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/memblock.h>
  24 #include <linux/memory.h>
  25 #include <linux/mm.h>
  26 #include <linux/module.h>
  27 #include <linux/printk.h>
  28 #include <linux/sched.h>
  29 #include <linux/slab.h>
  30 #include <linux/stacktrace.h>
  31 #include <linux/string.h>
  32 #include <linux/types.h>
  33 #include <linux/vmalloc.h>
  34 #include <linux/kasan.h>
  35
  36 #include "kasan.h"
  37 #include "../slab.h"
  38
  39 /*
  40  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
  41  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
  42  */
  43 static void kasan_poison_shadow(const void *address, size_t size, u8 value)
  44 {
  45         void *shadow_start, *shadow_end;
  46
  47         shadow_start = kasan_mem_to_shadow(address);
  48         shadow_end = kasan_mem_to_shadow(address + size);
  49
  50         memset(shadow_start, value, shadow_end - shadow_start);
  51 }
  52
  53 void kasan_unpoison_shadow(const void *address, size_t size)
  54 {
  55         kasan_poison_shadow(address, size, 0);
  56
  57         if (size & KASAN_SHADOW_MASK) {
  58                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
  59                 *shadow = size & KASAN_SHADOW_MASK;
  60         }
  61 }
  62
  63
  64 /*
  65  * All functions below always inlined so compiler could
  66  * perform better optimizations in each of __asan_loadX/__assn_storeX
  67  * depending on memory access size X.
  68  */
  69
  70 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
  71 {
  72         s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
  73
  74         if (unlikely(shadow_value)) {
  75                 s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
  76                 return unlikely(last_accessible_byte >= shadow_value);
  77         }
  78
  79         return false;
  80 }
  81
  82 static __always_inline bool memory_is_poisoned_2(unsigned long addr)
  83 {
  84         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
  85
  86         if (unlikely(*shadow_addr)) {
  87                 if (memory_is_poisoned_1(addr + 1))
  88                         return true;
  89
  90                 /*
  91                  * If single shadow byte covers 2-byte access, we don't
  92                  * need to do anything more. Otherwise, test the first
  93                  * shadow byte.
  94                  */
  95                 if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
  96                         return false;
  97
  98                 return unlikely(*(u8 *)shadow_addr);
  99         }
 100
 101         return false;
 102 }
 103
 104 static __always_inline bool memory_is_poisoned_4(unsigned long addr)
 105 {
 106         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 107
 108         if (unlikely(*shadow_addr)) {
 109                 if (memory_is_poisoned_1(addr + 3))
 110                         return true;
 111
 112                 /*
 113                  * If single shadow byte covers 4-byte access, we don't
 114                  * need to do anything more. Otherwise, test the first
 115                  * shadow byte.
 116                  */
 117                 if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
 118                         return false;
 119
 120                 return unlikely(*(u8 *)shadow_addr);
 121         }
 122
 123         return false;
 124 }
 125
 126 static __always_inline bool memory_is_poisoned_8(unsigned long addr)
 127 {
 128         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
 129
 130         if (unlikely(*shadow_addr)) {
 131                 if (memory_is_poisoned_1(addr + 7))
 132                         return true;
 133
 134                 /*
 135                  * If single shadow byte covers 8-byte access, we don't
 136                  * need to do anything more. Otherwise, test the first
 137                  * shadow byte.
 138                  */
 139                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 140                         return false;
 141
 142                 return unlikely(*(u8 *)shadow_addr);
 143         }
 144
 145         return false;
 146 }
 147
 148 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
 149 {
 150         u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);
 151
 152         if (unlikely(*shadow_addr)) {
 153                 u16 shadow_first_bytes = *(u16 *)shadow_addr;
 154
 155                 if (unlikely(shadow_first_bytes))
 156                         return true;
 157
 158                 /*
 159                  * If two shadow bytes covers 16-byte access, we don't
 160                  * need to do anything more. Otherwise, test the last
 161                  * shadow byte.
