsyms_names); + GET_SYM(kallsyms_markers); + GET_SYM(_stext); + GET_SYM(_etext); + GET_SYM(_sinittext); + GET_SYM(_einittext); + GET_SYM(__start_orc_unwind_ip); + GET_SYM(__stop_orc_unwind_ip); + GET_SYM(__start_orc_unwind); + + /* + * the GET_SYM macro can't be used here because these have + * to be renamed due to the inclusion of lib/extable.c + */ + if (!__start___ex_table_addr) { + if (strcmp("__start___ex_table", + strtab + sym->st_name) == 0) { + __start___ex_table_addr = sym->st_value; + continue; + } + } + + if (!__stop___ex_table_addr) { + if (strcmp("__stop___ex_table", + strtab + sym->st_name) == 0) { + __stop___ex_table_addr = sym->st_value; + continue; + } + } + } +} + +void parse_sections_headers(void *output, Elf64_Ehdr *ehdr, Elf64_Phdr *phdrs) +{ + Elf64_Phdr *phdr; + Elf64_Shdr *s; + Elf64_Shdr *text = NULL; + Elf64_Shdr *percpu = NULL; + char *secstrings; + const char *sname; + int num_sections = 0; + Elf64_Sym *symtab = NULL; + char *strtab = NULL; + long num_syms = 0; + void *dest; + int i; + char arg[MAX_FGKASLR_ARG_LENGTH]; + Elf64_Shdr shdr; + unsigned long shnum; + unsigned int shstrndx; + + debug_putstr("\nParsing ELF section headers... "); + + /* + * Even though fgkaslr may have been disabled, we still + * need to parse through the section headers to get the + * start and end of the percpu section. This is because + * if we were built with CONFIG_FG_KASLR, there are more + * relative relocations present in vmlinux.relocs than + * just the percpu, and only the percpu relocs need to be + * adjusted when using just normal base address kaslr. + */ + if (cmdline_find_option("fgkaslr", arg, sizeof(arg)) == 3 && + !strncmp(arg, "off", 3)) { + warn("FG_KASLR disabled on cmdline."); + nofgkaslr = 1; + } + + /* read the first section header */ + shnum = ehdr->e_shnum; + shstrndx = ehdr->e_shstrndx; + if (shnum == SHN_UNDEF || shstrndx == SHN_XINDEX) { + memcpy(&shdr, output + ehdr->e_shoff, sizeof(shdr)); + if (shnum == SHN_UNDEF) + shnum = shdr.sh_size; + if (shstrndx == SHN_XINDEX) + shstrndx = shdr.sh_link; + } + + /* we are going to need to allocate space for the section headers */ + sechdrs = malloc(sizeof(*sechdrs) * shnum); + if (!sechdrs) + error("Failed to allocate space for shdrs"); + + sections = malloc(sizeof(*sections) * shnum); + if (!sections) + error("Failed to allocate space for section pointers"); + + memcpy(sechdrs, output + ehdr->e_shoff, + sizeof(*sechdrs) * shnum); + + /* we need to allocate space for the section string table */ + s = &sechdrs[shstrndx]; + + secstrings = malloc(s->sh_size); + if (!secstrings) + error("Failed to allocate space for shstr"); + + memcpy(secstrings, output + s->sh_offset, s->sh_size); + + /* + * now we need to walk through the section headers and collect the + * sizes of the .text sections to be randomized. + */ + for (i = 0; i < shnum; i++) { + s = &sechdrs[i]; + sname = secstrings + s->sh_name; + + if (s->sh_type == SHT_SYMTAB) { + /* only one symtab per image */ + symtab = malloc(s->sh_size); + if (!symtab) + error("Failed to allocate space for symtab"); + + memcpy(symtab, output + s->sh_offset, s->sh_size); + num_syms = s->sh_size / sizeof(*symtab); + continue; + } + + if (s->sh_type == SHT_STRTAB && i != ehdr->e_shstrndx) { + strtab = malloc(s->sh_size); + if (!strtab) + error("Failed to allocate space for strtab"); + + memcpy(strtab, output + s->sh_offset, s->sh_size); + } + + if (!strcmp(sname, ".text")) { + text = s; + continue; + } + + if (!strcmp(sname, ".data..percpu")) { + /* get start addr for later */ + percpu = s; + } + + if (!(s->sh_flags & SHF_ALLOC) || + !(s->sh_flags & SHF_EXECINSTR) || + !