Merge tag 'compiler-attributes-for-linus-v5.11' of git://github.com/ojeda/linux
[linux-2.6-microblaze.git] / mm / kasan / report.c
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
29 #include <asm/sections.h>
30
31 #include <kunit/test.h>
32
33 #include "kasan.h"
34 #include "../slab.h"
35
36 static unsigned long kasan_flags;
37
38 #define KASAN_BIT_REPORTED      0
39 #define KASAN_BIT_MULTI_SHOT    1
40
41 bool kasan_save_enable_multi_shot(void)
42 {
43         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
44 }
45 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
46
47 void kasan_restore_multi_shot(bool enabled)
48 {
49         if (!enabled)
50                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
51 }
52 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
53
54 static int __init kasan_set_multi_shot(char *str)
55 {
56         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
57         return 1;
58 }
59 __setup("kasan_multi_shot", kasan_set_multi_shot);
60
61 static void print_error_description(struct kasan_access_info *info)
62 {
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));
69         else
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));
73 }
74
75 static DEFINE_SPINLOCK(report_lock);
76
77 static void start_report(unsigned long *flags)
78 {
79         /*
80          * Make sure we don't end up in loop.
81          */
82         kasan_disable_current();
83         spin_lock_irqsave(&report_lock, *flags);
84         pr_err("==================================================================\n");
85 }
86
87 static void end_report(unsigned long *flags)
88 {
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)) {
93                 /*
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().
98                  */
99                 panic_on_warn = 0;
100                 panic("panic_on_warn set ...\n");
101         }
102 #ifdef CONFIG_KASAN_HW_TAGS
103         if (kasan_flag_panic)
104                 panic("kasan.fault=panic set ...\n");
105 #endif
106         kasan_enable_current();
107 }
108
109 static void print_stack(depot_stack_handle_t stack)
110 {
111         unsigned long *entries;
112         unsigned int nr_entries;
113
114         nr_entries = stack_depot_fetch(stack, &entries);
115         stack_trace_print(entries, nr_entries, 0);
116 }
117
118 static void print_track(struct kasan_track *track, const char *prefix)
119 {
120         pr_err("%s by task %u:\n", prefix, track->pid);
121         if (track->stack) {
122                 print_stack(track->stack);
123         } else {
124                 pr_err("(stack is not available)\n");
125         }
126 }
127
128 struct page *kasan_addr_to_page(const void *addr)
129 {
130         if ((addr >= (void *)PAGE_OFFSET) &&
131                         (addr < high_memory))
132                 return virt_to_head_page(addr);
133         return NULL;
134 }
135
136 static void describe_object_addr(struct kmem_cache *cache, void *object,
137                                 const void *addr)
138 {
139         unsigned long access_addr = (unsigned long)addr;
140         unsigned long object_addr = (unsigned long)object;
141         const char *rel_type;
142         int rel_bytes;
143
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);
147
148         if (!addr)
149                 return;
150
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);
157         } else {
158                 rel_type = "inside";
159                 rel_bytes = access_addr - object_addr;
160         }
161
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));
166 }
167
168 static void describe_object_stacks(struct kmem_cache *cache, void *object,
169                                         const void *addr, u8 tag)
170 {
171         struct kasan_alloc_meta *alloc_meta;
172         struct kasan_track *free_track;
173
174         alloc_meta = kasan_get_alloc_meta(cache, object);
175         if (alloc_meta) {
176                 print_track(&alloc_meta->alloc_track, "Allocated");
177                 pr_err("\n");
178         }
179
180         free_track = kasan_get_free_track(cache, object, tag);
181         if (free_track) {
182                 print_track(free_track, "Freed");
183                 pr_err("\n");
184         }
185
186 #ifdef CONFIG_KASAN_GENERIC
187         if (!alloc_meta)
188                 return;
189         if (alloc_meta->aux_stack[0]) {
190                 pr_err("Last potentially related work creation:\n");
191                 print_stack(alloc_meta->aux_stack[0]);
192                 pr_err("\n");
193         }
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]);
197                 pr_err("\n");
198         }
199 #endif
200 }
201
202 static void describe_object(struct kmem_cache *cache, void *object,
203                                 const void *addr, u8 tag)
204 {
205         if (kasan_stack_collection_enabled())
206                 describe_object_stacks(cache, object, addr, tag);
207         describe_object_addr(cache, object, addr);
208 }
209
210 static inline bool kernel_or_module_addr(const void *addr)
211 {
212         if (addr >= (void *)_stext && addr < (void *)_end)
213                 return true;
214         if (is_module_address((unsigned long)addr))
215                 return true;
216         return false;
217 }
218
219 static inline bool init_task_stack_addr(const void *addr)
220 {
221         return addr >= (void *)&init_thread_union.stack &&
222                 (addr <= (void *)&init_thread_union.stack +
223                         sizeof(init_thread_union.stack));
224 }
225
226 static void print_address_description(void *addr, u8 tag)
227 {
228         struct page *page = kasan_addr_to_page(addr);
229
230         dump_stack();
231         pr_err("\n");
232
233         if (page && PageSlab(page)) {
234                 struct kmem_cache *cache = page->slab_cache;
235                 void *object = nearest_obj(cache, page, addr);
236
237                 describe_object(cache, object, addr, tag);
238         }
239
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);
243         }
244
245         if (page) {
246                 pr_err("The buggy address belongs to the page:\n");
247                 dump_page(page, "kasan: bad access detected");
248         }
249
250         print_address_stack_frame(addr);
251 }
252
253 static bool meta_row_is_guilty(const void *row, const void *addr)
254 {
255         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
256 }
257
258 static int meta_pointer_offset(const void *row, const void *addr)
259 {
260         /*
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
263          *  ...
