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1/*
2 * This file contains error reporting code.
3 *
4 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
6 *
7 * Some code borrowed from https://github.com/xairy/kasan-prototype 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/stackdepot.h>
22#include <linux/stacktrace.h>
23#include <linux/string.h>
24#include <linux/types.h>
25#include <linux/kasan.h>
26#include <linux/module.h>
27
28#include <asm/sections.h>
29
30#include "kasan.h"
31#include "../slab.h"
32
33/* Shadow layout customization. */
34#define SHADOW_BYTES_PER_BLOCK 1
35#define SHADOW_BLOCKS_PER_ROW 16
36#define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
37#define SHADOW_ROWS_AROUND_ADDR 2
38
39static const void *find_first_bad_addr(const void *addr, size_t size)
40{
41 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
42 const void *first_bad_addr = addr;
43
44 while (!shadow_val && first_bad_addr < addr + size) {
45 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
46 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
47 }
48 return first_bad_addr;
49}
50
51static void print_error_description(struct kasan_access_info *info)
52{
53 const char *bug_type = "unknown-crash";
54 u8 *shadow_addr;
55
56 info->first_bad_addr = find_first_bad_addr(info->access_addr,
57 info->access_size);
58
59 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
60
61 /*
62 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
63 * at the next shadow byte to determine the type of the bad access.
64 */
65 if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
66 shadow_addr++;
67
68 switch (*shadow_addr) {
69 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
70 /*
71 * In theory it's still possible to see these shadow values
72 * due to a data race in the kernel code.
73 */
74 bug_type = "out-of-bounds";
75 break;
76 case KASAN_PAGE_REDZONE:
77 case KASAN_KMALLOC_REDZONE:
78 bug_type = "slab-out-of-bounds";
79 break;
80 case KASAN_GLOBAL_REDZONE:
81 bug_type = "global-out-of-bounds";
82 break;
83 case KASAN_STACK_LEFT:
84 case KASAN_STACK_MID:
85 case KASAN_STACK_RIGHT:
86 case KASAN_STACK_PARTIAL:
87 bug_type = "stack-out-of-bounds";
88 break;
89 case KASAN_FREE_PAGE:
90 case KASAN_KMALLOC_FREE:
91 bug_type = "use-after-free";
92 break;
93 }
94
95 pr_err("BUG: KASAN: %s in %pS at addr %p\n",
96 bug_type, (void *)info->ip,
97 info->access_addr);
98 pr_err("%s of size %zu by task %s/%d\n",
99 info->is_write ? "Write" : "Read",
100 info->access_size, current->comm, task_pid_nr(current));
101}
102
103static inline bool kernel_or_module_addr(const void *addr)
104{
105 if (addr >= (void *)_stext && addr < (void *)_end)
106 return true;
107 if (is_module_address((unsigned long)addr))
108 return true;
109 return false;
110}
111
112static inline bool init_task_stack_addr(const void *addr)
113{
114 return addr >= (void *)&init_thread_union.stack &&
115 (addr <= (void *)&init_thread_union.stack +
116 sizeof(init_thread_union.stack));
117}
118
119#ifdef CONFIG_SLAB
120static void print_track(struct kasan_track *track)
121{
122 pr_err("PID = %u\n", track->pid);
123 if (track->stack) {
124 struct stack_trace trace;
125
126 depot_fetch_stack(track->stack, &trace);
127 print_stack_trace(&trace, 0);
128 } else {
129 pr_err("(stack is not available)\n");
130 }
131}
132
133static void object_err(struct kmem_cache *cache, struct page *page,
134 void *object, char *unused_reason)
135{
136 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
137 struct kasan_free_meta *free_info;
138
139 dump_stack();
140 pr_err("Object at %p, in cache %s\n", object, cache->name);
141 if (!(cache->flags & SLAB_KASAN))
142 return;
143 switch (alloc_info->state) {
144 case KASAN_STATE_INIT:
145 pr_err("Object not allocated yet\n");
146 break;
147 case KASAN_STATE_ALLOC:
148 pr_err("Object allocated with size %u bytes.\n",
149 alloc_info->alloc_size);
150 pr_err("Allocation:\n");
151 print_track(&alloc_info->track);
152 break;
153 case KASAN_STATE_FREE:
154 pr_err("Object freed, allocated with size %u bytes\n",
155 alloc_info->alloc_size);
156 free_info = get_free_info(cache, object);
157 pr_err("Allocation:\n");
158 print_track(&alloc_info->track);
159 pr_err("Deallocation:\n");
160 print_track(&free_info->track);
161 break;
162 }
163}
164#endif
165
166static void print_address_description(struct kasan_access_info *info)
167{
168 const void *addr = info->access_addr;
169
170 if ((addr >= (void *)PAGE_OFFSET) &&
171 (addr < high_memory)) {
172 struct page *page = virt_to_head_page(addr);
173
174 if (PageSlab(page)) {
175 void *object;
176 struct kmem_cache *cache = page->slab_cache;
177 object = nearest_obj(cache, page,
178 (void *)info->access_addr);
179 object_err(cache, page, object,
180 "kasan: bad access detected");
181 return;
182 }
183 dump_page(page, "kasan: bad access detected");
184 }
185
186 if (kernel_or_module_addr(addr)) {
187 if (!init_task_stack_addr(addr))
188 pr_err("Address belongs to variable %pS\n", addr);
189 }
190 dump_stack();
191}
192
193static bool row_is_guilty(const void *row, const void *guilty)
194{
195 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
196}
197
198static int shadow_pointer_offset(const void *row, const void *shadow)
199{
200 /* The length of ">ff00ff00ff00ff00: " is
201 * 3 + (BITS_PER_LONG/8)*2 chars.