(strstarts(sname, ".text"))) + continue; + + sections[num_sections] = s; + + num_sections++; + } + sections[num_sections] = NULL; + sections_size = num_sections; + + parse_symtab(symtab, strtab, num_syms); + + for (i = 0; i < ehdr->e_phnum; i++) { + phdr = &phdrs[i]; + + switch (phdr->p_type) { + case PT_LOAD: + if ((phdr->p_align % 0x200000) != 0) + error("Alignment of LOAD segment isn't multiple of 2MB"); + dest = output; + dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR); + if (!nofgkaslr && + (text && phdr->p_offset == text->sh_offset)) { + move_text(num_sections, secstrings, text, + output, dest, phdr); + } else { + if (percpu && + phdr->p_offset == percpu->sh_offset) { + percpu_start = percpu->sh_addr; + percpu_end = percpu_start + + phdr->p_filesz; + } + memmove(dest, output + phdr->p_offset, + phdr->p_filesz); + } + break; + default: /* Ignore other PT_* */ + break; + } + } + + /* we need to keep the section info to redo relocs */ + free(secstrings); + + free(phdrs); +} + diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index d7408af55738..6f596bd5b6e5 100644 --- a/arch/x86/boot/compressed/kaslr.c +++ b/arch/x86/boot/compressed/kaslr.c @@ -39,10 +39,6 @@ #include #include -/* Macros used by the included decompressor code below. */ -#define STATIC -#include - #ifdef CONFIG_X86_5LEVEL unsigned int __pgtable_l5_enabled; unsigned int pgdir_shift __ro_after_init = 39; diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 9652d5c2afda..5f08922fd12a 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -26,9 +26,6 @@ * it is not safe to place pointers in static structures. */ -/* Macros used by the included decompressor code below. */ -#define STATIC static - /* * Use normal definitions of mem*() from string.c. There are already * included header files which expect a definition of memset() and by @@ -49,6 +46,10 @@ struct boot_params *boot_params; memptr free_mem_ptr; memptr free_mem_end_ptr; +#ifdef CONFIG_FG_KASLR +unsigned long malloc_ptr; +int malloc_count; +#endif static char *vidmem; static int vidport; @@ -203,10 +204,21 @@ static void handle_relocations(void *output, unsigned long output_len, if (IS_ENABLED(CONFIG_X86_64)) delta = virt_addr - LOAD_PHYSICAL_ADDR; - if (!delta) { - debug_putstr("No relocation needed... "); - return; + /* + * it is possible to have delta be zero and + * still have enabled fg kaslr. We need to perform relocations + * for fgkaslr regardless of whether the base address has moved. + */ + if (!IS_ENABLED(CONFIG_FG_KASLR) || + cmdline_find_option_bool("nokaslr")) { + if (!delta) { + debug_putstr("No relocation needed... "); + return; + } } + + pre_relocations_cleanup(map); + debug_putstr("Performing relocations... "); /* @@ -230,35 +242,106 @@ static void handle_relocations(void *output, unsigned long output_len, */ for (reloc = output + output_len - sizeof(*reloc); *reloc; reloc--) { long extended = *reloc; + long value; + + /* + * if using fgkaslr, we might have moved the address + * of the relocation. Check it to see if it needs adjusting + * from the original address. + */ + (void)adjust_address(&extended); + extended += map; ptr = (unsigned long)extended; if (ptr < min_addr || ptr > max_addr) error("32-bit relocation outside of kernel!\n"); - *(uint32_t *)ptr += delta; + value = *(int32_t *)ptr; + + /* + * If using fgkaslr, the value of the relocation + * might need to be changed because it referred + * to an address that has moved. + */ + adjust_address(&value); + + value += delta; + + *(uint32_t *)ptr = value; } #ifdef CONFIG_X86_64 while (*--reloc) { long extended = *reloc; + long value; + long oldvalue; + Elf64_Shdr *s; + + /* + * if using fgkaslr, we might have moved the address + * of the relocation. Check it to see if it needs adjusting + * from the original address. + */ + s = adjust_address(&extended); + extended += map; ptr = (unsigned long)extended; if (ptr < min_addr || ptr > max_addr) error("inverse 32-bit relocation outside of kernel!