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/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                 /*
  90                  * If single shadow byte covers 2-byte access, we don't
  91                  * need to do anything more. Otherwise, test the first
  92                  * shadow byte.
  93                  */
  94                 if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
  95                         return false;
  96
  97                 return unlikely(*(u8 *)shadow_addr);
  98         }
  99
 100         return false;
 101 }
 102
 103 static __always_inline bool memory_is_poisoned_4(unsigned long addr)
 104 {
 105         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 106
 107         if (unlikely(*shadow_addr)) {
 108                 if (memory_is_poisoned_1(addr + 3))
 109                         return true;
 110
 111                 /*
 112                  * If single shadow byte covers 4-byte access, we don't
 113                  * need to do anything more. Otherwise, test the first
 114                  * shadow byte.
 115                  */
 116                 if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
 117                         return false;
 118
 119                 return unlikely(*(u8 *)shadow_addr);
 120         }
 121
 122         return false;
 123 }
 124
 125 static __always_inline bool memory_is_poisoned_8(unsigned long addr)
 126 {
 127         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 128
 129         if (unlikely(*shadow_addr)) {
 130                 if (memory_is_poisoned_1(addr + 7))
 131                         return true;
 132
 133                 /*
 134                  * If single shadow byte covers 8-byte access, we don't
 135                  * need to do anything more. Otherwise, test the first
 136                  * shadow byte.
 137                  */
 138                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 139                         return false;
 140
 141                 return unlikely(*(u8 *)shadow_addr);
 142         }
 143
 144         return false;
 145 }
 146
 147 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
 148 {
 149         u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);
 150
 151         if (unlikely(*shadow_addr)) {
 152                 u16 shadow_first_bytes = *(u16 *)shadow_addr;
 153
 154                 if (unlikely(shadow_first_bytes))
 155                         return true;
 156
 157                 /*
 158                  * If two shadow bytes covers 16-byte access, we don't
 159                  * need to do anything more. Otherwise, test the last
 160                  * shadow byte.
 161                  */
 162                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 163                         return false;
 164
 165                 return memory_is_poisoned_1(addr + 15);
 166         }
 167
 168         return false;
 169 }
 170
 171 static __always_inline unsigned long bytes_is_zero(const u8 *start,
 172                                         size_t size)
 173 {
 174         while (size) {
 175                 if (unlikely(*start))
 176                         return (unsigned long)start;
 177                 start++;
 178                 size--;
 179         }
 180
 181         return 0;
 182 }
 183
 184 static __always_inline unsigned long memory_is_zero(const void *start,
 185                                                 const void *end)
 186 {
 187         unsigned int words;
 188         unsigned long ret;
 189         unsigned int prefix = (unsigned long)start % 8;
 190
 191         if (end - start <= 16)
 192                 return bytes_is_zero(start, end - start);
 193
 194         if (prefix) {
 195                 prefix = 8 - prefix;
 196                 ret = bytes_is_zero(start, prefix);
 197                 if (unlikely(ret))
 198                         return ret;
 199                 start += prefix;
 200         }
 201
 202         words = (end - start) / 8;
 203         while (words) {
 204                 if (unlikely(*(u64 *)start))
 205                         return bytes_is_zero(start, 8);
 206                 start += 8;
 207                 words--;
 208         }
 209
 210         return bytes_is_zero(start, (end - start) % 8);
 211 }
 212
 213 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 214                                                 size_t size)
 215 {
 216         unsigned long ret;
 217
 218         ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
 219                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 220
 221         if (unlikely(ret)) {
 222                 unsigned long last_byte = addr + size - 1;
 223                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 224
 225                 if (unlikely(ret != (unsigned long)last_shadow ||
 226                         ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 227                         return true;
 228         }
 229         return false;
 230 }
 231
 232 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 233 {
 234         if (__builtin_constant_p(size)) {
 235                 switch (size) {
 236                 case 1:
 237                         return memory_is_poisoned_1(addr);
 238                 case 2:
