From: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> An ELF file's .note.gnu.property indicates features the executable file can support. For example, the property GNU_PROPERTY_X86_FEATURE_1_AND indicates the file supports GNU_PROPERTY_X86_FEATURE_1_IBT and/or GNU_PROPERTY_X86_FEATURE_1_SHSTK. This patch was part of the Control-flow Enforcement series; the original patch is here: https://lkml.org/lkml/2018/11/20/205. Dave Martin responded that ARM recently introduced new features to NT_GNU_PROPERTY_TYPE_0 with properties closely modelled on GNU_PROPERTY_X86_FEATURE_1_AND, and it is logical to split out the generic part. Here it is. With this patch, if an arch needs to setup features from ELF properties, it needs CONFIG_ARCH_USE_GNU_PROPERTY to be set, and a specific arch_setup_property(). For example, for X86_64: int arch_setup_property(void *ehdr, void *phdr, struct file *f, bool inter) { int r; uint32_t property; r = get_gnu_property(ehdr, phdr, f, GNU_PROPERTY_X86_FEATURE_1_AND, &property); ... } Signed-off-by: H.J. Lu <hjl.tools@xxxxxxxxx> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@xxxxxxxxx> Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> [rebase to v5.2-rc1] --- Notes from Dave: * For arm64 at least, I'm hoping we can rely on the PT_GNU_PROPERTY program header to find the program properties. If this works for x86 too, I think the code could be simplified considerably. Ideally we would always use that: having to exhaustively search all the notes in the image instead doesn't feel like the right design IMHO. This needs further discussion, and I make no attempt to address it for now. --- fs/Kconfig.binfmt | 4 + fs/Makefile | 1 + fs/binfmt_elf.c | 13 ++ fs/gnu_property.c | 363 +++++++++++++++++++++++++++++++++++++++++++++++ include/linux/elf.h | 12 ++ include/uapi/linux/elf.h | 8 ++ 6 files changed, 401 insertions(+) create mode 100644 fs/gnu_property.c diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt index b795f8d..175a1f5 100644 --- a/fs/Kconfig.binfmt +++ b/fs/Kconfig.binfmt @@ -35,6 +35,10 @@ config COMPAT_BINFMT_ELF config ARCH_BINFMT_ELF_STATE bool +config ARCH_USE_GNU_PROPERTY + bool + depends on 64BIT + config BINFMT_ELF_FDPIC bool "Kernel support for FDPIC ELF binaries" default y if !BINFMT_ELF diff --git a/fs/Makefile b/fs/Makefile index c9aea23..b69f18c 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -44,6 +44,7 @@ obj-$(CONFIG_BINFMT_ELF) += binfmt_elf.o obj-$(CONFIG_COMPAT_BINFMT_ELF) += compat_binfmt_elf.o obj-$(CONFIG_BINFMT_ELF_FDPIC) += binfmt_elf_fdpic.o obj-$(CONFIG_BINFMT_FLAT) += binfmt_flat.o +obj-$(CONFIG_ARCH_USE_GNU_PROPERTY) += gnu_property.o obj-$(CONFIG_FS_MBCACHE) += mbcache.o obj-$(CONFIG_FS_POSIX_ACL) += posix_acl.o diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index fa9e99a..18015fc 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1080,6 +1080,19 @@ static int load_elf_binary(struct linux_binprm *bprm) } if (interpreter) { + retval = arch_setup_property(&loc->interp_elf_ex, + interp_elf_phdata, + interpreter, true); + } else { + retval = arch_setup_property(&loc->elf_ex, + elf_phdata, + bprm->file, false); + } + + if (retval < 0) + goto out_free_dentry; + + if (interpreter) { unsigned long interp_map_addr = 0; elf_entry = load_elf_interp(&loc->interp_elf_ex, diff --git a/fs/gnu_property.c b/fs/gnu_property.c new file mode 100644 index 0000000..656ea39 --- /dev/null +++ b/fs/gnu_property.c @@ -0,0 +1,363 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Extract an ELF file's .note.gnu.property. + * + * The path from the ELF header to the note section is the following: + * elfhdr->elf_phdr->elf_note->property[]. + */ + +#include <uapi/linux/elf-em.h> +#include <linux/processor.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 gnu_property { + * u32 pr_type; + * u32 pr_datasz; + * }; + * u8 pr_data[pr_datasz]; + * }[]; + */ + +#define BUF_SIZE (PAGE_SIZE / 4) + +struct gnu_property { + u32 pr_type; + u32 pr_datasz; +}; + +typedef bool (test_item_fn)(void *buf, u32 *arg, u32 type); +typedef void *(next_item_fn)(void *buf, u32 *arg, u32 type); + +static inline bool test_note_type(void *buf, u32 *align, u32 note_type) +{ + struct elf_note *n = buf; + + return ((n->n_type == note_type) && (n->n_namesz == 4) && + (memcmp(n + 1, "GNU", 4) == 0)); +} + +static inline void *next_note(void *buf, u32 *align, u32 note_type) +{ + 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(void *buf, u32 *max_type, u32 pr_type) +{ + struct gnu_property *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 == pr_type); +} + +static inline void *next_property(void *buf, u32 *max_type, u32 pr_type) +{ + struct gnu_property *pr = buf; + + if ((buf + sizeof(*pr) + pr->pr_datasz < buf) || + (pr->pr_type > pr_type) || + (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 type, 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, type)) { + found = 1; + break; + } + + p = next_item(p, arg, type); + } + + *pos = (p + item_size <= buf) ? 