1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * This file contains common KASAN 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/export.h>
13 #include <linux/init.h>
14 #include <linux/kasan.h>
15 #include <linux/kernel.h>
16 #include <linux/linkage.h>
17 #include <linux/memblock.h>
18 #include <linux/memory.h>
19 #include <linux/mm.h>
20 #include <linux/module.h>
21 #include <linux/printk.h>
22 #include <linux/sched.h>
23 #include <linux/sched/clock.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/slab.h>
26 #include <linux/stackdepot.h>
27 #include <linux/stacktrace.h>
28 #include <linux/string.h>
29 #include <linux/types.h>
30 #include <linux/bug.h>
31
32 #include "kasan.h"
33 #include "../slab.h"
34
35 struct slab *kasan_addr_to_slab(const void *addr)
36 {
37 if (virt_addr_valid(addr))
38 return virt_to_slab(addr);
39 return NULL;
40 }
41
42 depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags)
43 {
44 unsigned long entries[KASAN_STACK_DEPTH];
45 unsigned int nr_entries;
46
47 nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
48 return stack_depot_save_flags(entries, nr_entries, flags, depot_flags);
49 }
50
51 void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack)
52 {
53 #ifdef CONFIG_KASAN_EXTRA_INFO
54 u32 cpu = raw_smp_processor_id();
55 u64 ts_nsec = local_clock();
56
57 track->cpu = cpu;
58 track->timestamp = ts_nsec >> 9;
59 #endif /* CONFIG_KASAN_EXTRA_INFO */
60 track->pid = current->pid;
61 track->stack = stack;
62 }
63
64 void kasan_save_track(struct kasan_track *track, gfp_t flags)
65 {
66 depot_stack_handle_t stack;
67
68 stack = kasan_save_stack(flags, STACK_DEPOT_FLAG_CAN_ALLOC);
69 kasan_set_track(track, stack);
70 }
71
72 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
73 void kasan_enable_current(void)
74 {
75 current->kasan_depth++;
76 }
77 EXPORT_SYMBOL(kasan_enable_current);
78
79 void kasan_disable_current(void)
80 {
81 current->kasan_depth--;
82 }
83 EXPORT_SYMBOL(kasan_disable_current);
84
85 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
86
87 void __kasan_unpoison_range(const void *address, size_t size)
88 {
89 if (is_kfence_address(address))
90 return;
91
92 kasan_unpoison(address, size, false);
93 }
94
95 #ifdef CONFIG_KASAN_STACK
96 /* Unpoison the entire stack for a task. */
97 void kasan_unpoison_task_stack(struct task_struct *task)
98 {
99 void *base = task_stack_page(task);
100
101 kasan_unpoison(base, THREAD_SIZE, false);
102 }
103
104 /* Unpoison the stack for the current task beyond a watermark sp value. */
105 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
106 {
107 /*
108 * Calculate the task stack base address. Avoid using 'current'
109 * because this function is called by early resume code which hasn't
110 * yet set up the percpu register (%gs).
111 */
112 void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
113
114 kasan_unpoison(base, watermark - base, false);
115 }
116 #endif /* CONFIG_KASAN_STACK */
117
118 bool __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
119 {
120 u8 tag;
121 unsigned long i;
122
123 if (unlikely(PageHighMem(page)))
124 return false;
125
126 if (!kasan_sample_page_alloc(order))
127 return false;
128
129 tag = kasan_random_tag();
130 kasan_unpoison(set_tag(page_address(page), tag),
131 PAGE_SIZE << order, init);
132 for (i = 0; i < (1 << order); i++)
133 page_kasan_tag_set(page + i, tag);
134
135 return true;
136 }
137
138 void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
139 {
140 if (likely(!PageHighMem(page)))
141 kasan_poison(page_address(page), PAGE_SIZE << order,
142 KASAN_PAGE_FREE, init);
143 }
144
145 void __kasan_poison_slab(struct slab *slab)
146 {
147 struct page *page = slab_page(slab);
148 unsigned long i;
149
150 for (i = 0; i < compound_nr(page); i++)
151 page_kasan_tag_reset(page + i);
152 kasan_poison(page_address(page), page_size(page),
153 KASAN_SLAB_REDZONE, false);
154 }
155
156 void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object)
157 {
158 kasan_unpoison(object, cache->object_size, false);
159 }
160
161 void __kasan_poison_new_object(struct kmem_cache *cache, void *object)
162 {
163 kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
164 KASAN_SLAB_REDZONE, false);
165 }
166
167 /*
168 * This function assigns a tag to an object considering the following:
169 * 1. A cache might have a constructor, which might save a pointer to a slab
170 * object somewhere (e.g. in the object itself). We preassign a tag for
171 * each object in caches with constructors during slab creation and reuse
172 * the same tag each time a particular object is allocated.
