1 // SPDX-License-Identifier: GPL-2.0 2 /* 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 by 9 * 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/stacktrace.h> 29 #include <linux/string.h> 30 #include <linux/types.h> 31 #include <linux/vmalloc.h> 32 #include <linux/bug.h> 33 34 #include "kasan.h" 35 #include "../slab.h" 36 37 /* 38 * All functions below always inlined so compiler could 39 * perform better optimizations in each of __asan_loadX/__assn_storeX 40 * depending on memory access size X. 41 */ 42 43 static __always_inline bool memory_is_poisoned_1(const void *addr) 44 { 45 s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr); 46 47 if (unlikely(shadow_value)) { 48 s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK; 49 return unlikely(last_accessible_byte >= shadow_value); 50 } 51 52 return false; 53 } 54 55 static __always_inline bool memory_is_poisoned_2_4_8(const void *addr, 56 unsigned long size) 57 { 58 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr); 59 60 /* 61 * Access crosses 8(shadow size)-byte boundary. Such access maps 62 * into 2 shadow bytes, so we need to check them both. 63 */ 64 if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1)) 65 return *shadow_addr || memory_is_poisoned_1(addr + size - 1); 66 67 return memory_is_poisoned_1(addr + size - 1); 68 } 69 70 static __always_inline bool memory_is_poisoned_16(const void *addr) 71 { 72 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr); 73 74 /* Unaligned 16-bytes access maps into 3 shadow bytes. */ 75 if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE))) 76 return *shadow_addr || memory_is_poisoned_1(addr + 15); 77 78 return *shadow_addr; 79 } 80 81 static __always_inline unsigned long bytes_is_nonzero(const u8 *start, 82 size_t size) 83 { 84 while (size) { 85 if (unlikely(*start)) 86 return (unsigned long)start; 87 start++; 88 size--; 89 } 90 91 return 0; 92 } 93 94 static __always_inline unsigned long memory_is_nonzero(const void *start, 95 const void *end) 96 { 97 unsigned int words; 98 unsigned long ret; 99 unsigned int prefix = (unsigned long)start % 8; 100 101 if (end - start <= 16) 102 return bytes_is_nonzero(start, end - start); 103 104 if (prefix) { 105 prefix = 8 - prefix; 106 ret = bytes_is_nonzero(start, prefix); 107 if (unlikely(ret)) 108 return ret; 109 start += prefix; 110 } 111 112 words = (end - start) / 8; 113 while (words) { 114 if (unlikely(*(u64 *)start)) 115 return bytes_is_nonzero(start, 8); 116 start += 8; 117 words--; 118 } 119 120 return bytes_is_nonzero(start, (end - start) % 8); 121 } 122 123 static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size) 124 { 125 unsigned long ret; 126 127 ret = memory_is_nonzero(kasan_mem_to_shadow(addr), 128 kasan_mem_to_shadow(addr + size - 1) + 1); 129 130 if (unlikely(ret)) { 131 const void *last_byte = addr + size - 1; 132 s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte); 133 s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK; 134 135 if (unlikely(ret != (unsigned long)last_shadow || 136 last_accessible_byte >= *last_shadow)) 137 return true; 138 } 139 return false; 140 } 141 142 static __always_inline bool memory_is_poisoned(const void *addr, size_t size) 143 { 144 if (__builtin_constant_p(size)) { 145 switch (size) { 146 case 1: 147 return memory_is_poisoned_1(addr); 148 case 2: 149 case 4: 150 case 8: 151 return memory_is_poisoned_2_4_8(addr, size); 152 case 16: 153 return memory_is_poisoned_16(addr); 154 default: 155 BUILD_BUG(); 156 } 157 } 158 159 return memory_is_poisoned_n(addr, size); 160 } 161 162 static __always_inline bool check_region_inline(const void *addr, 163 