diff options
Diffstat (limited to 'mm/kasan/generic.c')
| -rw-r--r-- | mm/kasan/generic.c | 588 |
1 files changed, 588 insertions, 0 deletions
diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c new file mode 100644 index 000000000000..2b8e73f5f6a7 --- /dev/null +++ b/mm/kasan/generic.c @@ -0,0 +1,588 @@ +// 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/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" + +/* + * Initialize Generic KASAN and enable runtime checks. + * This should be called from arch kasan_init() once shadow memory is ready. + */ +void __init kasan_init_generic(void) +{ + kasan_enable(); + + pr_info("KernelAddressSanitizer initialized (generic)\n"); +} + +/* + * 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_enabled()) + 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_enabled()) + 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, or + * 3. It is from a kmalloc cache which enables the debug option + * to store original size. + */ + if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor || + slub_debug_orig_size(cache)) { + 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) +{ + /* 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); +} + +/* + * This function avoids dynamic memory allocations and thus can be called from + * contexts that do not allow allocating memory. + */ +void kasan_record_aux_stack(void *addr) +{ + 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, 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; +} |