mm/kasan/common.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains common generic and tag-based KASAN code.
   4  *
   5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  *
   8  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   9  *        Andrey Konovalov <andreyknvl@gmail.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  */
  16
  17 #include <linux/export.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/init.h>
  20 #include <linux/kasan.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/sched/task_stack.h>
  31 #include <linux/slab.h>
  32 #include <linux/stacktrace.h>
  33 #include <linux/string.h>
  34 #include <linux/types.h>
  35 #include <linux/vmalloc.h>
  36 #include <linux/bug.h>
  37
  38 #include "kasan.h"
  39 #include "../slab.h"
  40
  41 static inline int in_irqentry_text(unsigned long ptr)
  42 {
  43         return (ptr >= (unsigned long)&__irqentry_text_start &&
  44                 ptr < (unsigned long)&__irqentry_text_end) ||
  45                 (ptr >= (unsigned long)&__softirqentry_text_start &&
  46                  ptr < (unsigned long)&__softirqentry_text_end);
  47 }
  48
  49 static inline void filter_irq_stacks(struct stack_trace *trace)
  50 {
  51         int i;
  52
  53         if (!trace->nr_entries)
  54                 return;
  55         for (i = 0; i < trace->nr_entries; i++)
  56                 if (in_irqentry_text(trace->entries[i])) {
  57                         /* Include the irqentry function into the stack. */
  58                         trace->nr_entries = i + 1;
  59                         break;
  60                 }
  61 }
  62
  63 static inline depot_stack_handle_t save_stack(gfp_t flags)
  64 {
  65         unsigned long entries[KASAN_STACK_DEPTH];
  66         struct stack_trace trace = {
  67                 .nr_entries = 0,
  68                 .entries = entries,
  69                 .max_entries = KASAN_STACK_DEPTH,
  70                 .skip = 0
  71         };
  72
  73         save_stack_trace(&trace);
  74         filter_irq_stacks(&trace);
  75         if (trace.nr_entries != 0 &&
  76             trace.entries[trace.nr_entries-1] == ULONG_MAX)
  77                 trace.nr_entries--;
  78
  79         return depot_save_stack(&trace, flags);
  80 }
  81
  82 static inline void set_track(struct kasan_track *track, gfp_t flags)
  83 {
  84         track->pid = current->pid;
  85         track->stack = save_stack(flags);
  86 }
  87
  88 void kasan_enable_current(void)
  89 {
  90         current->kasan_depth++;
  91 }
  92
  93 void kasan_disable_current(void)
  94 {
  95         current->kasan_depth--;
  96 }
  97
  98 void kasan_check_read(const volatile void *p, unsigned int size)
  99 {
 100         check_memory_region((unsigned long)p, size, false, _RET_IP_);
 101 }
 102 EXPORT_SYMBOL(kasan_check_read);
 103
 104 void kasan_check_write(const volatile void *p, unsigned int size)
 105 {
 106         check_memory_region((unsigned long)p, size, true, _RET_IP_);
 107 }
 108 EXPORT_SYMBOL(kasan_check_write);
 109
 110 #undef memset
 111 void *memset(void *addr, int c, size_t len)
 112 {
 113         check_memory_region((unsigned long)addr, len, true, _RET_IP_);
 114
 115         return __memset(addr, c, len);
 116 }
 117
 118 #undef memmove
 119 void *memmove(void *dest, const void *src, size_t len)
 120 {
 121         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 122         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 123
 124         return __memmove(dest, src, len);
 125 }
 126
 127 #undef memcpy
 128 void *memcpy(void *dest, const void *src, size_t len)
 129 {
 130         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 131         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 132
 133         return __memcpy(dest, src, len);
 134 }
 135
 136 /*
 137  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 138  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 139  */
 140 void kasan_poison_shadow(const void *address, size_t size, u8 value)
 141 {
 142         void *shadow_start, *shadow_end;
 143
 144         /*
 145          * Perform shadow offset calculation based on untagged address, as
 146          * some of the callers (e.g. kasan_poison_object_data) pass tagged
 147          * addresses to this function.
