arm64: add KASAN support

This patch adds arch specific code for kernel address sanitizer
(see Documentation/kasan.txt).

1/8 of kernel addresses reserved for shadow memory. There was no
big enough hole for this, so virtual addresses for shadow were
stolen from vmalloc area.

At early boot stage the whole shadow region populated with just
one physical page (kasan_zero_page). Later, this page reused
as readonly zero shadow for some memory that KASan currently
don't track (vmalloc).
After mapping the physical memory, pages for shadow memory are
allocated and mapped.

Functions like memset/memmove/memcpy do a lot of memory accesses.
If bad pointer passed to one of these function it is important
to catch this. Compiler's instrumentation cannot do this since
these functions are written in assembly.
KASan replaces memory functions with manually instrumented variants.
Original functions declared as weak symbols so strong definitions
in mm/kasan/kasan.c could replace them. Original functions have aliases
with '__' prefix in name, so we could call non-instrumented variant
if needed.
Some files built without kasan instrumentation (e.g. mm/slub.c).
Original mem* function replaced (via #define) with prefixed variants
to disable memory access checks for such files.

Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Andrey Ryabinin 2015-10-12 18:52:58 +03:00 committed by Catalin Marinas
parent fd2203dd35
commit 39d114ddc6
18 changed files with 288 additions and 6 deletions

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@ -48,6 +48,7 @@ config ARM64
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_BITREVERSE
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP
select HAVE_ARCH_KGDB
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK

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@ -55,6 +55,13 @@ else
TEXT_OFFSET := 0x00080000
endif
# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61)
# in 32-bit arithmetic
KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - 3)) \
- (1 << (64 - 32 - 3)) )) )
export TEXT_OFFSET GZFLAGS
core-y += arch/arm64/kernel/ arch/arm64/mm/

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@ -0,0 +1,36 @@
#ifndef __ASM_KASAN_H
#define __ASM_KASAN_H
#ifndef __ASSEMBLY__
#ifdef CONFIG_KASAN
#include <asm/memory.h>
/*
* KASAN_SHADOW_START: beginning of the kernel virtual addresses.
* KASAN_SHADOW_END: KASAN_SHADOW_START + 1/8 of kernel virtual addresses.
*/
#define KASAN_SHADOW_START (VA_START)
#define KASAN_SHADOW_END (KASAN_SHADOW_START + (1UL << (VA_BITS - 3)))
/*
* This value is used to map an address to the corresponding shadow
* address by the following formula:
* shadow_addr = (address >> 3) + KASAN_SHADOW_OFFSET;
*
* (1 << 61) shadow addresses - [KASAN_SHADOW_OFFSET,KASAN_SHADOW_END]
* cover all 64-bits of virtual addresses. So KASAN_SHADOW_OFFSET
* should satisfy the following equation:
* KASAN_SHADOW_OFFSET = KASAN_SHADOW_END - (1ULL << 61)
*/
#define KASAN_SHADOW_OFFSET (KASAN_SHADOW_END - (1ULL << (64 - 3)))
void kasan_init(void);
#else
static inline void kasan_init(void) { }
#endif
#endif
#endif

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@ -41,7 +41,14 @@
* fixed mappings and modules
*/
#define VMEMMAP_SIZE ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)
#ifndef CONFIG_KASAN
#define VMALLOC_START (VA_START)
#else
#include <asm/kasan.h>
#define VMALLOC_START (KASAN_SHADOW_END + SZ_64K)
#endif
#define VMALLOC_END (PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
#define vmemmap ((struct page *)(VMALLOC_END + SZ_64K))

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@ -36,17 +36,33 @@ extern __kernel_size_t strnlen(const char *, __kernel_size_t);
#define __HAVE_ARCH_MEMCPY
extern void *memcpy(void *, const void *, __kernel_size_t);
extern void *__memcpy(void *, const void *, __kernel_size_t);
#define __HAVE_ARCH_MEMMOVE
extern void *memmove(void *, const void *, __kernel_size_t);
extern void *__memmove(void *, const void *, __kernel_size_t);
#define __HAVE_ARCH_MEMCHR
extern void *memchr(const void *, int, __kernel_size_t);
#define __HAVE_ARCH_MEMSET
extern void *memset(void *, int, __kernel_size_t);
extern void *__memset(void *, int, __kernel_size_t);
#define __HAVE_ARCH_MEMCMP
extern int memcmp(const void *, const void *, size_t);
#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
/*
* For files that are not instrumented (e.g. mm/slub.c) we
* should use not instrumented version of mem* functions.
*/
#define memcpy(dst, src, len) __memcpy(dst, src, len)
#define memmove(dst, src, len) __memmove(dst, src, len)
#define memset(s, c, n) __memset(s, c, n)
#endif
#endif

