common.c 27 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/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 <asm/cacheflush.h>
38
39
#include <asm/tlbflush.h>

40
41
42
#include "kasan.h"
#include "../slab.h"

43
depot_stack_handle_t kasan_save_stack(gfp_t flags)
44
45
{
	unsigned long entries[KASAN_STACK_DEPTH];
46
	unsigned int nr_entries;
47

48
49
50
	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);
51
52
53
54
55
}

static inline void set_track(struct kasan_track *track, gfp_t flags)
{
	track->pid = current->pid;
56
	track->stack = kasan_save_stack(flags);
57
58
59
60
61
62
63
64
65
66
67
68
}

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

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

69
bool __kasan_check_read(const volatile void *p, unsigned int size)
70
{
71
	return check_memory_region((unsigned long)p, size, false, _RET_IP_);
72
}
73
EXPORT_SYMBOL(__kasan_check_read);
74

75
bool __kasan_check_write(const volatile void *p, unsigned int size)
76
{
77
	return check_memory_region((unsigned long)p, size, true, _RET_IP_);
78
}
79
EXPORT_SYMBOL(__kasan_check_write);
80
81
82
83

#undef memset
void *memset(void *addr, int c, size_t len)
{
84
85
	if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_))
		return NULL;
86
87
88
89

	return __memset(addr, c, len);
}

90
#ifdef __HAVE_ARCH_MEMMOVE
91
92
93
#undef memmove
void *memmove(void *dest, const void *src, size_t len)
{
94
95
96
	if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
	    !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
		return NULL;
97
98
99

	return __memmove(dest, src, len);
}
100
#endif
101
102
103
104

#undef memcpy
void *memcpy(void *dest, const void *src, size_t len)
{
105
106
107
	if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) ||
	    !check_memory_region((unsigned long)dest, len, true, _RET_IP_))
		return NULL;
108
109
110
111
112
113
114
115
116
117
118
119

	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;

120
121
122
123
124
125
126
	/*
	 * 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);

127
128
129
130
131
132
133
134
	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)
{
135
136
137
138
139
140
141
142
143
144
	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);
145
146
147

	if (size & KASAN_SHADOW_MASK) {
		u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
148
149
150
151
152

		if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
			*shadow = tag;
		else
			*shadow = size & KASAN_SHADOW_MASK;
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
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
	}
}

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)
{
200
201
202
	u8 tag;
	unsigned long i;

203
204
	if (unlikely(PageHighMem(page)))
		return;
205
206
207
208

	tag = random_tag();
	for (i = 0; i < (1 << order); i++)
		page_kasan_tag_set(page + i, tag);
209
	kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
}

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)
{
226
227
228
	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
		return 0;

229
230
231
232
233
234
235
236
237
238
239
240
241
242
	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;
243
	unsigned int redzone_size;
244
245
246
247
248
249
250
	int redzone_adjust;

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

	/* Add free meta. */
251
252
253
	if (IS_ENABLED(CONFIG_KASAN_GENERIC) &&
	    (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor ||
	     cache->object_size < sizeof(struct kasan_free_meta))) {
254
255
256
257
		cache->kasan_info.free_meta_offset = *size;
		*size += sizeof(struct kasan_free_meta);
	}

258
259
	redzone_size = optimal_redzone(cache->object_size);
	redzone_adjust = redzone_size -	(*size - cache->object_size);
260
261
262
263
	if (redzone_adjust > 0)
		*size += redzone_adjust;

	*size = min_t(unsigned int, KMALLOC_MAX_SIZE,
264
			max(*size, cache->object_size + redzone_size));
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300

	/*
	 * 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)
{
	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;
}

301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318

static void kasan_set_free_info(struct kmem_cache *cache,
		void *object, u8 tag)
{
	struct kasan_alloc_meta *alloc_meta;
	u8 idx = 0;

	alloc_meta = get_alloc_info(cache, object);

#ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY
	idx = alloc_meta->free_track_idx;
	alloc_meta->free_pointer_tag[idx] = tag;
	alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS;
#endif

	set_track(&alloc_meta->free_track[idx], GFP_NOWAIT);
}

319
320
void kasan_poison_slab(struct page *page)
{
321
322
	unsigned long i;

323
	for (i = 0; i < compound_nr(page); i++)
324
		page_kasan_tag_reset(page + i);
325
	kasan_poison_shadow(page_address(page), page_size(page),
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
			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
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;
410
411
412
413
414
415
416
417

	/* else CONFIG_KASAN_SW_TAGS: */
	if ((u8)shadow_byte == KASAN_TAG_INVALID)
		return true;
	if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte))
		return true;

	return false;
418
419
}

420
421
422
423
static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
			      unsigned long ip, bool quarantine)
{
	s8 shadow_byte;
424
425
	u8 tag;
	void *tagged_object;
426
427
	unsigned long rounded_up_size;

428
429
430
431
	tag = get_tag(object);
	tagged_object = object;
	object = reset_tag(object);

432
433
	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
	    object)) {
434
		kasan_report_invalid_free(tagged_object, ip);
435
436
437
438
439
440
441
442
		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));
443
444
	if (shadow_invalid(tag, shadow_byte)) {
		kasan_report_invalid_free(tagged_object, ip);
445
446
447
448
449
450
		return true;
	}

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

451
452
	if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
			unlikely(!(cache->flags & SLAB_KASAN)))
453
454
		return false;

455
456
	kasan_set_free_info(cache, object, tag);

457
	quarantine_put(get_free_info(cache, object), cache);
458
459

	return IS_ENABLED(CONFIG_KASAN_GENERIC);
460
461
462
463
464
465
466
}

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

467
static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object,
468
				size_t size, gfp_t flags, bool keep_tag)
469
470
471
{
	unsigned long redzone_start;
	unsigned long redzone_end;
472
	u8 tag = 0xff;
473
474
475
476
477
478
479
480
481
482
483
484

	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);

485
	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
486
		tag = assign_tag(cache, object, false, keep_tag);
487
488
489

	/* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
	kasan_unpoison_shadow(set_tag(object, tag), size);
490
491
492
493
494
495
	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);

496
	return set_tag(object, tag);
497
}
498

499
500
501
502
503
504
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);
}

505
506
507
void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object,
				size_t size, gfp_t flags)
{
508
	return __kasan_kmalloc(cache, object, size, flags, true);
509
}
510
511
EXPORT_SYMBOL(kasan_kmalloc);

512
513
void * __must_check kasan_kmalloc_large(const void *ptr, size_t size,
						gfp_t flags)
514
515
516
517
518
519
520
521
522
523
524
525
526
527
{
	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);
528
	redzone_end = (unsigned long)ptr + page_size(page);
529
530
531
532
533
534
535
536

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

	return (void *)ptr;
}

537
void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags)
538
539
540
541
542
543
544
545
546
547
548
{
	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
549
550
		return __kasan_kmalloc(page->slab_cache, object, size,
						flags, true);
551
552
553
554
555
556
557
558
559
}

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

	page = virt_to_head_page(ptr);

	if (unlikely(!PageSlab(page))) {
560
		if (ptr != page_address(page)) {
561
562
563
			kasan_report_invalid_free(ptr, ip);
			return;
		}
564
		kasan_poison_shadow(ptr, page_size(page), KASAN_FREE_PAGE);
565
566
567
568
569
570
571
	} else {
		__kasan_slab_free(page->slab_cache, ptr, ip, false);
	}
}

void kasan_kfree_large(void *ptr, unsigned long ip)
{
572
	if (ptr != page_address(virt_to_head_page(ptr)))
573
574
575
576
		kasan_report_invalid_free(ptr, ip);
	/* The object will be poisoned by page_alloc. */
}

