xref: /openbmc/linux/mm/kasan/report.c (revision 17c17567)
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 <kunit/test.h>
13 #include <linux/bitops.h>
14 #include <linux/ftrace.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/lockdep.h>
18 #include <linux/mm.h>
19 #include <linux/printk.h>
20 #include <linux/sched.h>
21 #include <linux/slab.h>
22 #include <linux/stackdepot.h>
23 #include <linux/stacktrace.h>
24 #include <linux/string.h>
25 #include <linux/types.h>
26 #include <linux/kasan.h>
27 #include <linux/module.h>
28 #include <linux/sched/task_stack.h>
29 #include <linux/uaccess.h>
30 #include <trace/events/error_report.h>
31 
32 #include <asm/sections.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 
42 enum kasan_arg_fault {
43 	KASAN_ARG_FAULT_DEFAULT,
44 	KASAN_ARG_FAULT_REPORT,
45 	KASAN_ARG_FAULT_PANIC,
46 	KASAN_ARG_FAULT_PANIC_ON_WRITE,
47 };
48 
49 static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
50 
51 /* kasan.fault=report/panic */
early_kasan_fault(char * arg)52 static 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 if (!strcmp(arg, "panic_on_write"))
62 		kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE;
63 	else
64 		return -EINVAL;
65 
66 	return 0;
67 }
68 early_param("kasan.fault", early_kasan_fault);
69 
kasan_set_multi_shot(char * str)70 static int __init kasan_set_multi_shot(char *str)
71 {
72 	set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
73 	return 1;
74 }
75 __setup("kasan_multi_shot", kasan_set_multi_shot);
76 
77 /*
78  * This function is used to check whether KASAN reports are suppressed for
79  * software KASAN modes via kasan_disable/enable_current() critical sections.
80  *
81  * This is done to avoid:
82  * 1. False-positive reports when accessing slab metadata,
83  * 2. Deadlocking when poisoned memory is accessed by the reporting code.
84  *
85  * Hardware Tag-Based KASAN instead relies on:
86  * For #1: Resetting tags via kasan_reset_tag().
87  * For #2: Suppression of tag checks via CPU, see report_suppress_start/end().
88  */
report_suppressed_sw(void)89 static bool report_suppressed_sw(void)
90 {
91 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
92 	if (current->kasan_depth)
93 		return true;
94 #endif
95 	return false;
96 }
97 
report_suppress_start(void)98 static void report_suppress_start(void)
99 {
100 #ifdef CONFIG_KASAN_HW_TAGS
101 	/*
102 	 * Disable preemption for the duration of printing a KASAN report, as
103 	 * hw_suppress_tag_checks_start() disables checks on the current CPU.
104 	 */
105 	preempt_disable();
106 	hw_suppress_tag_checks_start();
107 #else
108 	kasan_disable_current();
109 #endif
110 }
111 
report_suppress_stop(void)112 static void report_suppress_stop(void)
113 {
114 #ifdef CONFIG_KASAN_HW_TAGS
115 	hw_suppress_tag_checks_stop();
116 	preempt_enable();
117 #else
118 	kasan_enable_current();
119 #endif
120 }
121 
122 /*
123  * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
124  * is enabled. Note that KASAN tests effectively enable kasan_multi_shot
125  * for their duration.
126  */
report_enabled(void)127 static bool report_enabled(void)
128 {
129 	if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
130 		return true;
131 	return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
132 }
133 
134 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
135 
kasan_save_enable_multi_shot(void)136 bool kasan_save_enable_multi_shot(void)
137 {
138 	return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
139 }
140 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
141 
kasan_restore_multi_shot(bool enabled)142 void kasan_restore_multi_shot(bool enabled)
143 {
144 	if (!enabled)
145 		clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
146 }
147 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
148 
149 #endif
150 
151 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
152 
153 /*
154  * Whether the KASAN KUnit test suite is currently being executed.
155  * Updated in kasan_test.c.
