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 <a.ryabinin@samsung.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                 s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK;
 139
 140                 if (unlikely(shadow_first_bytes))
 141                         return true;
 142
 143                 if (likely(!last_byte))
 144                         return false;
 145
 146                 return memory_is_poisoned_1(addr + 15);
 147         }
 148
 149         return false;
 150 }
 151
 152 static __always_inline unsigned long bytes_is_zero(const u8 *start,
 153                                         size_t size)
 154 {
 155         while (size) {
 156                 if (unlikely(*start))
 157                         return (unsigned long)start;
 158                 start++;
 159                 size--;
 160         }
 161
 162         return 0;
 163 }
 164
 165 static __always_inline unsigned long memory_is_zero(const void *start,
 166                                                 const void *end)
 167 {
 168         unsigned int words;
 169         unsigned long ret;
 170         unsigned int prefix = (unsigned long)start % 8;
 171
 172         if (end - start <= 16)
 173                 return bytes_is_zero(start, end - start);
 174
 175         if (prefix) {
 176                 prefix = 8 - prefix;
 177                 ret = bytes_is_zero(start, prefix);
 178                 if (unlikely(ret))
 179                         return ret;
 180                 start += prefix;
 181         }
 182
 183         words = (end - start) / 8;
 184         while (words) {
 185                 if (unlikely(*(u64 *)start))
 186                         return bytes_is_zero(start, 8);
 187                 start += 8;
 188                 words--;
 189         }
 190
 191         return bytes_is_zero(start, (end - start) % 8);
 192 }
 193
 194 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 195                                                 size_t size)
 196 {
 197         unsigned long ret;
 198
 199         ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
 200                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 201
 202         if (unlikely(ret)) {
 203                 unsigned long last_byte = addr + size - 1;
 204                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 205
 206                 if (unlikely(ret != (unsigned long)last_shadow ||
 207                         ((last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 208                         return true;
 209         }
 210         return false;
 211 }
 212
 213 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 214 {
 215         if (__builtin_constant_p(size)) {
 216                 switch (size) {
 217                 case 1:
 218                         return memory_is_poisoned_1(addr);
 219                 case 2:
 220                         return memory_is_poisoned_2(addr);
 221                 case 4:
 222                         return memory_is_poisoned_4(addr);
 223                 case 8:
 224                         return memory_is_poisoned_8(addr);
 225                 case 16:
 226                         return memory_is_poisoned_16(addr);
 227                 default:
 228                         BUILD_BUG();
 229                 }
 230         }
 231
 232         return memory_is_poisoned_n(addr, size);
 233 }
 234
 235
 236 static __always_inline void check_memory_region(unsigned long addr,
 237                                                 size_t size, bool write)
 238 {
 239         struct kasan_access_info info;
 240
 241         if (unlikely(size == 0))
 242                 return;
 243
 244         if (unlikely((void *)addr <
 245                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 246                 info.access_addr = (void *)addr;
 247                 info.access_size = size;
 248                 info.is_write = write;
 249                 info.ip = _RET_IP_;
 250                 kasan_report_user_access(&info);
 251                 return;
 252         }
 253
 254         if (likely(!memory_is_poisoned(addr, size)))
 255                 return;
 256
 257         kasan_report(addr, size, write, _RET_IP_);
 258 }
 259
 260 void __asan_loadN(unsigned long addr, size_t size);
 261 void __asan_storeN(unsigned long addr, size_t size);
 262
 263 #undef memset
 264 void *memset(void *addr, int c, size_t len)
 265 {
 266         __asan_storeN((unsigned long)addr, len);
 267
 268         return __memset(addr, c, len);
 269 }
 270
 271 #undef memmove