 162                  */
 163                 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
 164                         return false;
 165
 166                 return memory_is_poisoned_1(addr + 15);
 167         }
 168
 169         return false;
 170 }
 171
 172 static __always_inline unsigned long bytes_is_zero(const u8 *start,
 173                                         size_t size)
 174 {
 175         while (size) {
 176                 if (unlikely(*start))
 177                         return (unsigned long)start;
 178                 start++;
 179                 size--;
 180         }
 181
 182         return 0;
 183 }
 184
 185 static __always_inline unsigned long memory_is_zero(const void *start,
 186                                                 const void *end)
 187 {
 188         unsigned int words;
 189         unsigned long ret;
 190         unsigned int prefix = (unsigned long)start % 8;
 191
 192         if (end - start <= 16)
 193                 return bytes_is_zero(start, end - start);
 194
 195         if (prefix) {
 196                 prefix = 8 - prefix;
 197                 ret = bytes_is_zero(start, prefix);
 198                 if (unlikely(ret))
 199                         return ret;
 200                 start += prefix;
 201         }
 202
 203         words = (end - start) / 8;
 204         while (words) {
 205                 if (unlikely(*(u64 *)start))
 206                         return bytes_is_zero(start, 8);
 207                 start += 8;
 208                 words--;
 209         }
 210
 211         return bytes_is_zero(start, (end - start) % 8);
 212 }
 213
 214 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 215                                                 size_t size)
 216 {
 217         unsigned long ret;
 218
 219         ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
 220                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 221
 222         if (unlikely(ret)) {
 223                 unsigned long last_byte = addr + size - 1;
 224                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 225
 226                 if (unlikely(ret != (unsigned long)last_shadow ||
 227                         ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 228                         return true;
 229         }
 230         return false;
 231 }
 232
 233 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 234 {
 235         if (__builtin_constant_p(size)) {
 236                 switch (size) {
 237                 case 1:
 238                         return memory_is_poisoned_1(addr);
 239                 case 2:
 240                         return memory_is_poisoned_2(addr);
 241                 case 4:
 242                         return memory_is_poisoned_4(addr);
 243                 case 8:
 244                         return memory_is_poisoned_8(addr);
 245                 case 16:
 246                         return memory_is_poisoned_16(addr);
 247                 default:
 248                         BUILD_BUG();
 249                 }
 250         }
 251
 252         return memory_is_poisoned_n(addr, size);
 253 }
 254
 255 static __always_inline void check_memory_region_inline(unsigned long addr,
 256                                                 size_t size, bool write,
 257                                                 unsigned long ret_ip)
 258 {
 259         if (unlikely(size == 0))
 260                 return;
 261
 262         if (unlikely((void *)addr <
 263                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 264                 kasan_report(addr, size, write, ret_ip);
 265                 return;
 266         }
 267
 268         if (likely(!memory_is_poisoned(addr, size)))
 269                 return;
 270
 271         kasan_report(addr, size, write, ret_ip);
 272 }
 273
 274 static void check_memory_region(unsigned long addr,
 275                                 size_t size, bool write,
 276                                 unsigned long ret_ip)
 277 {
 278         check_memory_region_inline(addr, size, write, ret_ip);
 279 }
 280
 281 void kasan_check_read(const void *p, unsigned int size)
 282 {
 283         check_memory_region((unsigned long)p, size, false, _RET_IP_);
 284 }
 285 EXPORT_SYMBOL(kasan_check_read);
 286
 287 void kasan_check_write(const void *p, unsigned int size)
 288 {
 289         check_memory_region((unsigned long)p, size, true, _RET_IP_);
 290 }
 291 EXPORT_SYMBOL(kasan_check_write);
 292
 293 #undef memset
 294 void *memset(void *addr, int c, size_t len)
 295 {
 296         check_memory_region((unsigned long)addr, len, true, _RET_IP_);
 297
 298         return __memset(addr, c, len);
 299 }
 300
 301 #undef memmove