size_t size, bool write, 164 unsigned long ret_ip) 165 { 166 if (!kasan_arch_is_ready()) 167 return true; 168 169 if (unlikely(size == 0)) 170 return true; 171 172 if (unlikely(addr + size < addr)) 173 return !kasan_report(addr, size, write, ret_ip); 174 175 if (unlikely(!addr_has_metadata(addr))) 176 return !kasan_report(addr, size, write, ret_ip); 177 178 if (likely(!memory_is_poisoned(addr, size))) 179 return true; 180 181 return !kasan_report(addr, size, write, ret_ip); 182 } 183 184 bool kasan_check_range(const void *addr, size_t size, bool write, 185 unsigned long ret_ip) 186 { 187 return check_region_inline(addr, size, write, ret_ip); 188 } 189 190 bool kasan_byte_accessible(const void *addr) 191 { 192 s8 shadow_byte; 193 194 if (!kasan_arch_is_ready()) 195 return true; 196 197 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr)); 198 199 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE; 200 } 201 202 void kasan_cache_shrink(struct kmem_cache *cache) 203 { 204 kasan_quarantine_remove_cache(cache); 205 } 206 207 void kasan_cache_shutdown(struct kmem_cache *cache) 208 { 209 if (!__kmem_cache_empty(cache)) 210 kasan_quarantine_remove_cache(cache); 211 } 212 213 static void register_global(struct kasan_global *global) 214 { 215 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE); 216 217 kasan_unpoison(global->beg, global->size, false); 218 219 kasan_poison(global->beg + aligned_size, 220 global->size_with_redzone - aligned_size, 221 KASAN_GLOBAL_REDZONE, false); 222 } 223 224 void __asan_register_globals(void *ptr, ssize_t size) 225 { 226 int i; 227 struct kasan_global *globals = ptr; 228 229 for (i = 0; i < size; i++) 230 register_global(&globals[i]); 231 } 232 EXPORT_SYMBOL(__asan_register_globals); 233 234 void __asan_unregister_globals(void *ptr, ssize_t size) 235 { 236 } 237 EXPORT_SYMBOL(__asan_unregister_globals); 238 239 #define DEFINE_ASAN_LOAD_STORE(size) \ 240 void __asan_load##size(void *addr) \ 241 { \ 242 check_region_inline(addr, size, false, _RET_IP_); \ 243 } \ 244 EXPORT_SYMBOL(__asan_load##size); \ 245 __alias(__asan_load##size) \ 246 void __asan_load##size##_noabort(void *); \ 247 EXPORT_SYMBOL(__asan_load##size##_noabort); \ 248 void __asan_store##size(void *addr) \ 249 { \ 250 check_region_inline(addr, size, true, _RET_IP_); \ 251 } \ 252 EXPORT_SYMBOL(__asan_store##size); \ 253 __alias(__asan_store##size) \ 254 void __asan_store##size##_noabort(void *); \ 255 EXPORT_SYMBOL(__asan_store##size##_noabort) 256 257 DEFINE_ASAN_LOAD_STORE(1); 258 DEFINE_ASAN_LOAD_STORE(2); 259 DEFINE_ASAN_LOAD_STORE(4); 260 DEFINE_ASAN_LOAD_STORE(8); 261 DEFINE_ASAN_LOAD_STORE(16); 262 263 void __asan_loadN(void *addr, ssize_t size) 264 { 265 kasan_check_range(addr, size, false, _RET_IP_); 266 } 267 EXPORT_SYMBOL(__asan_loadN); 268 269 __alias(__asan_loadN) 270 void __asan_loadN_noabort(void *, ssize_t); 271 EXPORT_SYMBOL(__asan_loadN_noabort); 272 273 void __asan_storeN(void *addr, ssize_t size) 274 { 275 kasan_check_range(addr, size, true, _RET_IP_); 276 } 277 EXPORT_SYMBOL(__asan_storeN); 278 279 __alias(__asan_storeN) 280 void __asan_storeN_noabort(void *, ssize_t); 281 EXPORT_SYMBOL(__asan_storeN_noabort); 282 283 /* to shut up compiler complaints */ 284 void __asan_handle_no_return(void) {} 285 EXPORT_SYMBOL(__asan_handle_no_return); 286 287 /* Emitted by compiler to poison alloca()ed objects. */ 288 void __asan_alloca_poison(void *addr, ssize_t size) 289 { 290 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE); 291 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) - 292 rounded_up_size; 293 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE); 