summaryrefslogtreecommitdiff
path: root/mm/kasan/generic.c
blob: a25ad40906154e35075c470a2ee86a1059763b26 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains core generic 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/interrupt.h>
#include <linux/init.h>
#include <linux/kasan.h>
#include <linux/kernel.h>
#include <linux/kfence.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>

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

/*
 * All functions below always inlined so compiler could
 * perform better optimizations in each of __asan_loadX/__assn_storeX
 * depending on memory access size X.
 */

static __always_inline bool memory_is_poisoned_1(unsigned long addr)
{
	s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);

	if (unlikely(shadow_value)) {
		s8 last_accessible_byte = addr & KASAN_GRANULE_MASK;
		return unlikely(last_accessible_byte >= shadow_value);
	}

	return false;
}

static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
						unsigned long size)
{
	u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);

	/*
	 * Access crosses 8(shadow size)-byte boundary. Such access maps
	 * into 2 shadow bytes, so we need to check them both.
	 */
	if (unlikely(((addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
		return *shadow_addr || memory_is_poisoned_1(addr + size - 1);

	return memory_is_poisoned_1(addr + size - 1);
}

static __always_inline bool memory_is_poisoned_16(unsigned long addr)
{
	u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);

	/* Unaligned 16-bytes access maps into 3 shadow bytes. */
	if (unlikely(!IS_ALIGNED(addr, KASAN_GRANULE_SIZE)))
		return *shadow_addr || memory_is_poisoned_1(addr + 15);

	return *shadow_addr;
}

static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
					size_t size)
{
	while (size) {
		if (unlikely(*start))
			return (unsigned long)start;
		start++;
		size--;
	}

	return 0;
}

static __always_inline unsigned long memory_is_nonzero(const void *start,
						const void *end)
{
	unsigned int words;
	unsigned long ret;
	unsigned int prefix = (unsigned long)start % 8;

	if (end - start <= 16)
		return bytes_is_nonzero(start, end - start);

	if (prefix) {
		prefix = 8 - prefix;
		ret = bytes_is_nonzero(start, prefix);
		if (unlikely(ret))
			return ret;
		start += prefix;
	}

	words = (end - start) / 8;
	while (words) {
		if (unlikely(*(u64 *)start))
			return bytes_is_nonzero(start, 8);
		start += 8;
		words--;
	}

	return bytes_is_nonzero(start, (end - start) % 8);
}

static __always_inline bool memory_is_poisoned_n(unsigned long addr,
						size_t size)
{
	unsigned long ret;

	ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
			kasan_mem_to_shadow((void *)addr + size - 1) + 1);

	if (unlikely(ret)) {
		unsigned long last_byte = addr + size - 1;
		s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);

		if (unlikely(ret != (unsigned long)last_shadow ||
			((long)(last_byte & KASAN_GRANULE_MASK) >= *last_shadow)))
			return true;
	}
	return false;
}

static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
{
	if (__builtin_constant_p(size)) {
		switch (size) {
		case 1:
			return memory_is_poisoned_1(addr);
		case 2:
		case 4:
		case 8:
			return memory_is_poisoned_2_4_8(addr, size);
		case 16:
			return memory_is_poisoned_16(addr);
		default:
			BUILD_BUG();
		}
	}

	return memory_is_poisoned_n(addr, size);
}

static __always_inline bool check_region_inline(unsigned long addr,
						size_t size, bool write,
						unsigned long ret_ip)
{
	if (!kasan_arch_is_ready())
		return true;

	if (unlikely(size == 0))
		return true;

	if (unlikely(addr + size < addr))
		return !kasan_report(addr, size, write, ret_ip);

	if (unlikely((void *)addr <
		kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
		return !kasan_report(addr, size, write, ret_ip);
	}

	if (likely(!memory_is_poisoned(addr, size)))
		return true;

	return !kasan_report(addr, size, write, ret_ip);
}

bool kasan_check_range(unsigned long addr, size_t size, bool write,
					unsigned long ret_ip)
{
	return check_region_inline(addr, size, write, ret_ip);
}

bool kasan_byte_accessible(const void *addr)
{
	s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));

	return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
}

void kasan_cache_shrink(struct kmem_cache *cache)
{
	kasan_quarantine_remove_cache(cache);
}

void kasan_cache_shutdown(struct kmem_cache *cache)
{
	if (!__kmem_cache_empty(cache))
		kasan_quarantine_remove_cache(cache);
}

static void register_global(struct kasan_global *global)
{
	size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);

	kasan_unpoison(global->beg, global->size, false);

	kasan_poison(global->beg + aligned_size,
		     global->size_with_redzone - aligned_size,
		     KASAN_GLOBAL_REDZONE, false);
}

void __asan_register_globals(struct kasan_global *globals, size_t size)
{
	int i;

	for (i = 0; i < size; i++)
		register_global(&globals[i]);
}
EXPORT_SYMBOL(__asan_register_globals);

void __asan_unregister_globals(struct kasan_global *globals, size_t size)
{
}
EXPORT_SYMBOL(__asan_unregister_globals);