 302 void *memmove(void *dest, const void *src, size_t len)
 303 {
 304         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 305         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 306
 307         return __memmove(dest, src, len);
 308 }
 309
 310 #undef memcpy
 311 void *memcpy(void *dest, const void *src, size_t len)
 312 {
 313         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 314         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 315
 316         return __memcpy(dest, src, len);
 317 }
 318
 319 void kasan_alloc_pages(struct page *page, unsigned int order)
 320 {
 321         if (likely(!PageHighMem(page)))
 322                 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 323 }
 324
 325 void kasan_free_pages(struct page *page, unsigned int order)
 326 {
 327         if (likely(!PageHighMem(page)))
 328                 kasan_poison_shadow(page_address(page),
 329                                 PAGE_SIZE << order,
 330                                 KASAN_FREE_PAGE);
 331 }
 332
 333 void kasan_poison_slab(struct page *page)
 334 {
 335         kasan_poison_shadow(page_address(page),
 336                         PAGE_SIZE << compound_order(page),
 337                         KASAN_KMALLOC_REDZONE);
 338 }
 339
 340 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 341 {
 342         kasan_unpoison_shadow(object, cache->object_size);
 343 }
 344
 345 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 346 {
 347         kasan_poison_shadow(object,
 348                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 349                         KASAN_KMALLOC_REDZONE);
 350 }
 351
 352 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
 353 {
 354         kasan_kmalloc(cache, object, cache->object_size);
 355 }
 356
 357 void kasan_slab_free(struct kmem_cache *cache, void *object)
 358 {
 359         unsigned long size = cache->object_size;
 360         unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 361
 362         /* RCU slabs could be legally used after free within the RCU period */
 363         if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
 364                 return;
 365
 366         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 367 }
 368
 369 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
 370 {
 371         unsigned long redzone_start;
 372         unsigned long redzone_end;
 373
 374         if (unlikely(object == NULL))
 375                 return;
 376
 377         redzone_start = round_up((unsigned long)(object + size),
 378                                 KASAN_SHADOW_SCALE_SIZE);
 379         redzone_end = round_up((unsigned long)object + cache->object_size,
 380                                 KASAN_SHADOW_SCALE_SIZE);
 381
 382         kasan_unpoison_shadow(object, size);
 383         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 384                 KASAN_KMALLOC_REDZONE);
 385 }
 386 EXPORT_SYMBOL(kasan_kmalloc);
 387
 388 void kasan_kmalloc_large(const void *ptr, size_t size)
 389 {
 390         struct page *page;
 391         unsigned long redzone_start;
 392         unsigned long redzone_end;
 393
 394         if (unlikely(ptr == NULL))
 395                 return;
 396
 397         page = virt_to_page(ptr);
 398         redzone_start = round_up((unsigned long)(ptr + size),
 399                                 KASAN_SHADOW_SCALE_SIZE);
 400         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 401
 402         kasan_unpoison_shadow(ptr, size);
 403         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 404                 KASAN_PAGE_REDZONE);
 405 }
 406
 407 void kasan_krealloc(const void *object, size_t size)
 408 {
 409         struct page *page;
 410
 411         if (unlikely(object == ZERO_SIZE_PTR))
 412                 return;
 413
 414         page = virt_to_head_page(object);
 415
 416         if (unlikely(!PageSlab(page)))
 417                 kasan_kmalloc_large(object, size);
 418         else
 419                 kasan_kmalloc(page->slab_cache, object, size);
 420 }
 421
 422 void kasan_kfree(void *ptr)
 423 {
 424         struct page *page;
 425
 426         page = virt_to_head_page(ptr);
 427
 428         if (unlikely(!PageSlab(page)))
 429                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 430                                 KASAN_FREE_PAGE);
 431         else
 432                 kasan_slab_free(page->slab_cache, ptr);
 433 }
 434
 435 void kasan_kfree_large(const void *ptr)
 436 {
 437         struct page *page = virt_to_page(ptr);
 438
 439         kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 440                         KASAN_FREE_PAGE);
 441 }
 442
 443 int kasan_module_alloc(void *addr, size_t size)
 444 {
