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/lockdep.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#include <linux/sched/task_stack.h>
28#include <linux/uaccess.h>
29#include <trace/events/error_report.h>
30
31#include <asm/sections.h>
32
33#include <kunit/test.h>
34
35#include "kasan.h"
36#include "../slab.h"
37
38static unsigned long kasan_flags;
39
40#define KASAN_BIT_REPORTED 0
41#define KASAN_BIT_MULTI_SHOT 1
42
43enum kasan_arg_fault {
44 KASAN_ARG_FAULT_DEFAULT,
45 KASAN_ARG_FAULT_REPORT,
46 KASAN_ARG_FAULT_PANIC,
47};
48
49static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
50
51/* kasan.fault=report/panic */
52static int __init early_kasan_fault(char *arg)
53{
54 if (!arg)
55 return -EINVAL;
56
57 if (!strcmp(arg, "report"))
58 kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
59 else if (!strcmp(arg, "panic"))
60 kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
61 else
62 return -EINVAL;
63
64 return 0;
65}
66early_param("kasan.fault", early_kasan_fault);
67
68static int __init kasan_set_multi_shot(char *str)
69{
70 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
71 return 1;
72}
73__setup("kasan_multi_shot", kasan_set_multi_shot);
74
75/*
76 * Used to suppress reports within kasan_disable/enable_current() critical
77 * sections, which are used for marking accesses to slab metadata.
78 */
79static bool report_suppressed(void)
80{
81#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
82 if (current->kasan_depth)
83 return true;
84#endif
85 return false;
86}
87
88/*
89 * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
90 * is enabled. Note that KASAN tests effectively enable kasan_multi_shot
91 * for their duration.
92 */
93static bool report_enabled(void)
94{
95 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
96 return true;
97 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
98}
99
100#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
101
102bool kasan_save_enable_multi_shot(void)
103{
104 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
105}
106EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
107
108void kasan_restore_multi_shot(bool enabled)
109{
110 if (!enabled)
111 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
112}
113EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
114
115#endif
116
117#if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
118static void update_kunit_status(bool sync)
119{
120 struct kunit *test;
121 struct kunit_resource *resource;
122 struct kunit_kasan_status *status;
123
124 test = current->kunit_test;
125 if (!test)
126 return;
127
128 resource = kunit_find_named_resource(test, "kasan_status");
129 if (!resource) {
130 kunit_set_failure(test);
131 return;
132 }
133
134 status = (struct kunit_kasan_status *)resource->data;
135 WRITE_ONCE(status->report_found, true);
136 WRITE_ONCE(status->sync_fault, sync);
137
138 kunit_put_resource(resource);
139}
140#else
141static void update_kunit_status(bool sync) { }
142#endif
143
144static DEFINE_SPINLOCK(report_lock);
145
146static void start_report(unsigned long *flags, bool sync)
147{
148 /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
149 disable_trace_on_warning();
150 /* Update status of the currently running KASAN test. */
151 update_kunit_status(sync);
152 /* Do not allow LOCKDEP mangling KASAN reports. */
153 lockdep_off();
154 /* Make sure we don't end up in loop. */
155 kasan_disable_current();
156 spin_lock_irqsave(&report_lock, *flags);
157 pr_err("==================================================================\n");
158}
159
160static void end_report(unsigned long *flags, void *addr)
161{
162 if (addr)
163 trace_error_report_end(ERROR_DETECTOR_KASAN,
164 (unsigned long)addr);
165 pr_err("==================================================================\n");
166 spin_unlock_irqrestore(&report_lock, *flags);
167 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
168 panic("panic_on_warn set ...\n");
169 if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
170 panic("kasan.fault=panic set ...\n");
171 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
172 lockdep_on();
173 kasan_enable_current();
174}
175
176static void print_error_description(struct kasan_report_info *info)
177{
178 if (info->type == KASAN_REPORT_INVALID_FREE) {
179 pr_err("BUG: KASAN: invalid-free in %pS\n", (void *)info->ip);
180 return;
181 }
182
183 if (info->type == KASAN_REPORT_DOUBLE_FREE) {
184 pr_err("BUG: KASAN: double-free in %pS\n", (void *)info->ip);
