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 of code borrowed from https://github.com/xairy/linux 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/memblock.h>
  23 #include <linux/memory.h>
  24 #include <linux/mm.h>
  25 #include <linux/module.h>
  26 #include <linux/printk.h>
  27 #include <linux/sched.h>
  28 #include <linux/slab.h>
  29 #include <linux/stacktrace.h>
  30 #include <linux/string.h>
  31 #include <linux/types.h>
  32 #include <linux/vmalloc.h>
  33 #include <linux/kasan.h>
  34
  35 #include "kasan.h"
  36 #include "../slab.h"
  37
  38 /*
  39  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
  40  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
  41  */
  42 static void kasan_poison_shadow(const void *address, size_t size, u8 value)
  43 {
  44         void *shadow_start, *shadow_end;
  45
  46         shadow_start = kasan_mem_to_shadow(address);
  47         shadow_end = kasan_mem_to_shadow(address + size);
  48
  49         memset(shadow_start, value, shadow_end - shadow_start);
  50 }
  51
  52 void kasan_unpoison_shadow(const void *address, size_t size)
  53 {
  54         kasan_poison_shadow(address, size, 0);
  55
  56         if (size & KASAN_SHADOW_MASK) {
  57                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
  58                 *shadow = size & KASAN_SHADOW_MASK;
  59         }
  60 }
  61
  62
  63 /*
  64  * All functions below always inlined so compiler could
  65  * perform better optimizations in each of __asan_loadX/__assn_storeX
  66  * depending on memory access size X.
  67  */
  68
  69 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
  70 {
  71         s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
  72
  73         if (unlikely(shadow_value)) {
  74                 s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
  75                 return unlikely(last_accessible_byte >= shadow_value);
  76         }
  77
  78         return false;
  79 }
  80
  81 static __always_inline bool memory_is_poisoned_2(unsigned long addr)
  82 {
  83         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
  84
  85         if (unlikely(*shadow_addr)) {
  86                 if (memory_is_poisoned_1(addr + 1))
  87                         return true;
  88
  89                 if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
  90                         return false;
  91
  92                 return unlikely(*(u8 *)shadow_addr);
  93         }
  94
  95         return false;
  96 }
  97
  98 static __always_inline bool memory_is_poisoned_4(unsigned long addr)
  99 {
 100         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 101
 102         if (unlikely(*shadow_addr)) {
 103                 if (memory_is_poisoned_1(addr + 3))
 104                         return true;
 105
 106                 if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
 107                         return false;
 108
 109                 return unlikely(*(u8 *)shadow_addr);
 110         }
 111
 112         return false;
 113 }
 114
 115 static __always_inline bool memory_is_poisoned_8(unsigned long addr)
 116 {
 117         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 118
 119         if (unlikely(*shadow_addr)) {
 120                 if (memory_is_poisoned_1(addr + 7))
 121                         return true;
 122
 123                 if (likely(((addr + 7) & KASAN_SHADOW_MASK) >= 7))
 124                         return false;
 125
 126                 return unlikely(*(u8 *)shadow_addr);
 127         }
 128
 129         return false;
 130 }
 131
 132 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
 133 {
 134         u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);
 135
 136         if (unlikely(*shadow_addr)) {
 137                 u16 shadow_first_bytes = *(u16 *)shadow_addr;
 138
 139                 if (unlikely(shadow_first_bytes))
 140                         return true;
 141
 142                 if (likely(IS_ALIGNED(addr, 8)))
 143                         return false;
 144
 145                 return memory_is_poisoned_1(addr + 15);
 146         }
 147
 148         return false;
 149 }
 150
 151 static __always_inline unsigned long bytes_is_zero(const u8 *start,
 152                                         size_t size)
 153 {
 154         while (size) {
 155                 if (unlikely(*start))
 156                         return (unsigned long)start;
 157                 start++;
 158                 size--;
 159         }
 160
 161         return 0;
 162 }
 163
 164 static __always_inline unsigned long memory_is_zero(const void *start,
 165                                                 const void *end)
 166 {
 167         unsigned int words;
 168         unsigned long ret;
 169         unsigned int prefix = (unsigned long)start % 8;
 170
 171         if (end - start <= 16)
 172                 return bytes_is_zero(start, end - start);
 173
 174         if (prefix) {
 175                 prefix = 8 - prefix;
 176                 ret = bytes_is_zero(start, prefix);
 177                 if (unlikely(ret))
 178                         return ret;
 179                 start += prefix;
 180         }
 181
 182         words = (end - start) / 8;
 183         while (words) {
 184                 if (unlikely(*(u64 *)start))
 185                         return bytes_is_zero(start, 8);
 186                 start += 8;
 187                 words--;
 188         }
 189
 190         return bytes_is_zero(start, (end - start) % 8);
 191 }
 192
 193 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 194                                                 size_t size)
 195 {
 196         unsigned long ret;
 197
 198         ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
