// SPDX-License-Identifier: GPL-2.0
/*
* This file contains core generic KASAN code.
*
* Copyright (c) 2014 Samsung Electronics Co., Ltd.
* Author: Andrey Ryabinin <[email protected]>
*
* Some code borrowed from https://github.com/xairy/kasan-prototype by
* Andrey Konovalov <[email protected]>
*/
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kfence.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>
#include "kasan.h"
#include "../slab.h"
/*
* All functions below always inlined so compiler could
* perform better optimizations in each of __asan_loadX/__assn_storeX
* depending on memory access size X.
*/
static __always_inline bool memory_is_poisoned_1(const void *addr)
{
s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr);
if (unlikely(shadow_value)) {
s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK;
return unlikely(last_accessible_byte >= shadow_value);
}
return false;
}
static __always_inline bool memory_is_poisoned_2_4_8(const void *addr,
unsigned long size)
{
u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr);
/*
* Access crosses 8(shadow size)-byte boundary. Such access maps
* into 2 shadow bytes, so we need to check them both.
*/
if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
return memory_is_poisoned_1(addr + size - 1);
}
static __always_inline bool memory_is_poisoned_16(const void *addr)
{
u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr);
/* Unaligned 16-bytes access maps into 3 shadow bytes. */
if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE)))
return *shadow_addr || memory_is_poisoned_1(addr + 15);
return *shadow_addr;
}
static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
size_t size)
{
while (size) {
if (unlikely(*start))
return (unsigned long)start;
start++;
size--;
}
return 0;
}
static __always_inline unsigned long memory_is_nonzero(const void *start,
const void *end)
{
unsigned int words;
unsigned long ret;
unsigned int prefix = (unsigned long)start % 8;
if (end - start <= 16)
return bytes_is_nonzero(start, end - start);
if (prefix) {
prefix = 8 - prefix;
ret = bytes_is_nonzero(start, prefix);
if (unlikely(ret))
return ret;
start += prefix;
}
words = (end - start) / 8;
while (words) {
if (unlikely(*(u64 *)start))
return bytes_is_nonzero(start, 8);
start += 8;
words--;
}
return bytes_is_nonzero(start, (end - start) % 8);
}
static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)
{
unsigned long ret;
ret = memory_is_nonzero(kasan_mem_to_shadow(addr),
kasan_mem_to_shadow(addr + size - 1) + 1);
if (unlikely(ret)) {
const void *last_byte = addr + size - 1;
s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte);
s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;
if (unlikely(ret != (unsigned long)last_shadow ||
last_accessible_byte >= *last_shadow))
return true;
}
return false;
}
static __always_inline bool memory_is_poisoned(const void *addr, size_t size)
{
if (__builtin_constant_p(size)) {
switch (size) {
case 1:
return memory_is_poisoned_1(addr);
case 2:
case 4:
case 8:
return memory_is_poisoned_2_4_8(addr, size);
case 16:
return memory_is_poisoned_16(addr);
default:
BUILD_BUG();
}
}
return memory_is_poisoned_n(addr, size);
}
static __always_inline bool check_region_inline(const void *addr,
size_t size, bool write,
unsigned long ret_ip)
{
if (!kasan_arch_is_ready())
return true;
if (unlikely(size == 0))
return true;
if (unlikely(addr + size < addr))
return !kasan_report(addr, size, write, ret_ip);
if (unlikely(!addr_has_metadata(addr)))
return !kasan_report(addr, size, write, ret_ip);
if (likely(!memory_is_poisoned(addr, size)))
return true;
return !kasan_report(addr, size, write, ret_ip);
}
bool kasan_check_range(const void *addr, size_t size, bool write,
unsigned long ret_ip)
{
return check_region_inline(addr, size, write, ret_ip);
}
bool kasan_byte_accessible(const void *addr)
{
s8 shadow_byte;
if (!kasan_arch_is_ready())
return true;
shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
}
void kasan_cache_shrink(struct kmem_cache *cache)
{
kasan_quarantine_remove_cache(cache);
}
void kasan_cache_shutdown(struct kmem_cache *cache)
{
if (!__kmem_cache_empty(cache))
kasan_quarantine_remove_cache(cache);
}
static void register_global(struct kasan_global *global)
{
size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
kasan_unpoison(global->beg, global->size, false);
kasan_poison(global->beg + aligned_size,
global->size_with_redzone - aligned_size,
KASAN_GLOBAL_REDZONE, false);
}
void __asan_register_globals(void *ptr, ssize_t size)
{
int i;
struct kasan_global *globals = ptr;
for (i = 0; i < size; i++)
register_global(&globals[i]);
}