0 : (u32)(p - buf); + return found; +} + +/* + * Search an NT_GNU_PROPERTY_TYPE_0 for the property of 'pr_type'. + */ +static int find_property(struct file *file, unsigned long desc_size, + loff_t file_offset, u8 *buf, + u32 pr_type, u32 *property) +{ + u32 buf_pos; + unsigned long read_size; + unsigned long done; + int found = 0; + int ret = 0; + u32 last_pr = 0; + + *property = 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 gnu_property), + test_property, next_property, + &last_pr, pr_type, &buf_pos); + + if ((!buf_pos) || found) + break; + + file_offset += buf_pos - read_size; + } + + if (found) { + struct gnu_property *pr = + (struct gnu_property *)(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) { + *property = *data; + } else { + file_offset += buf_pos - read_size; + file_offset += sizeof(*pr); + ret = kernel_read(file, property, 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, loff_t file_offset, + unsigned long note_size, u32 align, + u32 pr_type, u32 *property) +{ + 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; + + *property = 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, next_note, + &align, NT_GNU_PROPERTY_TYPE_0, &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_property(file, n->n_descsz, + file_offset + start, + buf, pr_type, property); + found++; + file_offset += total; + buf_pos += total; + } else if (!buf_pos || ret) { + ret = 0; + *property = 0; + break; + } + } + + kfree(buf); + return ret; +} + +/* + * Look at an ELF file's PT_NOTE segments, then NT_GNU_PROPERTY_TYPE_0, then + * the property of pr_type. + * + * Input: + * file: the file to search; + * phdr: the file's elf header; + * phnum: number of entries in phdr; + * pr_type: the property type. + * + * Output: + * The property found. + * + * Return: + * Zero or error. + */ +static int scan_segments_64(struct file *file, struct elf64_phdr *phdr, + int phnum, u32 pr_type, u32 *property) +{ + int i; + int err = 0; + + for (i = 0; i < phnum; i++, phdr++) { + if ((phdr->p_type != PT_NOTE) || (phdr->p_align != 8)) + continue; + + /* + * Search the PT_NOTE segment for NT_GNU_PROPERTY_TYPE_0. + */ + err = find_note_type_0(file, phdr->p_offset, phdr->p_filesz, + phdr->p_align, pr_type, property); + if (err) + return err; + } + + return 0; +} + +#ifdef CONFIG_COMPAT +static int scan_segments_32(struct file *file, struct elf32_phdr *phdr, + int phnum, u32 pr_type, u32 *property) +{ + int i; + int err = 0; + + for (i = 0; i < phnum; i++, phdr++) { + if ((phdr->p_type != PT_NOTE) || (phdr->p_align != 4)) + continue; + + /* + * Search the PT_NOTE segment for NT_GNU_PROPERTY_TYPE_0. + */ + err = find_note_type_0(file, phdr->p_offset, phdr->p_filesz, + phdr->p_align, pr_type, property); + if (err) + return err; + } + + return 0; +} +#endif + +int get_gnu_property(void *ehdr_p, void *phdr_p, struct file *f, + u32 pr_type, u32 *property) +{ + struct elf64_hdr *ehdr64 = ehdr_p; + int err = 0; + + *property = 0; + + if (ehdr64->e_ident[EI_CLASS] == ELFCLASS64) { + struct elf64_phdr *phdr64 = phdr_p; + + err = scan_segments_64(f, phdr64, ehdr64->e_phnum, + pr_type, property); + 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 = scan_segments_32(f, phdr32, ehdr32->e_phnum, + pr_type, property); + if (err < 0) + goto out; + } +#else + WARN_ONCE(1, "Exec of 32-bit app, but CONFIG_COMPAT is not enabled.\n"); + return -ENOTSUPP; +#endif + } + +out: + return err; +} diff --git a/include/linux/elf.h b/include/linux/elf.h index e3649b3..c15febe 100644 --- a/include/linux/elf.h +++ b/include/linux/elf.h @@ -56,4 +56,16 @@ static inline int elf_coredump_extra_notes_write(struct coredump_params *cprm) { extern int elf_coredump_extra_notes_size(void); extern int elf_coredump_extra_notes_write(struct coredump_params *cprm); #endif + +#ifdef CONFIG_ARCH_USE_GNU_PROPERTY +extern int arch_setup_property(void *ehdr, void *phdr, struct file *f, + bool interp); +extern int get_gnu_property(void *ehdr_p, void *phdr_p, struct file *f, + u32 pr_type, u32 *feature); +#else +static inline int arch_setup_property(void *ehdr, void *phdr, struct file *f, + bool interp) { return 0; } +static inline int get_gnu_property(void *ehdr_p, void *phdr_p, struct file *f, + u32 pr_type, u32 *feature) { return 0; } +#endif #endif /* _LINUX_ELF_H */ diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index 34c02e4..7b7603a 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 @@ -443,4 +444,11 @@ typedef struct elf64_note { Elf64_Word n_type; /* Content type */ } Elf64_Nhdr; +/* .note.gnu.property types */ +#define GNU_PROPERTY_X86_FEATURE_1_AND (0xc0000002) + +/* Bits of GNU_PROPERTY_X86_FEATURE_1_AND */ +#define GNU_PROPERTY_X86_FEATURE_1_IBT (0x00000001) +#define GNU_PROPERTY_X86_FEATURE_1_SHSTK (0x00000002) + #endif /* _UAPI_LINUX_ELF_H */ -- 2.1.4
