75206991ece0c331e64f0c7d7a335d3a45e2b9e7
[sfrench/cifs-2.6.git] / mm / kasan / report.c
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/bitops.h>
17 #include <linux/ftrace.h>
18 #include <linux/init.h>
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/printk.h>
22 #include <linux/sched.h>
23 #include <linux/slab.h>
24 #include <linux/stackdepot.h>
25 #include <linux/stacktrace.h>
26 #include <linux/string.h>
27 #include <linux/types.h>
28 #include <linux/kasan.h>
29 #include <linux/module.h>
30
31 #include <asm/sections.h>
32
33 #include "kasan.h"
34 #include "../slab.h"
35
36 /* Shadow layout customization. */
37 #define SHADOW_BYTES_PER_BLOCK 1
38 #define SHADOW_BLOCKS_PER_ROW 16
39 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
40 #define SHADOW_ROWS_AROUND_ADDR 2
41
42 static const void *find_first_bad_addr(const void *addr, size_t size)
43 {
44         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
45         const void *first_bad_addr = addr;
46
47         while (!shadow_val && first_bad_addr < addr + size) {
48                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
49                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
50         }
51         return first_bad_addr;
52 }
53
54 static bool addr_has_shadow(struct kasan_access_info *info)
55 {
56         return (info->access_addr >=
57                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
58 }
59
60 static const char *get_shadow_bug_type(struct kasan_access_info *info)
61 {
62         const char *bug_type = "unknown-crash";
63         u8 *shadow_addr;
64
65         info->first_bad_addr = find_first_bad_addr(info->access_addr,
66                                                 info->access_size);
67
68         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
69
70         /*
71          * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
72          * at the next shadow byte to determine the type of the bad access.
73          */
74         if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
75                 shadow_addr++;
76
77         switch (*shadow_addr) {
78         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
79                 /*
80                  * In theory it's still possible to see these shadow values
81                  * due to a data race in the kernel code.
82                  */
83                 bug_type = "out-of-bounds";
84                 break;
85         case KASAN_PAGE_REDZONE:
86         case KASAN_KMALLOC_REDZONE:
87                 bug_type = "slab-out-of-bounds";
88                 break;
89         case KASAN_GLOBAL_REDZONE:
90                 bug_type = "global-out-of-bounds";
91                 break;
92         case KASAN_STACK_LEFT:
93         case KASAN_STACK_MID:
94         case KASAN_STACK_RIGHT:
95         case KASAN_STACK_PARTIAL:
96                 bug_type = "stack-out-of-bounds";
97                 break;
98         case KASAN_FREE_PAGE:
99         case KASAN_KMALLOC_FREE:
100                 bug_type = "use-after-free";
101                 break;
102         case KASAN_USE_AFTER_SCOPE:
103                 bug_type = "use-after-scope";
104                 break;
105         case KASAN_ALLOCA_LEFT:
106         case KASAN_ALLOCA_RIGHT:
107                 bug_type = "alloca-out-of-bounds";
108                 break;
109         }
110
111         return bug_type;
112 }
113
114 static const char *get_wild_bug_type(struct kasan_access_info *info)
115 {
116         const char *bug_type = "unknown-crash";
117
118         if ((unsigned long)info->access_addr < PAGE_SIZE)
119                 bug_type = "null-ptr-deref";
120         else if ((unsigned long)info->access_addr < TASK_SIZE)
121                 bug_type = "user-memory-access";
122         else
123                 bug_type = "wild-memory-access";
124
125         return bug_type;
126 }
127
128 static const char *get_bug_type(struct kasan_access_info *info)
129 {
130         if (addr_has_shadow(info))
131                 return get_shadow_bug_type(info);
132         return get_wild_bug_type(info);
133 }
134
135 static void print_error_description(struct kasan_access_info *info)
136 {
137         const char *bug_type = get_bug_type(info);
138
139         pr_err("BUG: KASAN: %s in %pS\n",
140                 bug_type, (void *)info->ip);
141         pr_err("%s of size %zu at addr %px by task %s/%d\n",
142                 info->is_write ? "Write" : "Read", info->access_size,
143                 info->access_addr, current->comm, task_pid_nr(current));
144 }
145
146 static inline bool kernel_or_module_addr(const void *addr)
147 {
148         if (addr >= (void *)_stext && addr < (void *)_end)
149                 return true;
150         if (is_module_address((unsigned long)addr))
151                 return true;
152         return false;
153 }
154
155 static inline bool init_task_stack_addr(const void *addr)
156 {
157         return addr >= (void *)&init_thread_union.stack &&
158                 (addr <= (void *)&init_thread_union.stack +
159                         sizeof(init_thread_union.stack));
160 }
161
162 static DEFINE_SPINLOCK(report_lock);
163
164 static void kasan_start_report(unsigned long *flags)
165 {
166         /*
167          * Make sure we don't end up in loop.
