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(unsigned long addr) 44 { 45 s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr); 46 47 if (unlikely(shadow_value)) { 48 s8 last_accessible_byte = 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(unsigned long addr, 56 unsigned long size) 57 { 58 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)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(((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(unsigned long addr) 71 { 72 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr); 73 74 /* Unaligned 16-bytes access maps into 3 shadow bytes. */ 75 if (unlikely(!IS_ALIGNED(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(unsigned long addr, 124 size_t size) 125 { 126 unsigned long ret; 127 128 ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr), 129 kasan_mem_to_shadow((void *)addr + size - 1) + 1); 130 131 if (unlikely(ret)) { 132 unsigned long last_byte = addr + size - 1; 133 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte); 134 135 if (unlikely(ret != (unsigned long)last_shadow || 136 ((long)(last_byte & KASAN_GRANULE_MASK) >= *last_shadow))) 137 return true; 138 } 139 return false; 140 } 141 142 static __always_inline bool memory_is_poisoned(unsigned long 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(unsigned long 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((void *)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(unsigned long 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(struct kasan_global *globals, size_t size) 225 { 226 int i; 227 228 for (i = 0; i < size; i++) 229 register_global(&globals[i]); 230 } 231 EXPORT_SYMBOL(__asan_register_globals); 232 233 void __asan_unregister_globals(struct kasan_global *globals, size_t size) 234 { 235 } 236 EXPORT_SYMBOL(__asan_unregister_globals); 237 238 #define DEFINE_ASAN_LOAD_STORE(size) \ 239 void __asan_load##size(unsigned long addr) \ 240 { \ 241 check_region_inline(addr, size, false, _RET_IP_); \ 242 } \ 243 EXPORT_SYMBOL(__asan_load##size); \ 244 __alias(__asan_load##size) \ 245 void __asan_load##size##_noabort(unsigned long); \ 246 EXPORT_SYMBOL(__asan_load##size##_noabort); \ 247 void __asan_store##size(unsigned long addr) \ 248 { \ 249 check_region_inline(addr, size, true, _RET_IP_); \ 250 } \ 251 EXPORT_SYMBOL(__asan_store##size); \ 252 __alias(__asan_store##size) \ 253 void __asan_store##size##_noabort(unsigned long); \ 254 EXPORT_SYMBOL(__asan_store##size##_noabort) 255 256 DEFINE_ASAN_LOAD_STORE(1); 257 DEFINE_ASAN_LOAD_STORE(2); 258 DEFINE_ASAN_LOAD_STORE(4); 259 DEFINE_ASAN_LOAD_STORE(8); 260 DEFINE_ASAN_LOAD_STORE(16); 261 262 void __asan_loadN(unsigned long addr, size_t size) 263 { 264 kasan_check_range(addr, size, false, _RET_IP_); 265 } 266 EXPORT_SYMBOL(__asan_loadN); 267 268 __alias(__asan_loadN) 269 void __asan_loadN_noabort(unsigned long, size_t); 270 EXPORT_SYMBOL(__asan_loadN_noabort); 271 272 void __asan_storeN(unsigned long addr, size_t size) 273 { 274 kasan_check_range(addr, size, true, _RET_IP_); 275 } 276 EXPORT_SYMBOL(__asan_storeN); 277 278 __alias(__asan_storeN) 279 void __asan_storeN_noabort(unsigned long, size_t); 280 EXPORT_SYMBOL(__asan_storeN_noabort); 281 282 /* to shut up compiler complaints */ 283 void __asan_handle_no_return(void) {} 284 EXPORT_SYMBOL(__asan_handle_no_return); 285 286 /* Emitted by compiler to poison alloca()ed objects. */ 287 void __asan_alloca_poison(unsigned long addr, size_t size) 288 { 289 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE); 290 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) - 291 rounded_up_size; 292 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE); 293 294 const void *left_redzone = (const void *)(addr - 295 KASAN_ALLOCA_REDZONE_SIZE); 296 const void *right_redzone = (const void *)(addr + rounded_up_size); 297 298 WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE)); 299 300 kasan_unpoison((const void *)(addr + rounded_down_size), 301 size - rounded_down_size, false); 302 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE, 303 KASAN_ALLOCA_LEFT, false); 304 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE, 305 KASAN_ALLOCA_RIGHT, false); 306 } 307 EXPORT_SYMBOL(__asan_alloca_poison); 308 309 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */ 310 void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom) 311 { 312 if (unlikely(!stack_top || stack_top > stack_bottom)) 313 return; 314 315 kasan_unpoison(stack_top, stack_bottom - stack_top, false); 316 } 317 EXPORT_SYMBOL(__asan_allocas_unpoison); 318 319 /* Emitted by the compiler to [un]poison local variables. */ 320 #define DEFINE_ASAN_SET_SHADOW(byte) \ 321 void __asan_set_shadow_##byte(const void *addr, size_t size) \ 322 { \ 323 __memset((void *)addr, 0x##byte, size); \ 324 } \ 325 EXPORT_SYMBOL(__asan_set_shadow_##byte) 326 327 DEFINE_ASAN_SET_SHADOW(00); 328 DEFINE_ASAN_SET_SHADOW(f1); 329 DEFINE_ASAN_SET_SHADOW(f2); 330 DEFINE_ASAN_SET_SHADOW(f3); 331 DEFINE_ASAN_SET_SHADOW(f5); 332 DEFINE_ASAN_SET_SHADOW(f8); 333 334 /* Only allow cache merging when no per-object metadata is present. */ 335 slab_flags_t kasan_never_merge(void) 336 { 337 if (!kasan_requires_meta()) 338 return 0; 339 return SLAB_KASAN; 340 } 341 342 /* 343 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime. 344 * For larger allocations larger redzones are used. 345 */ 346 static inline unsigned int optimal_redzone(unsigned int object_size) 347 { 348 return 349 object_size <= 64 - 16 ? 