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1// SPDX-License-Identifier: GPL-2.02/*3 * This file contains core generic KASAN code.4 *5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>7 *8 * Some code borrowed from https://github.com/xairy/kasan-prototype by9 * Andrey Konovalov <andreyknvl@gmail.com>10 */11 12#include <linux/export.h>13#include <linux/interrupt.h>14#include <linux/init.h>15#include <linux/kasan.h>16#include <linux/kernel.h>17#include <linux/kfence.h>18#include <linux/kmemleak.h>19#include <linux/linkage.h>20#include <linux/memblock.h>21#include <linux/memory.h>22#include <linux/mm.h>23#include <linux/module.h>24#include <linux/printk.h>25#include <linux/sched.h>26#include <linux/sched/task_stack.h>27#include <linux/slab.h>28#include <linux/spinlock.h>29#include <linux/stackdepot.h>30#include <linux/stacktrace.h>31#include <linux/string.h>32#include <linux/types.h>33#include <linux/vmalloc.h>34#include <linux/bug.h>35 36#include "kasan.h"37#include "../slab.h"38 39/*40 * All functions below always inlined so compiler could41 * perform better optimizations in each of __asan_loadX/__assn_storeX42 * depending on memory access size X.43 */44 45static __always_inline bool memory_is_poisoned_1(const void *addr)46{47 s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr);48 49 if (unlikely(shadow_value)) {50 s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK;51 return unlikely(last_accessible_byte >= shadow_value);52 }53 54 return false;55}56 57static __always_inline bool memory_is_poisoned_2_4_8(const void *addr,58 unsigned long size)59{60 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr);61 62 /*63 * Access crosses 8(shadow size)-byte boundary. Such access maps64 * into 2 shadow bytes, so we need to check them both.65 */66 if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))67 return *shadow_addr || memory_is_poisoned_1(addr + size - 1);68 69 return memory_is_poisoned_1(addr + size - 1);70}71 72static __always_inline bool memory_is_poisoned_16(const void *addr)73{74 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr);75 76 /* Unaligned 16-bytes access maps into 3 shadow bytes. */77 if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE)))78 return *shadow_addr || memory_is_poisoned_1(addr + 15);79 80 return *shadow_addr;81}82 83static __always_inline unsigned long bytes_is_nonzero(const u8 *start,84 size_t size)85{86 while (size) {87 if (unlikely(*start))88 return (unsigned long)start;89 start++;90 size--;91 }92 93 return 0;94}95 96static __always_inline unsigned long memory_is_nonzero(const void *start,97 const void *end)98{99 unsigned int words;100 unsigned long ret;101 unsigned int prefix = (unsigned long)start % 8;102 103 if (end - start <= 16)104 return bytes_is_nonzero(start, end - start);105 106 if (prefix) {107 prefix = 8 - prefix;108 ret = bytes_is_nonzero(start, prefix);109 if (unlikely(ret))110 return ret;111 start += prefix;112 }113 114 words = (end - start) / 8;115 while (words) {116 if (unlikely(*(u64 *)start))117 return bytes_is_nonzero(start, 8);118 start += 8;119 words--;120 }121 122 return bytes_is_nonzero(start, (end - start) % 8);123}124 125static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)126{127 unsigned long ret;128 129 ret = memory_is_nonzero(kasan_mem_to_shadow(addr),130 kasan_mem_to_shadow(addr + size - 1) + 1);131 132 if (unlikely(ret)) {133 const void *last_byte = addr + size - 1;134 s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte);135 s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;136 137 if (unlikely(ret != (unsigned long)last_shadow ||138 last_accessible_byte >= *last_shadow))139 return true;140 }141 return false;142}143 144static __always_inline bool memory_is_poisoned(const void *addr, size_t size)145{146 if (__builtin_constant_p(size)) {147 switch (size) {148 case 1:149 return memory_is_poisoned_1(addr);150 case 2:151 case 4:152 case 8:153 return memory_is_poisoned_2_4_8(addr, size);154 case 16:155 return memory_is_poisoned_16(addr);156 default:157 BUILD_BUG();158 }159 }160 161 return memory_is_poisoned_n(addr, size);162}163 164static __always_inline