1/*
2 * This file contains error reporting code.
3 *
4 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
5 * Author: Andrey Ryabinin <a.ryabinin@samsung.com>
6 *
7 * Some of code borrowed from https://github.com/xairy/linux by
8 *        Andrey Konovalov <adech.fo@gmail.com>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 */
15
16#include <linux/kernel.h>
17#include <linux/mm.h>
18#include <linux/printk.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21#include <linux/stacktrace.h>
22#include <linux/string.h>
23#include <linux/types.h>
24#include <linux/kasan.h>
25
26#include <asm/sections.h>
27
28#include "kasan.h"
29#include "../slab.h"
30
31/* Shadow layout customization. */
32#define SHADOW_BYTES_PER_BLOCK 1
33#define SHADOW_BLOCKS_PER_ROW 16
34#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
35#define SHADOW_ROWS_AROUND_ADDR 2
36
37static const void *find_first_bad_addr(const void *addr, size_t size)
38{
39	u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
40	const void *first_bad_addr = addr;
41
42	while (!shadow_val && first_bad_addr < addr + size) {
43		first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
44		shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
45	}
46	return first_bad_addr;
47}
48
49static void print_error_description(struct kasan_access_info *info)
50{
51	const char *bug_type = "unknown crash";
52	u8 shadow_val;
53
54	info->first_bad_addr = find_first_bad_addr(info->access_addr,
55						info->access_size);
56
57	shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
58
59	switch (shadow_val) {
60	case KASAN_FREE_PAGE:
61	case KASAN_KMALLOC_FREE:
62		bug_type = "use after free";
63		break;
64	case KASAN_PAGE_REDZONE:
65	case KASAN_KMALLOC_REDZONE:
66	case KASAN_GLOBAL_REDZONE:
67	case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
68		bug_type = "out of bounds access";
69		break;
70	case KASAN_STACK_LEFT:
71	case KASAN_STACK_MID:
72	case KASAN_STACK_RIGHT:
73	case KASAN_STACK_PARTIAL:
74		bug_type = "out of bounds on stack";
75		break;
76	}
77
78	pr_err("BUG: KASan: %s in %pS at addr %p\n",
79		bug_type, (void *)info->ip,
80		info->access_addr);
81	pr_err("%s of size %zu by task %s/%d\n",
82		info->is_write ? "Write" : "Read",
83		info->access_size, current->comm, task_pid_nr(current));
84}
85
86static inline bool kernel_or_module_addr(const void *addr)
87{
88	return (addr >= (void *)_stext && addr < (void *)_end)
89		|| (addr >= (void *)MODULES_VADDR
90			&& addr < (void *)MODULES_END);
91}
92
93static inline bool init_task_stack_addr(const void *addr)
94{
95	return addr >= (void *)&init_thread_union.stack &&
96		(addr <= (void *)&init_thread_union.stack +
97			sizeof(init_thread_union.stack));
98}
99
100static void print_address_description(struct kasan_access_info *info)
101{
102	const void *addr = info->access_addr;
103
104	if ((addr >= (void *)PAGE_OFFSET) &&
105		(addr < high_memory)) {
106		struct page *page = virt_to_head_page(addr);
107
108		if (PageSlab(page)) {
109			void *object;
110			struct kmem_cache *cache = page->slab_cache;
111			void *last_object;
112
113			object = virt_to_obj(cache, page_address(page), addr);
114			last_object = page_address(page) +
115				page->objects * cache->size;
116
117			if (unlikely(object > last_object))
118				object = last_object; /* we hit into padding */
119
120			object_err(cache, page, object,
121				"kasan: bad access detected");
122			return;
123		}
124		dump_page(page, "kasan: bad access detected");
125	}
126
127	if (kernel_or_module_addr(addr)) {
128		if (!init_task_stack_addr(addr))
129			pr_err("Address belongs to variable %pS\n", addr);
130	}
131
132	dump_stack();
133}
134
135static bool row_is_guilty(const void *row, const void *guilty)
136{
137	return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
138}
139
140static int shadow_pointer_offset(const void *row, const void *shadow)
141{
142	/* The length of ">ff00ff00ff00ff00: " is
143	 *    3 + (BITS_PER_LONG/8)*2 chars.