168          */
169         kasan_disable_current();
170         spin_lock_irqsave(&report_lock, *flags);
171         pr_err("==================================================================\n");
172 }
173
174 static void kasan_end_report(unsigned long *flags)
175 {
176         pr_err("==================================================================\n");
177         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
178         spin_unlock_irqrestore(&report_lock, *flags);
179         if (panic_on_warn)
180                 panic("panic_on_warn set ...\n");
181         kasan_enable_current();
182 }
183
184 static void print_track(struct kasan_track *track, const char *prefix)
185 {
186         pr_err("%s by task %u:\n", prefix, track->pid);
187         if (track->stack) {
188                 struct stack_trace trace;
189
190                 depot_fetch_stack(track->stack, &trace);
191                 print_stack_trace(&trace, 0);
192         } else {
193                 pr_err("(stack is not available)\n");
194         }
195 }
196
197 static struct page *addr_to_page(const void *addr)
198 {
199         if ((addr >= (void *)PAGE_OFFSET) &&
200                         (addr < high_memory))
201                 return virt_to_head_page(addr);
202         return NULL;
203 }
204
205 static void describe_object_addr(struct kmem_cache *cache, void *object,
206                                 const void *addr)
207 {
208         unsigned long access_addr = (unsigned long)addr;
209         unsigned long object_addr = (unsigned long)object;
210         const char *rel_type;
211         int rel_bytes;
212
213         pr_err("The buggy address belongs to the object at %px\n"
214                " which belongs to the cache %s of size %d\n",
215                 object, cache->name, cache->object_size);
216
217         if (!addr)
218                 return;
219
220         if (access_addr < object_addr) {
221                 rel_type = "to the left";
222                 rel_bytes = object_addr - access_addr;
223         } else if (access_addr >= object_addr + cache->object_size) {
224                 rel_type = "to the right";
225                 rel_bytes = access_addr - (object_addr + cache->object_size);
226         } else {
227                 rel_type = "inside";
228                 rel_bytes = access_addr - object_addr;
229         }
230
231         pr_err("The buggy address is located %d bytes %s of\n"
232                " %d-byte region [%px, %px)\n",
233                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
234                 (void *)(object_addr + cache->object_size));
235 }
236
237 static void describe_object(struct kmem_cache *cache, void *object,
238                                 const void *addr)
239 {
240         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
241
242         if (cache->flags & SLAB_KASAN) {
243                 print_track(&alloc_info->alloc_track, "Allocated");
244                 pr_err("\n");
245                 print_track(&alloc_info->free_track, "Freed");
246                 pr_err("\n");
247         }
248
249         describe_object_addr(cache, object, addr);
250 }
251
252 static void print_address_description(void *addr)
253 {
254         struct page *page = addr_to_page(addr);
255
256         dump_stack();
257         pr_err("\n");
258
259         if (page && PageSlab(page)) {
260                 struct kmem_cache *cache = page->slab_cache;
261                 void *object = nearest_obj(cache, page, addr);
262
263                 describe_object(cache, object, addr);
264         }
265
266         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
267                 pr_err("The buggy address belongs to the variable:\n");
268                 pr_err(" %pS\n", addr);
269         }
270
271         if (page) {
272                 pr_err("The buggy address belongs to the page:\n");
273                 dump_page(page, "kasan: bad access detected");
274         }
275 }
276
277 static bool row_is_guilty(const void *row, const void *guilty)
278 {
279         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
280 }
281
282 static int shadow_pointer_offset(const void *row, const void *shadow)
283 {
284         /* The length of ">ff00ff00ff00ff00: " is
285          *    3 + (BITS_PER_LONG/8)*2 chars.
