common.c 19.2 KB
Newer Older
1
// SPDX-License-Identifier: GPL-2.0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
/*
 * This file contains common generic and tag-based KASAN code.
 *
 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
 *
 * Some code borrowed from https://github.com/xairy/kasan-prototype by
 *        Andrey Konovalov <andreyknvl@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kmemleak.h>
#include <linux/linkage.h>
#include <linux/memblock.h>
#include <linux/memory.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/bug.h>
37
#include <linux/uaccess.h>
38
39
40
41
42
43
44
45
46
47
48
49

#include "kasan.h"
#include "../slab.h"

static inline int in_irqentry_text(unsigned long ptr)
{
	return (ptr >= (unsigned long)&__irqentry_text_start &&
		ptr < (unsigned long)&__irqentry_text_end) ||
		(ptr >= (unsigned long)&__softirqentry_text_start &&
		 ptr < (unsigned long)&__softirqentry_text_end);
}

50
51
static inline unsigned int filter_irq_stacks(unsigned long *entries,
					     unsigned int nr_entries)
52
{
53
	unsigned int i;
54

55
56
	for (i = 0; i < nr_entries; i++) {
		if (in_irqentry_text(entries[i])) {
57
			/* Include the irqentry function into the stack. */
58
			return i + 1;
59
		}
60
61
	}
	return nr_entries;
62
63
64
65
66
}

static inline depot_stack_handle_t save_stack(gfp_t flags)
{
	unsigned long entries[KASAN_STACK_DEPTH];
67
	unsigned int nr_entries;
68

69
70
71
	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
	nr_entries = filter_irq_stacks(entries, nr_entries);
	return stack_depot_save(entries, nr_entries, flags);
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
}

static inline void set_track(struct kasan_track *track, gfp_t flags)
{
	track->pid = current->pid;
	track->stack = save_stack(flags);
}

void kasan_enable_current(void)
{
	current->kasan_depth++;
}

void kasan_disable_current(void)
{
	current->kasan_depth--;
}

90
bool __kasan_check_read(const volatile void *p, unsigned int size)
91
{
92
	return check_memory_region((unsigned long)p, size, false, _RET_IP_);
93
}
94
EXPORT_SYMBOL(__kasan_check_read);
95

96
bool __kasan_check_write(const volatile void *p, unsigned int size)
97
{
98
	return check_memory_region((unsigned long)p, size, true, _RET_IP_);
99
}
100
EXPORT_SYMBOL(__kasan_check_write);
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135

#undef memset
void *memset(void *addr, int c, size_t len)
{
	check_memory_region((unsigned long)addr, len, true, _RET_IP_);

	return __memset(addr, c, len);
}

#undef memmove
void *memmove(void *dest, const void *src, size_t len)
{
	check_memory_region((unsigned long)src, len, false, _RET_IP_);
	check_memory_region((unsigned long)dest, len, true, _RET_IP_);

	return __memmove(dest, src, len);
}

#undef memcpy
void *memcpy(void *dest, const void *src, size_t len)
{
	check_memory_region((unsigned long)src, len, false, _RET_IP_);
	check_memory_region((unsigned long)dest, len, true, _RET_IP_);

	return __memcpy(dest, src, len);
}

/*
 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
 */
void kasan_poison_shadow(const void *address, size_t size, u8 value)
{
	void *shadow_start, *shadow_end;

136
137
138
139
140
141
142
	/*
	 * Perform shadow offset calculation based on untagged address, as
	 * some of the callers (e.g. kasan_poison_object_data) pass tagged
	 * addresses to this function.
	 */
	address = reset_tag(address);

143
144
145
146
147
148
149
150
	shadow_start = kasan_mem_to_shadow(address);
	shadow_end = kasan_mem_to_shadow(address + size);

	__memset(shadow_start, value, shadow_end - shadow_start);
}

void kasan_unpoison_shadow(const void *address, size_t size)
{
151
152
153
154
155
156
157
158
159
160
	u8 tag = get_tag(address);