294 295 const void *left_redzone = (const void *)(addr - 296 KASAN_ALLOCA_REDZONE_SIZE); 297 const void *right_redzone = (const void *)(addr + rounded_up_size); 298 299 WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE)); 300 301 kasan_unpoison((const void *)(addr + rounded_down_size), 302 size - rounded_down_size, false); 303 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE, 304 KASAN_ALLOCA_LEFT, false); 305 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE, 306 KASAN_ALLOCA_RIGHT, false); 307 } 308 EXPORT_SYMBOL(__asan_alloca_poison); 309 310 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */ 311 void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom) 312 { 313 if (unlikely(!stack_top || stack_top > (void *)stack_bottom)) 314 return; 315 316 kasan_unpoison(stack_top, (void *)stack_bottom - stack_top, false); 317 } 318 EXPORT_SYMBOL(__asan_allocas_unpoison); 319 320 /* Emitted by the compiler to [un]poison local variables. */ 321 #define DEFINE_ASAN_SET_SHADOW(byte) \ 322 void __asan_set_shadow_##byte(const void *addr, ssize_t size) \ 323 { \ 324 __memset((void *)addr, 0x##byte, size); \ 325 } \ 326 EXPORT_SYMBOL(__asan_set_shadow_##byte) 327 328 DEFINE_ASAN_SET_SHADOW(00); 329 DEFINE_ASAN_SET_SHADOW(f1); 330 DEFINE_ASAN_SET_SHADOW(f2); 331 DEFINE_ASAN_SET_SHADOW(f3); 332 DEFINE_ASAN_SET_SHADOW(f5); 333 DEFINE_ASAN_SET_SHADOW(f8); 334 335 /* Only allow cache merging when no per-object metadata is present. */ 336 slab_flags_t kasan_never_merge(void) 337 { 338 if (!kasan_requires_meta()) 339 return 0; 340 return SLAB_KASAN; 341 } 342 343 /* 344 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime. 345 * For larger allocations larger redzones are used. 346 */ 347 static inline unsigned int optimal_redzone(unsigned int object_size) 348 { 349 return 350 object_size <= 64 - 16 ? 16 : 351 object_size <= 128 - 32 ? 32 : 352 object_size <= 512 - 64 ? 64 : 353 object_size <= 4096 - 128 ? 128 : 354 object_size <= (1 << 14) - 256 ? 256 : 355 object_size <= (1 << 15) - 512 ? 512 : 356 object_size <= (1 << 16) - 1024 ? 1024 : 2048; 357 } 358 359 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 360 slab_flags_t *flags) 361 { 362 unsigned int ok_size; 363 unsigned int optimal_size; 364 365 if (!kasan_requires_meta()) 366 return; 367 368 /* 369 * SLAB_KASAN is used to mark caches that are sanitized by KASAN 370 * and that thus have per-object metadata. 371 * Currently this flag is used in two places: 372 * 1. In slab_ksize() to account for per-object metadata when 373 * calculating the size of the accessible memory within the object. 374 * 2. In slab_common.c via kasan_never_merge() to prevent merging of 375 * caches with per-object metadata. 376 */ 377 *flags |= SLAB_KASAN; 378 379 ok_size = *size; 380 381 /* Add alloc meta into redzone. */ 382 cache->kasan_info.alloc_meta_offset = *size; 383 *size += sizeof(struct kasan_alloc_meta); 384 385 /* 386 * If alloc meta doesn't fit, don't add it. 387 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal 388 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for 389 * larger sizes. 390 */ 391 if (*size > KMALLOC_MAX_SIZE) { 392 cache->kasan_info.alloc_meta_offset = 0; 393 *size = ok_size; 394 /* Continue, since free meta might still fit. */ 395 } 396 397 /* 398 * Add free meta into redzone when it's not possible to store 399 * it in the object. This is the case when: 400 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can 401 * be touched after it was freed, or 402 * 2. Object has a constructor, which means it's expected to 403 * retain its content until the next allocation, or 404 * 3. Object is too small. 