 272 void *memmove(void *dest, const void *src, size_t len)
 273 {
 274         __asan_loadN((unsigned long)src, len);
 275         __asan_storeN((unsigned long)dest, len);
 276
 277         return __memmove(dest, src, len);
 278 }
 279
 280 #undef memcpy
 281 void *memcpy(void *dest, const void *src, size_t len)
 282 {
 283         __asan_loadN((unsigned long)src, len);
 284         __asan_storeN((unsigned long)dest, len);
 285
 286         return __memcpy(dest, src, len);
 287 }
 288
 289 void kasan_alloc_pages(struct page *page, unsigned int order)
 290 {
 291         if (likely(!PageHighMem(page)))
 292                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 293 }
 294
 295 void kasan_free_pages(struct page *page, unsigned int order)
 296 {
 297         if (likely(!PageHighMem(page)))
 298                 kasan_poison_shadow(page_address(page),
 299                                 PAGE_SIZE << order,
 300                                 KASAN_FREE_PAGE);
 301 }
 302
 303 void kasan_poison_slab(struct page *page)
 304 {
 305         kasan_poison_shadow(page_address(page),
 306                         PAGE_SIZE << compound_order(page),
 307                         KASAN_KMALLOC_REDZONE);
 308 }
 309
 310 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 311 {
 312         kasan_unpoison_shadow(object, cache->object_size);
 313 }
 314
 315 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 316 {
 317         kasan_poison_shadow(object,
 318                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 319                         KASAN_KMALLOC_REDZONE);
 320 }
 321
 322 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 323 {
 324         kasan_kmalloc(cache, object, cache->object_size);
 325 }
 326
 327 void kasan_slab_free(struct kmem_cache *cache, void *object)
 328 {
 329         unsigned long size = cache->object_size;
 330         unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 331
 332         /* RCU slabs could be legally used after free within the RCU period */
 333         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 334                 return;
 335
 336         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 337 }
 338
 339 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
 340 {
 341         unsigned long redzone_start;
 342         unsigned long redzone_end;
 343
 344         if (unlikely(object == NULL))
 345                 return;
 346
 347         redzone_start = round_up((unsigned long)(object + size),
 348                                 KASAN_SHADOW_SCALE_SIZE);
 349         redzone_end = round_up((unsigned long)object + cache->object_size,
 350                                 KASAN_SHADOW_SCALE_SIZE);
 351
 352         kasan_unpoison_shadow(object, size);
 353         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 354                 KASAN_KMALLOC_REDZONE);
 355 }
 356 EXPORT_SYMBOL(kasan_kmalloc);
 357
 358 void kasan_kmalloc_large(const void *ptr, size_t size)
 359 {
 360         struct page *page;
 361         unsigned long redzone_start;
 362         unsigned long redzone_end;
 363
 364         if (unlikely(ptr == NULL))
 365                 return;
 366
 367         page = virt_to_page(ptr);
 368         redzone_start = round_up((unsigned long)(ptr + size),
 369                                 KASAN_SHADOW_SCALE_SIZE);
 370         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 371
 372         kasan_unpoison_shadow(ptr, size);
 373         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 374                 KASAN_PAGE_REDZONE);
 375 }
 376
 377 void kasan_krealloc(const void *object, size_t size)
 378 {
 379         struct page *page;
 380
 381         if (unlikely(object == ZERO_SIZE_PTR))
 382                 return;
 383
 384         page = virt_to_head_page(object);
 385
 386         if (unlikely(!PageSlab(page)))
 387                 kasan_kmalloc_large(object, size);
 388         else
 389                 kasan_kmalloc(page->slab_cache, object, size);
 390 }
 391
 392 void kasan_kfree(void *ptr)
 393 {
 394         struct page *page;
 395
 396         page = virt_to_head_page(ptr);
 397
 398         if (unlikely(!PageSlab(page)))
 399                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 400                                 KASAN_FREE_PAGE);
 401         else
 402                 kasan_slab_free(page->slab_cache, ptr);
 403 }
 404
 405 void kasan_kfree_large(const void *ptr)
 406 {
 407         struct page *page = virt_to_page(ptr);
 408
 409         kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 410                         KASAN_FREE_PAGE);