	/*
	 * Perform shadow offset calculation based on untagged address, as
	 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
	 * addresses to this function.
	 */
	address = reset_tag(address);

	kasan_poison_shadow(address, size, tag);
161
162
163

	if (size & KASAN_SHADOW_MASK) {
		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
164
165
166
167
168

		if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
			*shadow = tag;
		else
			*shadow = size & KASAN_SHADOW_MASK;
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
	}
}

static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
{
	void *base = task_stack_page(task);
	size_t size = sp - base;

	kasan_unpoison_shadow(base, size);
}

/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
	__kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
}

/* Unpoison the stack for the current task beyond a watermark sp value. */
asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
{
	/*
	 * Calculate the task stack base address.  Avoid using 'current'
	 * because this function is called by early resume code which hasn't
	 * yet set up the percpu register (%gs).
	 */
	void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));

	kasan_unpoison_shadow(base, watermark - base);
}

/*
 * Clear all poison for the region between the current SP and a provided
 * watermark value, as is sometimes required prior to hand-crafted asm function
 * returns in the middle of functions.
 */
void kasan_unpoison_stack_above_sp_to(const void *watermark)
{
	const void *sp = __builtin_frame_address(0);
	size_t size = watermark - sp;

	if (WARN_ON(sp > watermark))
		return;
	kasan_unpoison_shadow(sp, size);
}

void kasan_alloc_pages(struct page *page, unsigned int order)
{
216
217
218
	u8 tag;
	unsigned long i;

219
220
	if (unlikely(PageHighMem(page)))
		return;
221
222
223
224

	tag = random_tag();
	for (i = 0; i < (1 << order); i++)
		page_kasan_tag_set(page + i, tag);
225
	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
}

void kasan_free_pages(struct page *page, unsigned int order)
{
	if (likely(!PageHighMem(page)))
		kasan_poison_shadow(page_address(page),
				PAGE_SIZE << order,
				KASAN_FREE_PAGE);
}

/*
 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
 * For larger allocations larger redzones are used.
 */
static inline unsigned int optimal_redzone(unsigned int object_size)
{
242
243
244
	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
		return 0;

245
246
247
248
249
250
251
252
253
254
255
256
257
258
	return
		object_size <= 64        - 16   ? 16 :
		object_size <= 128       - 32   ? 32 :
		object_size <= 512       - 64   ? 64 :
		object_size <= 4096      - 128  ? 128 :
		object_size <= (1 << 14) - 256  ? 256 :
		object_size <= (1 << 15) - 512  ? 512 :
		object_size <= (1 << 16) - 1024 ? 1024 : 2048;
}

void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
			slab_flags_t *flags)
{
	unsigned int orig_size = *size;
259
	unsigned int redzone_size;
260
261
262
263
264
265
266
	int redzone_adjust;

	/* Add alloc meta. */
	cache->kasan_info.alloc_meta_offset = *size;
	*size += sizeof(struct kasan_alloc_meta);

	/* Add free meta. */
267
268
269
	if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
	    (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
	     cache->object_size < sizeof(struct kasan_free_meta))) {
270
271
272
273
		cache->kasan_info.free_meta_offset = *size;
		*size += sizeof(struct kasan_free_meta);
	}

274
275
	redzone_size = optimal_redzone(cache->object_size);
	redzone_adjust = redzone_size -	(*size - cache->object_size);
276
277
278
279
	if (redzone_adjust > 0)
		*size += redzone_adjust;

	*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
280
			max(*size, cache->object_size + redzone_size));
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319

	/*
	 * If the metadata doesn't fit, don't enable KASAN at all.
	 */
	if (*size <= cache->kasan_info.alloc_meta_offset ||
			*size <= cache->kasan_info.free_meta_offset) {
		cache->kasan_info.alloc_meta_offset = 0;
		cache->kasan_info.free_meta_offset = 0;
		*size = orig_size;
		return;
	}

