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((void *)addr < 176 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) { 177 return !kasan_report(addr, size, write, ret_ip); 178 } 179 180 if (likely(!memory_is_poisoned(addr, size))) 181 return true; 182 183 return !kasan_report(addr, size, write, ret_ip); 184 } 185 186 bool kasan_check_range(unsigned long addr, size_t size, bool write, 187 unsigned long ret_ip) 188 { 189 return check_region_inline(addr, size, write, ret_ip); 190 } 191 192 bool kasan_byte_accessible(const void *addr) 193 { 194 s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr)); 195 196 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE; 197 } 198 199 void kasan_cache_shrink(struct kmem_cache *cache) 200 { 201 kasan_quarantine_remove_cache(cache); 202 } 203 204 void kasan_cache_shutdown(struct kmem_cache *cache) 205 { 206 if (!__kmem_cache_empty(cache)) 207 kasan_quarantine_remove_cache(cache); 208 } 209 210 static void register_global(struct kasan_global *global) 211 { 212 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE); 213 214 kasan_unpoison(global->beg, global->size, false); 215 216 kasan_poison(global->beg + aligned_size, 217 global->size_with_redzone - aligned_size, 218 KASAN_GLOBAL_REDZONE, false); 219 } 220 221 void __asan_register_globals(struct kasan_global *globals, size_t size) 222 { 223 int i; 224 225 for (i = 0; i < size; i++) 226 register_global(&globals[i]); 227 } 228 EXPORT_SYMBOL(__asan_register_globals); 229 230 void __asan_unregister_globals(struct kasan_global *globals, size_t size) 231 { 232 } 233 EXPORT_SYMBOL(__asan_unregister_globals); 234 235 #define DEFINE_ASAN_LOAD_STORE(size) \ 236 void __asan_load##size(unsigned long addr) \ 237 { \ 238 check_region_inline(addr, size, false, _RET_IP_); \ 239 } \ 240 EXPORT_SYMBOL(__asan_load##size); \ 241 __alias(__asan_load##size) \ 242 void __asan_load##size##_noabort(unsigned long); \ 243 EXPORT_SYMBOL(__asan_load##size##_noabort); \ 244 void __asan_store##size(unsigned long addr) \ 245 { \ 246 check_region_inline(addr, size, true, _RET_IP_); \ 247 } \ 248 EXPORT_SYMBOL(__asan_store##size); \ 249 __alias(__asan_store##size) \ 250 void __asan_store##size##_noabort(unsigned long); \ 251 EXPORT_SYMBOL(__asan_store##size##_noabort) 252 253 DEFINE_ASAN_LOAD_STORE(1); 254 DEFINE_ASAN_LOAD_STORE(2); 255 DEFINE_ASAN_LOAD_STORE(4); 256 DEFINE_ASAN_LOAD_STORE(8); 257 DEFINE_ASAN_LOAD_STORE(16); 258 259 void __asan_loadN(unsigned long addr, size_t size) 260 { 261 kasan_check_range(addr, size, false, _RET_IP_); 262 } 263 EXPORT_SYMBOL(__asan_loadN); 264 265 __alias(__asan_loadN) 266 void __asan_loadN_noabort(unsigned long, size_t); 267 EXPORT_SYMBOL(__asan_loadN_noabort); 268 269 void __asan_storeN(unsigned long addr, size_t size) 270 { 271 kasan_check_range(addr, size, true, _RET_IP_); 272 } 273 EXPORT_SYMBOL(__asan_storeN); 274 275 __alias(__asan_storeN) 276 void __asan_storeN_noabort(unsigned long, size_t); 277 EXPORT_SYMBOL(__asan_storeN_noabort); 278 279 /* to shut up compiler complaints */ 280 void __asan_handle_no_return(void) {} 281 EXPORT_SYMBOL(__asan_handle_no_return); 282 283 /* Emitted by compiler to poison alloca()ed objects. */ 284 void __asan_alloca_poison(unsigned long addr, size_t size) 285 { 286 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE); 287 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) - 288 rounded_up_size; 289 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE); 290 291 const void *left_redzone = (const void *)(addr - 292 