summaryrefslogtreecommitdiff
path: root/mm/kasan/report.c
blob: 8efc69473a37ad67675316e61888de73e006ab08 (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
/*
 * This file contains error reporting 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 <adech.fo@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/bitops.h>
#include <linux/ftrace.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/printk.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/stackdepot.h>
#include <linux/stacktrace.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/kasan.h>
#include <linux/module.h>

#include <asm/sections.h>

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

/* Shadow layout customization. */
#define SHADOW_BYTES_PER_BLOCK 1
#define SHADOW_BLOCKS_PER_ROW 16
#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
#define SHADOW_ROWS_AROUND_ADDR 2

static const void *find_first_bad_addr(const void *addr, size_t size)
{
	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
	const void *first_bad_addr = addr;

	while (!shadow_val && first_bad_addr < addr + size) {
		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
	}
	return first_bad_addr;
}

static bool addr_has_shadow(struct kasan_access_info *info)
{
	return (info->access_addr >=
		kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
}

static const char *get_shadow_bug_type(struct kasan_access_info *info)
{
	const char *bug_type = "unknown-crash";
	u8 *shadow_addr;

	info->first_bad_addr = find_first_bad_addr(info->access_addr,
						info->access_size);

	shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);

	/*
	 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
	 * at the next shadow byte to determine the type of the bad access.
	 */
	if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
		shadow_addr++;

	switch (*shadow_addr) {
	case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
		/*
		 * In theory it's still possible to see these shadow values
		 * due to a data race in the kernel code.
		 */
		bug_type = "out-of-bounds";
		break;
	case KASAN_PAGE_REDZONE:
	case KASAN_KMALLOC_REDZONE:
		bug_type = "slab-out-of-bounds";
		break;
	case KASAN_GLOBAL_REDZONE:
		bug_type = "global-out-of-bounds";
		break;
	case KASAN_STACK_LEFT:
	case KASAN_STACK_MID:
	case KASAN_STACK_RIGHT:
	case KASAN_STACK_PARTIAL:
		bug_type = "stack-out-of-bounds";
		break;
	case KASAN_FREE_PAGE:
	case KASAN_KMALLOC_FREE:
		bug_type = "use-after-free";
		break;
	case KASAN_USE_AFTER_SCOPE:
		bug_type = "use-after-scope";
		break;
	}

	return bug_type;
}

const char *get_wild_bug_type(struct kasan_access_info *info)
{
	const char *bug_type = "unknown-crash";

	if ((unsigned long)info->access_addr < PAGE_SIZE)
		bug_type = "null-ptr-deref";
	else if ((unsigned long)info->access_addr < TASK_SIZE)
		bug_type = "user-memory-access";
	else
		bug_type = "wild-memory-access";

	return bug_type;
}

static const char *get_bug_type(struct kasan_access_info *info)
{
	if (addr_has_shadow(info))
		return get_shadow_bug_type(info);
	return get_wild_bug_type(info);
}

static void print_error_description(struct kasan_access_info *info)
{
	const char *bug_type = get_bug_type(info);

	pr_err("BUG: KASAN: %s in %pS\n",
		bug_type, (void *)info->ip);
	pr_err("%s of size %zu at addr %p by task %s/%d\n",
		info->is_write ? "Write" : "Read", info->access_size,
		info->access_addr, current->comm, task_pid_nr(current));
}

static inline bool kernel_or_module_addr(const void *addr)
{
	if (addr >= (void *)_stext && addr < (void *)_end)
		return true;
	if (is_module_address((unsigned long)addr))
		return true;
	return false;
}

static inline bool init_task_stack_addr(const void *addr)
{
	return addr >= (void *)&init_thread_union.stack &&
		(addr <= (void *)&init_thread_union.stack +
			sizeof(init_thread_union.stack));
}

static DEFINE_SPINLOCK(report_lock);

static void kasan_start_report(unsigned long *flags)
{
	/*
	 * Make sure we don't end up in loop.
	 */
	kasan_disable_current();
	spin_lock_irqsave(&report_lock, *flags);
	pr_err("==================================================================\n");
}

static void kasan_end_report(unsigned long *flags)
{
	pr_err("==================================================================\n");
	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
	spin_unlock_irqrestore(&report_lock, *flags);
	if (panic_on_warn)
		panic("panic_on_warn set ...\n");
	kasan_enable_current();
}

static void print_track(struct kasan_track *track, const char *prefix)
{
	pr_err("%s by task %u:\n", prefix, track->pid);
	if (track->stack) {
		struct stack_trace trace;

		depot_fetch_stack(track->stack, &trace);
		print_stack_trace(&trace, 0);
	} else {
		pr_err("(stack is not available)\n");
	}
}

static struct page *addr_to_page(const void *addr)
{
	if ((addr >= (void *)PAGE_OFFSET) &&
			(addr < high_memory))
		return virt_to_head_page(addr);
	return NULL;
}

static void describe_object(struct kmem_cache *cache, void *object)
{
	struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);

	pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
		cache->object_size);

