mm/kasan/kasan.c

   1 /*
   2  * This file contains shadow memory manipulation code.
   3  *
   4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   6  *
   7  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   8  *        Andrey Konovalov <adech.fo@gmail.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17 #define DISABLE_BRANCH_PROFILING
  18
  19 #include <linux/export.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/kmemleak.h>
  23 #include <linux/linkage.h>
  24 #include <linux/memblock.h>
  25 #include <linux/memory.h>
  26 #include <linux/mm.h>
  27 #include <linux/module.h>
  28 #include <linux/printk.h>
  29 #include <linux/sched.h>
  30 #include <linux/slab.h>
  31 #include <linux/stacktrace.h>
  32 #include <linux/string.h>
  33 #include <linux/types.h>
  34 #include <linux/vmalloc.h>
  35 #include <linux/kasan.h>
  36
  37 #include "kasan.h"
  38 #include "../slab.h"
  39
  40 /*
  41  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
  42  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
  43  */
  44 static void kasan_poison_shadow(const void *address, size_t size, u8 value)
  45 {
  46         void *shadow_start, *shadow_end;
  47
  48         shadow_start = kasan_mem_to_shadow(address);
  49         shadow_end = kasan_mem_to_shadow(address + size);
  50
  51         memset(shadow_start, value, shadow_end - shadow_start);
  52 }
  53
  54 void kasan_unpoison_shadow(const void *address, size_t size)
  55 {
  56         kasan_poison_shadow(address, size, 0);
  57
  58         if (size & KASAN_SHADOW_MASK) {
  59                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
  60                 *shadow = size & KASAN_SHADOW_MASK;
  61         }
  62 }
  63
  64 static void __kasan_unpoison_stack(struct task_struct *task, void *sp)
  65 {
  66         void *base = task_stack_page(task);
  67         size_t size = sp - base;
  68
  69         kasan_unpoison_shadow(base, size);
  70 }
  71
  72 /* Unpoison the entire stack for a task. */
  73 void kasan_unpoison_task_stack(struct task_struct *task)
  74 {
  75         __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
  76 }
  77
  78 /* Unpoison the stack for the current task beyond a watermark sp value. */
  79 asmlinkage void kasan_unpoison_remaining_stack(void *sp)
  80 {
  81         __kasan_unpoison_stack(current, sp);
  82 }
  83
  84 /*
  85  * All functions below always inlined so compiler could
  86  * perform better optimizations in each of __asan_loadX/__assn_storeX
  87  * depending on memory access size X.
  88  */
  89
  90 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
  91 {
  92         s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
  93
  94         if (unlikely(shadow_value)) {
  95                 s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
  96                 return unlikely(last_accessible_byte >= shadow_value);
  97         }
  98
  99         return false;
 100 }
 101
 102 static __always_inline bool memory_is_poisoned_2(unsigned long addr)
 103 {
 104         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 105
 106         if (unlikely(*shadow_addr)) {
 107                 if (memory_is_poisoned_1(addr + 1))
 108                         return true;
 109
 110                 /*
 111                  * If single shadow byte covers 2-byte access, we don't
 112                  * need to do anything more. Otherwise, test the first
 113                  * shadow byte.
 114                  */
 115                 if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
 116                         return false;
 117
 118                 return unlikely(*(u8 *)shadow_addr);
 119         }
 120
 121         return false;
 122 }
 123
 124 static __always_inline bool memory_is_poisoned_4(unsigned long addr)
 125 {
 126         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 127
 128         if (unlikely(*shadow_addr)) {
 129                 if (memory_is_poisoned_1(addr + 3))
 130                         return true;
 131
 132                 /*
 133                  * If single shadow byte covers 4-byte access, we don't
 134                  * need to do anything more. Otherwise, test the first
 135                  * shadow byte.
 136                  */
 137                 if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
 138                         return false;
 139
 140                 return unlikely(*(u8 *)shadow_addr);
 141         }
 142
 143         return false;
 144 }
 145
 146 static __always_inline bool memory_is_poisoned_8(unsigned long addr)
 147 {
 148         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 149
 150         if (unlikely(*shadow_addr)) {
 151                 if (memory_is_poisoned_1(addr + 7))
 152                         return true;
 153
 154                 /*
 155                  * If single shadow byte covers 8-byte access, we don't
 156                  * need to do anything more. Otherwise, test the first
 157                  * shadow byte.
