[RFC,v6,22/26] x86/cet/shstk: ELF header parsing of Shadow Stack

Message ID	20181119214809.6086-23-yu-cheng.yu@intel.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <owner-linux-mm@kvack.org> Received-SPF: pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.93 as permitted sender) client-ip=192.55.52.93; From: Yu-cheng Yu <yu-cheng.yu@intel.com> To: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@amacapital.net>, Balbir Singh <bsingharora@gmail.com>, Cyrill Gorcunov <gorcunov@gmail.com>, Dave Hansen <dave.hansen@linux.intel.com>, Eugene Syromiatnikov <esyr@redhat.com>, Florian Weimer <fweimer@redhat.com>, "H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>, Jonathan Corbet <corbet@lwn.net>, Kees Cook <keescook@chromium.org>, Mike Kravetz <mike.kravetz@oracle.com>, Nadav Amit <nadav.amit@gmail.com>, Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>, Peter Zijlstra <peterz@infradead.org>, Randy Dunlap <rdunlap@infradead.org>, "Ravi V. Shankar" <ravi.v.shankar@intel.com>, Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com> Cc: Yu-cheng Yu <yu-cheng.yu@intel.com> Subject: [RFC PATCH v6 22/26] x86/cet/shstk: ELF header parsing of Shadow Stack Date: Mon, 19 Nov 2018 13:48:05 -0800 Message-Id: <20181119214809.6086-23-yu-cheng.yu@intel.com> In-Reply-To: <20181119214809.6086-1-yu-cheng.yu@intel.com> References: <20181119214809.6086-1-yu-cheng.yu@intel.com> Sender: owner-linux-mm@kvack.org Precedence: bulk
Series	Control-flow Enforcement: Shadow Stack \| expand [RFC,v6,00/26] Control-flow Enforcement: Shadow Stack [RFC,v6,01/26] Documentation/x86: Add CET description [RFC,v6,02/26] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (… [RFC,v6,03/26] x86/fpu/xstate: Change names to separate XSAVES system and user states [RFC,v6,04/26] x86/fpu/xstate: Introduce XSAVES system states [RFC,v6,05/26] x86/fpu/xstate: Add XSAVES system states for shadow stack [RFC,v6,06/26] x86/cet: Add control protection exception handler [RFC,v6,07/26] x86/cet/shstk: Add Kconfig option for user-mode shadow stack [RFC,v6,08/26] mm: Introduce VM_SHSTK for shadow stack memory [RFC,v6,09/26] mm/mmap: Prevent Shadow Stack VMA merges [RFC,v6,10/26] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW [RFC,v6,11/26] x86/mm: Introduce _PAGE_DIRTY_SW [RFC,v6,12/26] drm/i915/gvt: Update _PAGE_DIRTY to _PAGE_DIRTY_BITS [RFC,v6,13/26] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW [RFC,v6,14/26] x86/mm: Shadow stack page fault error checking [RFC,v6,15/26] mm: Handle shadow stack page fault [RFC,v6,16/26] mm: Handle THP/HugeTLB shadow stack page fault [RFC,v6,17/26] mm: Update can_follow_write_pte/pmd for shadow stack [RFC,v6,18/26] mm: Introduce do_mmap_locked() [RFC,v6,19/26] x86/cet/shstk: User-mode shadow stack support [RFC,v6,20/26] x86/cet/shstk: Introduce WRUSS instruction [RFC,v6,21/26] x86/cet/shstk: Signal handling for shadow stack [RFC,v6,22/26] x86/cet/shstk: ELF header parsing of Shadow Stack [RFC,v6,23/26] x86/cet/shstk: Handle thread shadow stack [RFC,v6,24/26] mm/mmap: Add Shadow stack pages to memory accounting [RFC,v6,25/26] x86/cet/shstk: Add arch_prctl functions for Shadow Stack [RFC,v6,26/26] x86/cet/shstk: Add Shadow Stack instructions to opcode map