185 return;
186 }
187
188 pr_err("BUG: KASAN: %s in %pS\n",
189 kasan_get_bug_type(info), (void *)info->ip);
190 if (info->access_size)
191 pr_err("%s of size %zu at addr %px by task %s/%d\n",
192 info->is_write ? "Write" : "Read", info->access_size,
193 info->access_addr, current->comm, task_pid_nr(current));
194 else
195 pr_err("%s at addr %px by task %s/%d\n",
196 info->is_write ? "Write" : "Read",
197 info->access_addr, current->comm, task_pid_nr(current));
198}
199
200static void print_track(struct kasan_track *track, const char *prefix)
201{
202 pr_err("%s by task %u:\n", prefix, track->pid);
203 if (track->stack) {
204 stack_depot_print(track->stack);
205 } else {
206 pr_err("(stack is not available)\n");
207 }
208}
209
210struct page *kasan_addr_to_page(const void *addr)
211{
212 if ((addr >= (void *)PAGE_OFFSET) &&
213 (addr < high_memory))
214 return virt_to_head_page(addr);
215 return NULL;
216}
217
218struct slab *kasan_addr_to_slab(const void *addr)
219{
220 if ((addr >= (void *)PAGE_OFFSET) &&
221 (addr < high_memory))
222 return virt_to_slab(addr);
223 return NULL;
224}
225
226static void describe_object_addr(struct kmem_cache *cache, void *object,
227 const void *addr)
228{
229 unsigned long access_addr = (unsigned long)addr;
230 unsigned long object_addr = (unsigned long)object;
231 const char *rel_type;
232 int rel_bytes;
233
234 pr_err("The buggy address belongs to the object at %px\n"
235 " which belongs to the cache %s of size %d\n",
236 object, cache->name, cache->object_size);
237
238 if (access_addr < object_addr) {
239 rel_type = "to the left";
240 rel_bytes = object_addr - access_addr;
241 } else if (access_addr >= object_addr + cache->object_size) {
242 rel_type = "to the right";
243 rel_bytes = access_addr - (object_addr + cache->object_size);
244 } else {
245 rel_type = "inside";
246 rel_bytes = access_addr - object_addr;
247 }
248
249 pr_err("The buggy address is located %d bytes %s of\n"
250 " %d-byte region [%px, %px)\n",
251 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
252 (void *)(object_addr + cache->object_size));
253}
254
255static void describe_object_stacks(struct kmem_cache *cache, void *object,
256 const void *addr, u8 tag)
257{
258 struct kasan_alloc_meta *alloc_meta;
259 struct kasan_track *free_track;
260
261 alloc_meta = kasan_get_alloc_meta(cache, object);
262 if (alloc_meta) {
263 print_track(&alloc_meta->alloc_track, "Allocated");
264 pr_err("\n");
265 }
266
267 free_track = kasan_get_free_track(cache, object, tag);
268 if (free_track) {
269 print_track(free_track, "Freed");
270 pr_err("\n");
271 }
272
273#ifdef CONFIG_KASAN_GENERIC
274 if (!alloc_meta)
275 return;
276 if (alloc_meta->aux_stack[0]) {
277 pr_err("Last potentially related work creation:\n");
278 stack_depot_print(alloc_meta->aux_stack[0]);
279 pr_err("\n");
280 }
281 if (alloc_meta->aux_stack[1]) {
282 pr_err("Second to last potentially related work creation:\n");
283 stack_depot_print(alloc_meta->aux_stack[1]);
284 pr_err("\n");
285 }
286#endif
287}
288
289static void describe_object(struct kmem_cache *cache, void *object,
290 const void *addr, u8 tag)
291{
292 if (kasan_stack_collection_enabled())
293 describe_object_stacks(cache, object, addr, tag);
294 describe_object_addr(cache, object, addr);
295}
296
297static inline bool kernel_or_module_addr(const void *addr)
298{
299 if (is_kernel((unsigned long)addr))
300 return true;
301 if (is_module_address((unsigned long)addr))
302 return true;
303 return false;
304}
305
306static inline bool init_task_stack_addr(const void *addr)
307{
308 return addr >= (void *)&init_thread_union.stack &&
309 (addr <= (void *)&init_thread_union.stack +
310 sizeof(init_thread_union.stack));
311}
312
313static void print_address_description(void *addr, u8 tag)
314{
315 struct page *page = kasan_addr_to_page(addr);
316
317 dump_stack_lvl(KERN_ERR);
318 pr_err("\n");
319
320 if (page && PageSlab(page)) {
321 struct slab *slab = page_slab(page);
322 struct kmem_cache *cache = slab->slab_cache;
323 void *object = nearest_obj(cache, slab, addr);
324
325 describe_object(cache, object, addr, tag);
326 pr_err("\n");
327 }
328
329 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
330 pr_err("The buggy address belongs to the variable:\n");
331 pr_err(" %pS\n", addr);
332 pr_err("\n");
333 }
334
335 if (object_is_on_stack(addr)) {
336 /*
337 * Currently, KASAN supports printing frame information only
338 * for accesses to the task's own stack.