156  */
157 static bool kasan_kunit_executing;
158 
kasan_kunit_test_suite_start(void)159 void kasan_kunit_test_suite_start(void)
160 {
161 	WRITE_ONCE(kasan_kunit_executing, true);
162 }
163 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
164 
kasan_kunit_test_suite_end(void)165 void kasan_kunit_test_suite_end(void)
166 {
167 	WRITE_ONCE(kasan_kunit_executing, false);
168 }
169 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);
170 
kasan_kunit_test_suite_executing(void)171 static bool kasan_kunit_test_suite_executing(void)
172 {
173 	return READ_ONCE(kasan_kunit_executing);
174 }
175 
176 #else /* CONFIG_KASAN_KUNIT_TEST */
177 
kasan_kunit_test_suite_executing(void)178 static inline bool kasan_kunit_test_suite_executing(void) { return false; }
179 
180 #endif /* CONFIG_KASAN_KUNIT_TEST */
181 
182 #if IS_ENABLED(CONFIG_KUNIT)
183 
fail_non_kasan_kunit_test(void)184 static void fail_non_kasan_kunit_test(void)
185 {
186 	struct kunit *test;
187 
188 	if (kasan_kunit_test_suite_executing())
189 		return;
190 
191 	test = current->kunit_test;
192 	if (test)
193 		kunit_set_failure(test);
194 }
195 
196 #else /* CONFIG_KUNIT */
197 
fail_non_kasan_kunit_test(void)198 static inline void fail_non_kasan_kunit_test(void) { }
199 
200 #endif /* CONFIG_KUNIT */
201 
202 static DEFINE_SPINLOCK(report_lock);
203 
start_report(unsigned long * flags,bool sync)204 static void start_report(unsigned long *flags, bool sync)
205 {
206 	fail_non_kasan_kunit_test();
207 	/* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
208 	disable_trace_on_warning();
209 	/* Do not allow LOCKDEP mangling KASAN reports. */
210 	lockdep_off();
211 	/* Make sure we don't end up in loop. */
212 	report_suppress_start();
213 	spin_lock_irqsave(&report_lock, *flags);
214 	pr_err("==================================================================\n");
215 }
216 
end_report(unsigned long * flags,const void * addr,bool is_write)217 static void end_report(unsigned long *flags, const void *addr, bool is_write)
218 {
219 	if (addr)
220 		trace_error_report_end(ERROR_DETECTOR_KASAN,
221 				       (unsigned long)addr);
222 	pr_err("==================================================================\n");
223 	spin_unlock_irqrestore(&report_lock, *flags);
224 	if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
225 		check_panic_on_warn("KASAN");
226 	switch (kasan_arg_fault) {
227 	case KASAN_ARG_FAULT_DEFAULT:
228 	case KASAN_ARG_FAULT_REPORT:
229 		break;
230 	case KASAN_ARG_FAULT_PANIC:
231 		panic("kasan.fault=panic set ...\n");
232 		break;
233 	case KASAN_ARG_FAULT_PANIC_ON_WRITE:
234 		if (is_write)
235 			panic("kasan.fault=panic_on_write set ...\n");
236 		break;
237 	}
238 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
239 	lockdep_on();
240 	report_suppress_stop();
241 }
242 
print_error_description(struct kasan_report_info * info)243 static void print_error_description(struct kasan_report_info *info)
244 {
245 	pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
246 
247 	if (info->type != KASAN_REPORT_ACCESS) {
248 		pr_err("Free of addr %px by task %s/%d\n",
249 			info->access_addr, current->comm, task_pid_nr(current));
250 		return;
251 	}
252 
253 	if (info->access_size)
254 		pr_err("%s of size %zu at addr %px by task %s/%d\n",
255 			info->is_write ? "Write" : "Read", info->access_size,
256 			info->access_addr, current->comm, task_pid_nr(current));
257 	else
258 		pr_err("%s at addr %px by task %s/%d\n",
259 			info->is_write ? "Write" : "Read",
260 			info->access_addr, current->comm, task_pid_nr(current));
261 }
262 
print_track(struct kasan_track * track,const char * prefix)263 static void print_track(struct kasan_track *track, const char *prefix)
264 {
265 	pr_err("%s by task %u:\n", prefix, track->pid);
266 	if (track->stack)
267 		stack_depot_print(track->stack);
268 	else
269 		pr_err("(stack is not available)\n");
270 }
271 
addr_to_page(const void * addr)272 static inline struct page *addr_to_page(const void *addr)
273 {
274 	if (virt_addr_valid(addr))
275 		return virt_to_head_page(addr);
276 	return NULL;
277 }
278 
describe_object_addr(const void * addr,struct kasan_report_info * info)279 static void describe_object_addr(const void *addr, struct kasan_report_info *info)
280 {
281 	unsigned long access_addr = (unsigned long)addr;
282 	unsigned long object_addr = (unsigned long)info->object;
283 	const char *rel_type, *region_state = "";
284 	int rel_bytes;
285 
286 	pr_err("The buggy address belongs to the object at %px\n"
287 	       " which belongs to the cache %s of size %d\n",
288 		info->object, info->cache->name, info->cache->object_size);
289 
290 	if (access_addr < object_addr) {
291 		rel_type = "to the left";
292 		rel_bytes = object_addr - access_addr;
293 	} else if (access_addr >= object_addr + info->alloc_size) {
294 		rel_type = "to the right";
295 		rel_bytes = access_addr - (object_addr + info->alloc_size);
296 	} else {
297 		rel_type = "inside";
298 		rel_bytes = access_addr - object_addr;
299 	}
300 
301 	/*
302 	 * Tag-Based modes use the stack ring to infer the bug type, but the
303 	 * memory region state description is generated based on the metadata.