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 86fb68f496a6..73dfb94cde71 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1925,6 +1925,9 @@ config X86_INTEL_CET config ARCH_HAS_SHSTK def_bool n +config ARCH_HAS_PROGRAM_PROPERTIES + def_bool n + config X86_INTEL_SHADOW_STACK_USER prompt "Intel Shadow Stack for user-mode" def_bool n @@ -1932,6 +1935,7 @@ config X86_INTEL_SHADOW_STACK_USER select ARCH_USES_HIGH_VMA_FLAGS select X86_INTEL_CET select ARCH_HAS_SHSTK + select ARCH_HAS_PROGRAM_PROPERTIES ---help--- Shadow stack provides hardware protection against program stack corruption. Only when all the following are true will an application diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index 69c0f892e310..557ed0ba71c7 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -381,4 +381,9 @@ struct va_alignment { extern struct va_alignment va_align; extern unsigned long align_vdso_addr(unsigned long); + +#ifdef CONFIG_ARCH_HAS_PROGRAM_PROPERTIES +extern int arch_setup_features(void *ehdr, void *phdr, struct file *file, + bool interp); +#endif #endif /* _ASM_X86_ELF_H */ diff --git a/arch/x86/include/uapi/asm/elf_property.h b/arch/x86/include/uapi/asm/elf_property.h new file mode 100644 index 000000000000..af361207718c --- /dev/null +++ b/arch/x86/include/uapi/asm/elf_property.h @@ -0,0 +1,15 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _UAPI_ASM_X86_ELF_PROPERTY_H +#define _UAPI_ASM_X86_ELF_PROPERTY_H + +/* + * pr_type + */ +#define GNU_PROPERTY_X86_FEATURE_1_AND (0xc0000002) + +/* + * Bits for GNU_PROPERTY_X86_FEATURE_1_AND + */ +#define GNU_PROPERTY_X86_FEATURE_1_SHSTK (0x00000002) + +#endif /* _UAPI_ASM_X86_ELF_PROPERTY_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index fbb2d91fb756..36b14ef410c8 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -141,6 +141,8 @@ obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o obj-$(CONFIG_X86_INTEL_CET) += cet.o +obj-$(CONFIG_ARCH_HAS_PROGRAM_PROPERTIES) += elf.o + ### # 64 bit specific files ifeq ($(CONFIG_X86_64),y) diff --git a/arch/x86/kernel/elf.c b/arch/x86/kernel/elf.c new file mode 100644 index 000000000000..60e396e2abe9 --- /dev/null +++ b/arch/x86/kernel/elf.c @@ -0,0 +1,358 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Look at an ELF file's .note.gnu.property and determine if the file + * supports shadow stack and/or indirect branch tracking. + * The path from the ELF header to the note section is the following: + * elfhdr->elf_phdr->elf_note->property[]. + */ + +#include <asm/cet.h> +#include <asm/elf_property.h> +#include <asm/prctl.h> +#include <asm/processor.h> +#include <uapi/linux/elf-em.h> +#include <uapi/linux/prctl.h> +#include <linux/binfmts.h> +#include <linux/elf.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/uaccess.h> +#include <linux/string.h> +#include <linux/compat.h> + +/* + * The .note.gnu.property layout: + * + * struct elf_note { + * u32 n_namesz; --> sizeof(n_name[]); always (4) + * u32 n_ndescsz;--> sizeof(property[]) + * u32 n_type; --> always NT_GNU_PROPERTY_TYPE_0 + * }; + * char n_name[4]; --> always 'GNU\0' + * + * struct { + * struct property_x86 { + * u32 pr_type; + * u32 pr_datasz; + * }; + * u8 pr_data[pr_datasz]; + * }[]; + */ + +#define BUF_SIZE (PAGE_SIZE / 4) + +struct property_x86 { + u32 pr_type; + u32 pr_datasz; +}; + +typedef bool (test_item_fn)(void *buf, u32 *arg); +typedef void *(next_item_fn)(void *buf, u32 *arg); + +static inline bool test_note_type_0(void *buf, u32 *align) +{ + struct elf_note *n = buf; + + return ((n->n_type == NT_GNU_PROPERTY_TYPE_0) && (n->n_namesz == 4) && + (memcmp(n + 1, "GNU", 4) == 0)); +} + +static inline void *next_note(void *buf, u32 *align) +{ + struct elf_note *n = buf; + u64 size; + + if (check_add_overflow((u64)sizeof(*n), (u64)n->n_namesz, &size)) + return NULL; + + size = round_up(size, *align); + + if (check_add_overflow(size, (u64)n->n_descsz, &size)) + return NULL; + + size = round_up(size, *align); + + if (buf + size < buf) + return NULL; + else + return (buf + size); +} + +static inline bool test_property_x86(void *buf, u32 *max_type) +{ + struct property_x86 *pr = buf; + + /* + * Property types must be in ascending order. + * Keep track of the max when testing each. + */ + if (pr->pr_type > *max_type) + *max_type = pr->pr_type; + + return (pr->pr_type == GNU_PROPERTY_X86_FEATURE_1_AND); +} + +static inline void *next_property(void *buf, u32 *max_type) +{ + struct property_x86 *pr = buf; + + if ((buf + sizeof(*pr) + pr->pr_datasz < buf) || + (pr->pr_type > GNU_PROPERTY_X86_FEATURE_1_AND) || + (pr->pr_type > *max_type)) + return NULL; + else + return (buf + sizeof(*pr) + pr->pr_datasz); +} + +/* + * Scan 'buf' for a pattern; return true if found. + * *pos is the distance from the beginning of buf to where + * the searched item or the next item is located. + */ +static int scan(u8 *buf, u32 buf_size, int item_size, test_item_fn test_item, + next_item_fn next_item, u32 *arg, u32 *pos) +{ + int found = 0; + u8 *p, *max; + + max = buf + buf_size; + if (max < buf) + return 0; + + p = buf; + + while ((p + item_size < max) && (p + item_size > buf)) { + if (test_item(p, arg)) { + found = 1; + break; + } + + p = next_item(p, arg); + } + + *pos = (p + item_size <= buf) ? 0 : (u32)(p - buf); + return found; +} + +/* + * Search a NT_GNU_PROPERTY_TYPE_0 for GNU_PROPERTY_X86_FEATURE_1_AND. + */ +static int find_feature_x86(struct file *file, unsigned long desc_size, + loff_t file_offset, u8 *buf, u32 *feature) +{ + u32 buf_pos; + unsigned long read_size; + unsigned long done; + int found = 0; + int ret = 0; + u32 last_pr = 0; + + *feature = 0; + buf_pos = 0; + + for (done = 0; done < desc_size; done += buf_pos) { + read_size = desc_size - done; + if (read_size > BUF_SIZE) + read_size = BUF_SIZE; + + ret = kernel_read(file, buf, read_size, &file_offset); + + if (ret != read_size) + return (ret < 0) ? ret : -EIO; + + ret = 0; + found = scan(buf, read_size, sizeof(struct property_x86), + test_property_x86, next_property, + &last_pr, &buf_pos); + + if ((!buf_pos) || found) + break; + + file_offset += buf_pos - read_size; + } + + if (found) { + struct property_x86 *pr = + (struct property_x86 *)(buf + buf_pos); + + if (pr->pr_datasz == 4) { + u32 *max = (u32 *)(buf + read_size); + u32 *data = (u32 *)((u8 *)pr + sizeof(*pr)); + + if (data + 1 <= max) { + *feature = *data; + } else { + file_offset += buf_pos - read_size; + file_offset += sizeof(*pr); + ret = kernel_read(file, feature, 4, + &file_offset); + } + } + } + + return ret; +} + +/* + * Search a PT_NOTE segment for NT_GNU_PROPERTY_TYPE_0. + */ +static int find_note_type_0(struct file *file, unsigned long note_size, + loff_t file_offset, u32 align, u32 *feature) +{ + u8 *buf; + u32 buf_pos; + unsigned long read_size; + unsigned long done; + int found = 0; + int ret = 0; + + buf = kmalloc(BUF_SIZE, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + *feature = 0; + buf_pos = 0; + + for (done = 0; done < note_size; done += buf_pos) { + read_size = note_size - done; + if (read_size > BUF_SIZE) + read_size = BUF_SIZE; + + ret = kernel_read(file, buf, read_size, &file_offset); + + if (ret != read_size) { + ret = (ret < 0) ? ret : -EIO; + kfree(buf); + return ret; + } + + /* + * item_size = sizeof(struct elf_note) + elf_note.n_namesz. + * n_namesz is 4 for the note type we look for. + */ + ret = scan(buf, read_size, sizeof(struct elf_note) + 