202 */
203 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
204 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
205}
206
207static void print_shadow_for_address(const void *addr)
208{
209 int i;
210 const void *shadow = kasan_mem_to_shadow(addr);
211 const void *shadow_row;
212
213 shadow_row = (void *)round_down((unsigned long)shadow,
214 SHADOW_BYTES_PER_ROW)
215 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
216
217 pr_err("Memory state around the buggy address:\n");
218
219 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
220 const void *kaddr = kasan_shadow_to_mem(shadow_row);
221 char buffer[4 + (BITS_PER_LONG/8)*2];
222 char shadow_buf[SHADOW_BYTES_PER_ROW];
223
224 snprintf(buffer, sizeof(buffer),
225 (i == 0) ? ">%p: " : " %p: ", kaddr);
226 /*
227 * We should not pass a shadow pointer to generic
228 * function, because generic functions may try to
229 * access kasan mapping for the passed address.
230 */
231 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
232 print_hex_dump(KERN_ERR, buffer,
233 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
234 shadow_buf, SHADOW_BYTES_PER_ROW, 0);
235
236 if (row_is_guilty(shadow_row, shadow))
237 pr_err("%*c\n",
238 shadow_pointer_offset(shadow_row, shadow),
239 '^');
240
241 shadow_row += SHADOW_BYTES_PER_ROW;
242 }
243}
244
245static DEFINE_SPINLOCK(report_lock);
246
247static void kasan_report_error(struct kasan_access_info *info)
248{
249 unsigned long flags;
250 const char *bug_type;
251
252 /*
253 * Make sure we don't end up in loop.
254 */
255 kasan_disable_current();
256 spin_lock_irqsave(&report_lock, flags);
257 pr_err("==================================================================\n");
258 if (info->access_addr <
259 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
260 if ((unsigned long)info->access_addr < PAGE_SIZE)
261 bug_type = "null-ptr-deref";
262 else if ((unsigned long)info->access_addr < TASK_SIZE)
263 bug_type = "user-memory-access";
264 else
265 bug_type = "wild-memory-access";
266 pr_err("BUG: KASAN: %s on address %p\n",
267 bug_type, info->access_addr);
268 pr_err("%s of size %zu by task %s/%d\n",
269 info->is_write ? "Write" : "Read",
270 info->access_size, current->comm,
271 task_pid_nr(current));
272 dump_stack();
273 } else {
274 print_error_description(info);
275 print_address_description(info);
276 print_shadow_for_address(info->first_bad_addr);
277 }
278 pr_err("==================================================================\n");
279 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
280 spin_unlock_irqrestore(&report_lock, flags);
281 kasan_enable_current();
282}
283
284void kasan_report(unsigned long addr, size_t size,
285 bool is_write, unsigned long ip)
286{
287 struct kasan_access_info info;
288
289 if (likely(!kasan_report_enabled()))
290 return;
291
292 info.access_addr = (void *)addr;
293 info.access_size = size;
294 info.is_write = is_write;
295 info.ip = ip;
296
297 kasan_report_error(&info);
298}
299
300
301#define DEFINE_ASAN_REPORT_LOAD(size) \
302void __asan_report_load##size##_noabort(unsigned long addr) \
303{ \
304 kasan_report(addr, size, false, _RET_IP_); \
305} \
306EXPORT_SYMBOL(__asan_report_load##size##_noabort)
307
308#define DEFINE_ASAN_REPORT_STORE(size) \
309void __asan_report_store##size##_noabort(unsigned long addr) \
310{ \
311 kasan_report(addr, size, true, _RET_IP_); \
312} \
313EXPORT_SYMBOL(__asan_report_store##size##_noabort)
314
315DEFINE_ASAN_REPORT_LOAD(1);
316DEFINE_ASAN_REPORT_LOAD(2);
317DEFINE_ASAN_REPORT_LOAD(4);
318DEFINE_ASAN_REPORT_LOAD(8);
319DEFINE_ASAN_REPORT_LOAD(16);
320DEFINE_ASAN_REPORT_STORE(1);
321DEFINE_ASAN_REPORT_STORE(2);
322DEFINE_ASAN_REPORT_STORE(4);
323DEFINE_ASAN_REPORT_STORE(8);
324DEFINE_ASAN_REPORT_STORE(16);
325
326void __asan_report_load_n_noabort(unsigned long addr, size_t size)
327{
328 kasan_report(addr, size, false, _RET_IP_);
329}
330EXPORT_SYMBOL(__asan_report_load_n_noabort);
331
332void __asan_report_store_n_noabort(unsigned long addr, size_t size)
333{
334 kasan_report(addr, size, true, _RET_IP_);
335}
336EXPORT_SYMBOL(__asan_report_store_n_noabort);