bool check_region_inline(const void *addr,165 size_t size, bool write,166 unsigned long ret_ip)167{168 if (!kasan_arch_is_ready())169 return true;170 171 if (unlikely(size == 0))172 return true;173 174 if (unlikely(addr + size < addr))175 return !kasan_report(addr, size, write, ret_ip);176 177 if (unlikely(!addr_has_metadata(addr)))178 return !kasan_report(addr, size, write, ret_ip);179 180 if (likely(!memory_is_poisoned(addr, size)))181 return true;182 183 return !kasan_report(addr, size, write, ret_ip);184}185 186bool kasan_check_range(const void *addr, size_t size, bool write,187 unsigned long ret_ip)188{189 return check_region_inline(addr, size, write, ret_ip);190}191 192bool kasan_byte_accessible(const void *addr)193{194 s8 shadow_byte;195 196 if (!kasan_arch_is_ready())197 return true;198 199 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));200 201 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;202}203 204void kasan_cache_shrink(struct kmem_cache *cache)205{206 kasan_quarantine_remove_cache(cache);207}208 209void kasan_cache_shutdown(struct kmem_cache *cache)210{211 if (!__kmem_cache_empty(cache))212 kasan_quarantine_remove_cache(cache);213}214 215static void register_global(struct kasan_global *global)216{217 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);218 219 kasan_unpoison(global->beg, global->size, false);220 221 kasan_poison(global->beg + aligned_size,222 global->size_with_redzone - aligned_size,223 KASAN_GLOBAL_REDZONE, false);224}225 226void __asan_register_globals(void *ptr, ssize_t size)227{228 int i;229 struct kasan_global *globals = ptr;230 231 for (i = 0; i < size; i++)232 register_global(&globals[i]);233}234EXPORT_SYMBOL(__asan_register_globals);235 236void __asan_unregister_globals(void *ptr, ssize_t size)237{238}239EXPORT_SYMBOL(__asan_unregister_globals);240 241#define DEFINE_ASAN_LOAD_STORE(size) \242 void __asan_load##size(void *addr) \243 { \244 check_region_inline(addr, size, false, _RET_IP_); \245 } \246 EXPORT_SYMBOL(__asan_load##size); \247 __alias(__asan_load##size) \248 void __asan_load##size##_noabort(void *); \249 EXPORT_SYMBOL(__asan_load##size##_noabort); \250 void __asan_store##size(void *addr) \251 { \252 check_region_inline(addr, size, true, _RET_IP_); \253 } \254 EXPORT_SYMBOL(__asan_store##size); \255 __alias(__asan_store##size) \256 void __asan_store##size##_noabort(void *); \257 EXPORT_SYMBOL(__asan_store##size##_noabort)258 259DEFINE_ASAN_LOAD_STORE(1);260DEFINE_ASAN_LOAD_STORE(2);261DEFINE_ASAN_LOAD_STORE(4);262DEFINE_ASAN_LOAD_STORE(8);263DEFINE_ASAN_LOAD_STORE(16);264 265void __asan_loadN(void *addr, ssize_t size)266{267 kasan_check_range(addr, size, false, _RET_IP_);268}269EXPORT_SYMBOL(__asan_loadN);270 271__alias(__asan_loadN)272void __asan_loadN_noabort(void *, ssize_t);273EXPORT_SYMBOL(__asan_loadN_noabort);274 275void __asan_storeN(void *addr, ssize_t size)276{277 kasan_check_range(addr, size, true, _RET_IP_);278}279EXPORT_SYMBOL(__asan_storeN);280 281__alias(__asan_storeN)282void __asan_storeN_noabort(void *, ssize_t);283EXPORT_SYMBOL(__asan_storeN_noabort);284 285/* to shut up compiler complaints */286void __asan_handle_no_return(void) {}287EXPORT_SYMBOL(__asan_handle_no_return);288 289/* Emitted by compiler to poison alloca()ed objects. */290void __asan_alloca_poison(void *addr, ssize_t size)291{292 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);293 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -294 rounded_up_size;295 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);296 297 const void *left_redzone = (const void *)(addr -298 KASAN_ALLOCA_REDZONE_SIZE);299 const void *right_redzone = (const void *)(addr + rounded_up_size);300 301 WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE));302 303 kasan_unpoison((const void *)(addr + rounded_down_size),304 size - rounded_down_size, false);305 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,306 KASAN_ALLOCA_LEFT, false);307 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,308 KASAN_ALLOCA_RIGHT, false);309}310EXPORT_SYMBOL(__asan_alloca_poison);311 