 158                  */
 159                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 160                         return false;
 161
 162                 return unlikely(*(u8 *)shadow_addr);
 163         }
 164
 165         return false;
 166 }
 167
 168 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
 169 {
 170         u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);
 171
 172         if (unlikely(*shadow_addr)) {
 173                 u16 shadow_first_bytes = *(u16 *)shadow_addr;
 174
 175                 if (unlikely(shadow_first_bytes))
 176                         return true;
 177
 178                 /*
 179                  * If two shadow bytes covers 16-byte access, we don't
 180                  * need to do anything more. Otherwise, test the last
 181                  * shadow byte.
 182                  */
 183                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 184                         return false;
 185
 186                 return memory_is_poisoned_1(addr + 15);
 187         }
 188
 189         return false;
 190 }
 191
 192 static __always_inline unsigned long bytes_is_zero(const u8 *start,
 193                                         size_t size)
 194 {
 195         while (size) {
 196                 if (unlikely(*start))
 197                         return (unsigned long)start;
 198                 start++;
 199                 size--;
 200         }
 201
 202         return 0;
 203 }
 204
 205 static __always_inline unsigned long memory_is_zero(const void *start,
 206                                                 const void *end)
 207 {
 208         unsigned int words;
 209         unsigned long ret;
 210         unsigned int prefix = (unsigned long)start % 8;
 211
 212         if (end - start <= 16)
 213                 return bytes_is_zero(start, end - start);
 214
 215         if (prefix) {
 216                 prefix = 8 - prefix;
 217                 ret = bytes_is_zero(start, prefix);
 218                 if (unlikely(ret))
 219                         return ret;
 220                 start += prefix;
 221         }
 222
 223         words = (end - start) / 8;
 224         while (words) {
 225                 if (unlikely(*(u64 *)start))
 226                         return bytes_is_zero(start, 8);
 227                 start += 8;
 228                 words--;
 229         }
 230
 231         return bytes_is_zero(start, (end - start) % 8);
 232 }
 233
 234 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 235                                                 size_t size)
 236 {
 237         unsigned long ret;
 238
 239         ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
 240                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 241
 242         if (unlikely(ret)) {
 243                 unsigned long last_byte = addr + size - 1;
 244                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 245
 246                 if (unlikely(ret != (unsigned long)last_shadow ||
 247                         ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 248                         return true;
 249         }
 250         return false;
 251 }
 252
 253 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 254 {
 255         if (__builtin_constant_p(size)) {
 256                 switch (size) {
 257                 case 1:
 258                         return memory_is_poisoned_1(addr);
 259                 case 2:
 260                         return memory_is_poisoned_2(addr);
 261                 case 4:
 262                         return memory_is_poisoned_4(addr);
 263                 case 8:
 264                         return memory_is_poisoned_8(addr);
 265                 case 16:
 266                         return memory_is_poisoned_16(addr);
 267                 default:
 268                         BUILD_BUG();
 269                 }
 270         }
 271
 272         return memory_is_poisoned_n(addr, size);
 273 }
 274
 275
 276 static __always_inline void check_memory_region(unsigned long addr,
 277                                                 size_t size, bool write)
 278 {
 279         if (unlikely(size == 0))
 280                 return;
 281
 282         if (unlikely((void *)addr <
 283                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 284                 kasan_report(addr, size, write, _RET_IP_);
 285                 return;
 286         }
 287
 288         if (likely(!memory_is_poisoned(addr, size)))
 289                 return;
 290
 291         kasan_report(addr, size, write, _RET_IP_);
 292 }
 293
 294 void __asan_loadN(unsigned long addr, size_t size);
 295 void __asan_storeN(unsigned long addr, size_t size);
 296
 297 #undef memset
 298 void *memset(void *addr, int c, size_t len)
 299 {
 300         __asan_storeN((unsigned long)addr, len);
 301
 302         return __memset(addr, c, len);
 303 }
 304
 305 #undef memmove
 306 void *memmove(void *dest, const void *src, size_t len)
 307 {
 308         __asan_loadN((unsigned long)src, len);
 309         __asan_storeN((unsigned long)dest, len);
 310
 311         return __memmove(dest, src, len);
 312 }
 313
 314 #undef memcpy
 315 void *memcpy(void *dest, const void *src, size_t len)
 316 {
 317         __asan_loadN((unsigned long)src, len);
 318         __asan_storeN((unsigned long)dest, len);
 319
 320         return __memcpy(dest, src, len);
 321 }
 322
 323 void kasan_alloc_pages(struct page *page, unsigned int order)
 324 {
 325         if (likely(!PageHighMem(page)))
 326                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 327 }
 328
 329 void kasan_free_pages(struct page *page, unsigned int order)
 330 {
 331         if (likely(!PageHighMem(page)))
 332                 kasan_poison_shadow(page_address(page),
 333                                 PAGE_SIZE << order,
 334                                 KASAN_FREE_PAGE);
 335 }
 336
 337 #ifdef CONFIG_SLAB
 338 /*
 339  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 340  * For larger allocations larger redzones are used.