286          */
287         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
288                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
289 }
290
291 static void print_shadow_for_address(const void *addr)
292 {
293         int i;
294         const void *shadow = kasan_mem_to_shadow(addr);
295         const void *shadow_row;
296
297         shadow_row = (void *)round_down((unsigned long)shadow,
298                                         SHADOW_BYTES_PER_ROW)
299                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
300
301         pr_err("Memory state around the buggy address:\n");
302
303         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
304                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
305                 char buffer[4 + (BITS_PER_LONG/8)*2];
306                 char shadow_buf[SHADOW_BYTES_PER_ROW];
307
308                 snprintf(buffer, sizeof(buffer),
309                         (i == 0) ? ">%px: " : " %px: ", kaddr);
310                 /*
311                  * We should not pass a shadow pointer to generic
312                  * function, because generic functions may try to
313                  * access kasan mapping for the passed address.
314                  */
315                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
316                 print_hex_dump(KERN_ERR, buffer,
317                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
318                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
319
320                 if (row_is_guilty(shadow_row, shadow))
321                         pr_err("%*c\n",
322                                 shadow_pointer_offset(shadow_row, shadow),
323                                 '^');
324
325                 shadow_row += SHADOW_BYTES_PER_ROW;
326         }
327 }
328
329 void kasan_report_invalid_free(void *object, unsigned long ip)
330 {
331         unsigned long flags;
332
333         kasan_start_report(&flags);
334         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
335         pr_err("\n");
336         print_address_description(object);
337         pr_err("\n");
338         print_shadow_for_address(object);
339         kasan_end_report(&flags);
340 }
341
342 static void kasan_report_error(struct kasan_access_info *info)
343 {
344         unsigned long flags;
345
346         kasan_start_report(&flags);
347
348         print_error_description(info);
349         pr_err("\n");
350
351         if (!addr_has_shadow(info)) {
352                 dump_stack();
353         } else {
354                 print_address_description((void *)info->access_addr);
355                 pr_err("\n");
356                 print_shadow_for_address(info->first_bad_addr);
357         }
358
359         kasan_end_report(&flags);
360 }
361
362 static unsigned long kasan_flags;
363
364 #define KASAN_BIT_REPORTED      0
365 #define KASAN_BIT_MULTI_SHOT    1
366
367 bool kasan_save_enable_multi_shot(void)
368 {
369         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
370 }
371 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
372
373 void kasan_restore_multi_shot(bool enabled)
374 {
375         if (!enabled)
376                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
377 }
378 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
379
380 static int __init kasan_set_multi_shot(char *str)
381 {
382         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
383         return 1;
384 }
385 __setup("kasan_multi_shot", kasan_set_multi_shot);
386
387 static inline bool kasan_report_enabled(void)
388 {
389         if (current->kasan_depth)
390                 return false;
391         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
392                 return true;
393         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
394 }
395
396 void kasan_report(unsigned long addr, size_t size,
397                 bool is_write, unsigned long ip)
398 {
399         struct kasan_access_info info;
400
401         if (likely(!kasan_report_enabled()))
402                 return;
403
404         disable_trace_on_warning();
405
406         info.access_addr = (void *)addr;
407         info.first_bad_addr = (void *)addr;
408         info.access_size = size;
409         info.is_write = is_write;
410         info.ip = ip;
411
412         kasan_report_error(&info);
413 }
414
415
416 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
417 void __asan_report_load##size##_noabort(unsigned long addr) \
418 {                                                         \
419         kasan_report(addr, size, false, _RET_IP_);        \
420 }                                                         \
421 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
422
423 #define DEFINE_ASAN_REPORT_STORE(size)                     \
424 void __asan_report_store##size##_noabort(unsigned long addr) \
425 {                                                          \
426         kasan_report(addr, size, true, _RET_IP_);          \
427 }                                                          \
428 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
429
430 DEFINE_ASAN_REPORT_LOAD(1);
431 DEFINE_ASAN_REPORT_LOAD(2);
432 DEFINE_ASAN_REPORT_LOAD(4);
433 DEFINE_ASAN_REPORT_LOAD(8);
434 DEFINE_ASAN_REPORT_LOAD(16);
435 DEFINE_ASAN_REPORT_STORE(1);
436 DEFINE_ASAN_REPORT_STORE(2);
437 DEFINE_ASAN_REPORT_STORE(4);
438 DEFINE_ASAN_REPORT_STORE(8);
439 DEFINE_ASAN_REPORT_STORE(16);
440
441 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
442 {
443         kasan_report(addr, size, false, _RET_IP_);
444 }
445 EXPORT_SYMBOL(__asan_report_load_n_noabort);
446
447 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
448 {
449         kasan_report(addr, size, true, _RET_IP_);
450 }
451 EXPORT_SYMBOL(__asan_report_store_n_noabort);