1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains common KASAN error reporting code.
5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
8 * Some code borrowed from https://github.com/xairy/kasan-prototype by
9 * Andrey Konovalov <andreyknvl@gmail.com>
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>
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>
32 #include <asm/sections.h>
37 static unsigned long kasan_flags;
39 #define KASAN_BIT_REPORTED 0
40 #define KASAN_BIT_MULTI_SHOT 1
42 enum kasan_arg_fault {
43 KASAN_ARG_FAULT_DEFAULT,
44 KASAN_ARG_FAULT_REPORT,
45 KASAN_ARG_FAULT_PANIC,
48 static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
50 /* kasan.fault=report/panic */
51 static int __init early_kasan_fault(char *arg)
56 if (!strcmp(arg, "report"))
57 kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
58 else if (!strcmp(arg, "panic"))
59 kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
65 early_param("kasan.fault", early_kasan_fault);
67 static int __init kasan_set_multi_shot(char *str)
69 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
72 __setup("kasan_multi_shot", kasan_set_multi_shot);
75 * Used to suppress reports within kasan_disable/enable_current() critical
76 * sections, which are used for marking accesses to slab metadata.
78 static bool report_suppressed(void)
80 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
81 if (current->kasan_depth)
88 * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
89 * is enabled. Note that KASAN tests effectively enable kasan_multi_shot
92 static bool report_enabled(void)
94 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
96 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
99 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
101 bool kasan_save_enable_multi_shot(void)
103 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
105 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
107 void kasan_restore_multi_shot(bool enabled)
110 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
112 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
116 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
119 * Whether the KASAN KUnit test suite is currently being executed.
120 * Updated in kasan_test.c.
122 static bool kasan_kunit_executing;
124 void kasan_kunit_test_suite_start(void)
126 WRITE_ONCE(kasan_kunit_executing, true);
128 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
130 void kasan_kunit_test_suite_end(void)
132 WRITE_ONCE(kasan_kunit_executing, false);
134 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);
136 static bool kasan_kunit_test_suite_executing(void)
138 return READ_ONCE(kasan_kunit_executing);
141 #else /* CONFIG_KASAN_KUNIT_TEST */
143 static inline bool kasan_kunit_test_suite_executing(void) { return false; }
145 #endif /* CONFIG_KASAN_KUNIT_TEST */
147 #if IS_ENABLED(CONFIG_KUNIT)
149 static void fail_non_kasan_kunit_test(void)
153 if (kasan_kunit_test_suite_executing())
156 test = current->kunit_test;
158 kunit_set_failure(test);
161 #else /* CONFIG_KUNIT */
163 static inline void fail_non_kasan_kunit_test(void) { }
165 #endif /* CONFIG_KUNIT */
167 static DEFINE_SPINLOCK(report_lock);
169 static void start_report(unsigned long *flags, bool sync)
171 fail_non_kasan_kunit_test();
172 /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
173 disable_trace_on_warning();
174 /* Do not allow LOCKDEP mangling KASAN reports. */
176 /* Make sure we don't end up in loop. */
177 kasan_disable_current();
178 spin_lock_irqsave(&report_lock, *flags);
179 pr_err("==================================================================\n");
182 static void end_report(unsigned long *flags, void *addr)
185 trace_error_report_end(ERROR_DETECTOR_KASAN,
186 (unsigned long)addr);
187 pr_err("==================================================================\n");
188 spin_unlock_irqrestore(&report_lock, *flags);
189 if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
190 check_panic_on_warn("KASAN");
191 if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
192 panic("kasan.fault=panic set ...\n");
193 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
195 kasan_enable_current();
198 static void print_error_description(struct kasan_report_info *info)
200 pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
202 if (info->type != KASAN_REPORT_ACCESS) {
203 pr_err("Free of addr %px by task %s/%d\n",
204 info->access_addr, current->comm, task_pid_nr(current));
208 if (info->access_size)
209 pr_err("%s of size %zu at addr %px by task %s/%d\n",
210 info->is_write ? "Write" : "Read", info->access_size,
211 info->access_addr, current->comm, task_pid_nr(current));
213 pr_err("%s at addr %px by task %s/%d\n",
214 info->is_write ? "Write" : "Read",
215 info->access_addr, current->comm, task_pid_nr(current));
218 static void print_track(struct kasan_track *track, const char *prefix)
220 pr_err("%s by task %u:\n", prefix, track->pid);
222 stack_depot_print(track->stack);
224 pr_err("(stack is not available)\n");
227 static inline struct page *addr_to_page(const void *addr)
229 if (virt_addr_valid(addr))
230 return virt_to_head_page(addr);
234 static void describe_object_addr(const void *addr, struct kasan_report_info *info)
236 unsigned long access_addr = (unsigned long)addr;
237 unsigned long object_addr = (unsigned long)info->object;
238 const char *rel_type, *region_state = "";
241 pr_err("The buggy address belongs to the object at %px\n"
242 " which belongs to the cache %s of size %d\n",
243 info->object, info->cache->name, info->cache->object_size);
245 if (access_addr < object_addr) {
246 rel_type = "to the left";
247 rel_bytes = object_addr - access_addr;
248 } else if (access_addr >= object_addr + info->alloc_size) {
249 rel_type = "to the right";
250 rel_bytes = access_addr - (object_addr + info->alloc_size);
253 rel_bytes = access_addr - object_addr;
257 * Tag-Based modes use the stack ring to infer the bug type, but the
258 * memory region state description is generated based on the metadata.