304 	 * Thus, defining the region state as below can contradict the metadata.
305 	 * Fixing this requires further improvements, so only infer the state
306 	 * for the Generic mode.
307 	 */
308 	if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
309 		if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
310 			region_state = "allocated ";
311 		else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
312 			region_state = "freed ";
313 	}
314 
315 	pr_err("The buggy address is located %d bytes %s of\n"
316 	       " %s%zu-byte region [%px, %px)\n",
317 	       rel_bytes, rel_type, region_state, info->alloc_size,
318 	       (void *)object_addr, (void *)(object_addr + info->alloc_size));
319 }
320 
describe_object_stacks(struct kasan_report_info * info)321 static void describe_object_stacks(struct kasan_report_info *info)
322 {
323 	if (info->alloc_track.stack) {
324 		print_track(&info->alloc_track, "Allocated");
325 		pr_err("\n");
326 	}
327 
328 	if (info->free_track.stack) {
329 		print_track(&info->free_track, "Freed");
330 		pr_err("\n");
331 	}
332 
333 	kasan_print_aux_stacks(info->cache, info->object);
334 }
335 
describe_object(const void * addr,struct kasan_report_info * info)336 static void describe_object(const void *addr, struct kasan_report_info *info)
337 {
338 	if (kasan_stack_collection_enabled())
339 		describe_object_stacks(info);
340 	describe_object_addr(addr, info);
341 }
342 
kernel_or_module_addr(const void * addr)343 static inline bool kernel_or_module_addr(const void *addr)
344 {
345 	if (is_kernel((unsigned long)addr))
346 		return true;
347 	if (is_module_address((unsigned long)addr))
348 		return true;
349 	return false;
350 }
351 
init_task_stack_addr(const void * addr)352 static inline bool init_task_stack_addr(const void *addr)
353 {
354 	return addr >= (void *)&init_thread_union.stack &&
355 		(addr <= (void *)&init_thread_union.stack +
356 			sizeof(init_thread_union.stack));
357 }
358 
print_address_description(void * addr,u8 tag,struct kasan_report_info * info)359 static void print_address_description(void *addr, u8 tag,
360 				      struct kasan_report_info *info)
361 {
362 	struct page *page = addr_to_page(addr);
363 
364 	dump_stack_lvl(KERN_ERR);
365 	pr_err("\n");
366 
367 	if (info->cache && info->object) {
368 		describe_object(addr, info);
369 		pr_err("\n");
370 	}
371 
372 	if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
373 		pr_err("The buggy address belongs to the variable:\n");
374 		pr_err(" %pS\n", addr);
375 		pr_err("\n");
376 	}
377 
378 	if (object_is_on_stack(addr)) {
379 		/*
380 		 * Currently, KASAN supports printing frame information only
381 		 * for accesses to the task's own stack.
382 		 */
383 		kasan_print_address_stack_frame(addr);
384 		pr_err("\n");
385 	}
386 
387 	if (is_vmalloc_addr(addr)) {
388 		struct vm_struct *va = find_vm_area(addr);
389 
390 		if (va) {
391 			pr_err("The buggy address belongs to the virtual mapping at\n"
392 			       " [%px, %px) created by:\n"
393 			       " %pS\n",
394 			       va->addr, va->addr + va->size, va->caller);
395 			pr_err("\n");
396 
397 			page = vmalloc_to_page(addr);
398 		}
399 	}
400 
401 	if (page) {
402 		pr_err("The buggy address belongs to the physical page:\n");
403 		dump_page(page, "kasan: bad access detected");
404 		pr_err("\n");
405 	}
406 }
407 
meta_row_is_guilty(const void * row,const void * addr)408 static bool meta_row_is_guilty(const void *row, const void *addr)
409 {
410 	return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
411 }
412 
meta_pointer_offset(const void * row,const void * addr)413 static int meta_pointer_offset(const void *row, const void *addr)
414 {
415 	/*
416 	 * Memory state around the buggy address:
417 	 *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
418 	 *  ...
