summaryrefslogtreecommitdiffstats
path: root/mm/kasan/common.c
blob: b5e08d4cefecc0effdef84544f94357a2963341c (plain)
1
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
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
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
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
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
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
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
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains common 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>
 */

#include <linux/export.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.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/bug.h>

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

depot_stack_handle_t kasan_save_stack(gfp_t flags)
{
	unsigned long entries[KASAN_STACK_DEPTH];
	unsigned int nr_entries;

	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);
}

void kasan_set_track(struct kasan_track *track, gfp_t flags)
{
	track->pid = current->pid;
	track->stack = kasan_save_stack(flags);
}

#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
void kasan_enable_current(void)
{
	current->kasan_depth++;
}

void kasan_disable_current(void)
{
	current->kasan_depth--;
}
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */

void __kasan_unpoison_range(const void *address, size_t size)
{
	kasan_unpoison(address, size);
}

#if CONFIG_KASAN_STACK
/* Unpoison the entire stack for a task. */
void kasan_unpoison_task_stack(struct task_struct *task)
{
	void *base = task_stack_page(task);

	kasan_unpoison(base, 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(base, watermark - base);
}
#endif /* CONFIG_KASAN_STACK */

/*
 * Only allow cache merging when stack collection is disabled and no metadata
 * is present.
 */
slab_flags_t __kasan_never_merge(void)
{
	if (kasan_stack_collection_enabled())
		return SLAB_KASAN;
	return 0;
}

void __kasan_alloc_pages(struct page *page, unsigned int order)
{
	u8 tag;
	unsigned long i;

	if (unlikely(PageHighMem(page)))
		return;

	tag = kasan_random_tag();
	for (i = 0; i < (1 << order); i++)
		page_kasan_tag_set(page + i, tag);
	kasan_unpoison(page_address(page), PAGE_SIZE << order);
}

void __kasan_free_pages(struct page *page, unsigned int order)
{
	if (likely(!PageHighMem(page)))
		kasan_poison(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)
{
	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 ok_size;
	unsigned int optimal_size;

	/*
	 * SLAB_KASAN is used to mark caches as ones that are sanitized by
	 * KASAN. Currently this flag is used in two places:
	 * 1. In slab_ksize() when calculating the size of the accessible
	 *    memory within the object.
	 * 2. In slab_common.c to prevent merging of sanitized caches.
	 */
	*flags |= SLAB_KASAN;

	if (!kasan_stack_collection_enabled())
		return;

	ok_size = *size;

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

	/*
	 * If alloc meta doesn't fit, don't add it.
	 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
	 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
	 * larger sizes.
	 */
	if (*size > KMALLOC_MAX_SIZE) {
		cache->kasan_info.alloc_meta_offset = 0;
		*size = ok_size;
		/* Continue, since free meta might still fit. */
	}

	/* Only the generic mode uses free meta or flexible redzones. */
	if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
		cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
		return;
	}

	/*
	 * Add free meta into redzone when it's not possible to store
	 * it in the object. This is the case when:
	 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
	 *    be touched after it was freed, or
	 * 2. Object has a constructor, which means it's expected to
	 *    retain its content until the next allocation, or
	 * 3. Object is too small.
	 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
	 */
	if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
	    cache->object_size < sizeof(struct kasan_free_meta)) {
		ok_size = *size;

		cache->kasan_info.free_meta_offset = *size;
		*size += sizeof(struct kasan_free_meta);

		/* If free meta doesn't fit, don't add it. */
		if (*size > KMALLOC_MAX_SIZE) {
			cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
			*size = ok_size;
		}
	}

	/* Calculate size with optimal redzone. */
	optimal_size = cache->object_size + optimal_redzone(cache->object_size);
	/* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
	if (optimal_size > KMALLOC_MAX_SIZE)
		optimal_size = KMALLOC_MAX_SIZE;
	/* Use optimal size if the size with added metas is not large enough. */
	if (*size < optimal_size)
		*size = optimal_size;
}

void __kasan_cache_create_kmalloc(struct kmem_cache *cache)
{
	cache->kasan_info.is_kmalloc = true;
}

size_t __kasan_metadata_size(struct kmem_cache *cache)
{
	if (!kasan_stack_collection_enabled())
		return 0;
	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 *kasan_get_alloc_meta(struct kmem_cache *cache,
					      const void *object)
{
	if (!cache->kasan_info.alloc_meta_offset)
		return NULL;
	return kasan_reset_tag(object) + cache->kasan_info.alloc_meta_offset;
}

