Line data Source code
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 <linux/bitops.h>
13 : #include <linux/ftrace.h>
14 : #include <linux/init.h>
15 : #include <linux/kernel.h>
16 : #include <linux/mm.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>
29 :
30 : #include <asm/sections.h>
31 :
32 : #include <kunit/test.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 0 : bool kasan_save_enable_multi_shot(void)
43 : {
44 0 : return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
45 : }
46 : EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
47 :
48 0 : void kasan_restore_multi_shot(bool enabled)
49 : {
50 0 : if (!enabled)
51 0 : clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
52 0 : }
53 : EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
54 :
55 0 : static int __init kasan_set_multi_shot(char *str)
56 : {
57 0 : set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
58 0 : return 1;
59 : }
60 : __setup("kasan_multi_shot", kasan_set_multi_shot);
61 :
62 0 : static void print_error_description(struct kasan_access_info *info)
63 : {
64 0 : pr_err("BUG: KASAN: %s in %pS\n",
65 : kasan_get_bug_type(info), (void *)info->ip);
66 0 : if (info->access_size)
67 0 : pr_err("%s of size %zu at addr %px by task %s/%d\n",
68 : info->is_write ? "Write" : "Read", info->access_size,
69 : info->access_addr, current->comm, task_pid_nr(current));
70 : else
71 0 : pr_err("%s at addr %px by task %s/%d\n",
72 : info->is_write ? "Write" : "Read",
73 : info->access_addr, current->comm, task_pid_nr(current));
74 0 : }
75 :
76 : static DEFINE_SPINLOCK(report_lock);
77 :
78 0 : static void start_report(unsigned long *flags)
79 : {
80 : /*
81 : * Make sure we don't end up in loop.
82 : */
83 0 : kasan_disable_current();
84 0 : spin_lock_irqsave(&report_lock, *flags);
85 0 : pr_err("==================================================================\n");
86 0 : }
87 :
88 0 : static void end_report(unsigned long *flags, unsigned long addr)
89 : {
90 0 : trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
91 0 : pr_err("==================================================================\n");
92 0 : add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
93 0 : spin_unlock_irqrestore(&report_lock, *flags);
94 0 : if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
95 : /*
96 : * This thread may hit another WARN() in the panic path.
97 : * Resetting this prevents additional WARN() from panicking the
98 : * system on this thread. Other threads are blocked by the
99 : * panic_mutex in panic().
100 : */
101 0 : panic_on_warn = 0;
102 0 : panic("panic_on_warn set ...\n");
103 : }
104 : #ifdef CONFIG_KASAN_HW_TAGS
105 : if (kasan_flag_panic)
106 : panic("kasan.fault=panic set ...\n");
107 : #endif
108 0 : kasan_enable_current();
109 0 : }
110 :
111 0 : static void print_stack(depot_stack_handle_t stack)
112 : {
113 0 : unsigned long *entries;
114 0 : unsigned int nr_entries;
115 :
116 0 : nr_entries = stack_depot_fetch(stack, &entries);
117 0 : stack_trace_print(entries, nr_entries, 0);
118 0 : }
119 :
120 0 : static void print_track(struct kasan_track *track, const char *prefix)
121 : {
122 0 : pr_err("%s by task %u:\n", prefix, track->pid);
123 0 : if (track->stack) {
124 0 : print_stack(track->stack);
125 : } else {
126 0 : pr_err("(stack is not available)\n");
127 : }
128 0 : }
129 :
130 734509 : struct page *kasan_addr_to_page(const void *addr)
131 : {
132 734509 : if ((addr >= (void *)PAGE_OFFSET) &&
133 734509 : (addr < high_memory))
134 733951 : return virt_to_head_page(addr);
135 : return NULL;
136 : }
137 :
138 0 : static void describe_object_addr(struct kmem_cache *cache, void *object,
139 : const void *addr)
140 : {
141 0 : unsigned long access_addr = (unsigned long)addr;
142 0 : unsigned long object_addr = (unsigned long)object;
143 0 : const char *rel_type;