 148          */
 149         address = reset_tag(address);
 150
 151         shadow_start = kasan_mem_to_shadow(address);
 152         shadow_end = kasan_mem_to_shadow(address + size);
 153
 154         __memset(shadow_start, value, shadow_end - shadow_start);
 155 }
 156
 157 void kasan_unpoison_shadow(const void *address, size_t size)
 158 {
 159         u8 tag = get_tag(address);
 160
 161         /*
 162          * Perform shadow offset calculation based on untagged address, as
 163          * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
 164          * addresses to this function.
 165          */
 166         address = reset_tag(address);
 167
 168         kasan_poison_shadow(address, size, tag);
 169
 170         if (size & KASAN_SHADOW_MASK) {
 171                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
 172
 173                 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 174                         *shadow = tag;
 175                 else
 176                         *shadow = size & KASAN_SHADOW_MASK;
 177         }
 178 }
 179
 180 static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
 181 {
 182         void *base = task_stack_page(task);
 183         size_t size = sp - base;
 184
 185         kasan_unpoison_shadow(base, size);
 186 }
 187
 188 /* Unpoison the entire stack for a task. */
 189 void kasan_unpoison_task_stack(struct task_struct *task)
 190 {
 191         __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
 192 }
 193
 194 /* Unpoison the stack for the current task beyond a watermark sp value. */
 195 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
 196 {
 197         /*
 198          * Calculate the task stack base address.  Avoid using 'current'
 199          * because this function is called by early resume code which hasn't
 200          * yet set up the percpu register (%gs).
 201          */
 202         void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
 203
 204         kasan_unpoison_shadow(base, watermark - base);
 205 }
 206
 207 /*
 208  * Clear all poison for the region between the current SP and a provided
 209  * watermark value, as is sometimes required prior to hand-crafted asm function
 210  * returns in the middle of functions.
 211  */
 212 void kasan_unpoison_stack_above_sp_to(const void *watermark)
 213 {
 214         const void *sp = __builtin_frame_address(0);
 215         size_t size = watermark - sp;
 216
 217         if (WARN_ON(sp > watermark))
 218                 return;
 219         kasan_unpoison_shadow(sp, size);
 220 }
 221
 222 void kasan_alloc_pages(struct page *page, unsigned int order)
 223 {
 224         u8 tag;
 225         unsigned long i;
 226
 227         if (unlikely(PageHighMem(page)))
 228                 return;
 229
 230         tag = random_tag();
 231         for (i = 0; i < (1 << order); i++)
 232                 page_kasan_tag_set(page + i, tag);
 233         kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 234 }
 235
 236 void kasan_free_pages(struct page *page, unsigned int order)
 237 {
 238         if (likely(!PageHighMem(page)))
 239                 kasan_poison_shadow(page_address(page),
 240                                 PAGE_SIZE << order,
 241                                 KASAN_FREE_PAGE);
 242 }
 243
 244 /*
 245  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 246  * For larger allocations larger redzones are used.
 247  */
 248 static inline unsigned int optimal_redzone(unsigned int object_size)
 249 {
 250         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 251                 return 0;
 252
 253         return
 254                 object_size <= 64        - 16   ? 16 :
 255                 object_size <= 128       - 32   ? 32 :
 256                 object_size <= 512       - 64   ? 64 :
 257                 object_size <= 4096      - 128  ? 128 :
 258                 object_size <= (1 << 14) - 256  ? 256 :
 259                 object_size <= (1 << 15) - 512  ? 512 :
 260                 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
 261 }
 262
 263 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 264                         slab_flags_t *flags)
 265 {
 266         unsigned int orig_size = *size;
 267         unsigned int redzone_size;
 268         int redzone_adjust;
 269
 270         /* Add alloc meta. */
 271         cache->kasan_info.alloc_meta_offset = *size;
 272         *size += sizeof(struct kasan_alloc_meta);
 273
 274         /* Add free meta. */
 275         if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
 276             (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
 277              cache->object_size < sizeof(struct kasan_free_meta))) {
 278                 cache->kasan_info.free_meta_offset = *size;
 279                 *size += sizeof(struct kasan_free_meta);
 280         }
 281
 282         redzone_size = optimal_redzone(cache->object_size);
 283         redzone_adjust = redzone_size - (*size - cache->object_size);
 284         if (redzone_adjust > 0)
 285                 *size += redzone_adjust;
 286
 287         *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
 288                         max(*size, cache->object_size + redzone_size));
 289
 290         /*
 291          * If the metadata doesn't fit, don't enable KASAN at all.
