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 #define __KASAN_INTERNAL
  18
  19 #include <linux/export.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/init.h>
  22 #include <linux/kasan.h>
  23 #include <linux/kernel.h>
  24 #include <linux/kmemleak.h>
  25 #include <linux/linkage.h>
  26 #include <linux/memblock.h>
  27 #include <linux/memory.h>
  28 #include <linux/mm.h>
  29 #include <linux/module.h>
  30 #include <linux/printk.h>
  31 #include <linux/sched.h>
  32 #include <linux/sched/task_stack.h>
  33 #include <linux/slab.h>
  34 #include <linux/stacktrace.h>
  35 #include <linux/string.h>
  36 #include <linux/types.h>
  37 #include <linux/vmalloc.h>
  38 #include <linux/bug.h>
  39
  40 #include "kasan.h"
  41 #include "../slab.h"
  42
  43 static inline int in_irqentry_text(unsigned long ptr)
  44 {
  45         return (ptr >= (unsigned long)&__irqentry_text_start &&
  46                 ptr < (unsigned long)&__irqentry_text_end) ||
  47                 (ptr >= (unsigned long)&__softirqentry_text_start &&
  48                  ptr < (unsigned long)&__softirqentry_text_end);
  49 }
  50
  51 static inline void filter_irq_stacks(struct stack_trace *trace)
  52 {
  53         int i;
  54
  55         if (!trace->nr_entries)
  56                 return;
  57         for (i = 0; i < trace->nr_entries; i++)
  58                 if (in_irqentry_text(trace->entries[i])) {
  59                         /* Include the irqentry function into the stack. */
  60                         trace->nr_entries = i + 1;
  61                         break;
  62                 }
  63 }
  64
  65 static inline depot_stack_handle_t save_stack(gfp_t flags)
  66 {
  67         unsigned long entries[KASAN_STACK_DEPTH];
  68         struct stack_trace trace = {
  69                 .nr_entries = 0,
  70                 .entries = entries,
  71                 .max_entries = KASAN_STACK_DEPTH,
  72                 .skip = 0
  73         };
  74
  75         save_stack_trace(&trace);
  76         filter_irq_stacks(&trace);
  77         if (trace.nr_entries != 0 &&
  78             trace.entries[trace.nr_entries-1] == ULONG_MAX)
  79                 trace.nr_entries--;
  80
  81         return depot_save_stack(&trace, flags);
  82 }
  83
  84 static inline void set_track(struct kasan_track *track, gfp_t flags)
  85 {
  86         track->pid = current->pid;
  87         track->stack = save_stack(flags);
  88 }
  89
  90 void kasan_enable_current(void)
  91 {
  92         current->kasan_depth++;
  93 }
  94
  95 void kasan_disable_current(void)
  96 {
  97         current->kasan_depth--;
  98 }
  99
 100 void kasan_check_read(const volatile void *p, unsigned int size)
 101 {
 102         check_memory_region((unsigned long)p, size, false, _RET_IP_);
 103 }
 104 EXPORT_SYMBOL(kasan_check_read);
 105
 106 void kasan_check_write(const volatile void *p, unsigned int size)
 107 {
 108         check_memory_region((unsigned long)p, size, true, _RET_IP_);
 109 }
 110 EXPORT_SYMBOL(kasan_check_write);
 111
 112 #undef memset
 113 void *memset(void *addr, int c, size_t len)
 114 {
 115         check_memory_region((unsigned long)addr, len, true, _RET_IP_);
 116
 117         return __memset(addr, c, len);
 118 }
 119
 120 #undef memmove
 121 void *memmove(void *dest, const void *src, size_t len)
 122 {
 123         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 124         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 125
 126         return __memmove(dest, src, len);
 127 }
 128
 129 #undef memcpy
 130 void *memcpy(void *dest, const void *src, size_t len)
 131 {
 132         check_memory_region((unsigned long)src, len, false, _RET_IP_);
 133         check_memory_region((unsigned long)dest, len, true, _RET_IP_);
 134
 135         return __memcpy(dest, src, len);
 136 }
 137
 138 /*
 139  * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 140  * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 141  */
 142 void kasan_poison_shadow(const void *address, size_t size, u8 value)
 143 {
 144         void *shadow_start, *shadow_end;
 145
 146         /*
 147          * Perform shadow offset calculation based on untagged address, as
 148          * some of the callers (e.g. kasan_poison_object_data) pass tagged
 149          * addresses to this function.