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

	print_track(&alloc_info->alloc_track, "Allocated");
	print_track(&alloc_info->free_track, "Freed");
}

void kasan_report_double_free(struct kmem_cache *cache, void *object,
			s8 shadow)
{
	unsigned long flags;

	kasan_start_report(&flags);
	pr_err("BUG: Double free or freeing an invalid pointer\n");
	pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
	dump_stack();
	describe_object(cache, object);
	kasan_end_report(&flags);
}

static void print_address_description(struct kasan_access_info *info)
{
	const void *addr = info->access_addr;
	struct page *page = addr_to_page(addr);

	if (page)
		dump_page(page, "kasan: bad access detected");

	dump_stack();

	if (page && PageSlab(page)) {
		struct kmem_cache *cache = page->slab_cache;
		void *object = nearest_obj(cache, page,	(void *)addr);

		describe_object(cache, object);
	}

	if (kernel_or_module_addr(addr)) {
		if (!init_task_stack_addr(addr))
			pr_err("Address belongs to variable %pS\n", addr);
	}
}

static bool row_is_guilty(const void *row, const void *guilty)
{
	return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
}

static int shadow_pointer_offset(const void *row, const void *shadow)
{
	/* The length of ">ff00ff00ff00ff00: " is
	 *    3 + (BITS_PER_LONG/8)*2 chars.
	 */
	return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
		(shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
}

static void print_shadow_for_address(const void *addr)
{
	int i;
	const void *shadow = kasan_mem_to_shadow(addr);
	const void *shadow_row;

	shadow_row = (void *)round_down((unsigned long)shadow,
					SHADOW_BYTES_PER_ROW)
		- SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;

	pr_err("Memory state around the buggy address:\n");

	for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
		const void *kaddr = kasan_shadow_to_mem(shadow_row);
		char buffer[4 + (BITS_PER_LONG/8)*2];
		char shadow_buf[SHADOW_BYTES_PER_ROW];

		snprintf(buffer, sizeof(buffer),
			(i == 0) ? ">%p: " : " %p: ", kaddr);
		/*
		 * We should not pass a shadow pointer to generic
		 * function, because generic functions may try to
		 * access kasan mapping for the passed address.
		 */
		memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
		print_hex_dump(KERN_ERR, buffer,
			DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
			shadow_buf, SHADOW_BYTES_PER_ROW, 0);

		if (row_is_guilty(shadow_row, shadow))
			pr_err("%*c\n",
				shadow_pointer_offset(shadow_row, shadow),
				'^');

		shadow_row += SHADOW_BYTES_PER_ROW;
	}
}

static void kasan_report_error(struct kasan_access_info *info)
{
	unsigned long flags;

	kasan_start_report(&flags);

	print_error_description(info);

	if (!addr_has_shadow(info)) {
		dump_stack();
	} else {
		print_address_description(info);
		print_shadow_for_address(info->first_bad_addr);
	}

	kasan_end_report(&flags);
}

static unsigned long kasan_flags;

#define KASAN_BIT_REPORTED	0
#define KASAN_BIT_MULTI_SHOT	1

bool kasan_save_enable_multi_shot(void)
{
	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);

void kasan_restore_multi_shot(bool enabled)
{
	if (!enabled)
		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
}
EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);

static int __init kasan_set_multi_shot(char *str)
{
	set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
	return 1;
}
__setup("kasan_multi_shot", kasan_set_multi_shot);

static inline bool kasan_report_enabled(void)
{
	if (current->kasan_depth)
		return false;
	if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
		return true;
	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
}

void kasan_report(unsigned long addr, size_t size,
		bool is_write, unsigned long ip)
{
	struct kasan_access_info info;

	if (likely(!kasan_report_enabled()))
		return;

	disable_trace_on_warning();

	info.access_addr = (void *)addr;
	info.access_size = size;
	info.is_write = is_write;
	info.ip = ip;

	kasan_report_error(&info);
}


#define DEFINE_ASAN_REPORT_LOAD(size)                     \
void __asan_report_load##size##_noabort(unsigned long addr) \
{                                                         \
	kasan_report(addr, size, false, _RET_IP_);	  \
}                                                         \
EXPORT_SYMBOL(__asan_report_load##size##_noabort)

#define DEFINE_ASAN_REPORT_STORE(size)                     \
void __asan_report_store##size##_noabort(unsigned long addr) \
{                                                          \
	kasan_report(addr, size, true, _RET_IP_);	   \
}                                                          \
EXPORT_SYMBOL(__asan_report_store##size##_noabort)

DEFINE_ASAN_REPORT_LOAD(1);
DEFINE_ASAN_REPORT_LOAD(2);
DEFINE_ASAN_REPORT_LOAD(4);
DEFINE_ASAN_REPORT_LOAD(8);
DEFINE_ASAN_REPORT_LOAD(16);
DEFINE_ASAN_REPORT_STORE(1);
DEFINE_ASAN_REPORT_STORE(2);
DEFINE_ASAN_REPORT_STORE(4);
DEFINE_ASAN_REPORT_STORE(8);
DEFINE_ASAN_REPORT_STORE(16);

void __asan_report_load_n_noabort(unsigned long addr, size_t size)
{
	kasan_report(addr, size, false, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_load_n_noabort);

void __asan_report_store_n_noabort(unsigned long addr, size_t size)
{
	kasan_report(addr, size, true, _RET_IP_);
}
EXPORT_SYMBOL(__asan_report_store_n_noabort);