312/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */313void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom)314{315 if (unlikely(!stack_top || stack_top > (void *)stack_bottom))316 return;317 318 kasan_unpoison(stack_top, (void *)stack_bottom - stack_top, false);319}320EXPORT_SYMBOL(__asan_allocas_unpoison);321 322/* Emitted by the compiler to [un]poison local variables. */323#define DEFINE_ASAN_SET_SHADOW(byte) \324 void __asan_set_shadow_##byte(const void *addr, ssize_t size) \325 { \326 __memset((void *)addr, 0x##byte, size); \327 } \328 EXPORT_SYMBOL(__asan_set_shadow_##byte)329 330DEFINE_ASAN_SET_SHADOW(00);331DEFINE_ASAN_SET_SHADOW(f1);332DEFINE_ASAN_SET_SHADOW(f2);333DEFINE_ASAN_SET_SHADOW(f3);334DEFINE_ASAN_SET_SHADOW(f5);335DEFINE_ASAN_SET_SHADOW(f8);336 337/*338 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.339 * For larger allocations larger redzones are used.340 */341static inline unsigned int optimal_redzone(unsigned int object_size)342{343 return344 object_size <= 64 - 16 ? 16 :345 object_size <= 128 - 32 ? 32 :346 object_size <= 512 - 64 ? 64 :347 object_size <= 4096 - 128 ? 128 :348 object_size <= (1 << 14) - 256 ? 256 :349 object_size <= (1 << 15) - 512 ? 512 :350 object_size <= (1 << 16) - 1024 ? 1024 : 2048;351}352 353void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,354 slab_flags_t *flags)355{356 unsigned int ok_size;357 unsigned int optimal_size;358 unsigned int rem_free_meta_size;359 unsigned int orig_alloc_meta_offset;360 361 if (!kasan_requires_meta())362 return;363 364 /*365 * SLAB_KASAN is used to mark caches that are sanitized by KASAN and366 * that thus have per-object metadata. Currently, this flag is used in367 * slab_ksize() to account for per-object metadata when calculating the368 * size of the accessible memory within the object. Additionally, we use369 * SLAB_NO_MERGE to prevent merging of caches with per-object metadata.370 */371 *flags |= SLAB_KASAN | SLAB_NO_MERGE;372 373 ok_size = *size;374 375 /* Add alloc meta into the redzone. */376 cache->kasan_info.alloc_meta_offset = *size;377 *size += sizeof(struct kasan_alloc_meta);378 379 /* If alloc meta doesn't fit, don't add it. */380 if (*size > KMALLOC_MAX_SIZE) {381 cache->kasan_info.alloc_meta_offset = 0;382 *size = ok_size;383 /* Continue, since free meta might still fit. */384 }385 386 ok_size = *size;387 orig_alloc_meta_offset = cache->kasan_info.alloc_meta_offset;388 389 /*390 * Store free meta in the redzone when it's not possible to store391 * it in the object. This is the case when:392 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can393 * be touched after it was freed, or394 * 2. Object has a constructor, which means it's expected to395 * retain its content until the next allocation.396 */397 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor) {398 cache->kasan_info.free_meta_offset = *size;399 *size += sizeof(struct kasan_free_meta);400 goto free_meta_added;401 }402 403 /*404 * Otherwise, if the object is large enough to contain free meta,405 * store it within the object.406 */407 if (sizeof(struct kasan_free_meta) <= cache->object_size) {408 /* cache->kasan_info.free_meta_offset = 0 is implied. */409 goto free_meta_added;410 }411 412 /*413 * For smaller objects, store the beginning of free meta within the414 * object and the end in the redzone. And thus shift the location of415 * alloc meta to free up space for free meta.416 * This is only possible when slub_debug is disabled, as otherwise417 * the end of free meta will overlap with slub_debug metadata.418 */419 if (!