577
#ifndef CONFIG_KASAN_VMALLOC
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
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,
594
			GFP_KERNEL,
595
596
597
598
			PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
			__builtin_return_address(0));

	if (ret) {
599
		__memset(ret, KASAN_SHADOW_INIT, shadow_size);
600
601
602
603
604
605
606
607
608
609
610
611
612
		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));
}
613
#endif
614
615
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

#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
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752

#ifdef CONFIG_KASAN_VMALLOC
static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
				      void *unused)
{
	unsigned long page;
	pte_t pte;

	if (likely(!pte_none(*ptep)))
		return 0;

	page = __get_free_page(GFP_KERNEL);
	if (!page)
		return -ENOMEM;

	memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
	pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);

	spin_lock(&init_mm.page_table_lock);
	if (likely(pte_none(*ptep))) {
		set_pte_at(&init_mm, addr, ptep, pte);
		page = 0;
	}
	spin_unlock(&init_mm.page_table_lock);
	if (page)
		free_page(page);
	return 0;
}

753
int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
754
755
756
757
{
	unsigned long shadow_start, shadow_end;
	int ret;

758
759
760
761
	if (!is_vmalloc_or_module_addr((void *)addr))
		return 0;

	shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
762
	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
763
	shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
	shadow_end = ALIGN(shadow_end, PAGE_SIZE);

	ret = apply_to_page_range(&init_mm, shadow_start,
				  shadow_end - shadow_start,
				  kasan_populate_vmalloc_pte, NULL);
	if (ret)
		return ret;

	flush_cache_vmap(shadow_start, shadow_end);

	/*
	 * We need to be careful about inter-cpu effects here. Consider:
	 *
	 *   CPU#0				  CPU#1
	 * WRITE_ONCE(p, vmalloc(100));		while (x = READ_ONCE(p)) ;
	 *					p[99] = 1;
	 *
	 * With compiler instrumentation, that ends up looking like this:
	 *
	 *   CPU#0				  CPU#1
	 * // vmalloc() allocates memory
	 * // let a = area->addr
	 * // we reach kasan_populate_vmalloc
	 * // and call kasan_unpoison_shadow:
	 * STORE shadow(a), unpoison_val
	 * ...
	 * STORE shadow(a+99), unpoison_val	x = LOAD p
	 * // rest of vmalloc process		<data dependency>
	 * STORE p, a				LOAD shadow(x+99)
	 *
	 * If there is no barrier between the end of unpoisioning the shadow
	 * and the store of the result to p, the stores could be committed
	 * in a different order by CPU#0, and CPU#1 could erroneously observe
	 * poison in the shadow.
	 *
	 * We need some sort of barrier between the stores.
	 *
	 * In the vmalloc() case, this is provided by a smp_wmb() in
	 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in
	 * get_vm_area() and friends, the caller gets shadow allocated but
	 * doesn't have any pages mapped into the virtual address space that
	 * has been reserved. Mapping those pages in will involve taking and
	 * releasing a page-table lock, which will provide the barrier.
	 */

	return 0;
}

/*
 * Poison the shadow for a vmalloc region. Called as part of the
 * freeing process at the time the region is freed.
 */
816
void kasan_poison_vmalloc(const void *start, unsigned long size)
817
{
818
819
820
	if (!is_vmalloc_or_module_addr(start))
		return;

821
822
823
824
	size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
	kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID);
}

