1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains common generic and tag-based 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>
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
17 #include <linux/bitops.h>
18 #include <linux/ftrace.h>
19 #include <linux/init.h>
20 #include <linux/kernel.h>
22 #include <linux/printk.h>
23 #include <linux/sched.h>
24 #include <linux/slab.h>
25 #include <linux/stackdepot.h>
26 #include <linux/stacktrace.h>
27 #include <linux/string.h>
28 #include <linux/types.h>
29 #include <linux/kasan.h>
30 #include <linux/module.h>
31 #include <linux/sched/task_stack.h>
32 #include <linux/uaccess.h>
34 #include <asm/sections.h>
36 #include <kunit/test.h>
41 /* Shadow layout customization. */
42 #define SHADOW_BYTES_PER_BLOCK 1
43 #define SHADOW_BLOCKS_PER_ROW 16
44 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
45 #define SHADOW_ROWS_AROUND_ADDR 2
47 static unsigned long kasan_flags;
49 #define KASAN_BIT_REPORTED 0
50 #define KASAN_BIT_MULTI_SHOT 1
52 bool kasan_save_enable_multi_shot(void)
54 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
56 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
58 void kasan_restore_multi_shot(bool enabled)
61 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
63 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
65 static int __init kasan_set_multi_shot(char *str)
67 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
70 __setup("kasan_multi_shot", kasan_set_multi_shot);
72 static void print_error_description(struct kasan_access_info *info)
74 pr_err("BUG: KASAN: %s in %pS\n",
75 get_bug_type(info), (void *)info->ip);
76 pr_err("%s of size %zu at addr %px by task %s/%d\n",
77 info->is_write ? "Write" : "Read", info->access_size,
78 info->access_addr, current->comm, task_pid_nr(current));
81 static DEFINE_SPINLOCK(report_lock);
83 static void start_report(unsigned long *flags)
86 * Make sure we don't end up in loop.
88 kasan_disable_current();
89 spin_lock_irqsave(&report_lock, *flags);
90 pr_err("==================================================================\n");
93 static void end_report(unsigned long *flags)
95 pr_err("==================================================================\n");
96 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
97 spin_unlock_irqrestore(&report_lock, *flags);
98 if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
99 check_panic_on_warn("KASAN");
100 kasan_enable_current();
103 static void print_stack(depot_stack_handle_t stack)
105 unsigned long *entries;
106 unsigned int nr_entries;
108 nr_entries = stack_depot_fetch(stack, &entries);
109 stack_trace_print(entries, nr_entries, 0);
112 static void print_track(struct kasan_track *track, const char *prefix)
114 pr_err("%s by task %u:\n", prefix, track->pid);
116 print_stack(track->stack);
118 pr_err("(stack is not available)\n");
122 struct page *kasan_addr_to_page(const void *addr)
124 if ((addr >= (void *)PAGE_OFFSET) &&
125 (addr < high_memory))
126 return virt_to_head_page(addr);
130 static void describe_object_addr(struct kmem_cache *cache, void *object,
133 unsigned long access_addr = (unsigned long)addr;
134 unsigned long object_addr = (unsigned long)object;
135 const char *rel_type;
138 pr_err("The buggy address belongs to the object at %px\n"
139 " which belongs to the cache %s of size %d\n",
140 object, cache->name, cache->object_size);
145 if (access_addr < object_addr) {
146 rel_type = "to the left";
147 rel_bytes = object_addr - access_addr;
148 } else if (access_addr >= object_addr + cache->object_size) {
149 rel_type = "to the right";
150 rel_bytes = access_addr - (object_addr + cache->object_size);
153 rel_bytes = access_addr - object_addr;
156 pr_err("The buggy address is located %d bytes %s of\n"
157 " %d-byte region [%px, %px)\n",
158 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
159 (void *)(object_addr + cache->object_size));
162 static void describe_object(struct kmem_cache *cache, void *object,
163 const void *addr, u8 tag)
165 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
167 if (cache->flags & SLAB_KASAN) {
168 struct kasan_track *free_track;
170 print_track(&alloc_info->alloc_track, "Allocated");
172 free_track = kasan_get_free_track(cache, object, tag);
174 print_track(free_track, "Freed");
178 #ifdef CONFIG_KASAN_GENERIC
179 if (alloc_info->aux_stack[0]) {
180 pr_err("Last call_rcu():\n");
181 print_stack(alloc_info->aux_stack[0]);
184 if (alloc_info->aux_stack[1]) {
185 pr_err("Second to last call_rcu():\n");
186 print_stack(alloc_info->aux_stack[1]);
192 describe_object_addr(cache, object, addr);
195 static inline bool kernel_or_module_addr(const void *addr)
197 if (addr >= (void *)_stext && addr < (void *)_end)
199 if (is_module_address((unsigned long)addr))
204 static inline bool init_task_stack_addr(const void *addr)
206 return addr >= (void *)&init_thread_union.stack &&
207 (addr <= (void *)&init_thread_union.stack +
208 sizeof(init_thread_union.stack));
211 static bool __must_check tokenize_frame_descr(const char **frame_descr,
212 char *token, size_t max_tok_len,
213 unsigned long *value)