\n"); - *(int32_t *)ptr -= delta; + value = *(int32_t *)ptr; + oldvalue = value; + + /* + * If using fgkaslr, these relocs will contain + * relative offsets which might need to be + * changed because it referred + * to an address that has moved. + */ + adjust_relative_offset(*reloc, &value, s); + + /* + * only percpu symbols need to have their values adjusted for + * base address kaslr since relative offsets within the .text + * and .text.* sections are ok wrt each other. + */ + if (is_percpu_addr(*reloc, oldvalue)) + value -= delta; + + *(int32_t *)ptr = value; } for (reloc--; *reloc; reloc--) { long extended = *reloc; + long value; + + /* + * if using fgkaslr, we might have moved the address + * of the relocation. Check it to see if it needs adjusting + * from the original address. + */ + (void)adjust_address(&extended); + extended += map; ptr = (unsigned long)extended; if (ptr < min_addr || ptr > max_addr) error("64-bit relocation outside of kernel!\n"); - *(uint64_t *)ptr += delta; + value = *(int64_t *)ptr; + + /* + * If using fgkaslr, the value of the relocation + * might need to be changed because it referred + * to an address that has moved. + */ + (void)adjust_address(&value); + + value += delta; + + *(uint64_t *)ptr = value; } + post_relocations_cleanup(map); #endif } #else @@ -296,6 +379,14 @@ static void parse_elf(void *output) memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum); + if (IS_ENABLED(CONFIG_FG_KASLR)) { + if (!cmdline_find_option_bool("nokaslr")) { + parse_sections_headers(output, &ehdr, phdrs); + return; + } + warn("FG_KASLR disabled: 'nokaslr' on cmdline."); + } + for (i = 0; i < ehdr.e_phnum; i++) { phdr = &phdrs[i]; diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 726e264410ff..e8e45f263eaf 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -39,6 +39,12 @@ /* misc.c */ extern memptr free_mem_ptr; extern memptr free_mem_end_ptr; +#define STATIC +#ifdef CONFIG_FG_KASLR +#define STATIC_RW_DATA extern +#endif +#include + extern struct boot_params *boot_params; void __putstr(const char *s); void __puthex(unsigned long value); @@ -74,6 +80,34 @@ struct mem_vector { unsigned long long size; }; +#ifdef CONFIG_X86_64 +#define Elf_Ehdr Elf64_Ehdr +#define Elf_Phdr Elf64_Phdr +#define Elf_Shdr Elf64_Shdr +#else +#define Elf_Ehdr Elf32_Ehdr +#define Elf_Phdr Elf32_Phdr +#define Elf_Shdr Elf32_Shdr +#endif + +#if CONFIG_FG_KASLR +void parse_sections_headers(void *output, Elf_Ehdr *ehdr, Elf_Phdr *phdrs); +void pre_relocations_cleanup(unsigned long map); +void post_relocations_cleanup(unsigned long map); +Elf_Shdr *adjust_address(long *address); +void adjust_relative_offset(long pc, long *value, Elf_Shdr *section); +bool is_percpu_addr(long pc, long offset); +#else +static inline void parse_sections_headers(void *output, Elf_Ehdr *ehdr, + Elf_Phdr *phdrs) { } +static inline void pre_relocations_cleanup(unsigned long map) { } +static inline void post_relocations_cleanup(unsigned long map) { } +static inline Elf_Shdr *adjust_address(long *address) { return NULL; } +static inline void adjust_relative_offset(long pc, long *value, + Elf_Shdr *section) { } +static inline bool is_percpu_addr(long pc, long offset) { return true; } +#endif /* CONFIG_FG_KASLR */ + #if CONFIG_RANDOMIZE_BASE /* kaslr.c */ void choose_random_location(unsigned long input, diff --git a/arch/x86/boot/compressed/utils.c b/arch/x86/boot/compressed/utils.c new file mode 100644 index 000000000000..ceefc58d7c71 --- /dev/null +++ b/arch/x86/boot/compressed/utils.c @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * utils.c + * + * This contains various libraries that are needed