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@ -7,6 +7,8 @@ AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
CFLAGS_efi-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
CFLAGS_armv8_deprecated.o := -I$(src)
KASAN_SANITIZE_efi-stub.o := n
CFLAGS_REMOVE_ftrace.o = -pg
CFLAGS_REMOVE_insn.o = -pg
CFLAGS_REMOVE_return_address.o = -pg

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@ -51,6 +51,9 @@ EXPORT_SYMBOL(strnlen);
EXPORT_SYMBOL(memset);
EXPORT_SYMBOL(memcpy);
EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(__memset);
EXPORT_SYMBOL(__memcpy);
EXPORT_SYMBOL(__memmove);
EXPORT_SYMBOL(memchr);
EXPORT_SYMBOL(memcmp);

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@ -444,6 +444,9 @@ __mmap_switched:
str_l x21, __fdt_pointer, x5 // Save FDT pointer
str_l x24, memstart_addr, x6 // Save PHYS_OFFSET
mov x29, #0
#ifdef CONFIG_KASAN
bl kasan_early_init
#endif
b start_kernel
ENDPROC(__mmap_switched)

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@ -80,6 +80,12 @@ __efistub_strcmp = __pi_strcmp;
__efistub_strncmp = __pi_strncmp;
__efistub___flush_dcache_area = __pi___flush_dcache_area;
#ifdef CONFIG_KASAN
__efistub___memcpy = __pi_memcpy;
__efistub___memmove = __pi_memmove;
__efistub___memset = __pi_memset;
#endif
__efistub__text = _text;
__efistub__end = _end;
__efistub__edata = _edata;

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@ -21,6 +21,7 @@
#include <linux/bitops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/moduleloader.h>
@ -34,9 +35,18 @@
void *module_alloc(unsigned long size)
{
return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
NUMA_NO_NODE, __builtin_return_address(0));
void *p;
p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR, MODULES_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
NUMA_NO_NODE, __builtin_return_address(0));
if (p && (kasan_module_alloc(p, size) < 0)) {
vfree(p);
return NULL;
}
return p;
}
enum aarch64_reloc_op {

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@ -54,6 +54,7 @@
#include <asm/elf.h>
#include <asm/cpufeature.h>
#include <asm/cpu_ops.h>
#include <asm/kasan.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/smp_plat.h>
@ -434,6 +435,9 @@ void __init setup_arch(char **cmdline_p)
paging_init();
relocate_initrd();
kasan_init();
request_standard_resources();
early_ioremap_reset();

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@ -68,7 +68,10 @@
stp \ptr, \regB, [\regC], \val
.endm
.weak memcpy
ENTRY(__memcpy)
ENTRY(memcpy)
#include "copy_template.S"
ret
ENDPIPROC(memcpy)
ENDPROC(__memcpy)

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@ -57,12 +57,14 @@ C_h .req x12
D_l .req x13
D_h .req x14
.weak memmove
ENTRY(__memmove)
ENTRY(memmove)
cmp dstin, src
b.lo memcpy
b.lo __memcpy
add tmp1, src, count
cmp dstin, tmp1
b.hs memcpy /* No overlap. */
b.hs __memcpy /* No overlap. */
add dst, dstin, count
add src, src, count
@ -195,3 +197,4 @@ ENTRY(memmove)
b.ne .Ltail63
ret
ENDPIPROC(memmove)
ENDPROC(__memmove)

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@ -54,6 +54,8 @@ dst .req x8
tmp3w .req w9
tmp3 .req x9
.weak memset
ENTRY(__memset)
ENTRY(memset)
mov dst, dstin /* Preserve return value. */
and A_lw, val, #255
@ -214,3 +216,4 @@ ENTRY(memset)
b.ne .Ltail_maybe_long
ret
ENDPIPROC(memset)
ENDPROC(__memset)

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@ -4,3 +4,6 @@ obj-y := dma-mapping.o extable.o fault.o init.o \
context.o proc.o pageattr.o
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
obj-$(CONFIG_ARM64_PTDUMP) += dump.o
obj-$(CONFIG_KASAN) += kasan_init.o
KASAN_SANITIZE_kasan_init.o := n

