1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * This file contains common KASAN error reporting code.
4 *
5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7 *
8 * Some code borrowed from https://github.com/xairy/kasan-prototype by
9 * Andrey Konovalov <andreyknvl@gmail.com>
10 */
11
12 #include <linux/bitops.h>
13 #include <linux/ftrace.h>
14 #include <linux/init.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/printk.h>
18 #include <linux/sched.h>
19 #include <linux/slab.h>
20 #include <linux/stackdepot.h>
21 #include <linux/stacktrace.h>
22 #include <linux/string.h>
23 #include <linux/types.h>
24 #include <linux/kasan.h>
25 #include <linux/module.h>
26 #include <linux/sched/task_stack.h>
27 #include <linux/uaccess.h>
28 #include <trace/events/error_report.h>
29
30 #include <asm/sections.h>
31
32 #include <kunit/test.h>
33
34 #include "kasan.h"
35 #include "../slab.h"
36
37 static unsigned long kasan_flags;
38
39 #define KASAN_BIT_REPORTED 0
40 #define KASAN_BIT_MULTI_SHOT 1
41
kasan_save_enable_multi_shot(void)42 bool kasan_save_enable_multi_shot(void)
43 {
44 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
45 }
46 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
47
kasan_restore_multi_shot(bool enabled)48 void kasan_restore_multi_shot(bool enabled)
49 {
50 if (!enabled)
51 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
52 }
53 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
54
kasan_set_multi_shot(char * str)55 static int __init kasan_set_multi_shot(char *str)
56 {
57 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
58 return 1;
59 }
60 __setup("kasan_multi_shot", kasan_set_multi_shot);
61
print_error_description(struct kasan_access_info * info)62 static void print_error_description(struct kasan_access_info *info)
63 {
64 pr_err("BUG: KASAN: %s in %pS\n",
65 kasan_get_bug_type(info), (void *)info->ip);
66 if (info->access_size)
67 pr_err("%s of size %zu at addr %px by task %s/%d\n",
68 info->is_write ? "Write" : "Read", info->access_size,
69 info->access_addr, current->comm, task_pid_nr(current));
70 else
71 pr_err("%s at addr %px by task %s/%d\n",
72 info->is_write ? "Write" : "Read",
73 info->access_addr, current->comm, task_pid_nr(current));
74 }
75
76 static DEFINE_SPINLOCK(report_lock);
77
start_report(unsigned long * flags)78 static void start_report(unsigned long *flags)
79 {
80 /*
81 * Make sure we don't end up in loop.
82 */
83 kasan_disable_current();
84 spin_lock_irqsave(&report_lock, *flags);
85 pr_err("==================================================================\n");
86 }
87
end_report(unsigned long * flags,unsigned long addr)88 static void end_report(unsigned long *flags, unsigned long addr)
89 {
90 if (!kasan_async_mode_enabled())
91 trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
92 pr_err("==================================================================\n");
93 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
94 spin_unlock_irqrestore(&report_lock, *flags);
95 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
96 /*
97 * This thread may hit another WARN() in the panic path.
98 * Resetting this prevents additional WARN() from panicking the
99 * system on this thread. Other threads are blocked by the
100 * panic_mutex in panic().