#define DEFINE_ASAN_LOAD_STORE(size)					\
	void __asan_load##size(unsigned long addr)			\
	{								\
		check_region_inline(addr, size, false, _RET_IP_);	\
	}								\
	EXPORT_SYMBOL(__asan_load##size);				\
	__alias(__asan_load##size)					\
	void __asan_load##size##_noabort(unsigned long);		\
	EXPORT_SYMBOL(__asan_load##size##_noabort);			\
	void __asan_store##size(unsigned long addr)			\
	{								\
		check_region_inline(addr, size, true, _RET_IP_);	\
	}								\
	EXPORT_SYMBOL(__asan_store##size);				\
	__alias(__asan_store##size)					\
	void __asan_store##size##_noabort(unsigned long);		\
	EXPORT_SYMBOL(__asan_store##size##_noabort)

DEFINE_ASAN_LOAD_STORE(1);
DEFINE_ASAN_LOAD_STORE(2);
DEFINE_ASAN_LOAD_STORE(4);
DEFINE_ASAN_LOAD_STORE(8);
DEFINE_ASAN_LOAD_STORE(16);

void __asan_loadN(unsigned long addr, size_t size)
{
	kasan_check_range(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_loadN);

__alias(__asan_loadN)
void __asan_loadN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_loadN_noabort);

void __asan_storeN(unsigned long addr, size_t size)
{
	kasan_check_range(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_storeN);

__alias(__asan_storeN)
void __asan_storeN_noabort(unsigned long, size_t);
EXPORT_SYMBOL(__asan_storeN_noabort);

/* to shut up compiler complaints */
void __asan_handle_no_return(void) {}
EXPORT_SYMBOL(__asan_handle_no_return);

/* Emitted by compiler to poison alloca()ed objects. */
void __asan_alloca_poison(unsigned long addr, size_t size)
{
	size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
	size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
			rounded_up_size;
	size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);

	const void *left_redzone = (const void *)(addr -
			KASAN_ALLOCA_REDZONE_SIZE);
	const void *right_redzone = (const void *)(addr + rounded_up_size);

	WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));

	kasan_unpoison((const void *)(addr + rounded_down_size),
			size - rounded_down_size, false);
	kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
		     KASAN_ALLOCA_LEFT, false);
	kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
		     KASAN_ALLOCA_RIGHT, false);
}
EXPORT_SYMBOL(__asan_alloca_poison);

/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
{
	if (unlikely(!stack_top || stack_top > stack_bottom))
		return;

	kasan_unpoison(stack_top, stack_bottom - stack_top, false);
}
EXPORT_SYMBOL(__asan_allocas_unpoison);

/* Emitted by the compiler to [un]poison local variables. */
#define DEFINE_ASAN_SET_SHADOW(byte) \
	void __asan_set_shadow_##byte(const void *addr, size_t size)	\
	{								\
		__memset((void *)addr, 0x##byte, size);			\
	}								\
	EXPORT_SYMBOL(__asan_set_shadow_##byte)

DEFINE_ASAN_SET_SHADOW(00);
DEFINE_ASAN_SET_SHADOW(f1);
DEFINE_ASAN_SET_SHADOW(f2);
DEFINE_ASAN_SET_SHADOW(f3);
DEFINE_ASAN_SET_SHADOW(f5);
DEFINE_ASAN_SET_SHADOW(f8);

static void __kasan_record_aux_stack(void *addr, bool can_alloc)
{
	struct slab *slab = kasan_addr_to_slab(addr);
	struct kmem_cache *cache;
	struct kasan_alloc_meta *alloc_meta;
	void *object;

	if (is_kfence_address(addr) || !slab)
		return;

	cache = slab->slab_cache;
	object = nearest_obj(cache, slab, addr);
	alloc_meta = kasan_get_alloc_meta(cache, object);
	if (!alloc_meta)
		return;

	alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
	alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT, can_alloc);
}

void kasan_record_aux_stack(void *addr)
{
	return __kasan_record_aux_stack(addr, true);
}

void kasan_record_aux_stack_noalloc(void *addr)
{
	return __kasan_record_aux_stack(addr, false);
}

void kasan_set_free_info(struct kmem_cache *cache,
				void *object, u8 tag)
{
	struct kasan_free_meta *free_meta;

	free_meta = kasan_get_free_meta(cache, object);
	if (!free_meta)
		return;

	kasan_set_track(&free_meta->free_track, GFP_NOWAIT);
	/* The object was freed and has free track set. */
	*(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK;
}

struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
				void *object, u8 tag)
{
	if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK)
		return NULL;
	/* Free meta must be present with KASAN_KMALLOC_FREETRACK. */
	return &kasan_get_free_meta(cache, object)->free_track;
}