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>
29 #include <asm/sections.h>
31 #include <kunit/test.h>
36 static unsigned long kasan_flags;
38 #define KASAN_BIT_REPORTED 0
39 #define KASAN_BIT_MULTI_SHOT 1
41 bool kasan_save_enable_multi_shot(void)
43 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
45 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
47 void kasan_restore_multi_shot(bool enabled)
50 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
52 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
54 static int __init kasan_set_multi_shot(char *str)
56 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
59 __setup("kasan_multi_shot", kasan_set_multi_shot);
61 static void print_error_description(struct kasan_access_info *info)
63 pr_err("BUG: KASAN: %s in %pS\n",
64 get_bug_type(info), (void *)info->ip);
65 if (info->access_size)
66 pr_err("%s of size %zu at addr %px by task %s/%d\n",
67 info->is_write ? "Write" : "Read", info->access_size,
68 info->access_addr, current->comm, task_pid_nr(current));
70 pr_err("%s at addr %px by task %s/%d\n",
71 info->is_write ? "Write" : "Read",
72 info->access_addr, current->comm, task_pid_nr(current));
75 static DEFINE_SPINLOCK(report_lock);
77 static void start_report(unsigned long *flags)
80 * Make sure we don't end up in loop.
82 kasan_disable_current();
83 spin_lock_irqsave(&report_lock, *flags);
84 pr_err("==================================================================\n");
87 static void end_report(unsigned long *flags)
89 pr_err("==================================================================\n");
90 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
91 spin_unlock_irqrestore(&report_lock, *flags);
92 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
94 * This thread may hit another WARN() in the panic path.
95 * Resetting this prevents additional WARN() from panicking the
96 * system on this thread. Other threads are blocked by the
97 * panic_mutex in panic().
100 panic("panic_on_warn set ...\n");
102 #ifdef CONFIG_KASAN_HW_TAGS
103 if (kasan_flag_panic)
104 panic("kasan.fault=panic set ...\n");
106 kasan_enable_current();
109 static void print_stack(depot_stack_handle_t stack)
111 unsigned long *entries;
112 unsigned int nr_entries;
114 nr_entries = stack_depot_fetch(stack, &entries);
115 stack_trace_print(entries, nr_entries, 0);
118 static void print_track(struct kasan_track *track, const char *prefix)
120 pr_err("%s by task %u:\n", prefix, track->pid);
122 print_stack(track->stack);
124 pr_err("(stack is not available)\n");
128 struct page *kasan_addr_to_page(const void *addr)
130 if ((addr >= (void *)PAGE_OFFSET) &&
131 (addr < high_memory))
132 return virt_to_head_page(addr);
136 static void describe_object_addr(struct kmem_cache *cache, void *object,
139 unsigned long access_addr = (unsigned long)addr;
140 unsigned long object_addr = (unsigned long)object;
141 const char *rel_type;
144 pr_err("The buggy address belongs to the object at %px\n"
145 " which belongs to the cache %s of size %d\n",
146 object, cache->name, cache->object_size);
151 if (access_addr < object_addr) {
152 rel_type = "to the left";
153 rel_bytes = object_addr - access_addr;
154 } else if (access_addr >= object_addr + cache->object_size) {
155 rel_type = "to the right";
156 rel_bytes = access_addr - (object_addr + cache->object_size);
159 rel_bytes = access_addr - object_addr;
162 pr_err("The buggy address is located %d bytes %s of\n"
163 " %d-byte region [%px, %px)\n",
164 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
165 (void *)(object_addr + cache->object_size));
168 static void describe_object_stacks(struct kmem_cache *cache, void *object,
169 const void *addr, u8 tag)
171 struct kasan_alloc_meta *alloc_meta;
172 struct kasan_track *free_track;
174 alloc_meta = kasan_get_alloc_meta(cache, object);
176 print_track(&alloc_meta->alloc_track, "Allocated");
180 free_track = kasan_get_free_track(cache, object, tag);
182 print_track(free_track, "Freed");
186 #ifdef CONFIG_KASAN_GENERIC
189 if (alloc_meta->aux_stack[0]) {
190 pr_err("Last potentially related work creation:\n");
191 print_stack(alloc_meta->aux_stack[0]);
194 if (alloc_meta->aux_stack[1]) {
195 pr_err("Second to last potentially related work creation:\n");
196 print_stack(alloc_meta->aux_stack[1]);
202 static void describe_object(struct kmem_cache *cache, void *object,
203 const void *addr, u8 tag)
205 if (kasan_stack_collection_enabled())
206 describe_object_stacks(cache, object, addr, tag);
207 describe_object_addr(cache, object, addr);
210 static inline bool kernel_or_module_addr(const void *addr)
212 if (addr >= (void *)_stext && addr < (void *)_end)
214 if (is_module_address((unsigned long)addr))
219 static inline bool init_task_stack_addr(const void *addr)
221 return addr >= (void *)&init_thread_union.stack &&
222 (addr <= (void *)&init_thread_union.stack +
223 sizeof(init_thread_union.stack));
226 static void print_address_description(void *addr, u8 tag)
228 struct page *page = kasan_addr_to_page(addr);
233 if (page && PageSlab(page)) {
234 struct kmem_cache *cache = page->slab_cache;
235 void *object = nearest_obj(cache, page, addr);
237 describe_object(cache, object, addr, tag);
240 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
241 pr_err("The buggy address belongs to the variable:\n");
242 pr_err(" %pS\n", addr);
246 pr_err("The buggy address belongs to the page:\n");
247 dump_page(page, "kasan: bad access detected");
250 print_address_stack_frame(addr);
253 static bool meta_row_is_guilty(const void *row, const void *addr)
255 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
258 static int meta_pointer_offset(const void *row, const void *addr)
261 * Memory state around the buggy address:
262 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
265 * The length of ">ff00ff00ff00ff00: " is
266 * 3 + (BITS_PER_LONG / 8) * 2 chars.