 150          */
 151         address = reset_tag(address);
 152
 153         shadow_start = kasan_mem_to_shadow(address);
 154         shadow_end = kasan_mem_to_shadow(address + size);
 155
 156         __memset(shadow_start, value, shadow_end - shadow_start);
 157 }
 158
 159 void kasan_unpoison_shadow(const void *address, size_t size)
 160 {
 161         u8 tag = get_tag(address);
 162
 163         /*
 164          * Perform shadow offset calculation based on untagged address, as
 165          * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
 166          * addresses to this function.
 167          */
 168         address = reset_tag(address);
 169
 170         kasan_poison_shadow(address, size, tag);
 171
 172         if (size & KASAN_SHADOW_MASK) {
 173                 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
 174
 175                 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 176                         *shadow = tag;
 177                 else
 178                         *shadow = size & KASAN_SHADOW_MASK;
 179         }
 180 }
 181
 182 static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
 183 {
 184         void *base = task_stack_page(task);
 185         size_t size = sp - base;
 186
 187         kasan_unpoison_shadow(base, size);
 188 }
 189
 190 /* Unpoison the entire stack for a task. */
 191 void kasan_unpoison_task_stack(struct task_struct *task)
 192 {
 193         __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
 194 }
 195
 196 /* Unpoison the stack for the current task beyond a watermark sp value. */
 197 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
 198 {
 199         /*
 200          * Calculate the task stack base address.  Avoid using 'current'
 201          * because this function is called by early resume code which hasn't
 202          * yet set up the percpu register (%gs).
 203          */
 204         void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
 205
 206         kasan_unpoison_shadow(base, watermark - base);
 207 }
 208
 209 /*
 210  * Clear all poison for the region between the current SP and a provided
 211  * watermark value, as is sometimes required prior to hand-crafted asm function
 212  * returns in the middle of functions.
 213  */
 214 void kasan_unpoison_stack_above_sp_to(const void *watermark)
 215 {
 216         const void *sp = __builtin_frame_address(0);
 217         size_t size = watermark - sp;
 218
 219         if (WARN_ON(sp > watermark))
 220                 return;
 221         kasan_unpoison_shadow(sp, size);
 222 }
 223
 224 void kasan_alloc_pages(struct page *page, unsigned int order)
 225 {
 226         u8 tag;
 227         unsigned long i;
 228
 229         if (unlikely(PageHighMem(page)))
 230                 return;
 231
 232         tag = random_tag();
 233         for (i = 0; i < (1 << order); i++)
 234                 page_kasan_tag_set(page + i, tag);
 235         kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
 236 }
 237
 238 void kasan_free_pages(struct page *page, unsigned int order)
 239 {
 240         if (likely(!PageHighMem(page)))
 241                 kasan_poison_shadow(page_address(page),
 242                                 PAGE_SIZE << order,
 243                                 KASAN_FREE_PAGE);
 244 }
 245
 246 /*
 247  * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 248  * For larger allocations larger redzones are used.
 249  */
 250 static inline unsigned int optimal_redzone(unsigned int object_size)
 251 {
 252         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 253                 return 0;
 254
 255         return
 256                 object_size <= 64        - 16   ? 16 :
 257                 object_size <= 128       - 32   ? 32 :
 258                 object_size <= 512       - 64   ? 64 :
 259                 object_size <= 4096      - 128  ? 128 :
 260                 object_size <= (1 << 14) - 256  ? 256 :
 261                 object_size <= (1 << 15) - 512  ? 512 :
 262                 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
 263 }
 264
 265 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
 266                         slab_flags_t *flags)
 267 {
 268         unsigned int orig_size = *size;
 269         unsigned int redzone_size;
 270         int redzone_adjust;
 271
 272         /* Add alloc meta. */
 273         cache->kasan_info.alloc_meta_offset = *size;
 274         *size += sizeof(struct kasan_alloc_meta);
 275
 276         /* Add free meta. */
 277         if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
 278             (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
 279              cache->object_size < sizeof(struct kasan_free_meta))) {
 280                 cache->kasan_info.free_meta_offset = *size;
 281                 *size += sizeof(struct kasan_free_meta);
 282         }
 283
 284         redzone_size = optimal_redzone(cache->object_size);
 285         redzone_adjust = redzone_size - (*size - cache->object_size);
 286         if (redzone_adjust > 0)
 287                 *size += redzone_adjust;
 288
 289         *size = min_t(unsigned int, KMALLOC_MAX_SIZE,
 290                         max(*size, cache->object_size + redzone_size));
 291
 292         /*
 293          * If the metadata doesn't fit, don't enable KASAN at all.