KASAN_ALLOCA_REDZONE_SIZE); 293 const void *right_redzone = (const void *)(addr + rounded_up_size); 294 295 WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE)); 296 297 kasan_unpoison((const void *)(addr + rounded_down_size), 298 size - rounded_down_size, false); 299 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE, 300 KASAN_ALLOCA_LEFT, false); 301 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE, 302 KASAN_ALLOCA_RIGHT, false); 303 } 304 EXPORT_SYMBOL(__asan_alloca_poison); 305 306 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */ 307 void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom) 308 { 309 if (unlikely(!stack_top || stack_top > stack_bottom)) 310 return; 311 312 kasan_unpoison(stack_top, stack_bottom - stack_top, false); 313 } 314 EXPORT_SYMBOL(__asan_allocas_unpoison); 315 316 /* Emitted by the compiler to [un]poison local variables. */ 317 #define DEFINE_ASAN_SET_SHADOW(byte) \ 318 void __asan_set_shadow_##byte(const void *addr, size_t size) \ 319 { \ 320 __memset((void *)addr, 0x##byte, size); \ 321 } \ 322 EXPORT_SYMBOL(__asan_set_shadow_##byte) 323 324 DEFINE_ASAN_SET_SHADOW(00); 325 DEFINE_ASAN_SET_SHADOW(f1); 326 DEFINE_ASAN_SET_SHADOW(f2); 327 DEFINE_ASAN_SET_SHADOW(f3); 328 DEFINE_ASAN_SET_SHADOW(f5); 329 DEFINE_ASAN_SET_SHADOW(f8); 330 331 /* Only allow cache merging when no per-object metadata is present. */ 332 slab_flags_t kasan_never_merge(void) 333 { 334 if (!kasan_requires_meta()) 335 return 0; 336 return SLAB_KASAN; 337 } 338 339 /* 340 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime. 341 * For larger allocations larger redzones are used. 342 */ 343 static inline unsigned int optimal_redzone(unsigned int object_size) 344 { 345 return 346 object_size <= 64 - 16 ? 16 : 347 object_size <= 128 - 32 ? 32 : 348 object_size <= 512 - 64 ? 64 : 349 object_size <= 4096 - 128 ? 128 : 350 object_size <= (1 << 14) - 256 ? 256 : 351 object_size <= (1 << 15) - 512 ? 512 : 352 object_size <= (1 << 16) - 1024 ? 1024 : 2048; 353 } 354 355 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 356 slab_flags_t *flags) 357 { 358 unsigned int ok_size; 359 unsigned int optimal_size; 360 361 if (!kasan_requires_meta()) 362 return; 363 364 /* 365 * SLAB_KASAN is used to mark caches that are sanitized by KASAN 366 * and that thus have per-object metadata. 367 * Currently this flag is used in two places: 368 * 1. In slab_ksize() to account for per-object metadata when 369 * calculating the size of the accessible memory within the object. 370 * 2. In slab_common.c via kasan_never_merge() to prevent merging of 371 * caches with per-object metadata. 372 */ 373 *flags |= SLAB_KASAN; 374 375 ok_size = *size; 376 377 /* Add alloc meta into redzone. */ 378 cache->kasan_info.alloc_meta_offset = *size; 379 *size += sizeof(struct kasan_alloc_meta); 380 381 /* 382 * If alloc meta doesn't fit, don't add it. 383 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal 384 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for 385 * larger sizes. 386 */ 387 if (*size > KMALLOC_MAX_SIZE) { 388 cache->kasan_info.alloc_meta_offset = 0; 389 *size = ok_size; 390 /* Continue, since free meta might still fit. */ 391 } 392 393 /* 394 * Add free meta into redzone when it's not possible to store 395 * it in the object. This is the case when: 396 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can 397 * be touched after it was freed, or 398 * 2. Object has a constructor, which means it's expected to 399 * retain its content until the next allocation, or 400 * 3. Object is too small. 