EXPORT_SYMBOL(__asan_register_globals);
void __asan_unregister_globals(void *ptr, ssize_t size)
{
}
EXPORT_SYMBOL(__asan_unregister_globals);
#define DEFINE_ASAN_LOAD_STORE(size) \
void __asan_load##size(void *addr) \
{ \
check_region_inline(addr, size, false, _RET_IP_); \
} \
EXPORT_SYMBOL(__asan_load##size); \
__alias(__asan_load##size) \
void __asan_load##size##_noabort(void *); \
EXPORT_SYMBOL(__asan_load##size##_noabort); \
void __asan_store##size(void *addr) \
{ \
check_region_inline(addr, size, true, _RET_IP_); \
} \
EXPORT_SYMBOL(__asan_store##size); \
__alias(__asan_store##size) \
void __asan_store##size##_noabort(void *); \
EXPORT_SYMBOL(__asan_store##size##_noabort)
DEFINE_ASAN_LOAD_STORE(1);
DEFINE_ASAN_LOAD_STORE(2);
DEFINE_ASAN_LOAD_STORE(4);
DEFINE_ASAN_LOAD_STORE(8);
DEFINE_ASAN_LOAD_STORE(16);
void __asan_loadN(void *addr, ssize_t size)
{
kasan_check_range(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_loadN);
__alias(__asan_loadN)
void __asan_loadN_noabort(void *, ssize_t);
EXPORT_SYMBOL(__asan_loadN_noabort);
void __asan_storeN(void *addr, ssize_t size)
{
kasan_check_range(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_storeN);
__alias(__asan_storeN)
void __asan_storeN_noabort(void *, ssize_t);
EXPORT_SYMBOL(__asan_storeN_noabort);
/* to shut up compiler complaints */
void __asan_handle_no_return(void) {}
EXPORT_SYMBOL(__asan_handle_no_return);
/* Emitted by compiler to poison alloca()ed objects. */
void __asan_alloca_poison(void *addr, ssize_t size)
{
size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
rounded_up_size;
size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
const void *left_redzone = (const void *)(addr -
KASAN_ALLOCA_REDZONE_SIZE);
const void *right_redzone = (const void *)(addr + rounded_up_size);
WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE));
kasan_unpoison((const void *)(addr + rounded_down_size),
size - rounded_down_size, false);
kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
KASAN_ALLOCA_LEFT, false);
kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
KASAN_ALLOCA_RIGHT, false);
}
EXPORT_SYMBOL(__asan_alloca_poison);
/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom)
{
if (unlikely(!stack_top || stack_top > (void *)stack_bottom))
return;
kasan_unpoison(stack_top, (void *)stack_bottom - stack_top, false);
}
EXPORT_SYMBOL(__asan_allocas_unpoison);
/* Emitted by the compiler to [un]poison local variables. */
#define DEFINE_ASAN_SET_SHADOW(byte) \
void __asan_set_shadow_##byte(const void *addr, ssize_t size) \
{ \
__memset((void *)addr, 0x##byte, size); \
} \
EXPORT_SYMBOL(__asan_set_shadow_##byte)
DEFINE_ASAN_SET_SHADOW(00);
DEFINE_ASAN_SET_SHADOW(f1);
DEFINE_ASAN_SET_SHADOW(f2);
DEFINE_ASAN_SET_SHADOW(f3);
DEFINE_ASAN_SET_SHADOW(f5);
DEFINE_ASAN_SET_SHADOW(f8);
/*
* Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
* For larger allocations larger redzones are used.
*/
static inline unsigned int optimal_redzone(unsigned int object_size)
{
return
object_size <= 64 - 16 ? 16 :
object_size <= 128 - 32 ? 32 :
object_size <= 512 - 64 ? 64 :
object_size <= 4096 - 128 ? 128 :
object_size <= (1 << 14) - 256 ? 256 :
object_size <= (1 << 15) - 512 ? 512 :
object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}
void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
slab_flags_t *flags)
{
unsigned int ok_size;
unsigned int optimal_size;
unsigned int rem_free_meta_size;
unsigned int orig_alloc_meta_offset;
if (!kasan_requires_meta())
return;
/*
* SLAB_KASAN is used to mark caches that are sanitized by KASAN and
* that thus have per-object metadata. Currently, this flag is used in
* slab_ksize() to account for per-object metadata when calculating the
* size of the accessible memory within the object. Additionally, we use
* SLAB_NO_MERGE to prevent merging of caches with per-object metadata.
*/
*flags |= SLAB_KASAN | SLAB_NO_MERGE;
ok_size = *size;
/* Add alloc meta into the redzone. */
cache->kasan_info.alloc_meta_offset = *size;
*size += sizeof(struct kasan_alloc_meta);
/* If alloc meta doesn't fit, don't add it. */
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.alloc_meta_offset = 0;
*size = ok_size;
/* Continue, since free meta might still fit. */
}
ok_size = *size;
orig_alloc_meta_offset = cache->kasan_info.alloc_meta_offset;
/*
* Store free meta in the redzone when it's not possible to store
* it in the object. This is the case when:
* 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
* be touched after it was freed, or
* 2. Object has a constructor, which means it's expected to
* retain its content until the next allocation.