#ifdef CONFIG_KASAN_GENERIC
struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
					    const void *object)
{
	BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
	if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
		return NULL;
	return kasan_reset_tag(object) + cache->kasan_info.free_meta_offset;
}
#endif

void __kasan_poison_slab(struct page *page)
{
	unsigned long i;

	for (i = 0; i < compound_nr(page); i++)
		page_kasan_tag_reset(page + i);
	kasan_poison(page_address(page), page_size(page),
		     KASAN_KMALLOC_REDZONE);
}

void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
{
	kasan_unpoison(object, cache->object_size);
}

void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
{
	kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
			KASAN_KMALLOC_REDZONE);
}

/*
 * 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.
 */
static inline u8 assign_tag(struct kmem_cache *cache,
					const void *object, bool init)
{
	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
		return 0xff;

	/*
	 * 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).
	 */
	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
		return init ? KASAN_TAG_KERNEL : kasan_random_tag();

	/* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
#ifdef CONFIG_SLAB
	/* For SLAB assign tags based on the object index in the freelist. */
	return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
#else
	/*
	 * For SLUB assign a random tag during slab creation, otherwise reuse
	 * the already assigned tag.
	 */
	return init ? kasan_random_tag() : get_tag(object);
#endif
}

void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
						const void *object)
{
	struct kasan_alloc_meta *alloc_meta;

	if (kasan_stack_collection_enabled()) {
		alloc_meta = kasan_get_alloc_meta(cache, object);
		if (alloc_meta)
			__memset(alloc_meta, 0, sizeof(*alloc_meta));
	}

	/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
	object = set_tag(object, assign_tag(cache, object, true));

	return (void *)object;
}

static inline bool ____kasan_slab_free(struct kmem_cache *cache,
				void *object, unsigned long ip, bool quarantine)
{
	u8 tag;
	void *tagged_object;

	tag = get_tag(object);
	tagged_object = object;
	object = kasan_reset_tag(object);

	if (is_kfence_address(object))
		return false;

	if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
	    object)) {
		kasan_report_invalid_free(tagged_object, ip);
		return true;
	}

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

	if (!kasan_byte_accessible(tagged_object)) {
		kasan_report_invalid_free(tagged_object, ip);
		return true;
	}

	kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
			KASAN_KMALLOC_FREE);

	if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
		return false;

	if (kasan_stack_collection_enabled())
		kasan_set_free_info(cache, object, tag);

	return kasan_quarantine_put(cache, object);
}

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

static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)
{
	if (ptr != page_address(virt_to_head_page(ptr))) {
		kasan_report_invalid_free(ptr, ip);
		return true;
	}

	if (!kasan_byte_accessible(ptr)) {
		kasan_report_invalid_free(ptr, ip);
		return true;
	}

	/*
	 * The object will be poisoned by kasan_free_pages() or
	 * kasan_slab_free_mempool().
	 */

	return false;
}

void __kasan_kfree_large(void *ptr, unsigned long ip)
{
	____kasan_kfree_large(ptr, ip);
}

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

	page = virt_to_head_page(ptr);

	/*
	 * Even though this function is only called for kmem_cache_alloc and
	 * kmalloc backed mempool allocations, those allocations can still be
	 * !PageSlab() when the size provided to kmalloc is larger than
	 * KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
	 */
	if (unlikely(!PageSlab(page))) {
		if (____kasan_kfree_large(ptr, ip))
			return;
		kasan_poison(ptr, page_size(page), KASAN_FREE_PAGE);
	} else {
		____kasan_slab_free(page->slab_cache, ptr, ip, false);
	}
}

static void set_alloc_info(struct kmem_cache *cache, void *object,
				gfp_t flags, bool is_kmalloc)
{
	struct kasan_alloc_meta *alloc_meta;

	/* Don't save alloc info for kmalloc caches in kasan_slab_alloc(). */
	if (cache->kasan_info.is_kmalloc && !is_kmalloc)
		return;

	alloc_meta = kasan_get_alloc_meta(cache, object);
	if (alloc_meta)
		kasan_set_track(&alloc_meta->alloc_track, flags);
}

void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
					void *object, gfp_t flags)
{
	u8 tag;
	void *tagged_object;

	if (gfpflags_allow_blocking(flags))
		kasan_quarantine_reduce();