173 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
174 * accessed after being freed. We preassign tags for objects in these
175 * caches as well.
176 */
177 static inline u8 assign_tag(struct kmem_cache *cache,
178 const void *object, bool init)
179 {
180 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
181 return 0xff;
182
183 /*
184 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
185 * set, assign a tag when the object is being allocated (init == false).
186 */
187 if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
188 return init ? KASAN_TAG_KERNEL : kasan_random_tag();
189
190 /*
191 * For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU,
192 * assign a random tag during slab creation, otherwise reuse
193 * the already assigned tag.
194 */
195 return init ? kasan_random_tag() : get_tag(object);
196 }
197
198 void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
199 const void *object)
200 {
201 /* Initialize per-object metadata if it is present. */
202 if (kasan_requires_meta())
203 kasan_init_object_meta(cache, object);
204
205 /* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
206 object = set_tag(object, assign_tag(cache, object, true));
207
208 return (void *)object;
209 }
210
211 static inline bool poison_slab_object(struct kmem_cache *cache, void *object,
212 unsigned long ip, bool init)
213 {
214 void *tagged_object;
215
216 if (!kasan_arch_is_ready())
217 return false;
218
219 tagged_object = object;
220 object = kasan_reset_tag(object);
221
222 if (unlikely(nearest_obj(cache, virt_to_slab(object), object) != object)) {
223 kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);
224 return true;
225 }
226
227 /* RCU slabs could be legally used after free within the RCU period. */
228 if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
229 return false;
230
231 if (!kasan_byte_accessible(tagged_object)) {
232 kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);
233 return true;
234 }
235
236 kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
237 KASAN_SLAB_FREE, init);
238
239 if (kasan_stack_collection_enabled())
240 kasan_save_free_info(cache, tagged_object);
241
242 return false;
243 }
244
245 bool __kasan_slab_free(struct kmem_cache *cache, void *object,
246 unsigned long ip, bool init)
247 {
248 if (is_kfence_address(object))
249 return false;
250
251 /*
252 * If the object is buggy, do not let slab put the object onto the
253 * freelist. The object will thus never be allocated again and its
254 * metadata will never get released.
255 */
256 if (poison_slab_object(cache, object, ip, init))
257 return true;
258
259 /*
260 * If the object is put into quarantine, do not let slab put the object
261 * onto the freelist for now. The object's metadata is kept until the
262 * object gets evicted from quarantine.
263 */
264 if (kasan_quarantine_put(cache, object))
265 return true;
266
267 /*
268 * Note: Keep per-object metadata to allow KASAN print stack traces for
269 * use-after-free-before-realloc bugs.
270 */
271
272 /* Let slab put the object onto the freelist. */
273 return false;
274 }
275
276 static inline bool check_page_allocation(void *ptr, unsigned long ip)
277 {
278 if (!kasan_arch_is_ready())
279 return false;
280
281 if (ptr != page_address(virt_to_head_page(ptr))) {
282 kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
283 return true;
284 }
285
286 if (!kasan_byte_accessible(ptr)) {
287 kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE);
288 return true;
289 }
290
291 return false;
292 }
293
294 void __kasan_kfree_large(void *ptr, unsigned long ip)
295 {
296 check_page_allocation(ptr, ip);
297
298 /* The object will be poisoned by kasan_poison_pages(). */
299 }
300
301 static inline void unpoison_slab_object(struct kmem_cache *cache, void *object,
302 gfp_t flags, bool init)
303 {
304 /*
305 * Unpoison the whole object. For kmalloc() allocations,
306 * poison_kmalloc_redzone() will do precise poisoning.