401 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied. 402 */ 403 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor || 404 cache->object_size < sizeof(struct kasan_free_meta)) { 405 ok_size = *size; 406 407 cache->kasan_info.free_meta_offset = *size; 408 *size += sizeof(struct kasan_free_meta); 409 410 /* If free meta doesn't fit, don't add it. */ 411 if (*size > KMALLOC_MAX_SIZE) { 412 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META; 413 *size = ok_size; 414 } 415 } 416 417 /* Calculate size with optimal redzone. */ 418 optimal_size = cache->object_size + optimal_redzone(cache->object_size); 419 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */ 420 if (optimal_size > KMALLOC_MAX_SIZE) 421 optimal_size = KMALLOC_MAX_SIZE; 422 /* Use optimal size if the size with added metas is not large enough. */ 423 if (*size < optimal_size) 424 *size = optimal_size; 425 } 426 427 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache, 428 const void *object) 429 { 430 if (!cache->kasan_info.alloc_meta_offset) 431 return NULL; 432 return (void *)object + cache->kasan_info.alloc_meta_offset; 433 } 434 435 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache, 436 const void *object) 437 { 438 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32); 439 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META) 440 return NULL; 441 return (void *)object + cache->kasan_info.free_meta_offset; 442 } 443 444 void kasan_init_object_meta(struct kmem_cache *cache, const void *object) 445 { 446 struct kasan_alloc_meta *alloc_meta; 447 448 alloc_meta = kasan_get_alloc_meta(cache, object); 449 if (alloc_meta) 450 __memset(alloc_meta, 0, sizeof(*alloc_meta)); 451 } 452 453 size_t kasan_metadata_size(struct kmem_cache *cache) 454 { 455 if (!kasan_requires_meta()) 456 return 0; 457 return (cache->kasan_info.alloc_meta_offset ? 458 sizeof(struct kasan_alloc_meta) : 0) + 459 ((cache->kasan_info.free_meta_offset && 460 cache->kasan_info.free_meta_offset != KASAN_NO_FREE_META) ? 461 sizeof(struct kasan_free_meta) : 0); 462 } 463 464 static void __kasan_record_aux_stack(void *addr, bool can_alloc) 465 { 466 struct slab *slab = kasan_addr_to_slab(addr); 467 struct kmem_cache *cache; 468 struct kasan_alloc_meta *alloc_meta; 469 void *object; 470 471 if (is_kfence_address(addr) || !slab) 472 return; 473 474 cache = slab->slab_cache; 475 object = nearest_obj(cache, slab, addr); 476 alloc_meta = kasan_get_alloc_meta(cache, object); 477 if (!alloc_meta) 478 return; 479 480 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0]; 481 alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT, can_alloc); 482 } 483 484 void kasan_record_aux_stack(void *addr) 485 { 486 return __kasan_record_aux_stack(addr, true); 487 } 488 489 void kasan_record_aux_stack_noalloc(void *addr) 490 { 491 return __kasan_record_aux_stack(addr, false); 492 } 493 494 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) 495 { 496 struct kasan_alloc_meta *alloc_meta; 497 498 alloc_meta = kasan_get_alloc_meta(cache, object); 499 if (alloc_meta) 500 kasan_set_track(&alloc_meta->alloc_track, flags); 501 } 502 503 void kasan_save_free_info(struct kmem_cache *cache, void *object) 504 { 505 struct kasan_free_meta *free_meta; 506 507 free_meta = kasan_get_free_meta(cache, object); 508 if (!free_meta) 509 return; 510 511 kasan_set_track(&free_meta->free_track, GFP_NOWAIT); 512 /* The object was freed and has free track set. */ 513 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK; 514 } 515