101 */
102 panic_on_warn = 0;
103 panic("panic_on_warn set ...\n");
104 }
105 #ifdef CONFIG_KASAN_HW_TAGS
106 if (kasan_flag_panic)
107 panic("kasan.fault=panic set ...\n");
108 #endif
109 kasan_enable_current();
110 }
111
print_stack(depot_stack_handle_t stack)112 static void print_stack(depot_stack_handle_t stack)
113 {
114 unsigned long *entries;
115 unsigned int nr_entries;
116
117 nr_entries = stack_depot_fetch(stack, &entries);
118 stack_trace_print(entries, nr_entries, 0);
119 }
120
print_track(struct kasan_track * track,const char * prefix)121 static void print_track(struct kasan_track *track, const char *prefix)
122 {
123 pr_err("%s by task %u:\n", prefix, track->pid);
124 if (track->stack) {
125 print_stack(track->stack);
126 } else {
127 pr_err("(stack is not available)\n");
128 }
129 }
130
kasan_addr_to_page(const void * addr)131 struct page *kasan_addr_to_page(const void *addr)
132 {
133 if ((addr >= (void *)PAGE_OFFSET) &&
134 (addr < high_memory))
135 return virt_to_head_page(addr);
136 return NULL;
137 }
138
describe_object_addr(struct kmem_cache * cache,void * object,const void * addr)139 static void describe_object_addr(struct kmem_cache *cache, void *object,
140 const void *addr)
141 {
142 unsigned long access_addr = (unsigned long)addr;
143 unsigned long object_addr = (unsigned long)object;
144 const char *rel_type;
145 int rel_bytes;
146
147 pr_err("The buggy address belongs to the object at %px\n"
148 " which belongs to the cache %s of size %d\n",
149 object, cache->name, cache->object_size);
150
151 if (!addr)
152 return;
153
154 if (access_addr < object_addr) {
155 rel_type = "to the left";
156 rel_bytes = object_addr - access_addr;
157 } else if (access_addr >= object_addr + cache->object_size) {
158 rel_type = "to the right";
159 rel_bytes = access_addr - (object_addr + cache->object_size);
160 } else {
161 rel_type = "inside";
162 rel_bytes = access_addr - object_addr;
163 }
164
165 pr_err("The buggy address is located %d bytes %s of\n"
166 " %d-byte region [%px, %px)\n",
167 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
168 (void *)(object_addr + cache->object_size));
169 }
170
describe_object_stacks(struct kmem_cache * cache,void * object,const void * addr,u8 tag)171 static void describe_object_stacks(struct kmem_cache *cache, void *object,
172 const void *addr, u8 tag)
173 {
174 struct kasan_alloc_meta *alloc_meta;
175 struct kasan_track *free_track;
176
177 alloc_meta = kasan_get_alloc_meta(cache, object);
178 if (alloc_meta) {
179 print_track(&alloc_meta->alloc_track, "Allocated");
180 pr_err("\n");
181 }
182
183 free_track = kasan_get_free_track(cache, object, tag);
184 if (free_track) {
185 print_track(free_track, "Freed");
186 pr_err("\n");
187 }
188
189 #ifdef CONFIG_KASAN_GENERIC
190 if (!alloc_meta)
191 return;
192 if (alloc_meta->aux_stack[0]) {
193 pr_err("Last potentially related work creation:\n");
194 print_stack(alloc_meta->aux_stack[0]);
195 pr_err("\n");
196 }
197 if (alloc_meta->aux_stack[1]) {
198 pr_err("Second to last potentially related work creation:\n");
199 print_stack(alloc_meta->aux_stack[1]);
200 pr_err("\n");
201 }
202 #endif
203 }
204
describe_object(struct kmem_cache * cache,void * object,const void * addr,u8 tag)205 static void describe_object(struct kmem_cache *cache, void *object,
206 const void *addr, u8 tag)
207 {
208 if (kasan_stack_collection_enabled())
209 describe_object_stacks(cache, object, addr, tag);
210 describe_object_addr(cache, object, addr);
211 }
212
kernel_or_module_addr(const void * addr)213 static inline bool kernel_or_module_addr(const void *addr)
214 {
215 if (addr >= (void *)_stext && addr < (void *)_end)
216 return true;
217 if (is_module_address((unsigned long)addr))
218 return true;
219 return false;
220 }
221
init_task_stack_addr(const void * addr)222 static inline bool init_task_stack_addr(const void *addr)
223 {
224 return addr >= (void *)&init_thread_union.stack &&
225 (addr <= (void *)&init_thread_union.stack +
226 sizeof(init_thread_union.stack));
227 }
228
print_address_description(void * addr,u8 tag)229 static void print_address_description(void *addr, u8 tag)
230 {
231 struct page *page = kasan_addr_to_page(addr);
232
233 dump_stack();
234 pr_err("\n");
235
236 if (page && PageSlab(page)) {
237 struct kmem_cache *cache = page->slab_cache;
238 void *object = nearest_obj(cache, page, addr);
239
240 describe_object(cache, object, addr, tag);
241 }
242
243 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
244 pr_err("The buggy address belongs to the variable:\n");
245 pr_err(" %pS\n", addr);
246 }
247
248 if (page) {
249 pr_err("The buggy address belongs to the page:\n");
250 dump_page(page, "kasan: bad access detected");
251 }
252
253 kasan_print_address_stack_frame(addr);
254 }
255
meta_row_is_guilty(const void * row,const void * addr)256 static bool meta_row_is_guilty(const void *row, const void *addr)
257 {
258 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
259 }
260
meta_pointer_offset(const void * row,const void * addr)261 static int meta_pointer_offset(const void *row, const void *addr)
262 {
263 /*
264 * Memory state around the buggy address:
265 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
266 * ...