215 const char *sep = strchr(*frame_descr, ' ');
218 sep = *frame_descr + strlen(*frame_descr);
221 const size_t tok_len = sep - *frame_descr;
223 if (tok_len + 1 > max_tok_len) {
224 pr_err("KASAN internal error: frame description too long: %s\n",
229 /* Copy token (+ 1 byte for '\0'). */
230 strlcpy(token, *frame_descr, tok_len + 1);
233 /* Advance frame_descr past separator. */
234 *frame_descr = sep + 1;
236 if (value != NULL && kstrtoul(token, 10, value)) {
237 pr_err("KASAN internal error: not a valid number: %s\n", token);
244 static void print_decoded_frame_descr(const char *frame_descr)
247 * We need to parse the following string:
248 * "n alloc_1 alloc_2 ... alloc_n"
249 * where alloc_i looks like
250 * "offset size len name"
251 * or "offset size len name:line".
255 unsigned long num_objects;
257 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
262 pr_err("this frame has %lu %s:\n", num_objects,
263 num_objects == 1 ? "object" : "objects");
265 while (num_objects--) {
266 unsigned long offset;
270 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
274 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
277 /* name length (unused) */
278 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
281 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
285 /* Strip line number; without filename it's not very helpful. */
286 strreplace(token, ':', '\0');
288 /* Finally, print object information. */
289 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
293 static bool __must_check get_address_stack_frame_info(const void *addr,
294 unsigned long *offset,
295 const char **frame_descr,
296 const void **frame_pc)
298 unsigned long aligned_addr;
299 unsigned long mem_ptr;
300 const u8 *shadow_bottom;
301 const u8 *shadow_ptr;
302 const unsigned long *frame;
304 BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
307 * NOTE: We currently only support printing frame information for
308 * accesses to the task's own stack.
310 if (!object_is_on_stack(addr))
313 aligned_addr = round_down((unsigned long)addr, sizeof(long));
314 mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE);
315 shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
316 shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
318 while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
320 mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
323 while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
325 mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
328 if (shadow_ptr < shadow_bottom)
331 frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
332 if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
333 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
338 *offset = (unsigned long)addr - (unsigned long)frame;
339 *frame_descr = (const char *)frame[1];
340 *frame_pc = (void *)frame[2];
345 static void print_address_stack_frame(const void *addr)
347 unsigned long offset;
348 const char *frame_descr;
349 const void *frame_pc;
351 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
354 if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
359 * get_address_stack_frame_info only returns true if the given addr is
360 * on the current task's stack.
363 pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
364 addr, current->comm, task_pid_nr(current), offset);
365 pr_err(" %pS\n", frame_pc);
370 print_decoded_frame_descr(frame_descr);
373 static void print_address_description(void *addr, u8 tag)
375 struct page *page = kasan_addr_to_page(addr);
380 if (page && PageSlab(page)) {
381 struct kmem_cache *cache = page->slab_cache;
382 void *object = nearest_obj(cache, page, addr);
384 describe_object(cache, object, addr, tag);
387 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
388 pr_err("The buggy address belongs to the variable:\n");
389 pr_err(" %pS\n", addr);
393 pr_err("The buggy address belongs to the page:\n");
394 dump_page(page, "kasan: bad access detected");
397 print_address_stack_frame(addr);
400 static bool row_is_guilty(const void *row, const void *guilty)
402 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
405 static int shadow_pointer_offset(const void *row, const void *shadow)
407 /* The length of ">ff00ff00ff00ff00: " is
408 * 3 + (BITS_PER_LONG/8)*2 chars.
410 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
411 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
414 static void print_shadow_for_address(const void *addr)
417 const void *shadow = kasan_mem_to_shadow(addr);
418 const void *shadow_row;
420 shadow_row = (void *)round_down((unsigned long)shadow,
421 SHADOW_BYTES_PER_ROW)
422 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
424 pr_err("Memory state around the buggy address:\n");
426 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
427 const void *kaddr = kasan_shadow_to_mem(shadow_row);
428 char buffer[4 + (BITS_PER_LONG/8)*2];
429 char shadow_buf[SHADOW_BYTES_PER_ROW];
431 snprintf(buffer, sizeof(buffer),
432 (i == 0) ? ">%px: " : " %px: ", kaddr);
434 * We should not pass a shadow pointer to generic
435 * function, because generic functions may try to
436 * access kasan mapping for the passed address.