 294          */
 295         if (*size <= cache->kasan_info.alloc_meta_offset ||
 296                         *size <= cache->kasan_info.free_meta_offset) {
 297                 cache->kasan_info.alloc_meta_offset = 0;
 298                 cache->kasan_info.free_meta_offset = 0;
 299                 *size = orig_size;
 300                 return;
 301         }
 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  * This function assigns a tag to an object considering the following:
 353  * 1. A cache might have a constructor, which might save a pointer to a slab
 354  *    object somewhere (e.g. in the object itself). We preassign a tag for
 355  *    each object in caches with constructors during slab creation and reuse
 356  *    the same tag each time a particular object is allocated.
 357  * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
 358  *    accessed after being freed. We preassign tags for objects in these
 359  *    caches as well.
 360  * 3. For SLAB allocator we can't preassign tags randomly since the freelist
 361  *    is stored as an array of indexes instead of a linked list. Assign tags
 362  *    based on objects indexes, so that objects that are next to each other
 363  *    get different tags.
 364  */
 365 static u8 assign_tag(struct kmem_cache *cache, const void *object,
 366                         bool init, bool keep_tag)
 367 {
 368         /*
 369          * 1. When an object is kmalloc()'ed, two hooks are called:
 370          *    kasan_slab_alloc() and kasan_kmalloc(). We assign the
 371          *    tag only in the first one.
 372          * 2. We reuse the same tag for krealloc'ed objects.
 373          */
 374         if (keep_tag)
 375                 return get_tag(object);
 376
 377         /*
 378          * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
 379          * set, assign a tag when the object is being allocated (init == false).
 380          */
 381         if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
 382                 return init ? KASAN_TAG_KERNEL : random_tag();
 383
 384         /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
 385 #ifdef CONFIG_SLAB
 386         /* For SLAB assign tags based on the object index in the freelist. */
 387         return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
 388 #else
 389         /*
 390          * For SLUB assign a random tag during slab creation, otherwise reuse
 391          * the already assigned tag.
 392          */
 393         return init ? random_tag() : get_tag(object);
 394 #endif
 395 }
 396
 397 void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
 398                                                 const void *object)
 399 {
 400         struct kasan_alloc_meta *alloc_info;
 401
 402         if (!(cache->flags & SLAB_KASAN))
 403                 return (void *)object;
 404
 405         alloc_info = get_alloc_info(cache, object);
 406         __memset(alloc_info, 0, sizeof(*alloc_info));
 407
 408         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 409                 object = set_tag(object,
 410                                 assign_tag(cache, object, true, false));
 411
 412         return (void *)object;
 413 }
 414
 415 static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
 416 {
 417         if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 418                 return shadow_byte < 0 ||
 419                         shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
 420         else
 421                 return tag != (u8)shadow_byte;
 422 }
 423
 424 static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
 425                               unsigned long ip, bool quarantine)
 426 {
 427         s8 shadow_byte;
 428         u8 tag;
 429         void *tagged_object;
 430         unsigned long rounded_up_size;
 431
 432         tag = get_tag(object);
 433         tagged_object = object;
 434         object = reset_tag(object);
 435
 436         if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
 437             object)) {
 438                 kasan_report_invalid_free(tagged_object, ip);
 439                 return true;
 440         }
 441
 442         /* RCU slabs could be legally used after free within the RCU period */
 443         if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
 444                 return false;
 445
 446         shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
 447         if (shadow_invalid(tag, shadow_byte)) {
 448                 kasan_report_invalid_free(tagged_object, ip);
 449                 return true;
 450         }
 451
 452         rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
 453         kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
 454
 455         if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
 456                         unlikely(!(cache->flags & SLAB_KASAN)))
 457                 return false;
 458