 199                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 200
 201         if (unlikely(ret)) {
 202                 unsigned long last_byte = addr + size - 1;
 203                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 204
 205                 if (unlikely(ret != (unsigned long)last_shadow ||
 206                         ((last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 207                         return true;
 208         }
 209         return false;
 210 }
 211
 212 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 213 {
 214         if (__builtin_constant_p(size)) {
 215                 switch (size) {
 216                 case 1:
 217                         return memory_is_poisoned_1(addr);
 218                 case 2:
 219                         return memory_is_poisoned_2(addr);
 220                 case 4:
 221                         return memory_is_poisoned_4(addr);
 222                 case 8:
 223                         return memory_is_poisoned_8(addr);
 224                 case 16:
 225                         return memory_is_poisoned_16(addr);
 226                 default:
 227                         BUILD_BUG();
 228                 }
 229         }
 230
 231         return memory_is_poisoned_n(addr, size);
 232 }
 233
 234
 235 static __always_inline void check_memory_region(unsigned long addr,
 236                                                 size_t size, bool write)
 237 {
 238         if (unlikely(size == 0))
 239                 return;
 240
 241         if (unlikely((void *)addr <
 242                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 243                 kasan_report(addr, size, write, _RET_IP_);
 244                 return;
 245         }
 246
 247         if (likely(!memory_is_poisoned(addr, size)))
 248                 return;
 249
 250         kasan_report(addr, size, write, _RET_IP_);
 251 }
 252
 253 void __asan_loadN(unsigned long addr, size_t size);
 254 void __asan_storeN(unsigned long addr, size_t size);
 255
 256 #undef memset
 257 void *memset(void *addr, int c, size_t len)
 258 {
 259         __asan_storeN((unsigned long)addr, len);
 260
 261         return __memset(addr, c, len);
 262 }
 263
 264 #undef memmove
 265 void *memmove(void *dest, const void *src, size_t len)
 266 {
 267         __asan_loadN((unsigned long)src, len);
 268         __asan_storeN((unsigned long)dest, len);
 269
 270         return __memmove(dest, src, len);
 271 }
 272
 273 #undef memcpy
 274 void *memcpy(void *dest, const void *src, size_t len)
 275 {
 276         __asan_loadN((unsigned long)src, len);
 277         __asan_storeN((unsigned long)dest, len);
 278
 279         return __memcpy(dest, src, len);
 280 }
 281
 282 void kasan_alloc_pages(struct page *page, unsigned int order)
 283 {
 284         if (likely(!PageHighMem(page)))
 285                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 286 }
 287
 288 void kasan_free_pages(struct page *page, unsigned int order)
 289 {
 290         if (likely(!PageHighMem(page)))
 291                 kasan_poison_shadow(page_address(page),
 292                                 PAGE_SIZE << order,
 293                                 KASAN_FREE_PAGE);
 294 }
 295
 296 void kasan_poison_slab(struct page *page)
 297 {
 298         kasan_poison_shadow(page_address(page),
 299                         PAGE_SIZE << compound_order(page),
 300                         KASAN_KMALLOC_REDZONE);
 301 }
 302
 303 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 304 {
 305         kasan_unpoison_shadow(object, cache->object_size);
 306 }
 307
 308 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 309 {
 310         kasan_poison_shadow(object,
 311                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 312                         KASAN_KMALLOC_REDZONE);
 313 }
 314
 315 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 316 {
 317         kasan_kmalloc(cache, object, cache->object_size);
 318 }
 319
 320 void kasan_slab_free(struct kmem_cache *cache, void *object)
 321 {
 322         unsigned long size = cache->object_size;
 323         unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 324
 325         /* RCU slabs could be legally used after free within the RCU period */
 326         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 327                 return;
 328
 329         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 330 }
 331
 332 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
 333 {
 334         unsigned long redzone_start;
 335         unsigned long redzone_end;
 336
 337         if (unlikely(object == NULL))
 338                 return;
 339
 340         redzone_start = round_up((unsigned long)(object + size),
 341                                 KASAN_SHADOW_SCALE_SIZE);
 342         redzone_end = round_up((unsigned long)object + cache->object_size,
 343                                 KASAN_SHADOW_SCALE_SIZE);
 344
 345         kasan_unpoison_shadow(object, size);
 346         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 347                 KASAN_KMALLOC_REDZONE);
 348 }
 349 EXPORT_SYMBOL(kasan_kmalloc);
 350
 351 void kasan_kmalloc_large(const void *ptr, size_t size)
 352 {
 353         struct page *page;
 354         unsigned long redzone_start;
 355         unsigned long redzone_end;
 356
 357         if (unlikely(ptr == NULL))
 358                 return;
 359
 360         page = virt_to_page(ptr);
 361         redzone_start = round_up((unsigned long)(ptr + size),
 362                                 KASAN_SHADOW_SCALE_SIZE);
 363         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 364
 365         kasan_unpoison_shadow(ptr, size);
