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1/*
2 * This file contains error reporting code.
3 *
4 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
2baf9e89 5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
0b24becc 6 *
5d0926ef 7 * Some code borrowed from https://github.com/xairy/kasan-prototype by
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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>
cd11016e 21#include <linux/stackdepot.h>
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22#include <linux/stacktrace.h>
23#include <linux/string.h>
24#include <linux/types.h>
25#include <linux/kasan.h>
527f215b 26#include <linux/module.h>
0b24becc 27
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28#include <asm/sections.h>
29
0b24becc 30#include "kasan.h"
0316bec2 31#include "../slab.h"
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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{
0952d87f 53 const char *bug_type = "unknown-crash";
cdf6a273 54 u8 *shadow_addr;
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55
56 info->first_bad_addr = find_first_bad_addr(info->access_addr,
57 info->access_size);
58
cdf6a273 59 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
0b24becc 60
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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) {
0952d87f 69 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
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70 /*
71 * In theory it's still possible to see these shadow values
72 * due to a data race in the kernel code.
73 */
0952d87f 74 bug_type = "out-of-bounds";
b8c73fc2 75 break;
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76 case KASAN_PAGE_REDZONE:
77 case KASAN_KMALLOC_REDZONE:
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78 bug_type = "slab-out-of-bounds";
79 break;
bebf56a1 80 case KASAN_GLOBAL_REDZONE:
0952d87f 81 bug_type = "global-out-of-bounds";
0b24becc 82 break;
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83 case KASAN_STACK_LEFT:
84 case KASAN_STACK_MID:
85 case KASAN_STACK_RIGHT:
86 case KASAN_STACK_PARTIAL:
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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";
c420f167 92 break;
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93 case KASAN_USE_AFTER_SCOPE:
94 bug_type = "use-after-scope";
95 break;
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96 }
97
25add7ec 98 pr_err("BUG: KASAN: %s in %pS at addr %p\n",
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99 bug_type, (void *)info->ip,
100 info->access_addr);
101 pr_err("%s of size %zu by task %s/%d\n",
102 info->is_write ? "Write" : "Read",
103 info->access_size, current->comm, task_pid_nr(current));
104}
105
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106static inline bool kernel_or_module_addr(const void *addr)
107{
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108 if (addr >= (void *)_stext && addr < (void *)_end)
109 return true;
110 if (is_module_address((unsigned long)addr))
111 return true;
112 return false;
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113}
114
115static inline bool init_task_stack_addr(const void *addr)
116{
117 return addr >= (void *)&init_thread_union.stack &&
118 (addr <= (void *)&init_thread_union.stack +
119 sizeof(init_thread_union.stack));
120}
121
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122static DEFINE_SPINLOCK(report_lock);
123
124static void kasan_start_report(unsigned long *flags)
125{
126 /*
127 * Make sure we don't end up in loop.
128 */
129 kasan_disable_current();
130 spin_lock_irqsave(&report_lock, *flags);
131 pr_err("==================================================================\n");
132}
133
134static void kasan_end_report(unsigned long *flags)
135{
136 pr_err("==================================================================\n");
137 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
138 spin_unlock_irqrestore(&report_lock, *flags);
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139 if (panic_on_warn)
140 panic("panic_on_warn set ...\n");
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141 kasan_enable_current();
142}
143
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144static void print_track(struct kasan_track *track)
145{
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146 pr_err("PID = %u\n", track->pid);
147 if (track->stack) {
148 struct stack_trace trace;
149
150 depot_fetch_stack(track->stack, &trace);
151 print_stack_trace(&trace, 0);
152 } else {
153 pr_err("(stack is not available)\n");
154 }
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155}
156
7e088978 157static void kasan_object_err(struct kmem_cache *cache, void *object)
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158{
159 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
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160
161 dump_stack();
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162 pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
163 cache->object_size);
164
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165 if (!(cache->flags & SLAB_KASAN))
166 return;
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167
168 pr_err("Allocated:\n");
169 print_track(&alloc_info->alloc_track);
170 pr_err("Freed:\n");
171 print_track(&alloc_info->free_track);
7ed2f9e6 172}
7ed2f9e6 173
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174void kasan_report_double_free(struct kmem_cache *cache, void *object,
175 s8 shadow)
176{
177 unsigned long flags;
178
179 kasan_start_report(&flags);
180 pr_err("BUG: Double free or freeing an invalid pointer\n");
181 pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
182 kasan_object_err(cache, object);
183 kasan_end_report(&flags);
184}
185
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186static void print_address_description(struct kasan_access_info *info)
187{
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188 const void *addr = info->access_addr;
189
190 if ((addr >= (void *)PAGE_OFFSET) &&
191 (addr < high_memory)) {
192 struct page *page = virt_to_head_page(addr);
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193
194 if (PageSlab(page)) {
195 void *object;
196 struct kmem_cache *cache = page->slab_cache;
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197 object = nearest_obj(cache, page,
198 (void *)info->access_addr);
7e088978 199 kasan_object_err(cache, object);
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200 return;
201 }
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202 dump_page(page, "kasan: bad access detected");
203 }
204
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205 if (kernel_or_module_addr(addr)) {
206 if (!init_task_stack_addr(addr))
207 pr_err("Address belongs to variable %pS\n", addr);
208 }
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209 dump_stack();
210}
211
212static bool row_is_guilty(const void *row, const void *guilty)
213{
214 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
215}
216
217static int shadow_pointer_offset(const void *row, const void *shadow)
218{
219 /* The length of ">ff00ff00ff00ff00: " is
220 * 3 + (BITS_PER_LONG/8)*2 chars.
