mm/kasan/generic.c

   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/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 could
  41  * perform better optimizations in each of __asan_loadX/__assn_storeX
  42  * depending on memory access size X.
  43  */
  44
  45 static __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
  57 static __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 maps
  64          * 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
  72 static __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
  83 static __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
  96 static __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
 125 static __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
 144 static __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
 164 static __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
 186 bool 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
 192 bool 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
 204 void kasan_cache_shrink(struct kmem_cache *cache)
 205 {
 206         kasan_quarantine_remove_cache(cache);
 207 }
 208
 209 void kasan_cache_shutdown(struct kmem_cache *cache)
 210 {
 211         if (!__kmem_cache_empty(cache))
 212                 kasan_quarantine_remove_cache(cache);
 213 }
 214
 215 static 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
 226 void __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 }
 234 EXPORT_SYMBOL(__asan_register_globals);
 235
 236 void __asan_unregister_globals(void *ptr, ssize_t size)
 237 {
 238 }
 239 EXPORT_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
 259 DEFINE_ASAN_LOAD_STORE(1);
 260 DEFINE_ASAN_LOAD_STORE(2);
 261 DEFINE_ASAN_LOAD_STORE(4);
 262 DEFINE_ASAN_LOAD_STORE(8);
 263 DEFINE_ASAN_LOAD_STORE(16);
 264
 265 void __asan_loadN(void *addr, ssize_t size)
 266 {
 267         kasan_check_range(addr, size, false, _RET_IP_);
 268 }
 269 EXPORT_SYMBOL(__asan_loadN);
 270
 271 __alias(__asan_loadN)
 272 void __asan_loadN_noabort(void *, ssize_t);
 273 EXPORT_SYMBOL(__asan_loadN_noabort);
 274
 275 void __asan_storeN(void *addr, ssize_t size)
 276 {
 277         kasan_check_range(addr, size, true, _RET_IP_);
 278 }
 279 EXPORT_SYMBOL(__asan_storeN);
 280
 281 __alias(__asan_storeN)
 282 void __asan_storeN_noabort(void *, ssize_t);
 283 EXPORT_SYMBOL(__asan_storeN_noabort);
 284
 285 /* to shut up compiler complaints */
 286 void __asan_handle_no_return(void) {}
 287 EXPORT_SYMBOL(__asan_handle_no_return);
 288
 289 /* Emitted by compiler to poison alloca()ed objects. */
 290 void __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 }
 310 EXPORT_SYMBOL(__asan_alloca_poison);
 311
 312 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
 313 void __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 }
 320 EXPORT_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
 330 DEFINE_ASAN_SET_SHADOW(00);
 331 DEFINE_ASAN_SET_SHADOW(f1);
 332 DEFINE_ASAN_SET_SHADOW(f2);
 333 DEFINE_ASAN_SET_SHADOW(f3);
 334 DEFINE_ASAN_SET_SHADOW(f5);
 335 DEFINE_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  */
 341 static inline unsigned int optimal_redzone(unsigned int object_size)
 342 {
 343         return
 344                 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
 353 void 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 and
 366          * that thus have per-object metadata. Currently, this flag is used in
 367          * slab_ksize() to account for per-object metadata when calculating the
 368          * size of the accessible memory within the object. Additionally, we use
 369          * 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 store
 391          * it in the object. This is the case when:
 392          * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
 393          *    be touched after it was freed, or
 394          * 2. Object has a constructor, which means it's expected to
 395          *    retain its content until the next allocation, or
 396          * 3. It is from a kmalloc cache which enables the debug option
 397          *    to store original size.
 398          */
 399         if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
 400              slub_debug_orig_size(cache)) {
 401                 cache->kasan_info.free_meta_offset = *size;
 402                 *size += sizeof(struct kasan_free_meta);
 403                 goto free_meta_added;
 404         }
 405
 406         /*
 407          * Otherwise, if the object is large enough to contain free meta,
 408          * store it within the object.
 409          */
 410         if (sizeof(struct kasan_free_meta) <= cache->object_size) {
 411                 /* cache->kasan_info.free_meta_offset = 0 is implied. */
 412                 goto free_meta_added;
 413         }
 414
 415         /*
 416          * For smaller objects, store the beginning of free meta within the
 417          * object and the end in the redzone. And thus shift the location of
 418          * alloc meta to free up space for free meta.
 419          * This is only possible when slub_debug is disabled, as otherwise
 420          * the end of free meta will overlap with slub_debug metadata.
 421          */
 422         if (!__slub_debug_enabled()) {
 423                 rem_free_meta_size = sizeof(struct kasan_free_meta) -
 424                                                         cache->object_size;
 425                 *size += rem_free_meta_size;
 426                 if (cache->kasan_info.alloc_meta_offset != 0)
 427                         cache->kasan_info.alloc_meta_offset += rem_free_meta_size;
 428                 goto free_meta_added;
 429         }
 430
 431         /*
 432          * If the object is small and slub_debug is enabled, store free meta
 433          * in the redzone after alloc meta.
