| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * This file contains core generic KASAN code. |
| * |
| * Copyright (c) 2014 Samsung Electronics Co., Ltd. |
| * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> |
| * |
| * Some code borrowed from https://github.com/xairy/kasan-prototype by |
| * Andrey Konovalov <andreyknvl@gmail.com> |
| */ |
| |
| #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/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); |
| |
| /* Only allow cache merging when no per-object metadata is present. */ |
| slab_flags_t kasan_never_merge(void) |
| { |
| if (!kasan_requires_meta()) |
| return 0; |
| return SLAB_KASAN; |
| } |
| |
| /* |
| * 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; |
| |
| 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 two places: |
| * 1. In slab_ksize() to account for per-object metadata when |
| * calculating the size of the accessible memory within the object. |
| * 2. In slab_common.c via kasan_never_merge() to prevent merging of |
| * caches with per-object metadata. |
| */ |
| *flags |= SLAB_KASAN; |
| |
| ok_size = *size; |
| |
| /* Add alloc meta into redzone. */ |
| cache->kasan_info.alloc_meta_offset = *size; |
| *size += sizeof(struct kasan_alloc_meta); |
| |
| /* |
| * If alloc meta doesn't fit, don't add it. |
| * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal |
| * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for |
| * larger sizes. |
| */ |
| if (*size > KMALLOC_MAX_SIZE) { |
| cache->kasan_info.alloc_meta_offset = 0; |
| *size = ok_size; |
| /* Continue, since free meta might still fit. */ |
| } |
| |
| /* |
| * Add free meta into 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, or |
| * 3. Object is too small. |
| * Otherwise cache->kasan_info.free_meta_offset = 0 is implied. |
| */ |
| if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor || |
| cache->object_size < sizeof(struct kasan_free_meta)) { |
| ok_size = *size; |
| |
| cache->kasan_info.free_meta_offset = *size; |
| *size += sizeof(struct kasan_free_meta); |
| |
| /* 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; |
| *size = ok_size; |
| } |
| } |
| |
| /* Calculate size with optimal redzone. */ |
| optimal_size = cache->object_size + optimal_redzone(cache->object_size); |
| /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */ |
| 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) |
| __memset(alloc_meta, 0, sizeof(*alloc_meta)); |
| } |
| |
| 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, bool can_alloc) |
| { |
| 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, can_alloc); |
| } |
| |
| void kasan_record_aux_stack(void *addr) |
| { |
| return __kasan_record_aux_stack(addr, true); |
| } |
| |
| void kasan_record_aux_stack_noalloc(void *addr) |
| { |
| return __kasan_record_aux_stack(addr, false); |
| } |
| |
| 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) |
| kasan_set_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; |
| |
| kasan_set_track(&free_meta->free_track, 0); |
| /* The object was freed and has free track set. */ |
| *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK; |
| } |