xref: /linux/mm/kasan/common.c (revision 8804d970fab45726b3c7cd7f240b31122aa94219)
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 #if defined(CONFIG_ARCH_DEFER_KASAN) || defined(CONFIG_KASAN_HW_TAGS)
36 /*
37  * Definition of the unified static key declared in kasan-enabled.h.
38  * This provides consistent runtime enable/disable across KASAN modes.
39  */
40 DEFINE_STATIC_KEY_FALSE(kasan_flag_enabled);
41 EXPORT_SYMBOL_GPL(kasan_flag_enabled);
42 #endif
43 
kasan_addr_to_slab(const void * addr)44 struct slab *kasan_addr_to_slab(const void *addr)
45 {
46 	if (virt_addr_valid(addr))
47 		return virt_to_slab(addr);
48 	return NULL;
49 }
50 
kasan_save_stack(gfp_t flags,depot_flags_t depot_flags)51 depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags)
52 {
53 	unsigned long entries[KASAN_STACK_DEPTH];
54 	unsigned int nr_entries;
55 
56 	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
57 	return stack_depot_save_flags(entries, nr_entries, flags, depot_flags);
58 }
59 
kasan_set_track(struct kasan_track * track,depot_stack_handle_t stack)60 void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack)
61 {
62 #ifdef CONFIG_KASAN_EXTRA_INFO
63 	u32 cpu = raw_smp_processor_id();
64 	u64 ts_nsec = local_clock();
65 
66 	track->cpu = cpu;
67 	track->timestamp = ts_nsec >> 9;
68 #endif /* CONFIG_KASAN_EXTRA_INFO */
69 	track->pid = current->pid;
70 	track->stack = stack;
71 }
72 
kasan_save_track(struct kasan_track * track,gfp_t flags)73 void kasan_save_track(struct kasan_track *track, gfp_t flags)
74 {
75 	depot_stack_handle_t stack;
76 
77 	stack = kasan_save_stack(flags, STACK_DEPOT_FLAG_CAN_ALLOC);
78 	kasan_set_track(track, stack);
79 }
80 
81 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
kasan_enable_current(void)82 void kasan_enable_current(void)
83 {
84 	current->kasan_depth++;
85 }
86 EXPORT_SYMBOL(kasan_enable_current);
87 
kasan_disable_current(void)88 void kasan_disable_current(void)
89 {
90 	current->kasan_depth--;
91 }
92 EXPORT_SYMBOL(kasan_disable_current);
93 
94 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
95 
__kasan_unpoison_range(const void * address,size_t size)96 void __kasan_unpoison_range(const void *address, size_t size)
97 {
98 	if (is_kfence_address(address))
99 		return;
100 
101 	kasan_unpoison(address, size, false);
102 }
103 
104 #ifdef CONFIG_KASAN_STACK
105 /* Unpoison the entire stack for a task. */
kasan_unpoison_task_stack(struct task_struct * task)106 void kasan_unpoison_task_stack(struct task_struct *task)
107 {
108 	void *base = task_stack_page(task);
109 
110 	kasan_unpoison(base, THREAD_SIZE, false);
111 }
112 
113 /* Unpoison the stack for the current task beyond a watermark sp value. */
kasan_unpoison_task_stack_below(const void * watermark)114 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
115 {
116 	/*
117 	 * Calculate the task stack base address.  Avoid using 'current'
118 	 * because this function is called by early resume code which hasn't
119 	 * yet set up the percpu register (%gs).
120 	 */
121 	void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
122 
123 	kasan_unpoison(base, watermark - base, false);
124 }
125 #endif /* CONFIG_KASAN_STACK */
126 
__kasan_unpoison_pages(struct page * page,unsigned int order,bool init)127 bool __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
128 {
129 	u8 tag;
130 	unsigned long i;
131 
132 	if (unlikely(PageHighMem(page)))
133 		return false;
134 
135 	if (!kasan_sample_page_alloc(order))
136 		return false;
137 
138 	tag = kasan_random_tag();
139 	kasan_unpoison(set_tag(page_address(page), tag),
140 		       PAGE_SIZE << order, init);
141 	for (i = 0; i < (1 << order); i++)
142 		page_kasan_tag_set(page + i, tag);
143 
144 	return true;
145 }
146 
__kasan_poison_pages(struct page * page,unsigned int order,bool init)147 void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
148 {
149 	if (likely(!PageHighMem(page)))
150 		kasan_poison(page_address(page), PAGE_SIZE << order,
151 			     KASAN_PAGE_FREE, init);
152 }
153 
__kasan_poison_slab(struct slab * slab)154 void __kasan_poison_slab(struct slab *slab)
155 {
156 	struct page *page = slab_page(slab);
157 	unsigned long i;
158 
159 	for (i = 0; i < compound_nr(page); i++)
160 		page_kasan_tag_reset(page + i);
161 	kasan_poison(page_address(page), page_size(page),
162 		     KASAN_SLAB_REDZONE, false);
163 }
164 
__kasan_unpoison_new_object(struct kmem_cache * cache,void * object)165 void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object)
166 {
167 	kasan_unpoison(object, cache->object_size, false);
168 }
169 
__kasan_poison_new_object(struct kmem_cache * cache,void * object)170 void __kasan_poison_new_object(struct kmem_cache *cache, void *object)
171 {
172 	kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
173 			KASAN_SLAB_REDZONE, false);
174 }
175 
176 /*
177  * This function assigns a tag to an object considering the following:
178  * 1. A cache might have a constructor, which might save a pointer to a slab
179  *    object somewhere (e.g. in the object itself). We preassign a tag for
180  *    each object in caches with constructors during slab creation and reuse
181  *    the same tag each time a particular object is allocated.