*/
if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor) {
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
goto free_meta_added;
}
/*
* Otherwise, if the object is large enough to contain free meta,
* store it within the object.
*/
if (sizeof(struct kasan_free_meta) <= cache->object_size) {
/* cache->kasan_info.free_meta_offset = 0 is implied. */
goto free_meta_added;
}
/*
* For smaller objects, store the beginning of free meta within the
* object and the end in the redzone. And thus shift the location of
* alloc meta to free up space for free meta.
* This is only possible when slub_debug is disabled, as otherwise
* the end of free meta will overlap with slub_debug metadata.
*/
if (!__slub_debug_enabled()) {
rem_free_meta_size = sizeof(struct kasan_free_meta) -
cache->object_size;
*size += rem_free_meta_size;
if (cache->kasan_info.alloc_meta_offset != 0)
cache->kasan_info.alloc_meta_offset += rem_free_meta_size;
goto free_meta_added;
}
/*
* If the object is small and slub_debug is enabled, store free meta
* in the redzone after alloc meta.
*/
cache->kasan_info.free_meta_offset = *size;
*size += sizeof(struct kasan_free_meta);
free_meta_added:
/* If free meta doesn't fit, don't add it. */
if (*size > KMALLOC_MAX_SIZE) {
cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;
*size = ok_size;
}
/* Calculate size with optimal redzone. */
optimal_size = cache->object_size + optimal_redzone(cache->object_size);
/* Limit it with KMALLOC_MAX_SIZE. */
if (optimal_size > KMALLOC_MAX_SIZE)
optimal_size = KMALLOC_MAX_SIZE;
/* Use optimal size if the size with added metas is not large enough. */
if (*size < optimal_size)
*size = optimal_size;
}
struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
const void *object)
{
if (!cache->kasan_info.alloc_meta_offset)
return NULL;
return (void *)object + cache->kasan_info.alloc_meta_offset;
}
struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
const void *object)
{
BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
return NULL;
return (void *)object + cache->kasan_info.free_meta_offset;
}
void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
{
struct kasan_alloc_meta *alloc_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
if (alloc_meta) {
/* Zero out alloc meta to mark it as invalid. */
__memset(alloc_meta, 0, sizeof(*alloc_meta));
}
/*
* Explicitly marking free meta as invalid is not required: the shadow
* value for the first 8 bytes of a newly allocated object is not
* KASAN_SLAB_FREE_META.
*/
}
static void release_alloc_meta(struct kasan_alloc_meta *meta)
{
/* Zero out alloc meta to mark it as invalid. */
__memset(meta, 0, sizeof(*meta));
}
static void release_free_meta(const void *object, struct kasan_free_meta *meta)
{
if (!kasan_arch_is_ready())
return;
/* Check if free meta is valid. */
if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
return;
/* Mark free meta as invalid. */
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
}
size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
{
struct kasan_cache *info = &cache->kasan_info;
if (!kasan_requires_meta())
return 0;
if (in_object)
return (info->free_meta_offset ?
0 : sizeof(struct kasan_free_meta));
else
return (info->alloc_meta_offset ?
sizeof(struct kasan_alloc_meta) : 0) +
((info->free_meta_offset &&
info->free_meta_offset != KASAN_NO_FREE_META) ?
sizeof(struct kasan_free_meta) : 0);
}
static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
{
struct slab *slab = kasan_addr_to_slab(addr);
struct kmem_cache *cache;
struct kasan_alloc_meta *alloc_meta;
void *object;
if (is_kfence_address(addr) || !slab)
return;
cache = slab->slab_cache;
object = nearest_obj(cache, slab, addr);
alloc_meta = kasan_get_alloc_meta(cache, object);
if (!alloc_meta)
return;
alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
}
void kasan_record_aux_stack(void *addr)
{
return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);
}
void kasan_record_aux_stack_noalloc(void *addr)
{
return __kasan_record_aux_stack(addr, 0);
}
void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
{
struct kasan_alloc_meta *alloc_meta;
alloc_meta = kasan_get_alloc_meta(cache, object);
if (!alloc_meta)
return;
/* Invalidate previous stack traces (might exist for krealloc or mempool). */
release_alloc_meta(alloc_meta);
kasan_save_track(&alloc_meta->alloc_track, flags);
}
void kasan_save_free_info(struct kmem_cache *cache, void *object)
{
struct kasan_free_meta *free_meta;
free_meta = kasan_get_free_meta(cache, object);
if (!free_meta)
return;
/* Invalidate previous stack trace (might exist for mempool). */
release_free_meta(object, free_meta);
kasan_save_track(&free_meta->free_track, 0);
/* Mark free meta as valid. */
*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;
}
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