4, + test_note_type_0, next_note, + &align, &buf_pos); + + file_offset += buf_pos - read_size; + + if (ret && !found) { + struct elf_note *n = + (struct elf_note *)(buf + buf_pos); + u64 start = round_up(sizeof(*n) + n->n_namesz, align); + u64 total = 0; + + if (check_add_overflow(start, (u64)n->n_descsz, &total)) { + ret = -EINVAL; + break; + } + total = round_up(total, align); + + ret = find_feature_x86(file, n->n_descsz, + file_offset + start, + buf, feature); + found++; + file_offset += total; + buf_pos += total; + } else if (!buf_pos || ret) { + ret = 0; + *feature = 0; + break; + } + } + + kfree(buf); + return ret; +} + +#ifdef CONFIG_COMPAT +static int check_notes_32(struct file *file, struct elf32_phdr *phdr, + int phnum, u32 *feature) +{ + int i; + int err = 0; + + for (i = 0; i < phnum; i++, phdr++) { + if ((phdr->p_type != PT_NOTE) || (phdr->p_align != 4)) + continue; + + err = find_note_type_0(file, phdr->p_filesz, phdr->p_offset, + phdr->p_align, feature); + if (err) + return err; + } + + return 0; +} +#endif + +#ifdef CONFIG_X86_64 +static int check_notes_64(struct file *file, struct elf64_phdr *phdr, + int phnum, u32 *feature) +{ + int i; + int err = 0; + + for (i = 0; i < phnum; i++, phdr++) { + if ((phdr->p_type != PT_NOTE) || (phdr->p_align != 8)) + continue; + + err = find_note_type_0(file, phdr->p_filesz, phdr->p_offset, + phdr->p_align, feature); + if (err) + return err; + } + + return 0; +} +#endif + +int arch_setup_features(void *ehdr_p, void *phdr_p, + struct file *file, bool interp) +{ + int err = 0; + u32 feature = 0; + + struct elf64_hdr *ehdr64 = ehdr_p; + + if (!cpu_x86_cet_enabled()) + return 0; + + if (ehdr64->e_ident[EI_CLASS] == ELFCLASS64) { + struct elf64_phdr *phdr64 = phdr_p; + + err = check_notes_64(file, phdr64, ehdr64->e_phnum, + &feature); + if (err < 0) + goto out; + } else { +#ifdef CONFIG_COMPAT + struct elf32_hdr *ehdr32 = ehdr_p; + + if (ehdr32->e_ident[EI_CLASS] == ELFCLASS32) { + struct elf32_phdr *phdr32 = phdr_p; + + err = check_notes_32(file, phdr32, ehdr32->e_phnum, + &feature); + if (err < 0) + goto out; + } +#else + WARN_ONCE(1, "Exec of 32-bit app, but CONFIG_COMPAT is not enabled.\n"); + return -ENOTSUPP; +#endif + } + + memset(&current->thread.cet, 0, sizeof(struct cet_status)); + + if (cpu_feature_enabled(X86_FEATURE_SHSTK)) { + if (feature & GNU_PROPERTY_X86_FEATURE_1_SHSTK) { + err = cet_setup_shstk(); + if (err < 0) + goto out; + } + } + +out: + return err; +} diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 54207327f98f..007ff0fbae84 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1081,6 +1081,21 @@ static int load_elf_binary(struct linux_binprm *bprm) goto out_free_dentry; } +#ifdef CONFIG_ARCH_HAS_PROGRAM_PROPERTIES + if (interpreter) { + retval = arch_setup_features(&loc->interp_elf_ex, + interp_elf_phdata, + interpreter, true); + } else { + retval = arch_setup_features(&loc->elf_ex, + elf_phdata, + bprm->file, false); + } + + if (retval < 0) + goto out_free_dentry; +#endif + if (elf_interpreter) { unsigned long interp_map_addr = 0; diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index c5358e0ae7c5..5ef25a565e88 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -372,6 +372,7 @@ typedef struct elf64_shdr { #define NT_PRFPREG 2 #define NT_PRPSINFO 3 #define NT_TASKSTRUCT 4 +#define NT_GNU_PROPERTY_TYPE_0 5 #define NT_AUXV 6 /* * Note to userspace developers: size of NT_SIGINFO note may increase

[RFC,v6,22/26] x86/cet/shstk: ELF header parsing of Shadow Stack

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