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 <linux/bitops.h>
13 #include <linux/ftrace.h>
14 #include <linux/init.h>
15 #include <linux/kernel.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>
30 #include <asm/sections.h>
32 #include <kunit/test.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 bool kasan_save_enable_multi_shot(void)
69 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
71 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
73 void kasan_restore_multi_shot(bool enabled)
76 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
78 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
80 static int __init kasan_set_multi_shot(char *str)
82 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
85 __setup("kasan_multi_shot", kasan_set_multi_shot);
87 static void print_error_description(struct kasan_access_info *info)
89 pr_err("BUG: KASAN: %s in %pS\n",
90 kasan_get_bug_type(info), (void *)info->ip);
91 if (info->access_size)
92 pr_err("%s of size %zu at addr %px by task %s/%d\n",
93 info->is_write ? "Write" : "Read", info->access_size,
94 info->access_addr, current->comm, task_pid_nr(current));
96 pr_err("%s at addr %px by task %s/%d\n",
97 info->is_write ? "Write" : "Read",
98 info->access_addr, current->comm, task_pid_nr(current));
101 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
102 static void update_kunit_status(bool sync)
105 struct kunit_resource *resource;
106 struct kunit_kasan_status *status;
108 test = current->kunit_test;
112 resource = kunit_find_named_resource(test, "kasan_status");
114 kunit_set_failure(test);
118 status = (struct kunit_kasan_status *)resource->data;
119 WRITE_ONCE(status->report_found, true);
120 WRITE_ONCE(status->sync_fault, sync);
122 kunit_put_resource(resource);
125 static void update_kunit_status(bool sync) { }
128 static DEFINE_SPINLOCK(report_lock);
130 static void start_report(unsigned long *flags, bool sync)
132 /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
133 disable_trace_on_warning();
134 /* Update status of the currently running KASAN test. */
135 update_kunit_status(sync);
136 /* Make sure we don't end up in loop. */
137 kasan_disable_current();
138 spin_lock_irqsave(&report_lock, *flags);
139 pr_err("==================================================================\n");
142 static void end_report(unsigned long *flags, void *addr)
145 trace_error_report_end(ERROR_DETECTOR_KASAN,
146 (unsigned long)addr);
147 pr_err("==================================================================\n");
148 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
149 spin_unlock_irqrestore(&report_lock, *flags);
150 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
151 panic("panic_on_warn set ...\n");
152 if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
153 panic("kasan.fault=panic set ...\n");
154 kasan_enable_current();
157 static void print_track(struct kasan_track *track, const char *prefix)
159 pr_err("%s by task %u:\n", prefix, track->pid);
161 stack_depot_print(track->stack);
163 pr_err("(stack is not available)\n");
167 struct page *kasan_addr_to_page(const void *addr)
169 if ((addr >= (void *)PAGE_OFFSET) &&
170 (addr < high_memory))
171 return virt_to_head_page(addr);
175 struct slab *kasan_addr_to_slab(const void *addr)
177 if ((addr >= (void *)PAGE_OFFSET) &&
178 (addr < high_memory))
179 return virt_to_slab(addr);
183 static void describe_object_addr(struct kmem_cache *cache, void *object,
186 unsigned long access_addr = (unsigned long)addr;
187 unsigned long object_addr = (unsigned long)object;
188 const char *rel_type;
191 pr_err("The buggy address belongs to the object at %px\n"
192 " which belongs to the cache %s of size %d\n",
193 object, cache->name, cache->object_size);
195 if (access_addr < object_addr) {
196 rel_type = "to the left";
197 rel_bytes = object_addr - access_addr;
198 } else if (access_addr >= object_addr + cache->object_size) {
199 rel_type = "to the right";
200 rel_bytes = access_addr - (object_addr + cache->object_size);
203 rel_bytes = access_addr - object_addr;
206 pr_err("The buggy address is located %d bytes %s of\n"
207 " %d-byte region [%px, %px)\n",
208 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
209 (void *)(object_addr + cache->object_size));
212 static void describe_object_stacks(struct kmem_cache *cache, void *object,
213 const void *addr, u8 tag)
215 struct kasan_alloc_meta *alloc_meta;
216 struct kasan_track *free_track;
218 alloc_meta = kasan_get_alloc_meta(cache, object);
220 print_track(&alloc_meta->alloc_track, "Allocated");
224 free_track = kasan_get_free_track(cache, object, tag);
226 print_track(free_track, "Freed");
230 #ifdef CONFIG_KASAN_GENERIC
233 if (alloc_meta->aux_stack[0]) {
234 pr_err("Last potentially related work creation:\n");
235 stack_depot_print(alloc_meta->aux_stack[0]);
238 if (alloc_meta->aux_stack[1]) {
239 pr_err("Second to last potentially related work creation:\n");
240 stack_depot_print(alloc_meta->aux_stack[1]);
246 static void describe_object(struct kmem_cache *cache, void *object,
247 const void *addr, u8 tag)
249 if (kasan_stack_collection_enabled())
250 describe_object_stacks(cache, object, addr, tag);
251 describe_object_addr(cache, object, addr);
254 static inline bool kernel_or_module_addr(const void *addr)
256 if (is_kernel((unsigned long)addr))
258 if (is_module_address((unsigned long)addr))
263 static inline bool init_task_stack_addr(const void *addr)
265 return addr >= (void *)&init_thread_union.stack &&
266 (addr <= (void *)&init_thread_union.stack +
267 sizeof(init_thread_union.stack));
270 static void print_address_description(void *addr, u8 tag)
272 struct page *page = kasan_addr_to_page(addr);
274 dump_stack_lvl(KERN_ERR);
277 if (page && PageSlab(page)) {
278 struct slab *slab = page_slab(page);
279 struct kmem_cache *cache = slab->slab_cache;
280 void *object = nearest_obj(cache, slab, addr);
282 describe_object(cache, object, addr, tag);
286 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
287 pr_err("The buggy address belongs to the variable:\n");
288 pr_err(" %pS\n", addr);
292 if (object_is_on_stack(addr)) {
294 * Currently, KASAN supports printing frame information only
295 * for accesses to the task's own stack.