144 0 : int rel_bytes;
145 :
146 0 : pr_err("The buggy address belongs to the object at %px\n"
147 : " which belongs to the cache %s of size %d\n",
148 : object, cache->name, cache->object_size);
149 :
150 0 : if (!addr)
151 : return;
152 :
153 0 : if (access_addr < object_addr) {
154 0 : rel_type = "to the left";
155 0 : rel_bytes = object_addr - access_addr;
156 0 : } else if (access_addr >= object_addr + cache->object_size) {
157 0 : rel_type = "to the right";
158 0 : rel_bytes = access_addr - (object_addr + cache->object_size);
159 : } else {
160 0 : rel_type = "inside";
161 0 : rel_bytes = access_addr - object_addr;
162 : }
163 :
164 0 : pr_err("The buggy address is located %d bytes %s of\n"
165 : " %d-byte region [%px, %px)\n",
166 : rel_bytes, rel_type, cache->object_size, (void *)object_addr,
167 : (void *)(object_addr + cache->object_size));
168 : }
169 :
170 0 : static void describe_object_stacks(struct kmem_cache *cache, void *object,
171 : const void *addr, u8 tag)
172 : {
173 0 : struct kasan_alloc_meta *alloc_meta;
174 0 : struct kasan_track *free_track;
175 :
176 0 : alloc_meta = kasan_get_alloc_meta(cache, object);
177 0 : if (alloc_meta) {
178 0 : print_track(&alloc_meta->alloc_track, "Allocated");
179 0 : pr_err("\n");
180 : }
181 :
182 0 : free_track = kasan_get_free_track(cache, object, tag);
183 0 : if (free_track) {
184 0 : print_track(free_track, "Freed");
185 0 : pr_err("\n");
186 : }
187 :
188 : #ifdef CONFIG_KASAN_GENERIC
189 0 : if (!alloc_meta)
190 : return;
191 0 : if (alloc_meta->aux_stack[0]) {
192 0 : pr_err("Last potentially related work creation:\n");
193 0 : print_stack(alloc_meta->aux_stack[0]);
194 0 : pr_err("\n");
195 : }
196 0 : if (alloc_meta->aux_stack[1]) {
197 0 : pr_err("Second to last potentially related work creation:\n");
198 0 : print_stack(alloc_meta->aux_stack[1]);
199 0 : pr_err("\n");
200 : }
201 : #endif
202 : }
203 :
204 0 : static void describe_object(struct kmem_cache *cache, void *object,
205 : const void *addr, u8 tag)
206 : {
207 0 : if (kasan_stack_collection_enabled())
208 0 : describe_object_stacks(cache, object, addr, tag);
209 0 : describe_object_addr(cache, object, addr);
210 0 : }
211 :
212 0 : static inline bool kernel_or_module_addr(const void *addr)
213 : {
214 0 : if (addr >= (void *)_stext && addr < (void *)_end)
215 0 : return true;
216 0 : if (is_module_address((unsigned long)addr))
217 : return true;
218 : return false;
219 : }
220 :
221 0 : static inline bool init_task_stack_addr(const void *addr)
222 : {
223 0 : return addr >= (void *)&init_thread_union.stack &&
224 : (addr <= (void *)&init_thread_union.stack +
225 : sizeof(init_thread_union.stack));
226 : }
227 :
228 0 : static void print_address_description(void *addr, u8 tag)
229 : {
230 0 : struct page *page = kasan_addr_to_page(addr);
231 :
232 0 : dump_stack();
233 0 : pr_err("\n");
234 :
235 0 : if (page && PageSlab(page)) {
236 0 : struct kmem_cache *cache = page->slab_cache;
237 0 : void *object = nearest_obj(cache, page, addr);
238 :
239 0 : describe_object(cache, object, addr, tag);
240 : }
241 :
242 0 : if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
243 0 : pr_err("The buggy address belongs to the variable:\n");
244 0 : pr_err(" %pS\n", addr);
245 : }
246 :
247 0 : if (page) {
248 0 : pr_err("The buggy address belongs to the page:\n");
249 0 : dump_page(page, "kasan: bad access detected");
250 : }
251 :
252 0 : kasan_print_address_stack_frame(addr);
253 0 : }
254 :
255 0 : static bool meta_row_is_guilty(const void *row, const void *addr)
256 : {
257 0 : return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
258 : }
259 :
260 0 : static int meta_pointer_offset(const void *row, const void *addr)
261 : {
262 : /*
263 : * Memory state around the buggy address:
264 : * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
265 : * ...