 341  */
 342 static size_t optimal_redzone(size_t object_size)
 343 {
 344         int rz =
 345                 object_size <= 64        - 16   ? 16 :
 346                 object_size <= 128       - 32   ? 32 :
 347                 object_size <= 512       - 64   ? 64 :
 348                 object_size <= 4096      - 128  ? 128 :
 349                 object_size <= (1 << 14) - 256  ? 256 :
 350                 object_size <= (1 << 15) - 512  ? 512 :
 351                 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
 352         return rz;
 353 }
 354
 355 void kasan_cache_create(struct kmem_cache *cache, size_t *size,
 356                         unsigned long *flags)
 357 {
 358         int redzone_adjust;
 359         /* Make sure the adjusted size is still less than
 360          * KMALLOC_MAX_CACHE_SIZE.
 361          * TODO: this check is only useful for SLAB, but not SLUB. We'll need
 362          * to skip it for SLUB when it starts using kasan_cache_create().
 363          */
 364         if (*size > KMALLOC_MAX_CACHE_SIZE -
 365             sizeof(struct kasan_alloc_meta) -
 366             sizeof(struct kasan_free_meta))
 367                 return;
 368         *flags |= SLAB_KASAN;
 369         /* Add alloc meta. */
 370         cache->kasan_info.alloc_meta_offset = *size;
 371         *size += sizeof(struct kasan_alloc_meta);
 372
 373         /* Add free meta. */
 374         if (cache->flags & SLAB_DESTROY_BY_RCU || cache->ctor ||
 375             cache->object_size < sizeof(struct kasan_free_meta)) {
 376                 cache->kasan_info.free_meta_offset = *size;
 377                 *size += sizeof(struct kasan_free_meta);
 378         }
 379         redzone_adjust = optimal_redzone(cache->object_size) -
 380                 (*size - cache->object_size);
 381         if (redzone_adjust > 0)
 382                 *size += redzone_adjust;
 383         *size = min(KMALLOC_MAX_CACHE_SIZE,
 384                     max(*size,
 385                         cache->object_size +
 386                         optimal_redzone(cache->object_size)));
 387 }
 388 #endif
 389
 390 void kasan_poison_slab(struct page *page)
 391 {
 392         kasan_poison_shadow(page_address(page),
 393                         PAGE_SIZE << compound_order(page),
 394                         KASAN_KMALLOC_REDZONE);
 395 }
 396
 397 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 398 {
 399         kasan_unpoison_shadow(object, cache->object_size);
 400 }
 401
 402 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 403 {
 404         kasan_poison_shadow(object,
 405                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 406                         KASAN_KMALLOC_REDZONE);
 407 #ifdef CONFIG_SLAB
 408         if (cache->flags & SLAB_KASAN) {
 409                 struct kasan_alloc_meta *alloc_info =
 410                         get_alloc_info(cache, object);
 411                 alloc_info->state = KASAN_STATE_INIT;
 412         }
 413 #endif
 414 }
 415
 416 static inline void set_track(struct kasan_track *track)
 417 {
 418         track->cpu = raw_smp_processor_id();
 419         track->pid = current->pid;
 420         track->when = jiffies;
 421 }
 422
 423 #ifdef CONFIG_SLAB
 424 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 425                                         const void *object)
 426 {
 427         return (void *)object + cache->kasan_info.alloc_meta_offset;
 428 }
 429
 430 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 431                                       const void *object)
 432 {
 433         return (void *)object + cache->kasan_info.free_meta_offset;
 434 }
 435 #endif
 436
 437 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 438 {
 439         kasan_kmalloc(cache, object, cache->object_size);
 440 }
 441
 442 void kasan_slab_free(struct kmem_cache *cache, void *object)
 443 {
 444         unsigned long size = cache->object_size;
 445         unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 446