339 */
340 kasan_print_address_stack_frame(addr);
341 pr_err("\n");
342 }
343
344 if (is_vmalloc_addr(addr)) {
345 struct vm_struct *va = find_vm_area(addr);
346
347 if (va) {
348 pr_err("The buggy address belongs to the virtual mapping at\n"
349 " [%px, %px) created by:\n"
350 " %pS\n",
351 va->addr, va->addr + va->size, va->caller);
352 pr_err("\n");
353
354 page = vmalloc_to_page(addr);
355 }
356 }
357
358 if (page) {
359 pr_err("The buggy address belongs to the physical page:\n");
360 dump_page(page, "kasan: bad access detected");
361 pr_err("\n");
362 }
363}
364
365static bool meta_row_is_guilty(const void *row, const void *addr)
366{
367 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
368}
369
370static int meta_pointer_offset(const void *row, const void *addr)
371{
372 /*
373 * Memory state around the buggy address:
374 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
375 * ...
376 *
377 * The length of ">ff00ff00ff00ff00: " is
378 * 3 + (BITS_PER_LONG / 8) * 2 chars.
379 * The length of each granule metadata is 2 bytes
380 * plus 1 byte for space.
381 */
382 return 3 + (BITS_PER_LONG / 8) * 2 +
383 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
384}
385
386static void print_memory_metadata(const void *addr)
387{
388 int i;
389 void *row;
390
391 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
392 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
393
394 pr_err("Memory state around the buggy address:\n");
395
396 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
397 char buffer[4 + (BITS_PER_LONG / 8) * 2];
398 char metadata[META_BYTES_PER_ROW];
399
400 snprintf(buffer, sizeof(buffer),
401 (i == 0) ? ">%px: " : " %px: ", row);
402
403 /*
404 * We should not pass a shadow pointer to generic
405 * function, because generic functions may try to
406 * access kasan mapping for the passed address.
407 */
408 kasan_metadata_fetch_row(&metadata[0], row);
409
410 print_hex_dump(KERN_ERR, buffer,
411 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
412 metadata, META_BYTES_PER_ROW, 0);
413
414 if (meta_row_is_guilty(row, addr))
415 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
416
417 row += META_MEM_BYTES_PER_ROW;
418 }
419}
420
421static void print_report(struct kasan_report_info *info)
422{
423 void *tagged_addr = info->access_addr;
424 void *untagged_addr = kasan_reset_tag(tagged_addr);
425 u8 tag = get_tag(tagged_addr);
426
427 print_error_description(info);
428 if (addr_has_metadata(untagged_addr))
429 kasan_print_tags(tag, info->first_bad_addr);
430 pr_err("\n");
431
432 if (addr_has_metadata(untagged_addr)) {
433 print_address_description(untagged_addr, tag);
434 print_memory_metadata(info->first_bad_addr);
435 } else {
436 dump_stack_lvl(KERN_ERR);
437 }
438}
439
440void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
441{
442 unsigned long flags;
443 struct kasan_report_info info;
444
445 /*
446 * Do not check report_suppressed(), as an invalid-free cannot be
447 * caused by accessing slab metadata and thus should not be
448 * suppressed by kasan_disable/enable_current() critical sections.