165
arch/arm64/mm/kasan_init.c Normal file
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@ -0,0 +1,165 @@
/*
* This file contains kasan initialization code for ARM64.
*
* Copyright (c) 2015 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#define pr_fmt(fmt) "kasan: " fmt
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/memblock.h>
#include <linux/start_kernel.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
unsigned long end)
{
pte_t *pte;
unsigned long next;
if (pmd_none(*pmd))
pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
pte = pte_offset_kernel(pmd, addr);
do {
next = addr + PAGE_SIZE;
set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
PAGE_KERNEL));
} while (pte++, addr = next, addr != end && pte_none(*pte));
}
static void __init kasan_early_pmd_populate(pud_t *pud,
unsigned long addr,
unsigned long end)
{
pmd_t *pmd;
unsigned long next;
if (pud_none(*pud))
pud_populate(&init_mm, pud, kasan_zero_pmd);
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
kasan_early_pte_populate(pmd, addr, next);
} while (pmd++, addr = next, addr != end && pmd_none(*pmd));
}
static void __init kasan_early_pud_populate(pgd_t *pgd,
unsigned long addr,
unsigned long end)
{
pud_t *pud;
unsigned long next;
if (pgd_none(*pgd))
pgd_populate(&init_mm, pgd, kasan_zero_pud);
pud = pud_offset(pgd, addr);
do {
next = pud_addr_end(addr, end);
kasan_early_pmd_populate(pud, addr, next);
} while (pud++, addr = next, addr != end && pud_none(*pud));
}
static void __init kasan_map_early_shadow(void)
{
unsigned long addr = KASAN_SHADOW_START;
unsigned long end = KASAN_SHADOW_END;
unsigned long next;
pgd_t *pgd;
pgd = pgd_offset_k(addr);
do {
next = pgd_addr_end(addr, end);
kasan_early_pud_populate(pgd, addr, next);
} while (pgd++, addr = next, addr != end);
}
void __init kasan_early_init(void)
{
BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
kasan_map_early_shadow();
}
static void __init clear_pgds(unsigned long start,
unsigned long end)
{
/*
* Remove references to kasan page tables from
* swapper_pg_dir. pgd_clear() can't be used
* here because it's nop on 2,3-level pagetable setups
*/
for (; start < end; start += PGDIR_SIZE)
set_pgd(pgd_offset_k(start), __pgd(0));
}
static void __init cpu_set_ttbr1(unsigned long ttbr1)
{
asm(
" msr ttbr1_el1, %0\n"
" isb"
:
: "r" (ttbr1));
}
void __init kasan_init(void)
{
struct memblock_region *reg;
/*
* We are going to perform proper setup of shadow memory.
* At first we should unmap early shadow (clear_pgds() call bellow).
* However, instrumented code couldn't execute without shadow memory.
* tmp_pg_dir used to keep early shadow mapped until full shadow
* setup will be finished.
*/
memcpy(tmp_pg_dir, swapper_pg_dir, sizeof(tmp_pg_dir));
cpu_set_ttbr1(__pa(tmp_pg_dir));
flush_tlb_all();
clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
kasan_mem_to_shadow((void *)MODULES_VADDR));
for_each_memblock(memory, reg) {
void *start = (void *)__phys_to_virt(reg->base);
void *end = (void *)__phys_to_virt(reg->base + reg->size);
if (start >= end)
break;
/*
* end + 1 here is intentional. We check several shadow bytes in
* advance to slightly speed up fastpath. In some rare cases
* we could cross boundary of mapped shadow, so we just map
* some more here.
*/
vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
(unsigned long)kasan_mem_to_shadow(end) + 1,
pfn_to_nid(virt_to_pfn(start)));
}
memset(kasan_zero_page, 0, PAGE_SIZE);
cpu_set_ttbr1(__pa(swapper_pg_dir));
flush_tlb_all();
/* At this point kasan is fully initialized. Enable error messages */
init_task.kasan_depth = 0;
pr_info("KernelAddressSanitizer initialized\n");
}

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@ -1,6 +1,14 @@
#
# Makefile for linux kernel
#
#
# ARM64 maps efi runtime services in userspace addresses
# which don't have KASAN shadow. So dereference of these addresses
# in efi_call_virt() will cause crash if this code instrumented.
#
KASAN_SANITIZE_runtime-wrappers.o := n
obj-$(CONFIG_EFI) += efi.o vars.o reboot.o
obj-$(CONFIG_EFI_VARS) += efivars.o
obj-$(CONFIG_EFI_ESRT) += esrt.o

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@ -5,10 +5,12 @@ else
call_threshold := 0
endif
KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
CFLAGS_KASAN := $(call cc-option, -fsanitize=kernel-address \
-fasan-shadow-offset=$(CONFIG_KASAN_SHADOW_OFFSET) \
-fasan-shadow-offset=$(KASAN_SHADOW_OFFSET) \
--param asan-stack=1 --param asan-globals=1 \
--param asan-instrumentation-with-call-threshold=$(call_threshold))