__slub_debug_enabled()) {420 rem_free_meta_size = sizeof(struct kasan_free_meta) -421 cache->object_size;422 *size += rem_free_meta_size;423 if (cache->kasan_info.alloc_meta_offset != 0)424 cache->kasan_info.alloc_meta_offset += rem_free_meta_size;425 goto free_meta_added;426 }427 428 /*429 * If the object is small and slub_debug is enabled, store free meta430 * in the redzone after alloc meta.431 */432 cache->kasan_info.free_meta_offset = *size;433 *size += sizeof(struct kasan_free_meta);434 435free_meta_added:436 /* If free meta doesn't fit, don't add it. */437 if (*size > KMALLOC_MAX_SIZE) {438 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;439 cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;440 *size = ok_size;441 }442 443 /* Calculate size with optimal redzone. */444 optimal_size = cache->object_size + optimal_redzone(cache->object_size);445 /* Limit it with KMALLOC_MAX_SIZE. */446 if (optimal_size > KMALLOC_MAX_SIZE)447 optimal_size = KMALLOC_MAX_SIZE;448 /* Use optimal size if the size with added metas is not large enough. */449 if (*size < optimal_size)450 *size = optimal_size;451}452 453struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,454 const void *object)455{456 if (!cache->kasan_info.alloc_meta_offset)457 return NULL;458 return (void *)object + cache->kasan_info.alloc_meta_offset;459}460 461struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,462 const void *object)463{464 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);465 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)466 return NULL;467 return (void *)object + cache->kasan_info.free_meta_offset;468}469 470void kasan_init_object_meta(struct kmem_cache *cache, const void *object)471{472 struct kasan_alloc_meta *alloc_meta;473 474 alloc_meta = kasan_get_alloc_meta(cache, object);475 if (alloc_meta) {476 /* Zero out alloc meta to mark it as invalid. */477 __memset(alloc_meta, 0, sizeof(*alloc_meta));478 }479 480 /*481 * Explicitly marking free meta as invalid is not required: the shadow482 * value for the first 8 bytes of a newly allocated object is not483 * KASAN_SLAB_FREE_META.484 */485}486 487static void release_alloc_meta(struct kasan_alloc_meta *meta)488{489 /* Zero out alloc meta to mark it as invalid. */490 __memset(meta, 0, sizeof(*meta));491}492 493static void release_free_meta(const void *object, struct kasan_free_meta *meta)494{495 if (!kasan_arch_is_ready())496 return;497 498 /* Check if free meta is valid. */499 if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)500 return;501 502 /* Mark free meta as invalid. */503 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;504}505 506size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)507{508 struct kasan_cache *info = &cache->kasan_info;509 510 if (!kasan_requires_meta())511 return 0;512 513 if (in_object)514 return (info->free_meta_offset ?515 0 : sizeof(struct kasan_free_meta));516 else517 return (info->alloc_meta_offset ?518 sizeof(struct kasan_alloc_meta) : 0) +519 ((info->free_meta_offset &&520 info->free_meta_offset != KASAN_NO_FREE_META) ?521 sizeof(struct kasan_free_meta) : 0);522}523 524static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)525{526 struct slab *slab = kasan_addr_to_slab(addr);527 struct kmem_cache *cache;528 struct kasan_alloc_meta *alloc_meta;529 void *object;530 531 if (is_kfence_address(addr) || !slab)532 return;533 534 cache = slab->slab_cache;535 object = nearest_obj(cache, slab, addr);536 alloc_meta = kasan_get_alloc_meta(cache, object);537 if (!alloc_meta)538 return;539 540 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];541 alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);542}543 544void kasan_record_aux_stack(void *addr)545{546 return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);547}548 549void kasan_record_aux_stack_noalloc(void *addr)550{551 return __kasan_record_aux_stack(addr, 0);552}553 554void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)555{556 struct kasan_alloc_meta *alloc_meta;557 558 alloc_meta = kasan_get_alloc_meta(cache, object);559 if (!alloc_meta)560 return;561 562 /* Invalidate previous stack traces (might exist for krealloc or mempool). */563 release_alloc_meta(alloc_meta);564 565 kasan_save_track(&alloc_meta->alloc_track, flags);566}567 568void kasan_save_free_info(struct kmem_cache *cache, void *object)569{570 struct kasan_free_meta *free_meta;571 572 free_meta = kasan_get_free_meta(cache, object);573 if (!free_meta)574 return;575 576 /* Invalidate previous stack trace (might exist for mempool). */577 release_free_meta(object, free_meta);578 579 kasan_save_track(&free_meta->free_track, 0);580 581 /* Mark free meta as valid. */582 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;583}584