 239                         return memory_is_poisoned_2(addr);
 240                 case 4:
 241                         return memory_is_poisoned_4(addr);
 242                 case 8:
 243                         return memory_is_poisoned_8(addr);
 244                 case 16:
 245                         return memory_is_poisoned_16(addr);
 246                 default:
 247                         BUILD_BUG();
 248                 }
 249         }
 250
 251         return memory_is_poisoned_n(addr, size);
 252 }
 253
 254
 255 static __always_inline void check_memory_region(unsigned long addr,
 256                                                 size_t size, bool write)
 257 {
 258         if (unlikely(size == 0))
 259                 return;
 260
 261         if (unlikely((void *)addr <
 262                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 263                 kasan_report(addr, size, write, _RET_IP_);
 264                 return;
 265         }
 266
 267         if (likely(!memory_is_poisoned(addr, size)))
 268                 return;
 269
 270         kasan_report(addr, size, write, _RET_IP_);
 271 }
 272
 273 void __asan_loadN(unsigned long addr, size_t size);
 274 void __asan_storeN(unsigned long addr, size_t size);
 275
 276 #undef memset
 277 void *memset(void *addr, int c, size_t len)
 278 {
 279         __asan_storeN((unsigned long)addr, len);
 280
 281         return __memset(addr, c, len);
 282 }
 283
 284 #undef memmove
 285 void *memmove(void *dest, const void *src, size_t len)
 286 {
 287         __asan_loadN((unsigned long)src, len);
 288         __asan_storeN((unsigned long)dest, len);
 289
 290         return __memmove(dest, src, len);
 291 }
 292
 293 #undef memcpy
 294 void *memcpy(void *dest, const void *src, size_t len)
 295 {
 296         __asan_loadN((unsigned long)src, len);
 297         __asan_storeN((unsigned long)dest, len);
 298
 299         return __memcpy(dest, src, len);
 300 }
 301
 302 void kasan_alloc_pages(struct page *page, unsigned int order)
 303 {
 304         if (likely(!PageHighMem(page)))
 305                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 306 }
 307
 308 void kasan_free_pages(struct page *page, unsigned int order)
 309 {
 310         if (likely(!PageHighMem(page)))
 311                 kasan_poison_shadow(page_address(page),
 312                                 PAGE_SIZE << order,
 313                                 KASAN_FREE_PAGE);
 314 }
 315
 316 void kasan_poison_slab(struct page *page)
 317 {
 318         kasan_poison_shadow(page_address(page),
 319                         PAGE_SIZE << compound_order(page),
 320                         KASAN_KMALLOC_REDZONE);
 321 }
 322
 323 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 324 {
 325         kasan_unpoison_shadow(object, cache->object_size);
 326 }
 327
 328 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 329 {
 330         kasan_poison_shadow(object,
 331                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 332                         KASAN_KMALLOC_REDZONE);
 333 }
 334
 335 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 336 {
 337         kasan_kmalloc(cache, object, cache->object_size);
 338 }
 339
 340 void kasan_slab_free(struct kmem_cache *cache, void *object)
 341 {
 342         unsigned long size = cache->object_size;
 343         unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 344
 345         /* RCU slabs could be legally used after free within the RCU period */
 346         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 347                 return;
 348
 349         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 350 }
 351
 352 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
 353 {
 354         unsigned long redzone_start;
 355         unsigned long redzone_end;
 356
 357         if (unlikely(object == NULL))
 358                 return;
 359
 360         redzone_start = round_up((unsigned long)(object + size),
 361                                 KASAN_SHADOW_SCALE_SIZE);
 362         redzone_end = round_up((unsigned long)object + cache->object_size,
 363                                 KASAN_SHADOW_SCALE_SIZE);
 364
 365         kasan_unpoison_shadow(object, size);
 366         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 367                 KASAN_KMALLOC_REDZONE);
 368 }
 369 EXPORT_SYMBOL(kasan_kmalloc);
 370
 371 void kasan_kmalloc_large(const void *ptr, size_t size)
 372 {
 373         struct page *page;
 374         unsigned long redzone_start;
 375         unsigned long redzone_end;
 376
 377         if (unlikely(ptr == NULL))
 378                 return;
 379
 380         page = virt_to_page(ptr);
 381         redzone_start = round_up((unsigned long)(ptr + size),
 382                                 KASAN_SHADOW_SCALE_SIZE);
 383         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 384
 385         kasan_unpoison_shadow(ptr, size);
 386         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 387                 KASAN_PAGE_REDZONE);
 388 }
 389
 390 void kasan_krealloc(const void *object, size_t size)
 391 {
 392         struct page *page;
 393
 394         if (unlikely(object == ZERO_SIZE_PTR))
 395                 return;
 396
 397         page = virt_to_head_page(object);
 398
 399         if (unlikely(!PageSlab(page)))