266 : *
267 : * The length of ">ff00ff00ff00ff00: " is
268 : * 3 + (BITS_PER_LONG / 8) * 2 chars.
269 : * The length of each granule metadata is 2 bytes
270 : * plus 1 byte for space.
271 : */
272 0 : return 3 + (BITS_PER_LONG / 8) * 2 +
273 0 : (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
274 : }
275 :
276 0 : static void print_memory_metadata(const void *addr)
277 : {
278 0 : int i;
279 0 : void *row;
280 :
281 0 : row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
282 0 : - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
283 :
284 0 : pr_err("Memory state around the buggy address:\n");
285 :
286 0 : for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
287 0 : char buffer[4 + (BITS_PER_LONG / 8) * 2];
288 0 : char metadata[META_BYTES_PER_ROW];
289 :
290 0 : snprintf(buffer, sizeof(buffer),
291 : (i == 0) ? ">%px: " : " %px: ", row);
292 :
293 : /*
294 : * We should not pass a shadow pointer to generic
295 : * function, because generic functions may try to
296 : * access kasan mapping for the passed address.
297 : */
298 0 : kasan_metadata_fetch_row(&metadata[0], row);
299 :
300 0 : print_hex_dump(KERN_ERR, buffer,
301 : DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
302 : metadata, META_BYTES_PER_ROW, 0);
303 :
304 0 : if (meta_row_is_guilty(row, addr))
305 0 : pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
306 :
307 0 : row += META_MEM_BYTES_PER_ROW;
308 : }
309 0 : }
310 :
311 59947 : static bool report_enabled(void)
312 : {
313 : #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
314 59947 : if (current->kasan_depth)
315 : return false;
316 : #endif
317 0 : if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
318 : return true;
319 0 : return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
320 : }
321 :
322 : #if IS_ENABLED(CONFIG_KUNIT)
323 : static void kasan_update_kunit_status(struct kunit *cur_test)
324 : {
325 : struct kunit_resource *resource;
326 : struct kunit_kasan_expectation *kasan_data;
327 :
328 : resource = kunit_find_named_resource(cur_test, "kasan_data");
329 :
330 : if (!resource) {
331 : kunit_set_failure(cur_test);
332 : return;
333 : }
334 :
335 : kasan_data = (struct kunit_kasan_expectation *)resource->data;
336 : WRITE_ONCE(kasan_data->report_found, true);
337 : kunit_put_resource(resource);
338 : }
339 : #endif /* IS_ENABLED(CONFIG_KUNIT) */
340 :
341 0 : void kasan_report_invalid_free(void *object, unsigned long ip)
342 : {
343 0 : unsigned long flags;
344 0 : u8 tag = get_tag(object);
345 :
346 0 : object = kasan_reset_tag(object);
347 :
348 : #if IS_ENABLED(CONFIG_KUNIT)
349 : if (current->kunit_test)
350 : kasan_update_kunit_status(current->kunit_test);
351 : #endif /* IS_ENABLED(CONFIG_KUNIT) */
352 :
353 0 : start_report(&flags);
354 0 : pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
355 0 : kasan_print_tags(tag, object);
356 0 : pr_err("\n");
357 0 : print_address_description(object, tag);
358 0 : pr_err("\n");
359 0 : print_memory_metadata(object);
360 0 : end_report(&flags, (unsigned long)object);
361 0 : }
362 :
363 0 : static void __kasan_report(unsigned long addr, size_t size, bool is_write,
364 : unsigned long ip)
365 : {
366 0 : struct kasan_access_info info;
367 0 : void *tagged_addr;
368 0 : void *untagged_addr;
369 0 : unsigned long flags;
370 :
371 : #if IS_ENABLED(CONFIG_KUNIT)