267 * The length of each granule metadata is 2 bytes
268 * plus 1 byte for space.
270 return 3 + (BITS_PER_LONG / 8) * 2 +
271 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
274 static void print_memory_metadata(const void *addr)
279 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
280 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
282 pr_err("Memory state around the buggy address:\n");
284 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
285 char buffer[4 + (BITS_PER_LONG / 8) * 2];
286 char metadata[META_BYTES_PER_ROW];
288 snprintf(buffer, sizeof(buffer),
289 (i == 0) ? ">%px: " : " %px: ", row);
292 * We should not pass a shadow pointer to generic
293 * function, because generic functions may try to
294 * access kasan mapping for the passed address.
296 metadata_fetch_row(&metadata[0], row);
298 print_hex_dump(KERN_ERR, buffer,
299 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
300 metadata, META_BYTES_PER_ROW, 0);
302 if (meta_row_is_guilty(row, addr))
303 pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
305 row += META_MEM_BYTES_PER_ROW;
309 static bool report_enabled(void)
311 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
312 if (current->kasan_depth)
315 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
317 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
320 #if IS_ENABLED(CONFIG_KUNIT)
321 static void kasan_update_kunit_status(struct kunit *cur_test)
323 struct kunit_resource *resource;
324 struct kunit_kasan_expectation *kasan_data;
326 resource = kunit_find_named_resource(cur_test, "kasan_data");
329 kunit_set_failure(cur_test);
333 kasan_data = (struct kunit_kasan_expectation *)resource->data;
334 kasan_data->report_found = true;
335 kunit_put_resource(resource);
337 #endif /* IS_ENABLED(CONFIG_KUNIT) */
339 void kasan_report_invalid_free(void *object, unsigned long ip)
342 u8 tag = get_tag(object);
344 object = kasan_reset_tag(object);
346 #if IS_ENABLED(CONFIG_KUNIT)
347 if (current->kunit_test)
348 kasan_update_kunit_status(current->kunit_test);
349 #endif /* IS_ENABLED(CONFIG_KUNIT) */
351 start_report(&flags);
352 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
353 print_tags(tag, object);
355 print_address_description(object, tag);
357 print_memory_metadata(object);
361 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
364 struct kasan_access_info info;
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) */
374 disable_trace_on_warning();
376 tagged_addr = (void *)addr;
377 untagged_addr = kasan_reset_tag(tagged_addr);
379 info.access_addr = tagged_addr;
380 if (addr_has_metadata(untagged_addr))
381 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
383 info.first_bad_addr = untagged_addr;
384 info.access_size = size;
385 info.is_write = is_write;
388 start_report(&flags);
390 print_error_description(&info);
391 if (addr_has_metadata(untagged_addr))
392 print_tags(get_tag(tagged_addr), info.first_bad_addr);
395 if (addr_has_metadata(untagged_addr)) {
396 print_address_description(untagged_addr, get_tag(tagged_addr));
398 print_memory_metadata(info.first_bad_addr);
406 bool kasan_report(unsigned long addr, size_t size, bool is_write,
409 unsigned long flags = user_access_save();
412 if (likely(report_enabled())) {
413 __kasan_report(addr, size, is_write, ip);
417 user_access_restore(flags);
422 #ifdef CONFIG_KASAN_INLINE
424 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
425 * canonical half of the address space) cause out-of-bounds shadow memory reads
426 * before the actual access. For addresses in the low canonical half of the
427 * address space, as well as most non-canonical addresses, that out-of-bounds
428 * shadow memory access lands in the non-canonical part of the address space.
429 * Help the user figure out what the original bogus pointer was.
431 void kasan_non_canonical_hook(unsigned long addr)
433 unsigned long orig_addr;
434 const char *bug_type;
436 if (addr < KASAN_SHADOW_OFFSET)
439 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
441 * For faults near the shadow address for NULL, we can be fairly certain
442 * that this is a KASAN shadow memory access.
443 * For faults that correspond to shadow for low canonical addresses, we
444 * can still be pretty sure - that shadow region is a fairly narrow
445 * chunk of the non-canonical address space.
446 * But faults that look like shadow for non-canonical addresses are a
447 * really large chunk of the address space. In that case, we still
448 * print the decoded address, but make it clear that this is not
449 * necessarily what's actually going on.
451 if (orig_addr < PAGE_SIZE)
452 bug_type = "null-ptr-deref";
453 else if (orig_addr < TASK_SIZE)
454 bug_type = "probably user-memory-access";
456 bug_type = "maybe wild-memory-access";
457 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
458 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);