16 : 350 object_size <= 128 - 32 ? 32 : 351 object_size <= 512 - 64 ? 64 : 352 object_size <= 4096 - 128 ? 128 : 353 object_size <= (1 << 14) - 256 ? 256 : 354 object_size <= (1 << 15) - 512 ? 512 : 355 object_size <= (1 << 16) - 1024 ? 1024 : 2048; 356 } 357 358 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 359 slab_flags_t *flags) 360 { 361 unsigned int ok_size; 362 unsigned int optimal_size; 363 364 if (!kasan_requires_meta()) 365 return; 366 367 /* 368 * SLAB_KASAN is used to mark caches that are sanitized by KASAN 369 * and that thus have per-object metadata. 370 * Currently this flag is used in two places: 371 * 1. In slab_ksize() to account for per-object metadata when 372 * calculating the size of the accessible memory within the object. 373 * 2. In slab_common.c via kasan_never_merge() to prevent merging of 374 * caches with per-object metadata. 375 */ 376 *flags |= SLAB_KASAN; 377 378 ok_size = *size; 379 380 /* Add alloc meta into redzone. */ 381 cache->kasan_info.alloc_meta_offset = *size; 382 *size += sizeof(struct kasan_alloc_meta); 383 384 /* 385 * If alloc meta doesn't fit, don't add it. 386 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal 387 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for 388 * larger sizes. 389 */ 390 if (*size > KMALLOC_MAX_SIZE) { 391 cache->kasan_info.alloc_meta_offset = 0; 392 *size = ok_size; 393 /* Continue, since free meta might still fit. */ 394 } 395 396 /* 397 * Add free meta into redzone when it's not possible to store 398 * it in the object. This is the case when: 399 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can 400 * be touched after it was freed, or 401 * 2. Object has a constructor, which means it's expected to 402 * retain its content until the next allocation, or 403 * 3. Object is too small. 404 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied. 405 */ 406 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor || 407 cache->object_size < sizeof(struct kasan_free_meta)) { 408 ok_size = *size; 409 410 cache->kasan_info.free_meta_offset = *size; 411 *size += sizeof(struct kasan_free_meta); 412 413 /* If free meta doesn't fit, don't add it. */ 414 if (*size > KMALLOC_MAX_SIZE) { 415 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META; 416 *size = ok_size; 417 } 418 } 419 420 /* Calculate size with optimal redzone. */ 421 optimal_size = cache->object_size + optimal_redzone(cache->object_size); 422 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */ 423 if (optimal_size > KMALLOC_MAX_SIZE) 424 optimal_size = KMALLOC_MAX_SIZE; 425 /* Use optimal size if the size with added metas is not large enough. */ 426 if (*size < optimal_size) 427 *size = optimal_size; 428 } 429 430 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache, 431 const void *object) 432 { 433 if (!cache->kasan_info.alloc_meta_offset) 434 return NULL; 435 return (void *)object + cache->kasan_info.alloc_meta_offset; 436 } 437 438 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache, 439 const void *object) 440 { 441 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32); 442 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META) 443 return NULL; 444 return (void *)object + cache->kasan_info.free_meta_offset; 445 } 446 447 void kasan_init_object_meta(struct kmem_cache *cache, const void *object) 448 { 449 struct kasan_alloc_meta *alloc_meta; 450 451 alloc_meta = kasan_get_alloc_meta(cache, object); 452 if (alloc_meta) 453 __memset(alloc_meta, 0, sizeof(*alloc_meta)); 454 } 455 456 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object) 457 { 458 struct kasan_cache *info = &cache->kasan_info; 459 460 if (!kasan_requires_meta()) 461 return 0; 462 463 if (in_object) 464 return (info->free_meta_offset ? 465 0 : sizeof(struct kasan_free_meta)); 466 else 467 return (info->alloc_meta_offset ? 468 sizeof(struct kasan_alloc_meta) : 0) + 469 ((info->free_meta_offset && 470 info->free_meta_offset != KASAN_NO_FREE_META) ? 471 sizeof(struct kasan_free_meta) : 0); 472 } 473 474 static void __kasan_record_aux_stack(void *addr, bool can_alloc) 475 { 476 struct slab *slab = kasan_addr_to_slab(addr); 477 struct kmem_cache *cache; 478 struct kasan_alloc_meta *alloc_meta; 479 void *object; 480 481 if (is_kfence_address(addr) || !slab) 482 return; 483 484 cache = slab->slab_cache; 485 object = nearest_obj(cache, slab, addr); 486 alloc_meta = kasan_get_alloc_meta(cache, object); 487 if (!alloc_meta) 488 return; 489 490 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0]; 491 alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT, can_alloc); 492 } 493 494 void kasan_record_aux_stack(void *addr) 495 { 496 return __kasan_record_aux_stack(addr, true); 497 } 498 499 void kasan_record_aux_stack_noalloc(void *addr) 500 { 501 return __kasan_record_aux_stack(addr, false); 502 } 503 504 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) 505 { 506 struct kasan_alloc_meta *alloc_meta; 507 508 alloc_meta = kasan_get_alloc_meta(cache, object); 509 if (alloc_meta) 510 kasan_set_track(&alloc_meta->alloc_track, flags); 511 } 512 513 void kasan_save_free_info(struct kmem_cache *cache, void *object) 514 { 515 struct kasan_free_meta *free_meta; 516 517 free_meta = kasan_get_free_meta(cache, object); 518 if (!free_meta) 519 return; 520 521 kasan_set_track(&free_meta->free_track, GFP_NOWAIT); 522 /* The object was freed and has free track set. */ 523 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK; 524 } 525