 292          */
 293         if (*size <= cache->kasan_info.alloc_meta_offset ||
 294                         *size <= cache->kasan_info.free_meta_offset) {
 295                 cache->kasan_info.alloc_meta_offset = 0;
 296                 cache->kasan_info.free_meta_offset = 0;
 297                 *size = orig_size;
 298                 return;
 299         }
 300
 301         cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
 302
 303         *flags |= SLAB_KASAN;
 304 }
 305
 306 size_t kasan_metadata_size(struct kmem_cache *cache)
 307 {
 308         return (cache->kasan_info.alloc_meta_offset ?
 309                 sizeof(struct kasan_alloc_meta) : 0) +
 310                 (cache->kasan_info.free_meta_offset ?
 311                 sizeof(struct kasan_free_meta) : 0);
 312 }
 313
 314 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 315                                         const void *object)
 316 {
 317         BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
 318         return (void *)object + cache->kasan_info.alloc_meta_offset;
 319 }
 320
 321 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 322                                       const void *object)
 323 {
 324         BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
 325         return (void *)object + cache->kasan_info.free_meta_offset;
 326 }
 327
 328 void kasan_poison_slab(struct page *page)
 329 {
 330         unsigned long i;
 331
 332         for (i = 0; i < (1 << compound_order(page)); i++)
 333                 page_kasan_tag_reset(page + i);
 334         kasan_poison_shadow(page_address(page),
 335                         PAGE_SIZE << compound_order(page),
 336                         KASAN_KMALLOC_REDZONE);
 337 }
 338
 339 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 340 {
 341         kasan_unpoison_shadow(object, cache->object_size);
 342 }
 343
 344 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 345 {
 346         kasan_poison_shadow(object,
 347                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 348                         KASAN_KMALLOC_REDZONE);
 349 }
 350
 351 /*
 352  * Since it's desirable to only call object contructors once during slab
 353  * allocation, we preassign tags to all such objects. Also preassign tags for
 354  * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports.
 355  * For SLAB allocator we can't preassign tags randomly since the freelist is
 356  * stored as an array of indexes instead of a linked list. Assign tags based
 357  * on objects indexes, so that objects that are next to each other get
 358  * different tags.
 359  * After a tag is assigned, the object always gets allocated with the same tag.
 360  * The reason is that we can't change tags for objects with constructors on
 361  * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor
 362  * code can save the pointer to the object somewhere (e.g. in the object
 363  * itself). Then if we retag it, the old saved pointer will become invalid.
 364  */
 365 static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new)
 366 {
 367         if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
 368                 return new ? KASAN_TAG_KERNEL : random_tag();
 369
 370 #ifdef CONFIG_SLAB
 371         return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
 372 #else
 373         return new ? random_tag() : get_tag(object);
 374 #endif
 375 }
 376
 377 void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
 378                                                 const void *object)
 379 {
 380         struct kasan_alloc_meta *alloc_info;
 381
 382         if (!(cache->flags & SLAB_KASAN))
 383                 return (void *)object;
 384
 385         alloc_info = get_alloc_info(cache, object);
 386         __memset(alloc_info, 0, sizeof(*alloc_info));
 387
 388         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 389                 object = set_tag(object, assign_tag(cache, object, true));
 390
 391         return (void *)object;
 392 }
 393
 394 void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
 395                                         gfp_t flags)
 396 {
 397         return kasan_kmalloc(cache, object, cache->object_size, flags);
 398 }
 399
 400 static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
 401 {
 402         if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 403                 return shadow_byte < 0 ||
 404                         shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
 405         else
 406                 return tag != (u8)shadow_byte;
 407 }
 408
 409 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 410                               unsigned long ip, bool quarantine)
 411 {
 412         s8 shadow_byte;
 413         u8 tag;
 414         void *tagged_object;
 415         unsigned long rounded_up_size;
 416
 417         tag = get_tag(object);
 418         tagged_object = object;
 419         object = reset_tag(object);
 420
 421         if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
 422             object)) {