419 	 *
420 	 * The length of ">ff00ff00ff00ff00: " is
421 	 *    3 + (BITS_PER_LONG / 8) * 2 chars.
422 	 * The length of each granule metadata is 2 bytes
423 	 *    plus 1 byte for space.
424 	 */
425 	return 3 + (BITS_PER_LONG / 8) * 2 +
426 		(addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
427 }
428 
print_memory_metadata(const void * addr)429 static void print_memory_metadata(const void *addr)
430 {
431 	int i;
432 	void *row;
433 
434 	row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
435 			- META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
436 
437 	pr_err("Memory state around the buggy address:\n");
438 
439 	for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
440 		char buffer[4 + (BITS_PER_LONG / 8) * 2];
441 		char metadata[META_BYTES_PER_ROW];
442 
443 		snprintf(buffer, sizeof(buffer),
444 				(i == 0) ? ">%px: " : " %px: ", row);
445 
446 		/*
447 		 * We should not pass a shadow pointer to generic
448 		 * function, because generic functions may try to
449 		 * access kasan mapping for the passed address.
450 		 */
451 		kasan_metadata_fetch_row(&metadata[0], row);
452 
453 		print_hex_dump(KERN_ERR, buffer,
454 			DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
455 			metadata, META_BYTES_PER_ROW, 0);
456 
457 		if (meta_row_is_guilty(row, addr))
458 			pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
459 
460 		row += META_MEM_BYTES_PER_ROW;
461 	}
462 }
463 
print_report(struct kasan_report_info * info)464 static void print_report(struct kasan_report_info *info)
465 {
466 	void *addr = kasan_reset_tag((void *)info->access_addr);
467 	u8 tag = get_tag((void *)info->access_addr);
468 
469 	print_error_description(info);
470 	if (addr_has_metadata(addr))
471 		kasan_print_tags(tag, info->first_bad_addr);
472 	pr_err("\n");
473 
474 	if (addr_has_metadata(addr)) {
475 		print_address_description(addr, tag, info);
476 		print_memory_metadata(info->first_bad_addr);
477 	} else {
478 		dump_stack_lvl(KERN_ERR);
479 	}
480 }
481 
complete_report_info(struct kasan_report_info * info)482 static void complete_report_info(struct kasan_report_info *info)
483 {
484 	void *addr = kasan_reset_tag((void *)info->access_addr);
485 	struct slab *slab;
486 
487 	if (info->type == KASAN_REPORT_ACCESS)
488 		info->first_bad_addr = kasan_find_first_bad_addr(
489 					(void *)info->access_addr, info->access_size);
490 	else
491 		info->first_bad_addr = addr;
492 
493 	slab = kasan_addr_to_slab(addr);
494 	if (slab) {
495 		info->cache = slab->slab_cache;
496 		info->object = nearest_obj(info->cache, slab, addr);
497 
498 		/* Try to determine allocation size based on the metadata. */
499 		info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
500 		/* Fallback to the object size if failed. */
501 		if (!info->alloc_size)
502 			info->alloc_size = info->cache->object_size;
503 	} else
504 		info->cache = info->object = NULL;
505 
506 	switch (info->type) {
507 	case KASAN_REPORT_INVALID_FREE:
508 		info->bug_type = "invalid-free";
509 		break;
510 	case KASAN_REPORT_DOUBLE_FREE:
511 		info->bug_type = "double-free";
512 		break;
513 	default:
514 		/* bug_type filled in by kasan_complete_mode_report_info. */
515 		break;
516 	}
517 
518 	/* Fill in mode-specific report info fields. */
519 	kasan_complete_mode_report_info(info);
520 }
521 
kasan_report_invalid_free(void * ptr,unsigned long ip,enum kasan_report_type type)522 void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
523 {
524 	unsigned long flags;
525 	struct kasan_report_info info;
526 
527 	/*
528 	 * Do not check report_suppressed_sw(), as an invalid-free cannot be
529 	 * caused by accessing poisoned memory and thus should not be suppressed
530 	 * by kasan_disable/enable_current() critical sections.
531 	 *
532 	 * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free()
533 	 * is triggered by explicit tag checks and not by the ones performed by
534 	 * the CPU. Thus, reporting invalid-free is not suppressed as well.