 459         set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
 460         quarantine_put(get_free_info(cache, object), cache);
 461
 462         return IS_ENABLED(CONFIG_KASAN_GENERIC);
 463 }
 464
 465 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
 466 {
 467         return __kasan_slab_free(cache, object, ip, true);
 468 }
 469
 470 static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
 471                                 size_t size, gfp_t flags, bool keep_tag)
 472 {
 473         unsigned long redzone_start;
 474         unsigned long redzone_end;
 475         u8 tag;
 476
 477         if (gfpflags_allow_blocking(flags))
 478                 quarantine_reduce();
 479
 480         if (unlikely(object == NULL))
 481                 return NULL;
 482
 483         redzone_start = round_up((unsigned long)(object + size),
 484                                 KASAN_SHADOW_SCALE_SIZE);
 485         redzone_end = round_up((unsigned long)object + cache->object_size,
 486                                 KASAN_SHADOW_SCALE_SIZE);
 487
 488         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 489                 tag = assign_tag(cache, object, false, keep_tag);
 490
 491         /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
 492         kasan_unpoison_shadow(set_tag(object, tag), size);
 493         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 494                 KASAN_KMALLOC_REDZONE);
 495
 496         if (cache->flags & SLAB_KASAN)
 497                 set_track(&get_alloc_info(cache, object)->alloc_track, flags);
 498
 499         return set_tag(object, tag);
 500 }
 501
 502 void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
 503                                         gfp_t flags)
 504 {
 505         return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
 506 }
 507
 508 void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
 509                                 size_t size, gfp_t flags)
 510 {
 511         return __kasan_kmalloc(cache, object, size, flags, true);
 512 }
 513 EXPORT_SYMBOL(kasan_kmalloc);
 514
 515 void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
 516                                                 gfp_t flags)
 517 {
 518         struct page *page;
 519         unsigned long redzone_start;
 520         unsigned long redzone_end;
 521
 522         if (gfpflags_allow_blocking(flags))
 523                 quarantine_reduce();
 524
 525         if (unlikely(ptr == NULL))
 526                 return NULL;
 527
 528         page = virt_to_page(ptr);
 529         redzone_start = round_up((unsigned long)(ptr + size),
 530                                 KASAN_SHADOW_SCALE_SIZE);
 531         redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
 532
 533         kasan_unpoison_shadow(ptr, size);
 534         kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
 535                 KASAN_PAGE_REDZONE);
 536
 537         return (void *)ptr;
 538 }
 539
 540 void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
 541 {
 542         struct page *page;
 543
 544         if (unlikely(object == ZERO_SIZE_PTR))
 545                 return (void *)object;
 546
 547         page = virt_to_head_page(object);
 548
 549         if (unlikely(!PageSlab(page)))
 550                 return kasan_kmalloc_large(object, size, flags);
 551         else
 552                 return __kasan_kmalloc(page->slab_cache, object, size,
 553                                                 flags, true);
 554 }
 555
 556 void kasan_poison_kfree(void *ptr, unsigned long ip)
 557 {
 558         struct page *page;
 559
 560         page = virt_to_head_page(ptr);
 561
 562         if (unlikely(!PageSlab(page))) {
 563                 if (ptr != page_address(page)) {
 564                         kasan_report_invalid_free(ptr, ip);
 565                         return;
 566                 }
 567                 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
 568                                 KASAN_FREE_PAGE);
 569         } else {
 570                 __kasan_slab_free(page->slab_cache, ptr, ip, false);
 571         }
 572 }
 573
 574 void kasan_kfree_large(void *ptr, unsigned long ip)
 575 {
 576         if (ptr != page_address(virt_to_head_page(ptr)))
 577                 kasan_report_invalid_free(ptr, ip);
 578         /* The object will be poisoned by page_alloc. */
 579 }
 580
 581 int kasan_module_alloc(void *addr, size_t size)
 582 {
 583         void *ret;
 584         size_t scaled_size;
 585         size_t shadow_size;
 586         unsigned long shadow_start;
 587
 588         shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
 589         scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
 590         shadow_size = round_up(scaled_size, PAGE_SIZE);
 591
 592         if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
 593                 return -EINVAL;
 594
 595         ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