 434          */
 435         cache->kasan_info.free_meta_offset = *size;
 436         *size += sizeof(struct kasan_free_meta);
 437
 438 free_meta_added:
 439         /* If free meta doesn't fit, don't add it. */
 440         if (*size > KMALLOC_MAX_SIZE) {
 441                 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
 442                 cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;
 443                 *size = ok_size;
 444         }
 445
 446         /* Calculate size with optimal redzone. */
 447         optimal_size = cache->object_size + optimal_redzone(cache->object_size);
 448         /* Limit it with KMALLOC_MAX_SIZE. */
 449         if (optimal_size > KMALLOC_MAX_SIZE)
 450                 optimal_size = KMALLOC_MAX_SIZE;
 451         /* Use optimal size if the size with added metas is not large enough. */
 452         if (*size < optimal_size)
 453                 *size = optimal_size;
 454 }
 455
 456 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
 457                                               const void *object)
 458 {
 459         if (!cache->kasan_info.alloc_meta_offset)
 460                 return NULL;
 461         return (void *)object + cache->kasan_info.alloc_meta_offset;
 462 }
 463
 464 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
 465                                             const void *object)
 466 {
 467         BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
 468         if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
 469                 return NULL;
 470         return (void *)object + cache->kasan_info.free_meta_offset;
 471 }
 472
 473 void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
 474 {
 475         struct kasan_alloc_meta *alloc_meta;
 476
 477         alloc_meta = kasan_get_alloc_meta(cache, object);
 478         if (alloc_meta) {
 479                 /* Zero out alloc meta to mark it as invalid. */
 480                 __memset(alloc_meta, 0, sizeof(*alloc_meta));
 481         }
 482
 483         /*
 484          * Explicitly marking free meta as invalid is not required: the shadow
 485          * value for the first 8 bytes of a newly allocated object is not
 486          * KASAN_SLAB_FREE_META.
 487          */
 488 }
 489
 490 static void release_alloc_meta(struct kasan_alloc_meta *meta)
 491 {
 492         /* Zero out alloc meta to mark it as invalid. */
 493         __memset(meta, 0, sizeof(*meta));
 494 }
 495
 496 static void release_free_meta(const void *object, struct kasan_free_meta *meta)
 497 {
 498         if (!kasan_arch_is_ready())
 499                 return;
 500
 501         /* Check if free meta is valid. */
 502         if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
 503                 return;
 504
 505         /* Mark free meta as invalid. */
 506         *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
 507 }
 508
 509 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
 510 {
 511         struct kasan_cache *info = &cache->kasan_info;
 512
 513         if (!kasan_requires_meta())
 514                 return 0;
 515
 516         if (in_object)
 517                 return (info->free_meta_offset ?
 518                         0 : sizeof(struct kasan_free_meta));
 519         else
 520                 return (info->alloc_meta_offset ?
 521                         sizeof(struct kasan_alloc_meta) : 0) +
 522                         ((info->free_meta_offset &&
 523                         info->free_meta_offset != KASAN_NO_FREE_META) ?
 524                         sizeof(struct kasan_free_meta) : 0);
 525 }
 526
 527 static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
 528 {
 529         struct slab *slab = kasan_addr_to_slab(addr);
 530         struct kmem_cache *cache;
 531         struct kasan_alloc_meta *alloc_meta;
 532         void *object;
 533
 534         if (is_kfence_address(addr) || !slab)
 535                 return;
 536
 537         cache = slab->slab_cache;
 538         object = nearest_obj(cache, slab, addr);
 539         alloc_meta = kasan_get_alloc_meta(cache, object);
 540         if (!alloc_meta)
 541                 return;
 542
 543         alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
 544         alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
 545 }
 546
 547 void kasan_record_aux_stack(void *addr)
 548 {
 549         return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC);
 550 }
 551
 552 void kasan_record_aux_stack_noalloc(void *addr)
 553 {
 554         return __kasan_record_aux_stack(addr, 0);
 555 }
 556
 557 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
 558 {
 559         struct kasan_alloc_meta *alloc_meta;
 560
 561         alloc_meta = kasan_get_alloc_meta(cache, object);
 562         if (!alloc_meta)
 563                 return;
 564
 565         /* Invalidate previous stack traces (might exist for krealloc or mempool). */
 566         release_alloc_meta(alloc_meta);
 567
 568         kasan_save_track(&alloc_meta->alloc_track, flags);
 569 }
 570
 571 void kasan_save_free_info(struct kmem_cache *cache, void *object)
 572 {
 573         struct kasan_free_meta *free_meta;
 574
 575         free_meta = kasan_get_free_meta(cache, object);
 576         if (!free_meta)
 577                 return;
 578
 579         /* Invalidate previous stack trace (might exist for mempool). */
 580         release_free_meta(object, free_meta);
 581
 582         kasan_save_track(&free_meta->free_track, 0);
 583
 584         /* Mark free meta as valid. */
 585         *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;
 586 }