535 	 */
536 	if (unlikely(!report_enabled()))
537 		return;
538 
539 	start_report(&flags, true);
540 
541 	memset(&info, 0, sizeof(info));
542 	info.type = type;
543 	info.access_addr = ptr;
544 	info.access_size = 0;
545 	info.is_write = false;
546 	info.ip = ip;
547 
548 	complete_report_info(&info);
549 
550 	print_report(&info);
551 
552 	/*
553 	 * Invalid free is considered a "write" since the allocator's metadata
554 	 * updates involves writes.
555 	 */
556 	end_report(&flags, ptr, true);
557 }
558 
559 /*
560  * kasan_report() is the only reporting function that uses
561  * user_access_save/restore(): kasan_report_invalid_free() cannot be called
562  * from a UACCESS region, and kasan_report_async() is not used on x86.
563  */
kasan_report(const void * addr,size_t size,bool is_write,unsigned long ip)564 bool kasan_report(const void *addr, size_t size, bool is_write,
565 			unsigned long ip)
566 {
567 	bool ret = true;
568 	unsigned long ua_flags = user_access_save();
569 	unsigned long irq_flags;
570 	struct kasan_report_info info;
571 
572 	if (unlikely(report_suppressed_sw()) || unlikely(!report_enabled())) {
573 		ret = false;
574 		goto out;
575 	}
576 
577 	start_report(&irq_flags, true);
578 
579 	memset(&info, 0, sizeof(info));
580 	info.type = KASAN_REPORT_ACCESS;
581 	info.access_addr = addr;
582 	info.access_size = size;
583 	info.is_write = is_write;
584 	info.ip = ip;
585 
586 	complete_report_info(&info);
587 
588 	print_report(&info);
589 
590 	end_report(&irq_flags, (void *)addr, is_write);
591 
592 out:
593 	user_access_restore(ua_flags);
594 
595 	return ret;
596 }
597 
598 #ifdef CONFIG_KASAN_HW_TAGS
kasan_report_async(void)599 void kasan_report_async(void)
600 {
601 	unsigned long flags;
602 
603 	/*
604 	 * Do not check report_suppressed_sw(), as
605 	 * kasan_disable/enable_current() critical sections do not affect
606 	 * Hardware Tag-Based KASAN.
607 	 */
608 	if (unlikely(!report_enabled()))
609 		return;
610 
611 	start_report(&flags, false);
612 	pr_err("BUG: KASAN: invalid-access\n");
613 	pr_err("Asynchronous fault: no details available\n");
614 	pr_err("\n");
615 	dump_stack_lvl(KERN_ERR);
616 	/*
617 	 * Conservatively set is_write=true, because no details are available.
618 	 * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.
619 	 */
620 	end_report(&flags, NULL, true);
621 }
622 #endif /* CONFIG_KASAN_HW_TAGS */
623 
624 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
625 /*
626  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
627  * canonical half of the address space) cause out-of-bounds shadow memory reads
628  * before the actual access. For addresses in the low canonical half of the
629  * address space, as well as most non-canonical addresses, that out-of-bounds
630  * shadow memory access lands in the non-canonical part of the address space.
631  * Help the user figure out what the original bogus pointer was.
632  */
kasan_non_canonical_hook(unsigned long addr)633 void kasan_non_canonical_hook(unsigned long addr)
634 {
635 	unsigned long orig_addr;
636 	const char *bug_type;
637 
638 	if (addr < KASAN_SHADOW_OFFSET)
639 		return;
640 
641 	orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
642 	/*
643 	 * For faults near the shadow address for NULL, we can be fairly certain
644 	 * that this is a KASAN shadow memory access.
645 	 * For faults that correspond to shadow for low canonical addresses, we
646 	 * can still be pretty sure - that shadow region is a fairly narrow
647 	 * chunk of the non-canonical address space.
648 	 * But faults that look like shadow for non-canonical addresses are a
649 	 * really large chunk of the address space. In that case, we still
650 	 * print the decoded address, but make it clear that this is not
651 	 * necessarily what's actually going on.
652 	 */
653 	if (orig_addr < PAGE_SIZE)
654 		bug_type = "null-ptr-deref";
655 	else if (orig_addr < TASK_SIZE)
656 		bug_type = "probably user-memory-access";
657 	else
658 		bug_type = "maybe wild-memory-access";
659 	pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
660 		 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
661 }
662 #endif
663