 423                 kasan_report_invalid_free(tagged_object, ip);
 424                 return true;
 425         }
 426
 427         /* RCU slabs could be legally used after free within the RCU period */
 428         if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 429                 return false;
 430
 431         shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 432         if (shadow_invalid(tag, shadow_byte)) {
 433                 kasan_report_invalid_free(tagged_object, ip);
 434                 return true;
 435         }
 436
 437         rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
 438         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 439
 440         if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
 441                         unlikely(!(cache->flags & SLAB_KASAN)))
 442                 return false;
 443
 444         set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
 445         quarantine_put(get_free_info(cache, object), cache);
 446
 447         return IS_ENABLED(CONFIG_KASAN_GENERIC);
 448 }
 449
 450 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 451 {
 452         return __kasan_slab_free(cache, object, ip, true);
 453 }
 454
 455 void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
 456                                         size_t size, gfp_t flags)
 457 {
 458         unsigned long redzone_start;
 459         unsigned long redzone_end;
 460         u8 tag;
 461
 462         if (gfpflags_allow_blocking(flags))
 463                 quarantine_reduce();
 464
 465         if (unlikely(object == NULL))
 466                 return NULL;
 467
 468         redzone_start = round_up((unsigned long)(object + size),
 469                                 KASAN_SHADOW_SCALE_SIZE);
 470         redzone_end = round_up((unsigned long)object + cache->object_size,
 471                                 KASAN_SHADOW_SCALE_SIZE);
 472
 473         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 474                 tag = assign_tag(cache, object, false);
 475
 476         /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
 477         kasan_unpoison_shadow(set_tag(object, tag), size);
 478         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 479                 KASAN_KMALLOC_REDZONE);
 480
 481         if (cache->flags & SLAB_KASAN)
 482                 set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 483
 484         return set_tag(object, tag);
 485 }
 486 EXPORT_SYMBOL(kasan_kmalloc);
 487
 488 void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
 489                                                 gfp_t flags)
 490 {
 491         struct page *page;
 492         unsigned long redzone_start;
 493         unsigned long redzone_end;
 494
 495         if (gfpflags_allow_blocking(flags))
 496                 quarantine_reduce();
 497
 498         if (unlikely(ptr == NULL))
 499                 return NULL;
 500
 501         page = virt_to_page(ptr);
 502         redzone_start = round_up((unsigned long)(ptr + size),
 503                                 KASAN_SHADOW_SCALE_SIZE);
 504         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 505
 506         kasan_unpoison_shadow(ptr, size);
 507         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 508                 KASAN_PAGE_REDZONE);
 509
 510         return (void *)ptr;
 511 }
 512
 513 void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
 514 {
 515         struct page *page;
 516
 517         if (unlikely(object == ZERO_SIZE_PTR))
 518                 return (void *)object;
 519
 520         page = virt_to_head_page(object);
 521
 522         if (unlikely(!PageSlab(page)))
 523                 return kasan_kmalloc_large(object, size, flags);
 524         else
 525                 return kasan_kmalloc(page->slab_cache, object, size, flags);
 526 }
 527
 528 void kasan_poison_kfree(void *ptr, unsigned long ip)
 529 {
 530         struct page *page;
 531
 532         page = virt_to_head_page(ptr);
 533
 534         if (unlikely(!PageSlab(page))) {
 535                 if (ptr != page_address(page)) {
 536                         kasan_report_invalid_free(ptr, ip);
 537                         return;
 538                 }
 539                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 540                                 KASAN_FREE_PAGE);
 541         } else {
 542                 __kasan_slab_free(page->slab_cache, ptr, ip, false);
 543         }
 544 }
 545
 546 void kasan_kfree_large(void *ptr, unsigned long ip)
 547 {
 548         if (ptr != page_address(virt_to_head_page(ptr)))
 549                 kasan_report_invalid_free(ptr, ip);
 550         /* The object will be poisoned by page_alloc. */
 551 }
 552
 553 int kasan_module_alloc(void *addr, size_t size)
 554 {
 555         void *ret;
 556         size_t scaled_size;
 557         size_t shadow_size;
 558         unsigned long shadow_start;
 559
 560         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 561         scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
 562         shadow_size = round_up(scaled_size, PAGE_SIZE);