259 * Thus, defining the region state as below can contradict the metadata.
260 * Fixing this requires further improvements, so only infer the state
261 * for the Generic mode.
263 if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
264 if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
265 region_state = "allocated ";
266 else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
267 region_state = "freed ";
270 pr_err("The buggy address is located %d bytes %s of\n"
271 " %s%zu-byte region [%px, %px)\n",
272 rel_bytes, rel_type, region_state, info->alloc_size,
273 (void *)object_addr, (void *)(object_addr + info->alloc_size));
276 static void describe_object_stacks(struct kasan_report_info *info)
278 if (info->alloc_track.stack) {
279 print_track(&info->alloc_track, "Allocated");
283 if (info->free_track.stack) {
284 print_track(&info->free_track, "Freed");
288 kasan_print_aux_stacks(info->cache, info->object);
291 static void describe_object(const void *addr, struct kasan_report_info *info)
293 if (kasan_stack_collection_enabled())
294 describe_object_stacks(info);
295 describe_object_addr(addr, info);
298 static inline bool kernel_or_module_addr(const void *addr)
300 if (is_kernel((unsigned long)addr))
302 if (is_module_address((unsigned long)addr))
307 static inline bool init_task_stack_addr(const void *addr)
309 return addr >= (void *)&init_thread_union.stack &&
310 (addr <= (void *)&init_thread_union.stack +
311 sizeof(init_thread_union.stack));
314 static void print_address_description(void *addr, u8 tag,
315 struct kasan_report_info *info)
317 struct page *page = addr_to_page(addr);
319 dump_stack_lvl(KERN_ERR);
322 if (info->cache && info->object) {
323 describe_object(addr, info);
327 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
328 pr_err("The buggy address belongs to the variable:\n");
329 pr_err(" %pS\n", addr);
333 if (object_is_on_stack(addr)) {
335 * Currently, KASAN supports printing frame information only
336 * for accesses to the task's own stack.
338 kasan_print_address_stack_frame(addr);
342 if (is_vmalloc_addr(addr)) {
343 struct vm_struct *va = find_vm_area(addr);
346 pr_err("The buggy address belongs to the virtual mapping at\n"
347 " [%px, %px) created by:\n"
349 va->addr, va->addr + va->size, va->caller);
352 page = vmalloc_to_page(addr);
357 pr_err("The buggy address belongs to the physical page:\n");
358 dump_page(page, "kasan: bad access detected");
363 static bool meta_row_is_guilty(const void *row, const void *addr)
365 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
368 static int meta_pointer_offset(const void *row, const void *addr)
371 * Memory state around the buggy address:
372 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
375 * The length of ">ff00ff00ff00ff00: " is
376 * 3 + (BITS_PER_LONG / 8) * 2 chars.
377 * The length of each granule metadata is 2 bytes
378 * plus 1 byte for space.
380 return 3 + (BITS_PER_LONG / 8) * 2 +
381 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
384 static void print_memory_metadata(const void *addr)
389 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
390 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
392 pr_err("Memory state around the buggy address:\n");
394 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
395 char buffer[4 + (BITS_PER_LONG / 8) * 2];
396 char metadata[META_BYTES_PER_ROW];
398 snprintf(buffer, sizeof(buffer),
399 (i == 0) ? ">%px: " : " %px: ", row);
402 * We should not pass a shadow pointer to generic
403 * function, because generic functions may try to
404 * access kasan mapping for the passed address.