221 */
222 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
223 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
224}
225
226static void print_shadow_for_address(const void *addr)
227{
228 int i;
229 const void *shadow = kasan_mem_to_shadow(addr);
230 const void *shadow_row;
231
232 shadow_row = (void *)round_down((unsigned long)shadow,
233 SHADOW_BYTES_PER_ROW)
234 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
235
236 pr_err("Memory state around the buggy address:\n");
237
238 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
239 const void *kaddr = kasan_shadow_to_mem(shadow_row);
240 char buffer[4 + (BITS_PER_LONG/8)*2];
f2377d4e 241 char shadow_buf[SHADOW_BYTES_PER_ROW];
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242
243 snprintf(buffer, sizeof(buffer),
244 (i == 0) ? ">%p: " : " %p: ", kaddr);
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245 /*
246 * We should not pass a shadow pointer to generic
247 * function, because generic functions may try to
248 * access kasan mapping for the passed address.
249 */
f2377d4e 250 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
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251 print_hex_dump(KERN_ERR, buffer,
252 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
f2377d4e 253 shadow_buf, SHADOW_BYTES_PER_ROW, 0);
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254
255 if (row_is_guilty(shadow_row, shadow))
256 pr_err("%*c\n",
257 shadow_pointer_offset(shadow_row, shadow),
258 '^');
259
260 shadow_row += SHADOW_BYTES_PER_ROW;
261 }
262}
263
e9121076 264static void kasan_report_error(struct kasan_access_info *info)
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265{
266 unsigned long flags;
e9121076 267 const char *bug_type;
0b24becc 268
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269 kasan_start_report(&flags);
270
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271 if (info->access_addr <
272 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
273 if ((unsigned long)info->access_addr < PAGE_SIZE)
274 bug_type = "null-ptr-deref";
275 else if ((unsigned long)info->access_addr < TASK_SIZE)
276 bug_type = "user-memory-access";
277 else
278 bug_type = "wild-memory-access";
25add7ec 279 pr_err("BUG: KASAN: %s on address %p\n",
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280 bug_type, info->access_addr);
281 pr_err("%s of size %zu by task %s/%d\n",
282 info->is_write ? "Write" : "Read",
283 info->access_size, current->comm,
284 task_pid_nr(current));
285 dump_stack();
286 } else {
287 print_error_description(info);
288 print_address_description(info);
289 print_shadow_for_address(info->first_bad_addr);
290 }
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291
292 kasan_end_report(&flags);
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293}
294
295void kasan_report(unsigned long addr, size_t size,
296 bool is_write, unsigned long ip)
297{
298 struct kasan_access_info info;
299
0ba8663c 300 if (likely(!kasan_report_enabled()))
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301 return;
302
303 info.access_addr = (void *)addr;
304 info.access_size = size;
305 info.is_write = is_write;
306 info.ip = ip;
e9121076 307
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308 kasan_report_error(&info);
309}
310
311
312#define DEFINE_ASAN_REPORT_LOAD(size) \
313void __asan_report_load##size##_noabort(unsigned long addr) \
314{ \
315 kasan_report(addr, size, false, _RET_IP_); \
316} \
317EXPORT_SYMBOL(__asan_report_load##size##_noabort)
318
319#define DEFINE_ASAN_REPORT_STORE(size) \
320void __asan_report_store##size##_noabort(unsigned long addr) \
321{ \
322 kasan_report(addr, size, true, _RET_IP_); \
323} \
324EXPORT_SYMBOL(__asan_report_store##size##_noabort)
325
326DEFINE_ASAN_REPORT_LOAD(1);
327DEFINE_ASAN_REPORT_LOAD(2);
328DEFINE_ASAN_REPORT_LOAD(4);
329DEFINE_ASAN_REPORT_LOAD(8);
330DEFINE_ASAN_REPORT_LOAD(16);
331DEFINE_ASAN_REPORT_STORE(1);
332DEFINE_ASAN_REPORT_STORE(2);
333DEFINE_ASAN_REPORT_STORE(4);
334DEFINE_ASAN_REPORT_STORE(8);
335DEFINE_ASAN_REPORT_STORE(16);
336
337void __asan_report_load_n_noabort(unsigned long addr, size_t size)
338{
339 kasan_report(addr, size, false, _RET_IP_);
340}
341EXPORT_SYMBOL(__asan_report_load_n_noabort);
342
343void __asan_report_store_n_noabort(unsigned long addr, size_t size)
344{
345 kasan_report(addr, size, true, _RET_IP_);
346}
347EXPORT_SYMBOL(__asan_report_store_n_noabort);