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         *flags |= SLAB_KASAN;
 302 }
 303
 304 size_t kasan_metadata_size(struct kmem_cache *cache)
 305 {
 306         return (cache->kasan_info.alloc_meta_offset ?
 307                 sizeof(struct kasan_alloc_meta) : 0) +
 308                 (cache->kasan_info.free_meta_offset ?
 309                 sizeof(struct kasan_free_meta) : 0);
 310 }
 311
 312 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
 313                                         const void *object)
 314 {
 315         BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
 316         return (void *)object + cache->kasan_info.alloc_meta_offset;
 317 }
 318
 319 struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
 320                                       const void *object)
 321 {
 322         BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
 323         return (void *)object + cache->kasan_info.free_meta_offset;
 324 }
 325
 326 void kasan_poison_slab(struct page *page)
 327 {
 328         unsigned long i;
 329
 330         for (i = 0; i < (1 << compound_order(page)); i++)
 331                 page_kasan_tag_reset(page + i);
 332         kasan_poison_shadow(page_address(page),
 333                         PAGE_SIZE << compound_order(page),
 334                         KASAN_KMALLOC_REDZONE);
 335 }
 336
 337 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 338 {
 339         kasan_unpoison_shadow(object, cache->object_size);
 340 }
 341
 342 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
 343 {
 344         kasan_poison_shadow(object,
 345                         round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
 346                         KASAN_KMALLOC_REDZONE);
 347 }
 348
 349 /*
 350  * Since it's desirable to only call object contructors once during slab
 351  * allocation, we preassign tags to all such objects. Also preassign tags for
 352  * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports.
 353  * For SLAB allocator we can't preassign tags randomly since the freelist is
 354  * stored as an array of indexes instead of a linked list. Assign tags based
 355  * on objects indexes, so that objects that are next to each other get
 356  * different tags.
 357  * After a tag is assigned, the object always gets allocated with the same tag.
 358  * The reason is that we can't change tags for objects with constructors on
 359  * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor
 360  * code can save the pointer to the object somewhere (e.g. in the object
 361  * itself). Then if we retag it, the old saved pointer will become invalid.
 362  */
 363 static u8 assign_tag(struct kmem_cache *cache, const void *object, bool new)
 364 {
 365         if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
 366                 return new ? KASAN_TAG_KERNEL : random_tag();
 367
 368 #ifdef CONFIG_SLAB
 369         return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
 370 #else
 371         return new ? random_tag() : get_tag(object);
 372 #endif
 373 }
 374
 375 void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
 376                                                 const void *object)
 377 {
 378         struct kasan_alloc_meta *alloc_info;
 379
 380         if (!(cache->flags & SLAB_KASAN))
 381                 return (void *)object;
 382
 383         alloc_info = get_alloc_info(cache, object);
 384         __memset(alloc_info, 0, sizeof(*alloc_info));
 385
 386         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 387                 object = set_tag(object, assign_tag(cache, object, true));
 388
 389         return (void *)object;
 390 }
 391
 392 void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
 393                                         gfp_t flags)
 394 {
 395         return kasan_kmalloc(cache, object, cache->object_size, flags);
 396 }
 397
 398 static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
 399 {
 400         if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 401                 return shadow_byte < 0 ||
 402                         shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
 403         else
 404                 return tag != (u8)shadow_byte;
 405 }
 406
 407 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 408                               unsigned long ip, bool quarantine)
 409 {
 410         s8 shadow_byte;
 411         u8 tag;
 412         void *tagged_object;
 413         unsigned long rounded_up_size;
 414
 415         tag = get_tag(object);
 416         tagged_object = object;
 417         object = reset_tag(object);
 418
 419         if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
 420             object)) {
 421                 kasan_report_invalid_free(tagged_object, ip);
 422                 return true;
 423         }
 424
 425         /* RCU slabs could be legally used after free within the RCU period */