449 */
450 if (unlikely(!report_enabled()))
451 return;
452
453 start_report(&flags, true);
454
455 info.type = type;
456 info.access_addr = ptr;
457 info.first_bad_addr = kasan_reset_tag(ptr);
458 info.access_size = 0;
459 info.is_write = false;
460 info.ip = ip;
461
462 print_report(&info);
463
464 end_report(&flags, ptr);
465}
466
467/*
468 * kasan_report() is the only reporting function that uses
469 * user_access_save/restore(): kasan_report_invalid_free() cannot be called
470 * from a UACCESS region, and kasan_report_async() is not used on x86.
471 */
472bool kasan_report(unsigned long addr, size_t size, bool is_write,
473 unsigned long ip)
474{
475 bool ret = true;
476 void *ptr = (void *)addr;
477 unsigned long ua_flags = user_access_save();
478 unsigned long irq_flags;
479 struct kasan_report_info info;
480
481 if (unlikely(report_suppressed()) || unlikely(!report_enabled())) {
482 ret = false;
483 goto out;
484 }
485
486 start_report(&irq_flags, true);
487
488 info.type = KASAN_REPORT_ACCESS;
489 info.access_addr = ptr;
490 info.first_bad_addr = kasan_find_first_bad_addr(ptr, size);
491 info.access_size = size;
492 info.is_write = is_write;
493 info.ip = ip;
494
495 print_report(&info);
496
497 end_report(&irq_flags, ptr);
498
499out:
500 user_access_restore(ua_flags);
501
502 return ret;
503}
504
505#ifdef CONFIG_KASAN_HW_TAGS
506void kasan_report_async(void)
507{
508 unsigned long flags;
509
510 /*
511 * Do not check report_suppressed(), as kasan_disable/enable_current()
512 * critical sections do not affect Hardware Tag-Based KASAN.
513 */
514 if (unlikely(!report_enabled()))
515 return;
516
517 start_report(&flags, false);
518 pr_err("BUG: KASAN: invalid-access\n");
519 pr_err("Asynchronous fault: no details available\n");
520 pr_err("\n");
521 dump_stack_lvl(KERN_ERR);
522 end_report(&flags, NULL);
523}
524#endif /* CONFIG_KASAN_HW_TAGS */
525
526#ifdef CONFIG_KASAN_INLINE
527/*
528 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
529 * canonical half of the address space) cause out-of-bounds shadow memory reads
530 * before the actual access. For addresses in the low canonical half of the
531 * address space, as well as most non-canonical addresses, that out-of-bounds
532 * shadow memory access lands in the non-canonical part of the address space.
533 * Help the user figure out what the original bogus pointer was.
534 */
535void kasan_non_canonical_hook(unsigned long addr)
536{
537 unsigned long orig_addr;
538 const char *bug_type;
539
540 if (addr < KASAN_SHADOW_OFFSET)
541 return;
542
543 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
544 /*
545 * For faults near the shadow address for NULL, we can be fairly certain
546 * that this is a KASAN shadow memory access.
547 * For faults that correspond to shadow for low canonical addresses, we
548 * can still be pretty sure - that shadow region is a fairly narrow
549 * chunk of the non-canonical address space.
550 * But faults that look like shadow for non-canonical addresses are a
551 * really large chunk of the address space. In that case, we still
552 * print the decoded address, but make it clear that this is not
553 * necessarily what's actually going on.
554 */
555 if (orig_addr < PAGE_SIZE)
556 bug_type = "null-ptr-deref";
557 else if (orig_addr < TASK_SIZE)
558 bug_type = "probably user-memory-access";
559 else
560 bug_type = "maybe wild-memory-access";
561 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
562 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
563}
564#endif
565

source code of linux/mm/kasan/report.c