307 */
308 kasan_unpoison(object, cache->object_size, init);
309
310 /* Save alloc info (if possible) for non-kmalloc() allocations. */
311 if (kasan_stack_collection_enabled() && !is_kmalloc_cache(cache))
312 kasan_save_alloc_info(cache, object, flags);
313 }
314
315 void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
316 void *object, gfp_t flags, bool init)
317 {
318 u8 tag;
319 void *tagged_object;
320
321 if (gfpflags_allow_blocking(flags))
322 kasan_quarantine_reduce();
323
324 if (unlikely(object == NULL))
325 return NULL;
326
327 if (is_kfence_address(object))
328 return (void *)object;
329
330 /*
331 * Generate and assign random tag for tag-based modes.
332 * Tag is ignored in set_tag() for the generic mode.
333 */
334 tag = assign_tag(cache, object, false);
335 tagged_object = set_tag(object, tag);
336
337 /* Unpoison the object and save alloc info for non-kmalloc() allocations. */
338 unpoison_slab_object(cache, tagged_object, flags, init);
339
340 return tagged_object;
341 }
342
343 static inline void poison_kmalloc_redzone(struct kmem_cache *cache,
344 const void *object, size_t size, gfp_t flags)
345 {
346 unsigned long redzone_start;
347 unsigned long redzone_end;
348
349 /*
350 * The redzone has byte-level precision for the generic mode.
351 * Partially poison the last object granule to cover the unaligned
352 * part of the redzone.
353 */
354 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
355 kasan_poison_last_granule((void *)object, size);
356
357 /* Poison the aligned part of the redzone. */
358 redzone_start = round_up((unsigned long)(object + size),
359 KASAN_GRANULE_SIZE);
360 redzone_end = round_up((unsigned long)(object + cache->object_size),
361 KASAN_GRANULE_SIZE);
362 kasan_poison((void *)redzone_start, redzone_end - redzone_start,
363 KASAN_SLAB_REDZONE, false);
364
365 /*
366 * Save alloc info (if possible) for kmalloc() allocations.
367 * This also rewrites the alloc info when called from kasan_krealloc().
368 */
369 if (kasan_stack_collection_enabled() && is_kmalloc_cache(cache))
370 kasan_save_alloc_info(cache, (void *)object, flags);
371
372 }
373
374 void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
375 size_t size, gfp_t flags)
376 {
377 if (gfpflags_allow_blocking(flags))
378 kasan_quarantine_reduce();
379
380 if (unlikely(object == NULL))
381 return NULL;
382
383 if (is_kfence_address(object))
384 return (void *)object;
385
386 /* The object has already been unpoisoned by kasan_slab_alloc(). */
387 poison_kmalloc_redzone(cache, object, size, flags);
388
389 /* Keep the tag that was set by kasan_slab_alloc(). */
390 return (void *)object;
391 }
392 EXPORT_SYMBOL(__kasan_kmalloc);
393
394 static inline void poison_kmalloc_large_redzone(const void *ptr, size_t size,
395 gfp_t flags)
396 {
397 unsigned long redzone_start;
398 unsigned long redzone_end;
399
400 /*
401 * The redzone has byte-level precision for the generic mode.
402 * Partially poison the last object granule to cover the unaligned
403 * part of the redzone.