 426         if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 427                 return false;
 428
 429         shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 430         if (shadow_invalid(tag, shadow_byte)) {
 431                 kasan_report_invalid_free(tagged_object, ip);
 432                 return true;
 433         }
 434
 435         rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
 436         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 437
 438         if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
 439                         unlikely(!(cache->flags & SLAB_KASAN)))
 440                 return false;
 441
 442         set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
 443         quarantine_put(get_free_info(cache, object), cache);
 444
 445         return IS_ENABLED(CONFIG_KASAN_GENERIC);
 446 }
 447
 448 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 449 {
 450         return __kasan_slab_free(cache, object, ip, true);
 451 }
 452
 453 void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
 454                                         size_t size, gfp_t flags)
 455 {
 456         unsigned long redzone_start;
 457         unsigned long redzone_end;
 458         u8 tag;
 459
 460         if (gfpflags_allow_blocking(flags))
 461                 quarantine_reduce();
 462
 463         if (unlikely(object == NULL))
 464                 return NULL;
 465
 466         redzone_start = round_up((unsigned long)(object + size),
 467                                 KASAN_SHADOW_SCALE_SIZE);
 468         redzone_end = round_up((unsigned long)object + cache->object_size,
 469                                 KASAN_SHADOW_SCALE_SIZE);
 470
 471         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 472                 tag = assign_tag(cache, object, false);
 473
 474         /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
 475         kasan_unpoison_shadow(set_tag(object, tag), size);
 476         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 477                 KASAN_KMALLOC_REDZONE);
 478
 479         if (cache->flags & SLAB_KASAN)
 480                 set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 481
 482         return set_tag(object, tag);
 483 }
 484 EXPORT_SYMBOL(kasan_kmalloc);
 485
 486 void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
 487                                                 gfp_t flags)
 488 {
 489         struct page *page;
 490         unsigned long redzone_start;
 491         unsigned long redzone_end;
 492
 493         if (gfpflags_allow_blocking(flags))
 494                 quarantine_reduce();
 495
 496         if (unlikely(ptr == NULL))
 497                 return NULL;
 498
 499         page = virt_to_page(ptr);
 500         redzone_start = round_up((unsigned long)(ptr + size),
 501                                 KASAN_SHADOW_SCALE_SIZE);
 502         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 503
 504         kasan_unpoison_shadow(ptr, size);
 505         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 506                 KASAN_PAGE_REDZONE);
 507
 508         return (void *)ptr;
 509 }
 510
 511 void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
 512 {
 513         struct page *page;
 514
 515         if (unlikely(object == ZERO_SIZE_PTR))
 516                 return (void *)object;
 517
 518         page = virt_to_head_page(object);
 519
 520         if (unlikely(!PageSlab(page)))
 521                 return kasan_kmalloc_large(object, size, flags);
 522         else
 523                 return kasan_kmalloc(page->slab_cache, object, size, flags);
 524 }
 525
 526 void kasan_poison_kfree(void *ptr, unsigned long ip)
 527 {
 528         struct page *page;
 529
 530         page = virt_to_head_page(ptr);
 531
 532         if (unlikely(!PageSlab(page))) {
 533                 if (ptr != page_address(page)) {
 534                         kasan_report_invalid_free(ptr, ip);
 535                         return;
 536                 }
 537                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 538                                 KASAN_FREE_PAGE);
 539         } else {
 540                 __kasan_slab_free(page->slab_cache, ptr, ip, false);
 541         }
 542 }
 543
 544 void kasan_kfree_large(void *ptr, unsigned long ip)
 545 {
 546         if (ptr != page_address(virt_to_head_page(ptr)))
 547                 kasan_report_invalid_free(ptr, ip);
 548         /* The object will be poisoned by page_alloc. */
 549 }
 550
 551 int kasan_module_alloc(void *addr, size_t size)
 552 {
 553         void *ret;
 554         size_t scaled_size;
 555         size_t shadow_size;
 556         unsigned long shadow_start;
 557
 558         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 559         scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
 560         shadow_size = round_up(scaled_size, PAGE_SIZE);
 561
 562         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 563                 return -EINVAL;