 447         /* RCU slabs could be legally used after free within the RCU period */
 448         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 449                 return;
 450
 451 #ifdef CONFIG_SLAB
 452         if (cache->flags & SLAB_KASAN) {
 453                 struct kasan_free_meta *free_info =
 454                         get_free_info(cache, object);
 455                 struct kasan_alloc_meta *alloc_info =
 456                         get_alloc_info(cache, object);
 457                 alloc_info->state = KASAN_STATE_FREE;
 458                 set_track(&free_info->track);
 459         }
 460 #endif
 461
 462         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 463 }
 464
 465 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
 466 {
 467         unsigned long redzone_start;
 468         unsigned long redzone_end;
 469
 470         if (unlikely(object == NULL))
 471                 return;
 472
 473         redzone_start = round_up((unsigned long)(object + size),
 474                                 KASAN_SHADOW_SCALE_SIZE);
 475         redzone_end = round_up((unsigned long)object + cache->object_size,
 476                                 KASAN_SHADOW_SCALE_SIZE);
 477
 478         kasan_unpoison_shadow(object, size);
 479         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 480                 KASAN_KMALLOC_REDZONE);
 481 #ifdef CONFIG_SLAB
 482         if (cache->flags & SLAB_KASAN) {
 483                 struct kasan_alloc_meta *alloc_info =
 484                         get_alloc_info(cache, object);
 485
 486                 alloc_info->state = KASAN_STATE_ALLOC;
 487                 alloc_info->alloc_size = size;
 488                 set_track(&alloc_info->track);
 489         }
 490 #endif
 491 }
 492 EXPORT_SYMBOL(kasan_kmalloc);
 493
 494 void kasan_kmalloc_large(const void *ptr, size_t size)
 495 {
 496         struct page *page;
 497         unsigned long redzone_start;
 498         unsigned long redzone_end;
 499
 500         if (unlikely(ptr == NULL))
 501                 return;
 502
 503         page = virt_to_page(ptr);
 504         redzone_start = round_up((unsigned long)(ptr + size),
 505                                 KASAN_SHADOW_SCALE_SIZE);
 506         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 507
 508         kasan_unpoison_shadow(ptr, size);
 509         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 510                 KASAN_PAGE_REDZONE);
 511 }
 512
 513 void kasan_krealloc(const void *object, size_t size)
 514 {
 515         struct page *page;
 516
 517         if (unlikely(object == ZERO_SIZE_PTR))
 518                 return;
 519
 520         page = virt_to_head_page(object);
 521
 522         if (unlikely(!PageSlab(page)))
 523                 kasan_kmalloc_large(object, size);
 524         else
 525                 kasan_kmalloc(page->slab_cache, object, size);
 526 }
 527
 528 void kasan_kfree(void *ptr)
 529 {
 530         struct page *page;
 531
 532         page = virt_to_head_page(ptr);
 533
 534         if (unlikely(!PageSlab(page)))
 535                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 536                                 KASAN_FREE_PAGE);
 537         else
 538                 kasan_slab_free(page->slab_cache, ptr);
 539 }
 540
 541 void kasan_kfree_large(const void *ptr)
 542 {
 543         struct page *page = virt_to_page(ptr);
 544
 545         kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 546                         KASAN_FREE_PAGE);
 547 }
 548
 549 int kasan_module_alloc(void *addr, size_t size)
 550 {
 551         void *ret;
 552         size_t shadow_size;
 553         unsigned long shadow_start;
 554
 555         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 556         shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
 557                         PAGE_SIZE);
 558
 559         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 560                 return -EINVAL;
 561
 562         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 563                         shadow_start + shadow_size,