 445         void *ret;
 446         size_t scaled_size;
 447         size_t shadow_size;
 448         unsigned long shadow_start;
 449
 450         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 451         scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
 452         shadow_size = round_up(scaled_size, PAGE_SIZE);
 453
 454         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 455                 return -EINVAL;
 456
 457         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 458                         shadow_start + shadow_size,
 459                         GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
 460                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 461                         __builtin_return_address(0));
 462
 463         if (ret) {
 464                 find_vm_area(addr)->flags |= VM_KASAN;
 465                 kmemleak_ignore(ret);
 466                 return 0;
 467         }
 468
 469         return -ENOMEM;
 470 }
 471
 472 void kasan_free_shadow(const struct vm_struct *vm)
 473 {
 474         if (vm->flags & VM_KASAN)
 475                 vfree(kasan_mem_to_shadow(vm->addr));
 476 }
 477
 478 static void register_global(struct kasan_global *global)
 479 {
 480         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 481
 482         kasan_unpoison_shadow(global->beg, global->size);
 483
 484         kasan_poison_shadow(global->beg + aligned_size,
 485                 global->size_with_redzone - aligned_size,
 486                 KASAN_GLOBAL_REDZONE);
 487 }
 488
 489 void __asan_register_globals(struct kasan_global *globals, size_t size)
 490 {
 491         int i;
 492
 493         for (i = 0; i < size; i++)
 494                 register_global(&globals[i]);
 495 }
 496 EXPORT_SYMBOL(__asan_register_globals);
 497
 498 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 499 {
 500 }
 501 EXPORT_SYMBOL(__asan_unregister_globals);
 502
 503 #define DEFINE_ASAN_LOAD_STORE(size)                                    \
 504         void __asan_load##size(unsigned long addr)                      \
 505         {                                                               \
 506                 check_memory_region_inline(addr, size, false, _RET_IP_);\
 507         }                                                               \
 508         EXPORT_SYMBOL(__asan_load##size);                               \
 509         __alias(__asan_load##size)                                      \
 510         void __asan_load##size##_noabort(unsigned long);                \
 511         EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
 512         void __asan_store##size(unsigned long addr)                     \
 513         {                                                               \
 514                 check_memory_region_inline(addr, size, true, _RET_IP_); \
 515         }                                                               \
 516         EXPORT_SYMBOL(__asan_store##size);                              \
 517         __alias(__asan_store##size)                                     \
 518         void __asan_store##size##_noabort(unsigned long);               \
 519         EXPORT_SYMBOL(__asan_store##size##_noabort)
 520
 521 DEFINE_ASAN_LOAD_STORE(1);
 522 DEFINE_ASAN_LOAD_STORE(2);
 523 DEFINE_ASAN_LOAD_STORE(4);
 524 DEFINE_ASAN_LOAD_STORE(8);
 525 DEFINE_ASAN_LOAD_STORE(16);
 526
 527 void __asan_loadN(unsigned long addr, size_t size)
 528 {
 529         check_memory_region(addr, size, false, _RET_IP_);
 530 }
 531 EXPORT_SYMBOL(__asan_loadN);
 532
 533 __alias(__asan_loadN)
 534 void __asan_loadN_noabort(unsigned long, size_t);
 535 EXPORT_SYMBOL(__asan_loadN_noabort);
 536
 537 void __asan_storeN(unsigned long addr, size_t size)
 538 {
 539         check_memory_region(addr, size, true, _RET_IP_);
 540 }
 541 EXPORT_SYMBOL(__asan_storeN);
 542
 543 __alias(__asan_storeN)
 544 void __asan_storeN_noabort(unsigned long, size_t);
 545 EXPORT_SYMBOL(__asan_storeN_noabort);
 546
 547 /* to shut up compiler complaints */
 548 void __asan_handle_no_return(void) {}
 549 EXPORT_SYMBOL(__asan_handle_no_return);
 550
 551 #ifdef CONFIG_MEMORY_HOTPLUG
 552 static int kasan_mem_notifier(struct notifier_block *nb,
 553                         unsigned long action, void *data)
 554 {
 555         return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
 556 }
 557
 558 static int __init kasan_memhotplug_init(void)
 559 {
 560         pr_err("WARNING: KASAN doesn't support memory hot-add\n");
 561         pr_err("Memory hot-add will be disabled\n");
 562
 563         hotplug_memory_notifier(kasan_mem_notifier, 0);
 564
 565         return 0;
 566 }
 567
 568 core_initcall(kasan_memhotplug_init);
 569 #endif