	*flags |= SLAB_KASAN;
}

size_t kasan_metadata_size(struct kmem_cache *cache)
{
	return (cache->kasan_info.alloc_meta_offset ?
		sizeof(struct kasan_alloc_meta) : 0) +
		(cache->kasan_info.free_meta_offset ?
		sizeof(struct kasan_free_meta) : 0);
}

struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache,
					const void *object)
{
	BUILD_BUG_ON(sizeof(struct kasan_alloc_meta) > 32);
	return (void *)object + cache->kasan_info.alloc_meta_offset;
}

struct kasan_free_meta *get_free_info(struct kmem_cache *cache,
				      const void *object)
{
	BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
	return (void *)object + cache->kasan_info.free_meta_offset;
}

void kasan_poison_slab(struct page *page)
{
320
321
322
323
	unsigned long i;

	for (i = 0; i < (1 << compound_order(page)); i++)
		page_kasan_tag_reset(page + i);
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
	kasan_poison_shadow(page_address(page),
			PAGE_SIZE << compound_order(page),
			KASAN_KMALLOC_REDZONE);
}

void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
{
	kasan_unpoison_shadow(object, cache->object_size);
}

void kasan_poison_object_data(struct kmem_cache *cache, void *object)
{
	kasan_poison_shadow(object,
			round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
			KASAN_KMALLOC_REDZONE);
}

341
/*
342
343
344
345
346
347
348
349
350
351
352
353
 * This function assigns a tag to an object considering the following:
 * 1. A cache might have a constructor, which might save a pointer to a slab
 *    object somewhere (e.g. in the object itself). We preassign a tag for
 *    each object in caches with constructors during slab creation and reuse
 *    the same tag each time a particular object is allocated.
 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
 *    accessed after being freed. We preassign tags for objects in these
 *    caches as well.
 * 3. For SLAB allocator we can't preassign tags randomly since the freelist
 *    is stored as an array of indexes instead of a linked list. Assign tags
 *    based on objects indexes, so that objects that are next to each other
 *    get different tags.
354
 */
355
static u8 assign_tag(struct kmem_cache *cache, const void *object,
356
			bool init, bool keep_tag)
357
{
358
359
360
361
362
363
364
	/*
	 * 1. When an object is kmalloc()'ed, two hooks are called:
	 *    kasan_slab_alloc() and kasan_kmalloc(). We assign the
	 *    tag only in the first one.
	 * 2. We reuse the same tag for krealloc'ed objects.
	 */
	if (keep_tag)
365
366
367
368
369
370
		return get_tag(object);

	/*
	 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
	 * set, assign a tag when the object is being allocated (init == false).
	 */
371
	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
372
		return init ? KASAN_TAG_KERNEL : random_tag();
373

374
	/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
375
#ifdef CONFIG_SLAB
376
	/* For SLAB assign tags based on the object index in the freelist. */
377
378
	return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
#else
379
380
381
382
383
	/*
	 * For SLUB assign a random tag during slab creation, otherwise reuse
	 * the already assigned tag.
	 */
	return init ? random_tag() : get_tag(object);
384
385
386
#endif
}

387
388
void * __must_check kasan_init_slab_obj(struct kmem_cache *cache,
						const void *object)
389
390
391
392
393
394
395
396
397
{
	struct kasan_alloc_meta *alloc_info;

	if (!(cache->flags & SLAB_KASAN))
		return (void *)object;

	alloc_info = get_alloc_info(cache, object);
	__memset(alloc_info, 0, sizeof(*alloc_info));

398
	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
399
400
		object = set_tag(object,
				assign_tag(cache, object, true, false));
401

402
403
404
	return (void *)object;
}

405
406
407
408
409
410
411
412
413
static inline bool shadow_invalid(u8 tag, s8 shadow_byte)
{
	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
		return shadow_byte < 0 ||
			shadow_byte >= KASAN_SHADOW_SCALE_SIZE;
	else
		return tag != (u8)shadow_byte;
}

414
415
416
417
static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
			      unsigned long ip, bool quarantine)
{
	s8 shadow_byte;
418
419
	u8 tag;
	void *tagged_object;
420
421
	unsigned long rounded_up_size;

422
423
424
425
	tag = get_tag(object);
	tagged_object = object;
	object = reset_tag(object);

426
427
	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
	    object)) {
428
		kasan_report_invalid_free(tagged_object, ip);
429
430
431
432
433
434
435
436
		return true;
	}