 564                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 565                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 566                         __builtin_return_address(0));
 567
 568         if (ret) {
 569                 find_vm_area(addr)->flags |= VM_KASAN;
 570                 kmemleak_ignore(ret);
 571                 return 0;
 572         }
 573
 574         return -ENOMEM;
 575 }
 576
 577 void kasan_free_shadow(const struct vm_struct *vm)
 578 {
 579         if (vm->flags & VM_KASAN)
 580                 vfree(kasan_mem_to_shadow(vm->addr));
 581 }
 582
 583 static void register_global(struct kasan_global *global)
 584 {
 585         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 586
 587         kasan_unpoison_shadow(global->beg, global->size);
 588
 589         kasan_poison_shadow(global->beg + aligned_size,
 590                 global->size_with_redzone - aligned_size,
 591                 KASAN_GLOBAL_REDZONE);
 592 }
 593
 594 void __asan_register_globals(struct kasan_global *globals, size_t size)
 595 {
 596         int i;
 597
 598         for (i = 0; i < size; i++)
 599                 register_global(&globals[i]);
 600 }
 601 EXPORT_SYMBOL(__asan_register_globals);
 602
 603 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 604 {
 605 }
 606 EXPORT_SYMBOL(__asan_unregister_globals);
 607
 608 #define DEFINE_ASAN_LOAD_STORE(size)                            \
 609         void __asan_load##size(unsigned long addr)              \
 610         {                                                       \
 611                 check_memory_region(addr, size, false);         \
 612         }                                                       \
 613         EXPORT_SYMBOL(__asan_load##size);                       \
 614         __alias(__asan_load##size)                              \
 615         void __asan_load##size##_noabort(unsigned long);        \
 616         EXPORT_SYMBOL(__asan_load##size##_noabort);             \
 617         void __asan_store##size(unsigned long addr)             \
 618         {                                                       \
 619                 check_memory_region(addr, size, true);          \
 620         }                                                       \
 621         EXPORT_SYMBOL(__asan_store##size);                      \
 622         __alias(__asan_store##size)                             \
 623         void __asan_store##size##_noabort(unsigned long);       \
 624         EXPORT_SYMBOL(__asan_store##size##_noabort)
 625
 626 DEFINE_ASAN_LOAD_STORE(1);
 627 DEFINE_ASAN_LOAD_STORE(2);
 628 DEFINE_ASAN_LOAD_STORE(4);
 629 DEFINE_ASAN_LOAD_STORE(8);
 630 DEFINE_ASAN_LOAD_STORE(16);
 631
 632 void __asan_loadN(unsigned long addr, size_t size)
 633 {
 634         check_memory_region(addr, size, false);
 635 }
 636 EXPORT_SYMBOL(__asan_loadN);
 637
 638 __alias(__asan_loadN)
 639 void __asan_loadN_noabort(unsigned long, size_t);
 640 EXPORT_SYMBOL(__asan_loadN_noabort);
 641
 642 void __asan_storeN(unsigned long addr, size_t size)
 643 {
 644         check_memory_region(addr, size, true);
 645 }
 646 EXPORT_SYMBOL(__asan_storeN);
 647
 648 __alias(__asan_storeN)
 649 void __asan_storeN_noabort(unsigned long, size_t);
 650 EXPORT_SYMBOL(__asan_storeN_noabort);
 651
 652 /* to shut up compiler complaints */
 653 void __asan_handle_no_return(void) {}
 654 EXPORT_SYMBOL(__asan_handle_no_return);
 655
 656 #ifdef CONFIG_MEMORY_HOTPLUG
 657 static int kasan_mem_notifier(struct notifier_block *nb,
 658                         unsigned long action, void *data)
 659 {
 660         return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
 661 }
 662
 663 static int __init kasan_memhotplug_init(void)
 664 {
 665         pr_err("WARNING: KASAN doesn't support memory hot-add\n");
 666         pr_err("Memory hot-add will be disabled\n");
 667
 668         hotplug_memory_notifier(kasan_mem_notifier, 0);
 669
 670         return 0;
 671 }
 672
 673 module_init(kasan_memhotplug_init);
 674 #endif