 366         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 367                 KASAN_PAGE_REDZONE);
 368 }
 369
 370 void kasan_krealloc(const void *object, size_t size)
 371 {
 372         struct page *page;
 373
 374         if (unlikely(object == ZERO_SIZE_PTR))
 375                 return;
 376
 377         page = virt_to_head_page(object);
 378
 379         if (unlikely(!PageSlab(page)))
 380                 kasan_kmalloc_large(object, size);
 381         else
 382                 kasan_kmalloc(page->slab_cache, object, size);
 383 }
 384
 385 void kasan_kfree(void *ptr)
 386 {
 387         struct page *page;
 388
 389         page = virt_to_head_page(ptr);
 390
 391         if (unlikely(!PageSlab(page)))
 392                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 393                                 KASAN_FREE_PAGE);
 394         else
 395                 kasan_slab_free(page->slab_cache, ptr);
 396 }
 397
 398 void kasan_kfree_large(const void *ptr)
 399 {
 400         struct page *page = virt_to_page(ptr);
 401
 402         kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 403                         KASAN_FREE_PAGE);
 404 }
 405
 406 int kasan_module_alloc(void *addr, size_t size)
 407 {
 408         void *ret;
 409         size_t shadow_size;
 410         unsigned long shadow_start;
 411
 412         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 413         shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
 414                         PAGE_SIZE);
 415
 416         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 417                 return -EINVAL;
 418
 419         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 420                         shadow_start + shadow_size,
 421                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 422                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 423                         __builtin_return_address(0));
 424
 425         if (ret) {
 426                 find_vm_area(addr)->flags |= VM_KASAN;
 427                 return 0;
 428         }
 429
 430         return -ENOMEM;
 431 }
 432
 433 void kasan_free_shadow(const struct vm_struct *vm)
 434 {
 435         if (vm->flags & VM_KASAN)
 436                 vfree(kasan_mem_to_shadow(vm->addr));
 437 }
 438
 439 static void register_global(struct kasan_global *global)
 440 {
 441         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 442
 443         kasan_unpoison_shadow(global->beg, global->size);
 444
 445         kasan_poison_shadow(global->beg + aligned_size,
 446                 global->size_with_redzone - aligned_size,
 447                 KASAN_GLOBAL_REDZONE);
 448 }
 449
 450 void __asan_register_globals(struct kasan_global *globals, size_t size)
 451 {
 452         int i;
 453
 454         for (i = 0; i < size; i++)
 455                 register_global(&globals[i]);
 456 }
 457 EXPORT_SYMBOL(__asan_register_globals);
 458
 459 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 460 {
 461 }
 462 EXPORT_SYMBOL(__asan_unregister_globals);
 463
 464 #define DEFINE_ASAN_LOAD_STORE(size)                            \
 465         void __asan_load##size(unsigned long addr)              \
 466         {                                                       \
 467                 check_memory_region(addr, size, false);         \
 468         }                                                       \
 469         EXPORT_SYMBOL(__asan_load##size);                       \
 470         __alias(__asan_load##size)                              \
 471         void __asan_load##size##_noabort(unsigned long);        \
 472         EXPORT_SYMBOL(__asan_load##size##_noabort);             \
 473         void __asan_store##size(unsigned long addr)             \
 474         {                                                       \
 475                 check_memory_region(addr, size, true);          \
 476         }                                                       \
 477         EXPORT_SYMBOL(__asan_store##size);                      \
 478         __alias(__asan_store##size)                             \
 479         void __asan_store##size##_noabort(unsigned long);       \
 480         EXPORT_SYMBOL(__asan_store##size##_noabort)
 481
 482 DEFINE_ASAN_LOAD_STORE(1);
 483 DEFINE_ASAN_LOAD_STORE(2);
 484 DEFINE_ASAN_LOAD_STORE(4);
 485 DEFINE_ASAN_LOAD_STORE(8);
 486 DEFINE_ASAN_LOAD_STORE(16);
 487
 488 void __asan_loadN(unsigned long addr, size_t size)
 489 {
 490         check_memory_region(addr, size, false);
 491 }
 492 EXPORT_SYMBOL(__asan_loadN);
 493
 494 __alias(__asan_loadN)
 495 void __asan_loadN_noabort(unsigned long, size_t);
 496 EXPORT_SYMBOL(__asan_loadN_noabort);
 497
 498 void __asan_storeN(unsigned long addr, size_t size)
 499 {
 500         check_memory_region(addr, size, true);
 501 }
 502 EXPORT_SYMBOL(__asan_storeN);
 503
 504 __alias(__asan_storeN)
 505 void __asan_storeN_noabort(unsigned long, size_t);
 506 EXPORT_SYMBOL(__asan_storeN_noabort);
 507
 508 /* to shut up compiler complaints */
 509 void __asan_handle_no_return(void) {}
 510 EXPORT_SYMBOL(__asan_handle_no_return);
 511
 512 #ifdef CONFIG_MEMORY_HOTPLUG
 513 static int kasan_mem_notifier(struct notifier_block *nb,
 514                         unsigned long action, void *data)
 515 {
 516         return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
 517 }
 518
 519 static int __init kasan_memhotplug_init(void)
 520 {
 521         pr_err("WARNING: KASAN doesn't support memory hot-add\n");
 522         pr_err("Memory hot-add will be disabled\n");
 523
 524         hotplug_memory_notifier(kasan_mem_notifier, 0);
 525
 526         return 0;
 527 }
 528
 529 module_init(kasan_memhotplug_init);
 530 #endif