	/* RCU slabs could be legally used after free within the RCU period */
	if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
		return false;

	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object));
437
438
	if (shadow_invalid(tag, shadow_byte)) {
		kasan_report_invalid_free(tagged_object, ip);
439
440
441
442
443
444
		return true;
	}

	rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE);
	kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);

445
446
	if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
			unlikely(!(cache->flags & SLAB_KASAN)))
447
448
449
450
		return false;

	set_track(&get_alloc_info(cache, object)->free_track, GFP_NOWAIT);
	quarantine_put(get_free_info(cache, object), cache);
451
452

	return IS_ENABLED(CONFIG_KASAN_GENERIC);
453
454
455
456
457
458
459
}

bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
{
	return __kasan_slab_free(cache, object, ip, true);
}

460
static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
461
				size_t size, gfp_t flags, bool keep_tag)
462
463
464
{
	unsigned long redzone_start;
	unsigned long redzone_end;
465
	u8 tag = 0xff;
466
467
468
469
470
471
472
473
474
475
476
477

	if (gfpflags_allow_blocking(flags))
		quarantine_reduce();

	if (unlikely(object == NULL))
		return NULL;

	redzone_start = round_up((unsigned long)(object + size),
				KASAN_SHADOW_SCALE_SIZE);
	redzone_end = round_up((unsigned long)object + cache->object_size,
				KASAN_SHADOW_SCALE_SIZE);

478
	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
479
		tag = assign_tag(cache, object, false, keep_tag);
480
481
482

	/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
	kasan_unpoison_shadow(set_tag(object, tag), size);
483
484
485
486
487
488
	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
		KASAN_KMALLOC_REDZONE);

	if (cache->flags & SLAB_KASAN)
		set_track(&get_alloc_info(cache, object)->alloc_track, flags);

489
	return set_tag(object, tag);
490
}
491

492
493
494
495
496
497
void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object,
					gfp_t flags)
{
	return __kasan_kmalloc(cache, object, cache->object_size, flags, false);
}

498
499
500
void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
				size_t size, gfp_t flags)
{
501
	return __kasan_kmalloc(cache, object, size, flags, true);
502
}
503
504
EXPORT_SYMBOL(kasan_kmalloc);

505
506
void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
						gfp_t flags)
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
{
	struct page *page;
	unsigned long redzone_start;
	unsigned long redzone_end;

	if (gfpflags_allow_blocking(flags))
		quarantine_reduce();

	if (unlikely(ptr == NULL))
		return NULL;

	page = virt_to_page(ptr);
	redzone_start = round_up((unsigned long)(ptr + size),
				KASAN_SHADOW_SCALE_SIZE);
	redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));

	kasan_unpoison_shadow(ptr, size);
	kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
		KASAN_PAGE_REDZONE);

	return (void *)ptr;
}

530
void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
531
532
533
534
535
536
537
538
539
540
541
{
	struct page *page;

	if (unlikely(object == ZERO_SIZE_PTR))
		return (void *)object;

	page = virt_to_head_page(object);

	if (unlikely(!PageSlab(page)))
		return kasan_kmalloc_large(object, size, flags);
	else
542
543
		return __kasan_kmalloc(page->slab_cache, object, size,
						flags, true);
544
545
546
547
548
549
550
551
552
}

void kasan_poison_kfree(void *ptr, unsigned long ip)
{
	struct page *page;

	page = virt_to_head_page(ptr);

	if (unlikely(!PageSlab(page))) {
553
		if (ptr != page_address(page)) {
554
555
556
557
558
559
560
561
562
563
564
565
			kasan_report_invalid_free(ptr, ip);
			return;
		}
		kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
				KASAN_FREE_PAGE);
	} else {
		__kasan_slab_free(page->slab_cache, ptr, ip, false);
	}
}

void kasan_kfree_large(void *ptr, unsigned long ip)
{
566
	if (ptr != page_address(virt_to_head_page(ptr)))
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
		kasan_report_invalid_free(ptr, ip);
	/* The object will be poisoned by page_alloc. */
}

int kasan_module_alloc(void *addr, size_t size)
{
	void *ret;
	size_t scaled_size;
	size_t shadow_size;
	unsigned long shadow_start;

	shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
	scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT;
	shadow_size = round_up(scaled_size, PAGE_SIZE);

	if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
		return -EINVAL;

	ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
			shadow_start + shadow_size,
587
			GFP_KERNEL,
588
589
590
591
			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
			__builtin_return_address(0));

	if (ret) {
592
		__memset(ret, KASAN_SHADOW_INIT, shadow_size);
593
594
595
596
597
598
599
600
601
602
603
604
605
606
		find_vm_area(addr)->flags |= VM_KASAN;
		kmemleak_ignore(ret);
		return 0;
	}

	return -ENOMEM;
}

void kasan_free_shadow(const struct vm_struct *vm)
{
	if (vm->flags & VM_KASAN)
		vfree(kasan_mem_to_shadow(vm->addr));
}

607
608
609
610
611
612
613
614
615
extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip);

void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
{
	unsigned long flags = user_access_save();
	__kasan_report(addr, size, is_write, ip);
	user_access_restore(flags);
}

616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
#ifdef CONFIG_MEMORY_HOTPLUG
static bool shadow_mapped(unsigned long addr)
{
	pgd_t *pgd = pgd_offset_k(addr);
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (pgd_none(*pgd))
		return false;
	p4d = p4d_offset(pgd, addr);
	if (p4d_none(*p4d))
		return false;
	pud = pud_offset(p4d, addr);
	if (pud_none(*pud))
		return false;

	/*
	 * We can't use pud_large() or pud_huge(), the first one is
	 * arch-specific, the last one depends on HUGETLB_PAGE.  So let's abuse
	 * pud_bad(), if pud is bad then it's bad because it's huge.
	 */
	if (pud_bad(*pud))
		return true;
	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
		return false;

	if (pmd_bad(*pmd))
		return true;
	pte = pte_offset_kernel(pmd, addr);
	return !pte_none(*pte);
}

static int __meminit kasan_mem_notifier(struct notifier_block *nb,
			unsigned long action, void *data)
{
	struct memory_notify *mem_data = data;
	unsigned long nr_shadow_pages, start_kaddr, shadow_start;
	unsigned long shadow_end, shadow_size;

	nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
	start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
	shadow_size = nr_shadow_pages << PAGE_SHIFT;
	shadow_end = shadow_start + shadow_size;

	if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
		WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
		return NOTIFY_BAD;

	switch (action) {
	case MEM_GOING_ONLINE: {
		void *ret;

		/*
		 * If shadow is mapped already than it must have been mapped
		 * during the boot. This could happen if we onlining previously
		 * offlined memory.
		 */
		if (shadow_mapped(shadow_start))
			return NOTIFY_OK;

		ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
					shadow_end, GFP_KERNEL,
					PAGE_KERNEL, VM_NO_GUARD,
					pfn_to_nid(mem_data->start_pfn),
					__builtin_return_address(0));
		if (!ret)
			return NOTIFY_BAD;

		kmemleak_ignore(ret);
		return NOTIFY_OK;
	}
	case MEM_CANCEL_ONLINE:
	case MEM_OFFLINE: {
		struct vm_struct *vm;

		/*
		 * shadow_start was either mapped during boot by kasan_init()
		 * or during memory online by __vmalloc_node_range().
		 * In the latter case we can use vfree() to free shadow.
		 * Non-NULL result of the find_vm_area() will tell us if
		 * that was the second case.
		 *
		 * Currently it's not possible to free shadow mapped
		 * during boot by kasan_init(). It's because the code
		 * to do that hasn't been written yet. So we'll just
		 * leak the memory.
		 */
		vm = find_vm_area((void *)shadow_start);
		if (vm)
			vfree((void *)shadow_start);
	}
	}

	return NOTIFY_OK;
}

static int __init kasan_memhotplug_init(void)
{
	hotplug_memory_notifier(kasan_mem_notifier, 0);

	return 0;
}

core_initcall(kasan_memhotplug_init);
#endif