438 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
439 print_hex_dump(KERN_ERR, buffer,
440 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
441 shadow_buf, SHADOW_BYTES_PER_ROW, 0);
443 if (row_is_guilty(shadow_row, shadow))
445 shadow_pointer_offset(shadow_row, shadow),
448 shadow_row += SHADOW_BYTES_PER_ROW;
452 static bool report_enabled(void)
454 if (current->kasan_depth)
456 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
458 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
461 #if IS_ENABLED(CONFIG_KUNIT)
462 static void kasan_update_kunit_status(struct kunit *cur_test)
464 struct kunit_resource *resource;
465 struct kunit_kasan_expectation *kasan_data;
467 resource = kunit_find_named_resource(cur_test, "kasan_data");
470 kunit_set_failure(cur_test);
474 kasan_data = (struct kunit_kasan_expectation *)resource->data;
475 kasan_data->report_found = true;
476 kunit_put_resource(resource);
478 #endif /* IS_ENABLED(CONFIG_KUNIT) */
480 void kasan_report_invalid_free(void *object, unsigned long ip)
483 u8 tag = get_tag(object);
485 object = reset_tag(object);
487 #if IS_ENABLED(CONFIG_KUNIT)
488 if (current->kunit_test)
489 kasan_update_kunit_status(current->kunit_test);
490 #endif /* IS_ENABLED(CONFIG_KUNIT) */
492 start_report(&flags);
493 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
494 print_tags(tag, object);
496 print_address_description(object, tag);
498 print_shadow_for_address(object);
502 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
505 struct kasan_access_info info;
510 #if IS_ENABLED(CONFIG_KUNIT)
511 if (current->kunit_test)
512 kasan_update_kunit_status(current->kunit_test);
513 #endif /* IS_ENABLED(CONFIG_KUNIT) */
515 disable_trace_on_warning();
517 tagged_addr = (void *)addr;
518 untagged_addr = reset_tag(tagged_addr);
520 info.access_addr = tagged_addr;
521 if (addr_has_shadow(untagged_addr))
522 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
524 info.first_bad_addr = untagged_addr;
525 info.access_size = size;
526 info.is_write = is_write;
529 start_report(&flags);
531 print_error_description(&info);
532 if (addr_has_shadow(untagged_addr))
533 print_tags(get_tag(tagged_addr), info.first_bad_addr);
536 if (addr_has_shadow(untagged_addr)) {
537 print_address_description(untagged_addr, get_tag(tagged_addr));
539 print_shadow_for_address(info.first_bad_addr);
547 bool kasan_report(unsigned long addr, size_t size, bool is_write,
550 unsigned long flags = user_access_save();
553 if (likely(report_enabled())) {
554 __kasan_report(addr, size, is_write, ip);
558 user_access_restore(flags);
564 * With CONFIG_KASAN, accesses to bogus pointers (outside the high
565 * canonical half of the address space) cause out-of-bounds shadow memory reads
566 * before the actual access. For addresses in the low canonical half of the
567 * address space, as well as most non-canonical addresses, that out-of-bounds
568 * shadow memory access lands in the non-canonical part of the address space.
569 * Help the user figure out what the original bogus pointer was.
571 void kasan_non_canonical_hook(unsigned long addr)
573 unsigned long orig_addr;
574 const char *bug_type;
576 if (addr < KASAN_SHADOW_OFFSET)
579 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
581 * For faults near the shadow address for NULL, we can be fairly certain
582 * that this is a KASAN shadow memory access.
583 * For faults that correspond to shadow for low canonical addresses, we
584 * can still be pretty sure - that shadow region is a fairly narrow
585 * chunk of the non-canonical address space.
586 * But faults that look like shadow for non-canonical addresses are a
587 * really large chunk of the address space. In that case, we still
588 * print the decoded address, but make it clear that this is not
589 * necessarily what's actually going on.
591 if (orig_addr < PAGE_SIZE)
592 bug_type = "null-ptr-deref";
593 else if (orig_addr < TASK_SIZE)
594 bug_type = "probably user-memory-access";
596 bug_type = "maybe wild-memory-access";
597 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
598 orig_addr, orig_addr + KASAN_SHADOW_MASK);