 400                 kasan_kmalloc_large(object, size);
 401         else
 402                 kasan_kmalloc(page->slab_cache, object, size);
 403 }
 404
 405 void kasan_kfree(void *ptr)
 406 {
 407         struct page *page;
 408
 409         page = virt_to_head_page(ptr);
 410
 411         if (unlikely(!PageSlab(page)))
 412                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 413                                 KASAN_FREE_PAGE);
 414         else
 415                 kasan_slab_free(page->slab_cache, ptr);
 416 }
 417
 418 void kasan_kfree_large(const void *ptr)
 419 {
 420         struct page *page = virt_to_page(ptr);
 421
 422         kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 423                         KASAN_FREE_PAGE);
 424 }
 425
 426 int kasan_module_alloc(void *addr, size_t size)
 427 {
 428         void *ret;
 429         size_t shadow_size;
 430         unsigned long shadow_start;
 431
 432         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 433         shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
 434                         PAGE_SIZE);
 435
 436         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 437                 return -EINVAL;
 438
 439         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 440                         shadow_start + shadow_size,
 441                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 442                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 443                         __builtin_return_address(0));
 444
 445         if (ret) {
 446                 find_vm_area(addr)->flags |= VM_KASAN;
 447                 return 0;
 448         }
 449
 450         return -ENOMEM;
 451 }
 452
 453 void kasan_free_shadow(const struct vm_struct *vm)
 454 {
 455         if (vm->flags & VM_KASAN)
 456                 vfree(kasan_mem_to_shadow(vm->addr));
 457 }
 458
 459 static void register_global(struct kasan_global *global)
 460 {
 461         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 462
 463         kasan_unpoison_shadow(global->beg, global->size);
 464
 465         kasan_poison_shadow(global->beg + aligned_size,
 466                 global->size_with_redzone - aligned_size,
 467                 KASAN_GLOBAL_REDZONE);
 468 }
 469
 470 void __asan_register_globals(struct kasan_global *globals, size_t size)
 471 {
 472         int i;
 473
 474         for (i = 0; i < size; i++)
 475                 register_global(&globals[i]);
 476 }
 477 EXPORT_SYMBOL(__asan_register_globals);
 478
 479 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 480 {
 481 }
 482 EXPORT_SYMBOL(__asan_unregister_globals);
 483
 484 #define DEFINE_ASAN_LOAD_STORE(size)                            \
 485         void __asan_load##size(unsigned long addr)              \
 486         {                                                       \
 487                 check_memory_region(addr, size, false);         \
 488         }                                                       \
 489         EXPORT_SYMBOL(__asan_load##size);                       \
 490         __alias(__asan_load##size)                              \
 491         void __asan_load##size##_noabort(unsigned long);        \
 492         EXPORT_SYMBOL(__asan_load##size##_noabort);             \
 493         void __asan_store##size(unsigned long addr)             \
 494         {                                                       \
 495                 check_memory_region(addr, size, true);          \
 496         }                                                       \
 497         EXPORT_SYMBOL(__asan_store##size);                      \
 498         __alias(__asan_store##size)                             \
 499         void __asan_store##size##_noabort(unsigned long);       \
 500         EXPORT_SYMBOL(__asan_store##size##_noabort)
 501
 502 DEFINE_ASAN_LOAD_STORE(1);
 503 DEFINE_ASAN_LOAD_STORE(2);
 504 DEFINE_ASAN_LOAD_STORE(4);
 505 DEFINE_ASAN_LOAD_STORE(8);
 506 DEFINE_ASAN_LOAD_STORE(16);
 507
 508 void __asan_loadN(unsigned long addr, size_t size)
 509 {
 510         check_memory_region(addr, size, false);
 511 }
 512 EXPORT_SYMBOL(__asan_loadN);
 513
 514 __alias(__asan_loadN)
 515 void __asan_loadN_noabort(unsigned long, size_t);
 516 EXPORT_SYMBOL(__asan_loadN_noabort);
 517
 518 void __asan_storeN(unsigned long addr, size_t size)
 519 {
 520         check_memory_region(addr, size, true);
 521 }
 522 EXPORT_SYMBOL(__asan_storeN);
 523
 524 __alias(__asan_storeN)
 525 void __asan_storeN_noabort(unsigned long, size_t);
 526 EXPORT_SYMBOL(__asan_storeN_noabort);
 527
 528 /* to shut up compiler complaints */
 529 void __asan_handle_no_return(void) {}
 530 EXPORT_SYMBOL(__asan_handle_no_return);
 531
 532 #ifdef CONFIG_MEMORY_HOTPLUG
 533 static int kasan_mem_notifier(struct notifier_block *nb,
 534                         unsigned long action, void *data)
 535 {
 536         return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
 537 }
 538
 539 static int __init kasan_memhotplug_init(void)
 540 {
 541         pr_err("WARNING: KASAN doesn't support memory hot-add\n");
 542         pr_err("Memory hot-add will be disabled\n");
 543
 544         hotplug_memory_notifier(kasan_mem_notifier, 0);
 545
 546         return 0;
 547 }
 548
 549 module_init(kasan_memhotplug_init);
 550 #endif