267 *
268 * The length of ">ff00ff00ff00ff00: " is
269 * 3 + (BITS_PER_LONG / 8) * 2 chars.
270 * The length of each granule metadata is 2 bytes
271 * plus 1 byte for space.
272 */
273 return 3 + (BITS_PER_LONG / 8) * 2 +
274 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
275 }
276
print_memory_metadata(const void * addr)277 static void print_memory_metadata(const void *addr)
278 {
279 int i;
280 void *row;
281
282 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
283 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
284
285 pr_err("Memory state around the buggy address:\n");
286
287 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
288 char buffer[4 + (BITS_PER_LONG / 8) * 2];
289 char metadata[META_BYTES_PER_ROW];
290
291 snprintf(buffer, sizeof(buffer),
292 (i == 0) ? ">%px: " : " %px: ", row);
293
294 /*
295 * We should not pass a shadow pointer to generic
296 * function, because generic functions may try to
297 * access kasan mapping for the passed address.
298 */
299 kasan_metadata_fetch_row(&metadata[0], row);
300
301 print_hex_dump(KERN_ERR, buffer,
302 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
303 metadata, META_BYTES_PER_ROW, 0);
304
305 if (meta_row_is_guilty(row, addr))
306 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
307
308 row += META_MEM_BYTES_PER_ROW;
309 }
310 }
311
report_enabled(void)312 static bool report_enabled(void)
313 {
314 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
315 if (current->kasan_depth)
316 return false;
317 #endif
318 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
319 return true;
320 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
321 }
322
323 #if IS_ENABLED(CONFIG_KUNIT)
kasan_update_kunit_status(struct kunit * cur_test)324 static void kasan_update_kunit_status(struct kunit *cur_test)
325 {
326 struct kunit_resource *resource;
327 struct kunit_kasan_expectation *kasan_data;
328
329 resource = kunit_find_named_resource(cur_test, "kasan_data");
330
331 if (!resource) {
332 kunit_set_failure(cur_test);
333 return;
334 }
335
336 kasan_data = (struct kunit_kasan_expectation *)resource->data;
337 WRITE_ONCE(kasan_data->report_found, true);
338 kunit_put_resource(resource);
339 }
340 #endif /* IS_ENABLED(CONFIG_KUNIT) */
341
kasan_report_invalid_free(void * object,unsigned long ip)342 void kasan_report_invalid_free(void *object, unsigned long ip)
343 {
344 unsigned long flags;
345 u8 tag = get_tag(object);
346
347 object = kasan_reset_tag(object);
348
349 #if IS_ENABLED(CONFIG_KUNIT)
350 if (current->kunit_test)
351 kasan_update_kunit_status(current->kunit_test);
352 #endif /* IS_ENABLED(CONFIG_KUNIT) */
353
354 start_report(&flags);
355 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
356 kasan_print_tags(tag, object);
357 pr_err("\n");
358 print_address_description(object, tag);
359 pr_err("\n");
360 print_memory_metadata(object);
361 end_report(&flags, (unsigned long)object);
362 }
363
364 #ifdef CONFIG_KASAN_HW_TAGS
kasan_report_async(void)365 void kasan_report_async(void)
366 {
367 unsigned long flags;
368
369 #if IS_ENABLED(CONFIG_KUNIT)
370 if (current->kunit_test)
371 kasan_update_kunit_status(current->kunit_test);
372 #endif /* IS_ENABLED(CONFIG_KUNIT) */
373
374 start_report(&flags);
375 pr_err("BUG: KASAN: invalid-access\n");
376 pr_err("Asynchronous mode enabled: no access details available\n");
377 pr_err("\n");
378 dump_stack();
379 end_report(&flags, 0);
380 }