for fgkaslr + */ +#define __DISABLE_EXPORTS +#define _LINUX_KPROBES_H +#define NOKPROBE_SYMBOL(fname) +#include "../../../../lib/sort.c" +#include "../../../../lib/bsearch.c" + diff --git a/arch/x86/boot/compressed/vmlinux.symbols b/arch/x86/boot/compressed/vmlinux.symbols new file mode 100644 index 000000000000..cc86e79a2a3d --- /dev/null +++ b/arch/x86/boot/compressed/vmlinux.symbols @@ -0,0 +1,17 @@ +kallsyms_offsets +kallsyms_addresses +kallsyms_num_syms +kallsyms_relative_base +kallsyms_names +kallsyms_token_table +kallsyms_token_index +kallsyms_markers +__start___ex_table +__stop___ex_table +_sinittext +_einittext +_stext +_etext +__start_orc_unwind_ip +__stop_orc_unwind_ip +__start_orc_unwind diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h index 680c320363db..6918d33eb5ef 100644 --- a/arch/x86/include/asm/boot.h +++ b/arch/x86/include/asm/boot.h @@ -26,8 +26,19 @@ #ifdef CONFIG_KERNEL_BZIP2 # define BOOT_HEAP_SIZE 0x400000 -#else /* !CONFIG_KERNEL_BZIP2 */ -# define BOOT_HEAP_SIZE 0x10000 +#elif CONFIG_FG_KASLR +/* + * We need extra boot heap when using fgkaslr because we make a copy + * of the original decompressed kernel to avoid issues with writing + * over ourselves when shuffling the sections. We also need extra + * space for resorting kallsyms after shuffling. This value could + * be decreased if free() would release memory properly, or if we + * could avoid the kernel copy. It would need to be increased if we + * find additional tables that need to be resorted. + */ +# define BOOT_HEAP_SIZE 0x4000000 +#else /* !CONFIG_KERNEL_BZIP2 && !CONFIG_FG_KASLR */ +# define BOOT_HEAP_SIZE 0x10000 #endif #ifdef CONFIG_X86_64 diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index 34c02e4290fe..a85d1792d5a8 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -298,6 +298,7 @@ typedef struct elf64_phdr { #define SHN_LIVEPATCH 0xff20 #define SHN_ABS 0xfff1 #define SHN_COMMON 0xfff2 +#define SHN_XINDEX 0xffff #define SHN_HIRESERVE 0xffff typedef struct elf32_shdr { From patchwork Thu May 21 16:56:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563507 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 488B0739 for ; Thu, 21 May 2020 16:58:57 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id AD451207F7 for ; Thu, 21 May 2020 16:58:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD451207F7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18843-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 1786 invoked by uid 550); 21 May 2020 16:57:44 -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 Received: (qmail 1699 invoked from network); 21 May 2020 16:57:43 -0000 IronPort-SDR: OWhkU06VlFODHGaXPHi48zhmxZ4o+8/YQ3Txg04aSf/sbEjqjxtY0dEK/ta0UTlM/+3azEBL24 rJr9MHBBHSwA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: RqdF6pIwNmwj2eRxUyIu8U3E3pSodnd5ySfbax65wnHVdU3X57VIgUZ+Jh4ejMDUtCOvwiFO4A 8JFljtHzZxzg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094801" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de Cc: arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck Subject: [PATCH v2 8/9] kallsyms: Hide layout Date: Thu, 21 May 2020 09:56:39 -0700 Message-Id: <20200521165641.15940-9-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 This patch makes /proc/kallsyms display alphabetically by symbol name rather than sorted by address in order to hide the newly randomized address layout. Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck --- kernel/kallsyms.c | 138 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 137 insertions(+), 1 deletion(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 16c8c605f4b0..558963b275ec 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -25,6 +25,7 @@ #include #include #include +#include /* * These will be re-linked against their real values @@ -446,6 +447,11 @@ struct kallsym_iter { int show_value; }; +struct kallsyms_iter_list { + struct kallsym_iter iter; + struct list_head next; +}; + int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name) { @@ -660,6 +666,121 @@ int kallsyms_show_value(void) } } +static int sorted_show(struct seq_file *m, void *p) +{ + struct list_head *list = m->private; + struct kallsyms_iter_list *iter; + int rc; + + if (list_empty(list)) + return 0; + + iter = list_first_entry(list, struct kallsyms_iter_list, next); + + m->private = iter; + rc = s_show(m, p); + m->private = list; + + list_del(&iter->next); + kfree(iter); + + return rc; +} + +static void *sorted_start(struct seq_file *m, loff_t *pos) +{ + return m->private; +} + +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos) +{ + struct list_head *list = m->private; + + (*pos)++; + + if (list_empty(list)) + return NULL; + + return p; +} + +static const struct seq_operations kallsyms_sorted_op = { + .start = sorted_start, + .next = sorted_next, + .stop = s_stop, + .show = sorted_show +}; + +static int kallsyms_list_cmp(void *priv, struct list_head *a, + struct list_head *b) +{ + struct kallsyms_iter_list *iter_a, *iter_b; + + iter_a = list_entry(a, struct kallsyms_iter_list, next); + iter_b = list_entry(b, struct kallsyms_iter_list, next); + + return strcmp(iter_a->iter.name, iter_b->iter.name); +} + +int get_all_symbol_name(void *data, const char *name, struct module *mod, + unsigned long addr) +{ + unsigned long sym_pos; + struct kallsyms_iter_list *node, *last; + struct list_head *head = (struct list_head *)data; + + node = kmalloc(sizeof(*node), GFP_KERNEL); + if (!node) + return -ENOMEM; + + if (list_empty(head)) { + sym_pos = 0; + memset(node, 0, sizeof(*node)); + reset_iter(&node->iter, 0); + node->iter.show_value = kallsyms_show_value(); + } else { + last = list_first_entry(head, struct kallsyms_iter_list, next); + memcpy(node, last, sizeof(*node)); + sym_pos = last->iter.pos; + } + + INIT_LIST_HEAD(&node->next); + list_add(&node->next, head); + + /* + * update_iter returns false when at end of file + * which in this case we don't care about and can + * safely ignore. update_iter() will increment + * the value of iter->pos, for ksymbol_core. + */ + if (sym_pos >= kallsyms_num_syms) + sym_pos++; + + (void)update_iter(&node->iter, sym_pos); + + return 0; +} + +static int kallsyms_sorted_open(struct inode *inode, struct file *file) +{ + int ret; + struct list_head *list; + + list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list)); + if (!list) + return -ENOMEM; + + INIT_LIST_HEAD(list); + + ret = kallsyms_on_each_symbol(get_all_symbol_name, list); + if (ret != 0) + return ret; + + list_sort(NULL, list, kallsyms_list_cmp); + + return 0; +} + static int kallsyms_open(struct inode *inode, struct file *file) { /* @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = { .proc_release = seq_release_private, }; +static const struct proc_ops kallsyms_sorted_proc_ops = { + .proc_open = kallsyms_sorted_open, + .proc_read = seq_read, + .proc_lseek = seq_lseek, + .proc_release = seq_release_private, +}; + static int __init kallsyms_init(void) { - proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); + /* + * When fine grained kaslr is enabled, we need to + * print out the symbols sorted by name rather than by + * by address, because this reveals the randomization order. + */ + if (!IS_ENABLED(CONFIG_FG_KASLR)) + proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); + else + proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops); return 0; } device_initcall(kallsyms_init); From patchwork Thu May 21 16:56:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11563511 