 564
 565         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 566                         shadow_start + shadow_size,
 567                         GFP_KERNEL,
 568                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 569                         __builtin_return_address(0));
 570
 571         if (ret) {
 572                 __memset(ret, KASAN_SHADOW_INIT, shadow_size);
 573                 find_vm_area(addr)->flags |= VM_KASAN;
 574                 kmemleak_ignore(ret);
 575                 return 0;
 576         }
 577
 578         return -ENOMEM;
 579 }
 580
 581 void kasan_free_shadow(const struct vm_struct *vm)
 582 {
 583         if (vm->flags & VM_KASAN)
 584                 vfree(kasan_mem_to_shadow(vm->addr));
 585 }
 586
 587 #ifdef CONFIG_MEMORY_HOTPLUG
 588 static bool shadow_mapped(unsigned long addr)
 589 {
 590         pgd_t *pgd = pgd_offset_k(addr);
 591         p4d_t *p4d;
 592         pud_t *pud;
 593         pmd_t *pmd;
 594         pte_t *pte;
 595
 596         if (pgd_none(*pgd))
 597                 return false;
 598         p4d = p4d_offset(pgd, addr);
 599         if (p4d_none(*p4d))
 600                 return false;
 601         pud = pud_offset(p4d, addr);
 602         if (pud_none(*pud))
 603                 return false;
 604
 605         /*
 606          * We can't use pud_large() or pud_huge(), the first one is
 607          * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
 608          * pud_bad(), if pud is bad then it's bad because it's huge.
 609          */
 610         if (pud_bad(*pud))
 611                 return true;
 612         pmd = pmd_offset(pud, addr);
 613         if (pmd_none(*pmd))
 614                 return false;
 615
 616         if (pmd_bad(*pmd))
 617                 return true;
 618         pte = pte_offset_kernel(pmd, addr);
 619         return !pte_none(*pte);
 620 }
 621
 622 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 623                         unsigned long action, void *data)
 624 {
 625         struct memory_notify *mem_data = data;
 626         unsigned long nr_shadow_pages, start_kaddr, shadow_start;
 627         unsigned long shadow_end, shadow_size;
 628
 629         nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
 630         start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
 631         shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
 632         shadow_size = nr_shadow_pages << PAGE_SHIFT;
 633         shadow_end = shadow_start + shadow_size;
 634
 635         if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
 636                 WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
 637                 return NOTIFY_BAD;
 638
 639         switch (action) {
 640         case MEM_GOING_ONLINE: {
 641                 void *ret;
 642
 643                 /*
 644                  * If shadow is mapped already than it must have been mapped
 645                  * during the boot. This could happen if we onlining previously
 646                  * offlined memory.
 647                  */
 648                 if (shadow_mapped(shadow_start))
 649                         return NOTIFY_OK;
 650
 651                 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 652                                         shadow_end, GFP_KERNEL,
 653                                         PAGE_KERNEL, VM_NO_GUARD,
 654                                         pfn_to_nid(mem_data->start_pfn),
 655                                         __builtin_return_address(0));
 656                 if (!ret)
 657                         return NOTIFY_BAD;
 658
 659                 kmemleak_ignore(ret);
 660                 return NOTIFY_OK;
 661         }
 662         case MEM_CANCEL_ONLINE:
 663         case MEM_OFFLINE: {
 664                 struct vm_struct *vm;
 665
 666                 /*
 667                  * shadow_start was either mapped during boot by kasan_init()
 668                  * or during memory online by __vmalloc_node_range().
 669                  * In the latter case we can use vfree() to free shadow.
 670                  * Non-NULL result of the find_vm_area() will tell us if
 671                  * that was the second case.
 672                  *
 673                  * Currently it's not possible to free shadow mapped
 674                  * during boot by kasan_init(). It's because the code
 675                  * to do that hasn't been written yet. So we'll just
 676                  * leak the memory.
 677                  */
 678                 vm = find_vm_area((void *)shadow_start);
 679                 if (vm)
 680                         vfree((void *)shadow_start);
 681         }
 682         }
 683
 684         return NOTIFY_OK;
 685 }
 686
 687 static int __init kasan_memhotplug_init(void)
 688 {
 689         hotplug_memory_notifier(kasan_mem_notifier, 0);
 690
 691         return 0;
 692 }
 693
 694 core_initcall(kasan_memhotplug_init);
 695 #endif