381 #endif /* CONFIG_KASAN_HW_TAGS */
382
__kasan_report(unsigned long addr,size_t size,bool is_write,unsigned long ip)383 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
384 unsigned long ip)
385 {
386 struct kasan_access_info info;
387 void *tagged_addr;
388 void *untagged_addr;
389 unsigned long flags;
390
391 #if IS_ENABLED(CONFIG_KUNIT)
392 if (current->kunit_test)
393 kasan_update_kunit_status(current->kunit_test);
394 #endif /* IS_ENABLED(CONFIG_KUNIT) */
395
396 disable_trace_on_warning();
397
398 tagged_addr = (void *)addr;
399 untagged_addr = kasan_reset_tag(tagged_addr);
400
401 info.access_addr = tagged_addr;
402 if (addr_has_metadata(untagged_addr))
403 info.first_bad_addr =
404 kasan_find_first_bad_addr(tagged_addr, size);
405 else
406 info.first_bad_addr = untagged_addr;
407 info.access_size = size;
408 info.is_write = is_write;
409 info.ip = ip;
410
411 start_report(&flags);
412
413 print_error_description(&info);
414 if (addr_has_metadata(untagged_addr))
415 kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
416 pr_err("\n");
417
418 if (addr_has_metadata(untagged_addr)) {
419 print_address_description(untagged_addr, get_tag(tagged_addr));
420 pr_err("\n");
421 print_memory_metadata(info.first_bad_addr);
422 } else {
423 dump_stack();
424 }
425
426 end_report(&flags, addr);
427 }
428
kasan_report(unsigned long addr,size_t size,bool is_write,unsigned long ip)429 bool kasan_report(unsigned long addr, size_t size, bool is_write,
430 unsigned long ip)
431 {
432 unsigned long flags = user_access_save();
433 bool ret = false;
434
435 if (likely(report_enabled())) {
436 __kasan_report(addr, size, is_write, ip);
437 ret = true;
438 }
439
440 user_access_restore(flags);
441
442 return ret;
443 }
444
445 #ifdef CONFIG_KASAN_INLINE
446 /*
447 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
448 * canonical half of the address space) cause out-of-bounds shadow memory reads
449 * before the actual access. For addresses in the low canonical half of the
450 * address space, as well as most non-canonical addresses, that out-of-bounds
451 * shadow memory access lands in the non-canonical part of the address space.
452 * Help the user figure out what the original bogus pointer was.
453 */
kasan_non_canonical_hook(unsigned long addr)454 void kasan_non_canonical_hook(unsigned long addr)
455 {
456 unsigned long orig_addr;
457 const char *bug_type;
458
459 if (addr < KASAN_SHADOW_OFFSET)
460 return;
461
462 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
463 /*
464 * For faults near the shadow address for NULL, we can be fairly certain
465 * that this is a KASAN shadow memory access.
466 * For faults that correspond to shadow for low canonical addresses, we
467 * can still be pretty sure - that shadow region is a fairly narrow
468 * chunk of the non-canonical address space.
469 * But faults that look like shadow for non-canonical addresses are a
470 * really large chunk of the address space. In that case, we still
471 * print the decoded address, but make it clear that this is not
472 * necessarily what's actually going on.
473 */
474 if (orig_addr < PAGE_SIZE)
475 bug_type = "null-ptr-deref";
476 else if (orig_addr < TASK_SIZE)
477 bug_type = "probably user-memory-access";
478 else
479 bug_type = "maybe wild-memory-access";
480 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
481 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
482 }
483 #endif
484