297 kasan_print_address_stack_frame(addr);
301 if (is_vmalloc_addr(addr)) {
302 struct vm_struct *va = find_vm_area(addr);
305 pr_err("The buggy address belongs to the virtual mapping at\n"
306 " [%px, %px) created by:\n"
308 va->addr, va->addr + va->size, va->caller);
311 page = vmalloc_to_page(page);
316 pr_err("The buggy address belongs to the physical page:\n");
317 dump_page(page, "kasan: bad access detected");
322 static bool meta_row_is_guilty(const void *row, const void *addr)
324 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
327 static int meta_pointer_offset(const void *row, const void *addr)
330 * Memory state around the buggy address:
331 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
334 * The length of ">ff00ff00ff00ff00: " is
335 * 3 + (BITS_PER_LONG / 8) * 2 chars.
336 * The length of each granule metadata is 2 bytes
337 * plus 1 byte for space.
339 return 3 + (BITS_PER_LONG / 8) * 2 +
340 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
343 static void print_memory_metadata(const void *addr)
348 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
349 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
351 pr_err("Memory state around the buggy address:\n");
353 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
354 char buffer[4 + (BITS_PER_LONG / 8) * 2];
355 char metadata[META_BYTES_PER_ROW];
357 snprintf(buffer, sizeof(buffer),
358 (i == 0) ? ">%px: " : " %px: ", row);
361 * We should not pass a shadow pointer to generic
362 * function, because generic functions may try to
363 * access kasan mapping for the passed address.
365 kasan_metadata_fetch_row(&metadata[0], row);
367 print_hex_dump(KERN_ERR, buffer,
368 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
369 metadata, META_BYTES_PER_ROW, 0);
371 if (meta_row_is_guilty(row, addr))
372 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
374 row += META_MEM_BYTES_PER_ROW;
378 static bool report_enabled(void)
380 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
381 if (current->kasan_depth)
384 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
386 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
389 void kasan_report_invalid_free(void *object, unsigned long ip)
392 u8 tag = get_tag(object);
394 object = kasan_reset_tag(object);
396 start_report(&flags, true);
397 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
398 kasan_print_tags(tag, object);
400 print_address_description(object, tag);
401 print_memory_metadata(object);
402 end_report(&flags, object);
405 #ifdef CONFIG_KASAN_HW_TAGS
406 void kasan_report_async(void)
410 start_report(&flags, false);
411 pr_err("BUG: KASAN: invalid-access\n");
412 pr_err("Asynchronous mode enabled: no access details available\n");
414 dump_stack_lvl(KERN_ERR);
415 end_report(&flags, NULL);
417 #endif /* CONFIG_KASAN_HW_TAGS */
419 static void print_report(struct kasan_access_info *info)
421 void *tagged_addr = info->access_addr;
422 void *untagged_addr = kasan_reset_tag(tagged_addr);
423 u8 tag = get_tag(tagged_addr);
425 print_error_description(info);
426 if (addr_has_metadata(untagged_addr))
427 kasan_print_tags(tag, info->first_bad_addr);
430 if (addr_has_metadata(untagged_addr)) {
431 print_address_description(untagged_addr, tag);
432 print_memory_metadata(info->first_bad_addr);
434 dump_stack_lvl(KERN_ERR);
438 static void __kasan_report(void *addr, size_t size, bool is_write,
441 struct kasan_access_info info;
444 start_report(&flags, true);
446 info.access_addr = addr;
447 if (addr_has_metadata(addr))
448 info.first_bad_addr = kasan_find_first_bad_addr(addr, size);
450 info.first_bad_addr = addr;
451 info.access_size = size;
452 info.is_write = is_write;
457 end_report(&flags, addr);
460 bool kasan_report(unsigned long addr, size_t size, bool is_write,
463 unsigned long flags = user_access_save();
466 if (likely(report_enabled())) {
467 __kasan_report((void *)addr, size, is_write, ip);
471 user_access_restore(flags);
476 #ifdef CONFIG_KASAN_INLINE
478 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
479 * canonical half of the address space) cause out-of-bounds shadow memory reads
480 * before the actual access. For addresses in the low canonical half of the
481 * address space, as well as most non-canonical addresses, that out-of-bounds
482 * shadow memory access lands in the non-canonical part of the address space.
483 * Help the user figure out what the original bogus pointer was.
485 void kasan_non_canonical_hook(unsigned long addr)
487 unsigned long orig_addr;
488 const char *bug_type;
490 if (addr < KASAN_SHADOW_OFFSET)
493 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
495 * For faults near the shadow address for NULL, we can be fairly certain
496 * that this is a KASAN shadow memory access.
497 * For faults that correspond to shadow for low canonical addresses, we
498 * can still be pretty sure - that shadow region is a fairly narrow
499 * chunk of the non-canonical address space.
500 * But faults that look like shadow for non-canonical addresses are a
501 * really large chunk of the address space. In that case, we still
502 * print the decoded address, but make it clear that this is not
503 * necessarily what's actually going on.
505 if (orig_addr < PAGE_SIZE)
506 bug_type = "null-ptr-deref";
507 else if (orig_addr < TASK_SIZE)
508 bug_type = "probably user-memory-access";
510 bug_type = "maybe wild-memory-access";
511 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
512 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);