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

	if (is_kfence_address(object))
		return (void *)object;

	/*
	 * Generate and assign random tag for tag-based modes.
	 * Tag is ignored in set_tag() for the generic mode.
	 */
	tag = assign_tag(cache, object, false);
	tagged_object = set_tag(object, tag);

	/*
	 * Unpoison the whole object.
	 * For kmalloc() allocations, kasan_kmalloc() will do precise poisoning.
	 */
	kasan_unpoison(tagged_object, cache->object_size);

	/* Save alloc info (if possible) for non-kmalloc() allocations. */
	if (kasan_stack_collection_enabled())
		set_alloc_info(cache, (void *)object, flags, false);

	return tagged_object;
}

static inline void *____kasan_kmalloc(struct kmem_cache *cache,
				const void *object, size_t size, gfp_t flags)
{
	unsigned long redzone_start;
	unsigned long redzone_end;

	if (gfpflags_allow_blocking(flags))
		kasan_quarantine_reduce();

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

	if (is_kfence_address(kasan_reset_tag(object)))
		return (void *)object;

	/*
	 * The object has already been unpoisoned by kasan_slab_alloc() for
	 * kmalloc() or by kasan_krealloc() for krealloc().
	 */

	/*
	 * The redzone has byte-level precision for the generic mode.
	 * Partially poison the last object granule to cover the unaligned
	 * part of the redzone.
	 */
	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
		kasan_poison_last_granule((void *)object, size);

	/* Poison the aligned part of the redzone. */
	redzone_start = round_up((unsigned long)(object + size),
				KASAN_GRANULE_SIZE);
	redzone_end = round_up((unsigned long)(object + cache->object_size),
				KASAN_GRANULE_SIZE);
	kasan_poison((void *)redzone_start, redzone_end - redzone_start,
			   KASAN_KMALLOC_REDZONE);

	/*
	 * Save alloc info (if possible) for kmalloc() allocations.
	 * This also rewrites the alloc info when called from kasan_krealloc().
	 */
	if (kasan_stack_collection_enabled())
		set_alloc_info(cache, (void *)object, flags, true);

	/* Keep the tag that was set by kasan_slab_alloc(). */
	return (void *)object;
}

void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
					size_t size, gfp_t flags)
{
	return ____kasan_kmalloc(cache, object, size, flags);
}
EXPORT_SYMBOL(__kasan_kmalloc);

void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
						gfp_t flags)
{
	unsigned long redzone_start;
	unsigned long redzone_end;

	if (gfpflags_allow_blocking(flags))
		kasan_quarantine_reduce();

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

	/*
	 * The object has already been unpoisoned by kasan_alloc_pages() for
	 * alloc_pages() or by kasan_krealloc() for krealloc().
	 */

	/*
	 * The redzone has byte-level precision for the generic mode.
	 * Partially poison the last object granule to cover the unaligned
	 * part of the redzone.
	 */
	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
		kasan_poison_last_granule(ptr, size);

	/* Poison the aligned part of the redzone. */
	redzone_start = round_up((unsigned long)(ptr + size),
				KASAN_GRANULE_SIZE);
	redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
	kasan_poison((void *)redzone_start, redzone_end - redzone_start,
		     KASAN_PAGE_REDZONE);

	return (void *)ptr;
}

void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
{
	struct page *page;

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

	/*
	 * Unpoison the object's data.
	 * Part of it might already have been unpoisoned, but it's unknown
	 * how big that part is.
	 */
	kasan_unpoison(object, size);

	page = virt_to_head_page(object);

	/* Piggy-back on kmalloc() instrumentation to poison the redzone. */
	if (unlikely(!PageSlab(page)))
		return __kasan_kmalloc_large(object, size, flags);
	else
		return ____kasan_kmalloc(page->slab_cache, object, size, flags);
}

bool __kasan_check_byte(const void *address, unsigned long ip)
{
	if (!kasan_byte_accessible(address)) {
		kasan_report((unsigned long)address, 1, false, ip);
		return false;
	}
	return true;
}