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 687EC739 for ; Thu, 21 May 2020 16:59:10 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id A544B20826 for ; Thu, 21 May 2020 16:59:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A544B20826 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18844-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 1850 invoked by uid 550); 21 May 2020 16:57:45 -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 Received: (qmail 1794 invoked from network); 21 May 2020 16:57:44 -0000 IronPort-SDR: NvE/nsVOaoy3HN5d/ETJb1PkrFr0JoPSxHWUCMNqe5jSq89kcJcBF6kdiNctBwIZM2IYQQ0ESY s8ySbpyXW8fA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: P6wEIu2SJuHDHQwXasz9m0NGvmkDLrrsa3c9q3cdsZubQS+kjPmQIawnk21iMKnMaiJT4kinct gDO85ZACgdEQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,418,1583222400"; d="scan'208";a="309094841" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, "H. Peter Anvin" , Jessica Yu Cc: arjan@linux.intel.com, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Ard Biesheuvel , Tony Luck Subject: [PATCH v2 9/9] module: Reorder functions Date: Thu, 21 May 2020 09:56:40 -0700 Message-Id: <20200521165641.15940-10-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200521165641.15940-1-kristen@linux.intel.com> References: <20200521165641.15940-1-kristen@linux.intel.com> MIME-Version: 1.0 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 --- arch/x86/Kconfig | 1 + arch/x86/Makefile | 3 ++ init/Kconfig | 11 +++++++ kernel/module.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 96 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 50e83ea57d70..d0bdd5c8c432 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2187,6 +2187,7 @@ config FG_KASLR bool "Function Granular Kernel Address Space Layout Randomization" depends on $(cc-option, -ffunction-sections) depends on RANDOMIZE_BASE && X86_64 + select MODULE_FG_KASLR help This option improves the randomness of the kernel text over basic Kernel Address Space Layout Randomization (KASLR) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index b65ec63c7db7..8c830c37c74c 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -51,6 +51,9 @@ ifdef CONFIG_X86_NEED_RELOCS LDFLAGS_vmlinux := --emit-relocs --discard-none endif +ifdef CONFIG_MODULE_FG_KASLR + KBUILD_CFLAGS_MODULE += -ffunction-sections +endif # # Prevent GCC from generating any FP code by mistake. # diff --git a/init/Kconfig b/init/Kconfig index 74a5ac65644f..b19920413bcc 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2227,6 +2227,17 @@ config UNUSED_KSYMS_WHITELIST one per line. The path can be absolute, or relative to the kernel source tree. +config MODULE_FG_KASLR + depends on $(cc-option, -ffunction-sections) + bool "Module Function Granular Layout Randomization" + 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 646f1e2330d2..e3cd619c60c2 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -53,6 +53,7 @@ #include #include #include +#include #include #include "module-internal.h" @@ -2370,6 +2371,83 @@ static long get_offset(struct module *mod, unsigned int *size, return ret; } +/* + * 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--) { + /* + * 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 (sec == 0) + return; + + text_list = kmalloc_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) || + 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]; + + /* + * 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 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); + } + + kfree(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 sizes, and place the offsets into sh_entsize fields: high bit means it @@ -2460,6 +2538,9 @@ 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)