372 : if (current->kunit_test)
373 : kasan_update_kunit_status(current->kunit_test);
374 : #endif /* IS_ENABLED(CONFIG_KUNIT) */
375 :
376 0 : disable_trace_on_warning();
377 :
378 0 : tagged_addr = (void *)addr;
379 0 : untagged_addr = kasan_reset_tag(tagged_addr);
380 :
381 0 : info.access_addr = tagged_addr;
382 0 : if (addr_has_metadata(untagged_addr))
383 0 : info.first_bad_addr =
384 0 : kasan_find_first_bad_addr(tagged_addr, size);
385 : else
386 0 : info.first_bad_addr = untagged_addr;
387 0 : info.access_size = size;
388 0 : info.is_write = is_write;
389 0 : info.ip = ip;
390 :
391 0 : start_report(&flags);
392 :
393 0 : print_error_description(&info);
394 0 : if (addr_has_metadata(untagged_addr))
395 0 : kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
396 0 : pr_err("\n");
397 :
398 0 : if (addr_has_metadata(untagged_addr)) {
399 0 : print_address_description(untagged_addr, get_tag(tagged_addr));
400 0 : pr_err("\n");
401 0 : print_memory_metadata(info.first_bad_addr);
402 : } else {
403 0 : dump_stack();
404 : }
405 :
406 0 : end_report(&flags, addr);
407 0 : }
408 :
409 59947 : bool kasan_report(unsigned long addr, size_t size, bool is_write,
410 : unsigned long ip)
411 : {
412 59947 : unsigned long flags = user_access_save();
413 59947 : bool ret = false;
414 :
415 59947 : if (likely(report_enabled())) {
416 0 : __kasan_report(addr, size, is_write, ip);
417 0 : ret = true;
418 : }
419 :
420 59947 : user_access_restore(flags);
421 :
422 59947 : return ret;
423 : }
424 :
425 : #ifdef CONFIG_KASAN_INLINE
426 : /*
427 : * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
428 : * canonical half of the address space) cause out-of-bounds shadow memory reads
429 : * before the actual access. For addresses in the low canonical half of the
430 : * address space, as well as most non-canonical addresses, that out-of-bounds
431 : * shadow memory access lands in the non-canonical part of the address space.
432 : * Help the user figure out what the original bogus pointer was.
433 : */
434 0 : void kasan_non_canonical_hook(unsigned long addr)
435 : {
436 0 : unsigned long orig_addr;
437 0 : const char *bug_type;
438 :
439 0 : if (addr < KASAN_SHADOW_OFFSET)
440 : return;
441 :
442 0 : orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
443 : /*
444 : * For faults near the shadow address for NULL, we can be fairly certain
445 : * that this is a KASAN shadow memory access.
446 : * For faults that correspond to shadow for low canonical addresses, we
447 : * can still be pretty sure - that shadow region is a fairly narrow
448 : * chunk of the non-canonical address space.
449 : * But faults that look like shadow for non-canonical addresses are a
450 : * really large chunk of the address space. In that case, we still
451 : * print the decoded address, but make it clear that this is not
452 : * necessarily what's actually going on.
453 : */
454 0 : if (orig_addr < PAGE_SIZE)
455 : bug_type = "null-ptr-deref";
456 0 : else if (orig_addr < TASK_SIZE)
457 : bug_type = "probably user-memory-access";
458 : else
459 0 : bug_type = "maybe wild-memory-access";
460 0 : pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
461 : orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
462 : }
463 : #endif
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