 563
 564         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 565                 return -EINVAL;
 566
 567         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 568                         shadow_start + shadow_size,
 569                         GFP_KERNEL,
 570                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 571                         __builtin_return_address(0));
 572
 573         if (ret) {
 574                 __memset(ret, KASAN_SHADOW_INIT, shadow_size);
 575                 find_vm_area(addr)->flags |= VM_KASAN;
 576                 kmemleak_ignore(ret);
 577                 return 0;
 578         }
 579
 580         return -ENOMEM;
 581 }
 582
 583 void kasan_free_shadow(const struct vm_struct *vm)
 584 {
 585         if (vm->flags & VM_KASAN)
 586                 vfree(kasan_mem_to_shadow(vm->addr));
 587 }
 588
 589 #ifdef CONFIG_MEMORY_HOTPLUG
 590 static bool shadow_mapped(unsigned long addr)
 591 {
 592         pgd_t *pgd = pgd_offset_k(addr);
 593         p4d_t *p4d;
 594         pud_t *pud;
 595         pmd_t *pmd;
 596         pte_t *pte;
 597
 598         if (pgd_none(*pgd))
 599                 return false;
 600         p4d = p4d_offset(pgd, addr);
 601         if (p4d_none(*p4d))
 602                 return false;
 603         pud = pud_offset(p4d, addr);
 604         if (pud_none(*pud))
 605                 return false;
 606
 607         /*
 608          * We can't use pud_large() or pud_huge(), the first one is
 609          * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
 610          * pud_bad(), if pud is bad then it's bad because it's huge.
 611          */
 612         if (pud_bad(*pud))
 613                 return true;
 614         pmd = pmd_offset(pud, addr);
 615         if (pmd_none(*pmd))
 616                 return false;
 617
 618         if (pmd_bad(*pmd))
 619                 return true;
 620         pte = pte_offset_kernel(pmd, addr);
 621         return !pte_none(*pte);
 622 }
 623
 624 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 625                         unsigned long action, void *data)
 626 {
 627         struct memory_notify *mem_data = data;
 628         unsigned long nr_shadow_pages, start_kaddr, shadow_start;
 629         unsigned long shadow_end, shadow_size;
 630
 631         nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
 632         start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
 633         shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
 634         shadow_size = nr_shadow_pages << PAGE_SHIFT;
 635         shadow_end = shadow_start + shadow_size;
 636
 637         if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
 638                 WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
 639                 return NOTIFY_BAD;
 640
 641         switch (action) {
 642         case MEM_GOING_ONLINE: {
 643                 void *ret;
 644
 645                 /*
 646                  * If shadow is mapped already than it must have been mapped
 647                  * during the boot. This could happen if we onlining previously
 648                  * offlined memory.
 649                  */
 650                 if (shadow_mapped(shadow_start))
 651                         return NOTIFY_OK;
 652
 653                 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 654                                         shadow_end, GFP_KERNEL,
 655                                         PAGE_KERNEL, VM_NO_GUARD,
 656                                         pfn_to_nid(mem_data->start_pfn),
 657                                         __builtin_return_address(0));
 658                 if (!ret)
 659                         return NOTIFY_BAD;
 660
 661                 kmemleak_ignore(ret);
 662                 return NOTIFY_OK;
 663         }
 664         case MEM_CANCEL_ONLINE:
 665         case MEM_OFFLINE: {
 666                 struct vm_struct *vm;
 667
 668                 /*
 669                  * shadow_start was either mapped during boot by kasan_init()
 670                  * or during memory online by __vmalloc_node_range().
 671                  * In the latter case we can use vfree() to free shadow.
 672                  * Non-NULL result of the find_vm_area() will tell us if
 673                  * that was the second case.
 674                  *
 675                  * Currently it's not possible to free shadow mapped
 676                  * during boot by kasan_init(). It's because the code
 677                  * to do that hasn't been written yet. So we'll just
 678                  * leak the memory.
 679                  */
 680                 vm = find_vm_area((void *)shadow_start);
 681                 if (vm)
 682                         vfree((void *)shadow_start);
 683         }
 684         }
 685
 686         return NOTIFY_OK;
 687 }
 688
 689 static int __init kasan_memhotplug_init(void)
 690 {
 691         hotplug_memory_notifier(kasan_mem_notifier, 0);
 692
 693         return 0;
 694 }
 695
 696 core_initcall(kasan_memhotplug_init);
 697 #endif