406 kasan_metadata_fetch_row(&metadata[0], row);
408 print_hex_dump(KERN_ERR, buffer,
409 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
410 metadata, META_BYTES_PER_ROW, 0);
412 if (meta_row_is_guilty(row, addr))
413 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
415 row += META_MEM_BYTES_PER_ROW;
419 static void print_report(struct kasan_report_info *info)
421 void *addr = kasan_reset_tag(info->access_addr);
422 u8 tag = get_tag(info->access_addr);
424 print_error_description(info);
425 if (addr_has_metadata(addr))
426 kasan_print_tags(tag, info->first_bad_addr);
429 if (addr_has_metadata(addr)) {
430 print_address_description(addr, tag, info);
431 print_memory_metadata(info->first_bad_addr);
433 dump_stack_lvl(KERN_ERR);
437 static void complete_report_info(struct kasan_report_info *info)
439 void *addr = kasan_reset_tag(info->access_addr);
442 if (info->type == KASAN_REPORT_ACCESS)
443 info->first_bad_addr = kasan_find_first_bad_addr(
444 info->access_addr, info->access_size);
446 info->first_bad_addr = addr;
448 slab = kasan_addr_to_slab(addr);
450 info->cache = slab->slab_cache;
451 info->object = nearest_obj(info->cache, slab, addr);
453 /* Try to determine allocation size based on the metadata. */
454 info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
455 /* Fallback to the object size if failed. */
456 if (!info->alloc_size)
457 info->alloc_size = info->cache->object_size;
459 info->cache = info->object = NULL;
461 switch (info->type) {
462 case KASAN_REPORT_INVALID_FREE:
463 info->bug_type = "invalid-free";
465 case KASAN_REPORT_DOUBLE_FREE:
466 info->bug_type = "double-free";
469 /* bug_type filled in by kasan_complete_mode_report_info. */
473 /* Fill in mode-specific report info fields. */
474 kasan_complete_mode_report_info(info);
477 void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
480 struct kasan_report_info info;
483 * Do not check report_suppressed(), as an invalid-free cannot be
484 * caused by accessing slab metadata and thus should not be
485 * suppressed by kasan_disable/enable_current() critical sections.
487 if (unlikely(!report_enabled()))
490 start_report(&flags, true);
492 memset(&info, 0, sizeof(info));
494 info.access_addr = ptr;
495 info.access_size = 0;
496 info.is_write = false;
499 complete_report_info(&info);
503 end_report(&flags, ptr);
507 * kasan_report() is the only reporting function that uses
508 * user_access_save/restore(): kasan_report_invalid_free() cannot be called
509 * from a UACCESS region, and kasan_report_async() is not used on x86.
511 bool kasan_report(unsigned long addr, size_t size, bool is_write,
515 void *ptr = (void *)addr;
516 unsigned long ua_flags = user_access_save();
517 unsigned long irq_flags;
518 struct kasan_report_info info;
520 if (unlikely(report_suppressed()) || unlikely(!report_enabled())) {
525 start_report(&irq_flags, true);
527 memset(&info, 0, sizeof(info));
528 info.type = KASAN_REPORT_ACCESS;
529 info.access_addr = ptr;
530 info.access_size = size;
531 info.is_write = is_write;
534 complete_report_info(&info);
538 end_report(&irq_flags, ptr);
541 user_access_restore(ua_flags);
546 #ifdef CONFIG_KASAN_HW_TAGS
547 void kasan_report_async(void)
552 * Do not check report_suppressed(), as kasan_disable/enable_current()
553 * critical sections do not affect Hardware Tag-Based KASAN.
555 if (unlikely(!report_enabled()))
558 start_report(&flags, false);
559 pr_err("BUG: KASAN: invalid-access\n");
560 pr_err("Asynchronous fault: no details available\n");
562 dump_stack_lvl(KERN_ERR);
563 end_report(&flags, NULL);
565 #endif /* CONFIG_KASAN_HW_TAGS */
567 #ifdef CONFIG_KASAN_INLINE
569 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
570 * canonical half of the address space) cause out-of-bounds shadow memory reads
571 * before the actual access. For addresses in the low canonical half of the
572 * address space, as well as most non-canonical addresses, that out-of-bounds
573 * shadow memory access lands in the non-canonical part of the address space.
574 * Help the user figure out what the original bogus pointer was.
576 void kasan_non_canonical_hook(unsigned long addr)
578 unsigned long orig_addr;
579 const char *bug_type;
581 if (addr < KASAN_SHADOW_OFFSET)
584 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
586 * For faults near the shadow address for NULL, we can be fairly certain
587 * that this is a KASAN shadow memory access.
588 * For faults that correspond to shadow for low canonical addresses, we
589 * can still be pretty sure - that shadow region is a fairly narrow
590 * chunk of the non-canonical address space.
591 * But faults that look like shadow for non-canonical addresses are a
592 * really large chunk of the address space. In that case, we still
593 * print the decoded address, but make it clear that this is not
594 * necessarily what's actually going on.
596 if (orig_addr < PAGE_SIZE)
597 bug_type = "null-ptr-deref";
598 else if (orig_addr < TASK_SIZE)
599 bug_type = "probably user-memory-access";
601 bug_type = "maybe wild-memory-access";
602 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
603 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);