404 */
405 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
406 kasan_poison_last_granule(ptr, size);
407
408 /* Poison the aligned part of the redzone. */
409 redzone_start = round_up((unsigned long)(ptr + size), KASAN_GRANULE_SIZE);
410 redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
411 kasan_poison((void *)redzone_start, redzone_end - redzone_start,
412 KASAN_PAGE_REDZONE, false);
413 }
414
415 void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
416 gfp_t flags)
417 {
418 if (gfpflags_allow_blocking(flags))
419 kasan_quarantine_reduce();
420
421 if (unlikely(ptr == NULL))
422 return NULL;
423
424 /* The object has already been unpoisoned by kasan_unpoison_pages(). */
425 poison_kmalloc_large_redzone(ptr, size, flags);
426
427 /* Keep the tag that was set by alloc_pages(). */
428 return (void *)ptr;
429 }
430
431 void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
432 {
433 struct slab *slab;
434
435 if (gfpflags_allow_blocking(flags))
436 kasan_quarantine_reduce();
437
438 if (unlikely(object == ZERO_SIZE_PTR))
439 return (void *)object;
440
441 if (is_kfence_address(object))
442 return (void *)object;
443
444 /*
445 * Unpoison the object's data.
446 * Part of it might already have been unpoisoned, but it's unknown
447 * how big that part is.
448 */
449 kasan_unpoison(object, size, false);
450
451 slab = virt_to_slab(object);
452
453 /* Piggy-back on kmalloc() instrumentation to poison the redzone. */
454 if (unlikely(!slab))
455 poison_kmalloc_large_redzone(object, size, flags);
456 else
457 poison_kmalloc_redzone(slab->slab_cache, object, size, flags);
458
459 return (void *)object;
460 }
461
462 bool __kasan_mempool_poison_pages(struct page *page, unsigned int order,
463 unsigned long ip)
464 {
465 unsigned long *ptr;
466
467 if (unlikely(PageHighMem(page)))
468 return true;
469
470 /* Bail out if allocation was excluded due to sampling. */
471 if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
472 page_kasan_tag(page) == KASAN_TAG_KERNEL)
473 return true;
474
475 ptr = page_address(page);
476
477 if (check_page_allocation(ptr, ip))
478 return false;
479
480 kasan_poison(ptr, PAGE_SIZE << order, KASAN_PAGE_FREE, false);
481
482 return true;
483 }
484
485 void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
486 unsigned long ip)
487 {
488 __kasan_unpoison_pages(page, order, false);
489 }
490
491 bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
492 {
493 struct folio *folio = virt_to_folio(ptr);
494 struct slab *slab;
495
496 /*
497 * This function can be called for large kmalloc allocation that get
498 * their memory from page_alloc. Thus, the folio might not be a slab.
499 */
500 if (unlikely(!folio_test_slab(folio))) {
501 if (check_page_allocation(ptr, ip))
502 return false;
503 kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
504 return true;
505 }
506
507 if (is_kfence_address(ptr))
508 return false;
509
510 slab = folio_slab(folio);
511 return !poison_slab_object(slab->slab_cache, ptr, ip, false);
512 }
513
514 void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)
515 {
516 struct slab *slab;
517 gfp_t flags = 0; /* Might be executing under a lock. */
518
519 slab = virt_to_slab(ptr);
520
521 /*
522 * This function can be called for large kmalloc allocation that get
523 * their memory from page_alloc.
524 */
525 if (unlikely(!slab)) {
526 kasan_unpoison(ptr, size, false);
527 poison_kmalloc_large_redzone(ptr, size, flags);
528 return;
529 }
530
531 if (is_kfence_address(ptr))
532 return;
533
534 /* Unpoison the object and save alloc info for non-kmalloc() allocations. */
535 unpoison_slab_object(slab->slab_cache, ptr, flags, false);
536
537 /* Poison the redzone and save alloc info for kmalloc() allocations. */
538 if (is_kmalloc_cache(slab->slab_cache))
539 poison_kmalloc_redzone(slab->slab_cache, ptr, size, flags);
540 }
541
542 bool __kasan_check_byte(const void *address, unsigned long ip)
543 {
544 if (!kasan_byte_accessible(address)) {
545 kasan_report(address, 1, false, ip);
546 return false;
547 }
548 return true;
549 }
550
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