825
826
827
828
829
830
831
832
void kasan_unpoison_vmalloc(const void *start, unsigned long size)
{
	if (!is_vmalloc_or_module_addr(start))
		return;

	kasan_unpoison_shadow(start, size);
}

833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
					void *unused)
{
	unsigned long page;

	page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT);

	spin_lock(&init_mm.page_table_lock);

	if (likely(!pte_none(*ptep))) {
		pte_clear(&init_mm, addr, ptep);
		free_page(page);
	}
	spin_unlock(&init_mm.page_table_lock);

	return 0;
}

/*
 * Release the backing for the vmalloc region [start, end), which
 * lies within the free region [free_region_start, free_region_end).
 *
 * This can be run lazily, long after the region was freed. It runs
 * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
 * infrastructure.
 *
 * How does this work?
 * -------------------
 *
 * We have a region that is page aligned, labelled as A.
 * That might not map onto the shadow in a way that is page-aligned:
 *
 *                    start                     end
 *                    v                         v
 * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc
 *  -------- -------- --------          -------- --------
 *      |        |       |                 |        |
 *      |        |       |         /-------/        |
 *      \-------\|/------/         |/---------------/
 *              |||                ||
 *             |??AAAAAA|AAAAAAAA|AA??????|                < shadow
 *                 (1)      (2)      (3)
 *
 * First we align the start upwards and the end downwards, so that the
 * shadow of the region aligns with shadow page boundaries. In the
 * example, this gives us the shadow page (2). This is the shadow entirely
 * covered by this allocation.
 *
 * Then we have the tricky bits. We want to know if we can free the
 * partially covered shadow pages - (1) and (3) in the example. For this,
 * we are given the start and end of the free region that contains this
 * allocation. Extending our previous example, we could have:
 *
 *  free_region_start                                    free_region_end
 *  |                 start                     end      |
 *  v                 v                         v        v
 * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc
 *  -------- -------- --------          -------- --------
 *      |        |       |                 |        |
 *      |        |       |         /-------/        |
 *      \-------\|/------/         |/---------------/
 *              |||                ||
 *             |FFAAAAAA|AAAAAAAA|AAF?????|                < shadow
 *                 (1)      (2)      (3)
 *
 * Once again, we align the start of the free region up, and the end of
 * the free region down so that the shadow is page aligned. So we can free
 * page (1) - we know no allocation currently uses anything in that page,
 * because all of it is in the vmalloc free region. But we cannot free
 * page (3), because we can't be sure that the rest of it is unused.
 *
 * We only consider pages that contain part of the original region for
 * freeing: we don't try to free other pages from the free region or we'd
 * end up trying to free huge chunks of virtual address space.
 *
 * Concurrency
 * -----------
 *
 * How do we know that we're not freeing a page that is simultaneously
 * being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
 *
 * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
 * at the same time. While we run under free_vmap_area_lock, the population
 * code does not.
 *
 * free_vmap_area_lock instead operates to ensure that the larger range
 * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
 * the per-cpu region-finding algorithm both run under free_vmap_area_lock,
 * no space identified as free will become used while we are running. This
 * means that so long as we are careful with alignment and only free shadow
 * pages entirely covered by the free region, we will not run in to any
 * trouble - any simultaneous allocations will be for disjoint regions.
 */
void kasan_release_vmalloc(unsigned long start, unsigned long end,
			   unsigned long free_region_start,
			   unsigned long free_region_end)
{
	void *shadow_start, *shadow_end;
	unsigned long region_start, region_end;
932
	unsigned long size;
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954

	region_start = ALIGN(start, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);
	region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);

	free_region_start = ALIGN(free_region_start,
				  PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);

	if (start != region_start &&
	    free_region_start < region_start)
		region_start -= PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;

	free_region_end = ALIGN_DOWN(free_region_end,
				     PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE);

	if (end != region_end &&
	    free_region_end > region_end)
		region_end += PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE;

	shadow_start = kasan_mem_to_shadow((void *)region_start);
	shadow_end = kasan_mem_to_shadow((void *)region_end);

	if (shadow_end > shadow_start) {
955
956
957
958
959
		size = shadow_end - shadow_start;
		apply_to_existing_page_range(&init_mm,
					     (unsigned long)shadow_start,
					     size, kasan_depopulate_vmalloc_pte,
					     NULL);
960
961
962
963
964
		flush_tlb_kernel_range((unsigned long)shadow_start,
				       (unsigned long)shadow_end);
	}
}
#endif