405 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied. 406 */ 407 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor || 408 cache->object_size < sizeof(struct kasan_free_meta)) { 409 ok_size = *size; 410 411 cache->kasan_info.free_meta_offset = *size; 412 *size += sizeof(struct kasan_free_meta); 413 414 /* If free meta doesn't fit, don't add it. */ 415 if (*size > KMALLOC_MAX_SIZE) { 416 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META; 417 *size = ok_size; 418 } 419 } 420 421 /* Calculate size with optimal redzone. */ 422 optimal_size = cache->object_size + optimal_redzone(cache->object_size); 423 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */ 424 if (optimal_size > KMALLOC_MAX_SIZE) 425 optimal_size = KMALLOC_MAX_SIZE; 426 /* Use optimal size if the size with added metas is not large enough. */ 427 if (*size < optimal_size) 428 *size = optimal_size; 429 } 430 431 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache, 432 const void *object) 433 { 434 if (!cache->kasan_info.alloc_meta_offset) 435 return NULL; 436 return (void *)object + cache->kasan_info.alloc_meta_offset; 437 } 438 439 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache, 440 const void *object) 441 { 442 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32); 443 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META) 444 return NULL; 445 return (void *)object + cache->kasan_info.free_meta_offset; 446 } 447 448 void kasan_init_object_meta(struct kmem_cache *cache, const void *object) 449 { 450 struct kasan_alloc_meta *alloc_meta; 451 452 alloc_meta = kasan_get_alloc_meta(cache, object); 453 if (alloc_meta) 454 __memset(alloc_meta, 0, sizeof(*alloc_meta)); 455 } 456 457 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object) 458 { 459 struct kasan_cache *info = &cache->kasan_info; 460 461 if (!kasan_requires_meta()) 462 return 0; 463 464 if (in_object) 465 return (info->free_meta_offset ? 466 0 : sizeof(struct kasan_free_meta)); 467 else 468 return (info->alloc_meta_offset ? 469 sizeof(struct kasan_alloc_meta) : 0) + 470 ((info->free_meta_offset && 471 info->free_meta_offset != KASAN_NO_FREE_META) ? 472 sizeof(struct kasan_free_meta) : 0); 473 } 474 475 static void __kasan_record_aux_stack(void *addr, bool can_alloc) 476 { 477 struct slab *slab = kasan_addr_to_slab(addr); 478 struct kmem_cache *cache; 479 struct kasan_alloc_meta *alloc_meta; 480 void *object; 481 482 if (is_kfence_address(addr) || !slab) 483 return; 484 485 cache = slab->slab_cache; 486 object = nearest_obj(cache, slab, addr); 487 alloc_meta = kasan_get_alloc_meta(cache, object); 488 if (!alloc_meta) 489 return; 490 491 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0]; 492 alloc_meta->aux_stack[0] = kasan_save_stack(0, can_alloc); 493 } 494 495 void kasan_record_aux_stack(void *addr) 496 { 497 return __kasan_record_aux_stack(addr, true); 498 } 499 500 void kasan_record_aux_stack_noalloc(void *addr) 501 { 502 return __kasan_record_aux_stack(addr, false); 503 } 504 505 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) 506 { 507 struct kasan_alloc_meta *alloc_meta; 508 509 alloc_meta = kasan_get_alloc_meta(cache, object); 510 if (alloc_meta) 511 kasan_set_track(&alloc_meta->alloc_track, flags); 512 } 513 514 void kasan_save_free_info(struct kmem_cache *cache, void *object) 515 { 516 struct kasan_free_meta *free_meta; 517 518 free_meta = kasan_get_free_meta(cache, object); 519 if (!free_meta) 520 return; 521 522 kasan_set_track(&free_meta->free_track, 0); 523 /* The object was freed and has free track set. */ 524 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK; 525 } 526