144	 */
145	return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
146		(shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
147}
148
149static void print_shadow_for_address(const void *addr)
150{
151	int i;
152	const void *shadow = kasan_mem_to_shadow(addr);
153	const void *shadow_row;
154
155	shadow_row = (void *)round_down((unsigned long)shadow,
156					SHADOW_BYTES_PER_ROW)
157		- SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
158
159	pr_err("Memory state around the buggy address:\n");
160
161	for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
162		const void *kaddr = kasan_shadow_to_mem(shadow_row);
163		char buffer[4 + (BITS_PER_LONG/8)*2];
164
165		snprintf(buffer, sizeof(buffer),
166			(i == 0) ? ">%p: " : " %p: ", kaddr);
167
168		kasan_disable_current();
169		print_hex_dump(KERN_ERR, buffer,
170			DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
171			shadow_row, SHADOW_BYTES_PER_ROW, 0);
172		kasan_enable_current();
173
174		if (row_is_guilty(shadow_row, shadow))
175			pr_err("%*c\n",
176				shadow_pointer_offset(shadow_row, shadow),
177				'^');
178
179		shadow_row += SHADOW_BYTES_PER_ROW;
180	}
181}
182
183static DEFINE_SPINLOCK(report_lock);
184
185void kasan_report_error(struct kasan_access_info *info)
186{
187	unsigned long flags;
188
189	spin_lock_irqsave(&report_lock, flags);
190	pr_err("================================="
191		"=================================\n");
192	print_error_description(info);
193	print_address_description(info);
194	print_shadow_for_address(info->first_bad_addr);
195	pr_err("================================="
196		"=================================\n");
197	spin_unlock_irqrestore(&report_lock, flags);
198}
199
200void kasan_report_user_access(struct kasan_access_info *info)
201{
202	unsigned long flags;
203
204	spin_lock_irqsave(&report_lock, flags);
205	pr_err("================================="
206		"=================================\n");
207	pr_err("BUG: KASan: user-memory-access on address %p\n",
208		info->access_addr);
209	pr_err("%s of size %zu by task %s/%d\n",
210		info->is_write ? "Write" : "Read",
211		info->access_size, current->comm, task_pid_nr(current));
212	dump_stack();
213	pr_err("================================="
214		"=================================\n");
215	spin_unlock_irqrestore(&report_lock, flags);
216}
217
218void kasan_report(unsigned long addr, size_t size,
219		bool is_write, unsigned long ip)
220{
221	struct kasan_access_info info;
222
223	if (likely(!kasan_enabled()))
224		return;
225
226	info.access_addr = (void *)addr;
227	info.access_size = size;
228	info.is_write = is_write;
229	info.ip = ip;
230	kasan_report_error(&info);
231}
232
233
234#define DEFINE_ASAN_REPORT_LOAD(size)                     \
235void __asan_report_load##size##_noabort(unsigned long addr) \
236{                                                         \
237	kasan_report(addr, size, false, _RET_IP_);	  \
238}                                                         \
239EXPORT_SYMBOL(__asan_report_load##size##_noabort)
240
241#define DEFINE_ASAN_REPORT_STORE(size)                     \
242void __asan_report_store##size##_noabort(unsigned long addr) \
243{                                                          \
244	kasan_report(addr, size, true, _RET_IP_);	   \
245}                                                          \
246EXPORT_SYMBOL(__asan_report_store##size##_noabort)
247
248DEFINE_ASAN_REPORT_LOAD(1);
249DEFINE_ASAN_REPORT_LOAD(2);
250DEFINE_ASAN_REPORT_LOAD(4);
251DEFINE_ASAN_REPORT_LOAD(8);
252DEFINE_ASAN_REPORT_LOAD(16);
253DEFINE_ASAN_REPORT_STORE(1);
254DEFINE_ASAN_REPORT_STORE(2);
255DEFINE_ASAN_REPORT_STORE(4);
256DEFINE_ASAN_REPORT_STORE(8);
257DEFINE_ASAN_REPORT_STORE(16);
258
259void __asan_report_load_n_noabort(unsigned long addr, size_t size)
260{
261	kasan_report(addr, size, false, _RET_IP_);
262}
263EXPORT_SYMBOL(__asan_report_load_n_noabort);
264
265void __asan_report_store_n_noabort(unsigned long addr, size_t size)
266{
267	kasan_report(addr, size, true, _RET_IP_);
268}
269EXPORT_SYMBOL(__asan_report_store_n_noabort);
270