 411 }
 412
 413 int kasan_module_alloc(void *addr, size_t size)
 414 {
 415         void *ret;
 416         size_t shadow_size;
 417         unsigned long shadow_start;
 418
 419         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 420         shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
 421                         PAGE_SIZE);
 422
 423         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 424                 return -EINVAL;
 425
 426         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 427                         shadow_start + shadow_size,
 428                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 429                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 430                         __builtin_return_address(0));
 431
 432         if (ret) {
 433                 find_vm_area(addr)->flags |= VM_KASAN;
 434                 return 0;
 435         }
 436
 437         return -ENOMEM;
 438 }
 439
 440 void kasan_free_shadow(const struct vm_struct *vm)
 441 {
 442         if (vm->flags & VM_KASAN)
 443                 vfree(kasan_mem_to_shadow(vm->addr));
 444 }
 445
 446 static void register_global(struct kasan_global *global)
 447 {
 448         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 449
 450         kasan_unpoison_shadow(global->beg, global->size);
 451
 452         kasan_poison_shadow(global->beg + aligned_size,
 453                 global->size_with_redzone - aligned_size,
 454                 KASAN_GLOBAL_REDZONE);
 455 }
 456
 457 void __asan_register_globals(struct kasan_global *globals, size_t size)
 458 {
 459         int i;
 460
 461         for (i = 0; i < size; i++)
 462                 register_global(&globals[i]);
 463 }
 464 EXPORT_SYMBOL(__asan_register_globals);
 465
 466 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 467 {
 468 }
 469 EXPORT_SYMBOL(__asan_unregister_globals);
 470
 471 #define DEFINE_ASAN_LOAD_STORE(size)                            \
 472         void __asan_load##size(unsigned long addr)              \
 473         {                                                       \
 474                 check_memory_region(addr, size, false);         \
 475         }                                                       \
 476         EXPORT_SYMBOL(__asan_load##size);                       \
 477         __alias(__asan_load##size)                              \
 478         void __asan_load##size##_noabort(unsigned long);        \
 479         EXPORT_SYMBOL(__asan_load##size##_noabort);             \
 480         void __asan_store##size(unsigned long addr)             \
 481         {                                                       \
 482                 check_memory_region(addr, size, true);          \
 483         }                                                       \
 484         EXPORT_SYMBOL(__asan_store##size);                      \
 485         __alias(__asan_store##size)                             \
 486         void __asan_store##size##_noabort(unsigned long);       \
 487         EXPORT_SYMBOL(__asan_store##size##_noabort)
 488
 489 DEFINE_ASAN_LOAD_STORE(1);
 490 DEFINE_ASAN_LOAD_STORE(2);
 491 DEFINE_ASAN_LOAD_STORE(4);
 492 DEFINE_ASAN_LOAD_STORE(8);
 493 DEFINE_ASAN_LOAD_STORE(16);
 494
 495 void __asan_loadN(unsigned long addr, size_t size)
 496 {
 497         check_memory_region(addr, size, false);
 498 }
 499 EXPORT_SYMBOL(__asan_loadN);
 500
 501 __alias(__asan_loadN)
 502 void __asan_loadN_noabort(unsigned long, size_t);
 503 EXPORT_SYMBOL(__asan_loadN_noabort);
 504
 505 void __asan_storeN(unsigned long addr, size_t size)
 506 {
 507         check_memory_region(addr, size, true);
 508 }
 509 EXPORT_SYMBOL(__asan_storeN);
 510
 511 __alias(__asan_storeN)
 512 void __asan_storeN_noabort(unsigned long, size_t);
 513 EXPORT_SYMBOL(__asan_storeN_noabort);
 514
 515 /* to shut up compiler complaints */
 516 void __asan_handle_no_return(void) {}
 517 EXPORT_SYMBOL(__asan_handle_no_return);
 518
 519 #ifdef CONFIG_MEMORY_HOTPLUG
 520 static int kasan_mem_notifier(struct notifier_block *nb,
 521                         unsigned long action, void *data)
 522 {
 523         return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
 524 }
 525
 526 static int __init kasan_memhotplug_init(void)
 527 {
 528         pr_err("WARNING: KASan doesn't support memory hot-add\n");
 529         pr_err("Memory hot-add will be disabled\n");
 530
 531         hotplug_memory_notifier(kasan_mem_notifier, 0);
 532
 533         return 0;
 534 }
 535
 536 module_init(kasan_memhotplug_init);
 537 #endif