 596                         shadow_start + shadow_size,
 597                         GFP_KERNEL,
 598                         PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
 599                         __builtin_return_address(0));
 600
 601         if (ret) {
 602                 __memset(ret, KASAN_SHADOW_INIT, shadow_size);
 603                 find_vm_area(addr)->flags |= VM_KASAN;
 604                 kmemleak_ignore(ret);
 605                 return 0;
 606         }
 607
 608         return -ENOMEM;
 609 }
 610
 611 void kasan_free_shadow(const struct vm_struct *vm)
 612 {
 613         if (vm->flags & VM_KASAN)
 614                 vfree(kasan_mem_to_shadow(vm->addr));
 615 }
 616
 617 #ifdef CONFIG_MEMORY_HOTPLUG
 618 static bool shadow_mapped(unsigned long addr)
 619 {
 620         pgd_t *pgd = pgd_offset_k(addr);
 621         p4d_t *p4d;
 622         pud_t *pud;
 623         pmd_t *pmd;
 624         pte_t *pte;
 625
 626         if (pgd_none(*pgd))
 627                 return false;
 628         p4d = p4d_offset(pgd, addr);
 629         if (p4d_none(*p4d))
 630                 return false;
 631         pud = pud_offset(p4d, addr);
 632         if (pud_none(*pud))
 633                 return false;
 634
 635         /*
 636          * We can't use pud_large() or pud_huge(), the first one is
 637          * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
 638          * pud_bad(), if pud is bad then it's bad because it's huge.
 639          */
 640         if (pud_bad(*pud))
 641                 return true;
 642         pmd = pmd_offset(pud, addr);
 643         if (pmd_none(*pmd))
 644                 return false;
 645
 646         if (pmd_bad(*pmd))
 647                 return true;
 648         pte = pte_offset_kernel(pmd, addr);
 649         return !pte_none(*pte);
 650 }
 651
 652 static int __meminit kasan_mem_notifier(struct notifier_block *nb,
 653                         unsigned long action, void *data)
 654 {
 655         struct memory_notify *mem_data = data;
 656         unsigned long nr_shadow_pages, start_kaddr, shadow_start;
 657         unsigned long shadow_end, shadow_size;
 658
 659         nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
 660         start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
 661         shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
 662         shadow_size = nr_shadow_pages << PAGE_SHIFT;
 663         shadow_end = shadow_start + shadow_size;
 664
 665         if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
 666                 WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
 667                 return NOTIFY_BAD;
 668
 669         switch (action) {
 670         case MEM_GOING_ONLINE: {
 671                 void *ret;
 672
 673                 /*
 674                  * If shadow is mapped already than it must have been mapped
 675                  * during the boot. This could happen if we onlining previously
 676                  * offlined memory.
 677                  */
 678                 if (shadow_mapped(shadow_start))
 679                         return NOTIFY_OK;
 680
 681                 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
 682                                         shadow_end, GFP_KERNEL,
 683                                         PAGE_KERNEL, VM_NO_GUARD,
 684                                         pfn_to_nid(mem_data->start_pfn),
 685                                         __builtin_return_address(0));
 686                 if (!ret)
 687                         return NOTIFY_BAD;
 688
 689                 kmemleak_ignore(ret);
 690                 return NOTIFY_OK;
 691         }
 692         case MEM_CANCEL_ONLINE:
 693         case MEM_OFFLINE: {
 694                 struct vm_struct *vm;
 695
 696                 /*
 697                  * shadow_start was either mapped during boot by kasan_init()
 698                  * or during memory online by __vmalloc_node_range().
 699                  * In the latter case we can use vfree() to free shadow.
 700                  * Non-NULL result of the find_vm_area() will tell us if
 701                  * that was the second case.
 702                  *
 703                  * Currently it's not possible to free shadow mapped
 704                  * during boot by kasan_init(). It's because the code
 705                  * to do that hasn't been written yet. So we'll just
 706                  * leak the memory.
 707                  */
 708                 vm = find_vm_area((void *)shadow_start);
 709                 if (vm)
 710                         vfree((void *)shadow_start);
 711         }
 712         }
 713
 714         return NOTIFY_OK;
 715 }
 716
 717 static int __init kasan_memhotplug_init(void)
 718 {
 719         hotplug_memory_notifier(kasan_mem_notifier, 0);
 720
 721         return 0;
 722 }
 723
 724 core_initcall(kasan_memhotplug_init);
 725 #endif