264          *
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.
269          */
270         return 3 + (BITS_PER_LONG / 8) * 2 +
271                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
272 }
273
274 static void print_memory_metadata(const void *addr)
275 {
276         int i;
277         void *row;
278
279         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
280                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
281
282         pr_err("Memory state around the buggy address:\n");
283
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];
287
288                 snprintf(buffer, sizeof(buffer),
289                                 (i == 0) ? ">%px: " : " %px: ", row);
290
291                 /*
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.
295                  */
296                 metadata_fetch_row(&metadata[0], row);
297
298                 print_hex_dump(KERN_ERR, buffer,
299                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
300                         metadata, META_BYTES_PER_ROW, 0);
301
302                 if (meta_row_is_guilty(row, addr))
303                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
304
305                 row += META_MEM_BYTES_PER_ROW;
306         }
307 }
308
309 static bool report_enabled(void)
310 {
311 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
312         if (current->kasan_depth)
313                 return false;
314 #endif
315         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
316                 return true;
317         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
318 }
319
320 #if IS_ENABLED(CONFIG_KUNIT)
321 static void kasan_update_kunit_status(struct kunit *cur_test)
322 {
323         struct kunit_resource *resource;
324         struct kunit_kasan_expectation *kasan_data;
325
326         resource = kunit_find_named_resource(cur_test, "kasan_data");
327
328         if (!resource) {
329                 kunit_set_failure(cur_test);
330                 return;
331         }
332
333         kasan_data = (struct kunit_kasan_expectation *)resource->data;
334         kasan_data->report_found = true;
335         kunit_put_resource(resource);
336 }
337 #endif /* IS_ENABLED(CONFIG_KUNIT) */
338
339 void kasan_report_invalid_free(void *object, unsigned long ip)
340 {
341         unsigned long flags;
342         u8 tag = get_tag(object);
343
344         object = kasan_reset_tag(object);
345
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) */
350
351         start_report(&flags);
352         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
353         print_tags(tag, object);
354         pr_err("\n");
355         print_address_description(object, tag);
356         pr_err("\n");
357         print_memory_metadata(object);
358         end_report(&flags);
359 }
360
361 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
362                                 unsigned long ip)
363 {
364         struct kasan_access_info info;
365         void *tagged_addr;
366         void *untagged_addr;
367         unsigned long flags;
368
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) */
373
374         disable_trace_on_warning();
375
376         tagged_addr = (void *)addr;
377         untagged_addr = kasan_reset_tag(tagged_addr);
378
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);
382         else
383                 info.first_bad_addr = untagged_addr;
384         info.access_size = size;
385         info.is_write = is_write;
386         info.ip = ip;
387
388         start_report(&flags);
389
390         print_error_description(&info);
391         if (addr_has_metadata(untagged_addr))
392                 print_tags(get_tag(tagged_addr), info.first_bad_addr);
393         pr_err("\n");
394
395         if (addr_has_metadata(untagged_addr)) {
396                 print_address_description(untagged_addr, get_tag(tagged_addr));
397                 pr_err("\n");
398                 print_memory_metadata(info.first_bad_addr);
399         } else {
400                 dump_stack();
401         }
402
403         end_report(&flags);
404 }
405
406 bool kasan_report(unsigned long addr, size_t size, bool is_write,
407                         unsigned long ip)
408 {
409         unsigned long flags = user_access_save();
410         bool ret = false;
411
412         if (likely(report_enabled())) {
413                 __kasan_report(addr, size, is_write, ip);
414                 ret = true;
415         }
416
417         user_access_restore(flags);
418
419         return ret;
420 }
421
422 #ifdef CONFIG_KASAN_INLINE
423 /*
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.
430  */
431 void kasan_non_canonical_hook(unsigned long addr)
432 {
433         unsigned long orig_addr;
434         const char *bug_type;
435
436         if (addr < KASAN_SHADOW_OFFSET)
437                 return;
438
439         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
440         /*
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.
450          */
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";
455         else
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);
459 }
460 #endif