182  * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
183  *    accessed after being freed. We preassign tags for objects in these
184  *    caches as well.
185  */
assign_tag(struct kmem_cache * cache,const void * object,bool init)186 static inline u8 assign_tag(struct kmem_cache *cache,
187 					const void *object, bool init)
188 {
189 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
190 		return 0xff;
191 
192 	/*
193 	 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
194 	 * set, assign a tag when the object is being allocated (init == false).
195 	 */
196 	if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
197 		return init ? KASAN_TAG_KERNEL : kasan_random_tag();
198 
199 	/*
200 	 * For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU,
201 	 * assign a random tag during slab creation, otherwise reuse
202 	 * the already assigned tag.
203 	 */
204 	return init ? kasan_random_tag() : get_tag(object);
205 }
206 
__kasan_init_slab_obj(struct kmem_cache * cache,const void * object)207 void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
208 						const void *object)
209 {
210 	/* Initialize per-object metadata if it is present. */
211 	if (kasan_requires_meta())
212 		kasan_init_object_meta(cache, object);
213 
214 	/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
215 	object = set_tag(object, assign_tag(cache, object, true));
216 
217 	return (void *)object;
218 }
219 
220 /* Returns true when freeing the object is not safe. */
check_slab_allocation(struct kmem_cache * cache,void * object,unsigned long ip)221 static bool check_slab_allocation(struct kmem_cache *cache, void *object,
222 				  unsigned long ip)
223 {
224 	void *tagged_object = object;
225 
226 	object = kasan_reset_tag(object);
227 
228 	if (unlikely(nearest_obj(cache, virt_to_slab(object), object) != object)) {
229 		kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);
230 		return true;
231 	}
232 
233 	if (!kasan_byte_accessible(tagged_object)) {
234 		kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);
235 		return true;
236 	}
237 
238 	return false;
239 }
240 
poison_slab_object(struct kmem_cache * cache,void * object,bool init)241 static inline void poison_slab_object(struct kmem_cache *cache, void *object,
242 				      bool init)
243 {
244 	void *tagged_object = object;
245 
246 	object = kasan_reset_tag(object);
247 
248 	kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
249 			KASAN_SLAB_FREE, init);
250 
251 	if (kasan_stack_collection_enabled())
252 		kasan_save_free_info(cache, tagged_object);
253 }
254 
__kasan_slab_pre_free(struct kmem_cache * cache,void * object,unsigned long ip)255 bool __kasan_slab_pre_free(struct kmem_cache *cache, void *object,
256 				unsigned long ip)
257 {
258 	if (is_kfence_address(object))
259 		return false;
260 	return check_slab_allocation(cache, object, ip);
261 }
262 
__kasan_slab_free(struct kmem_cache * cache,void * object,bool init,bool still_accessible,bool no_quarantine)263 bool __kasan_slab_free(struct kmem_cache *cache, void *object, bool init,
264 		       bool still_accessible, bool no_quarantine)
265 {
266 	if (is_kfence_address(object))
267 		return false;
268 
269 	/*
270 	 * If this point is reached with an object that must still be
271 	 * accessible under RCU, we can't poison it; in that case, also skip the
272 	 * quarantine. This should mostly only happen when CONFIG_SLUB_RCU_DEBUG
273 	 * has been disabled manually.
274 	 *
275 	 * Putting the object on the quarantine wouldn't help catch UAFs (since
276 	 * we can't poison it here), and it would mask bugs caused by
277 	 * SLAB_TYPESAFE_BY_RCU users not being careful enough about object
278 	 * reuse; so overall, putting the object into the quarantine here would
279 	 * be counterproductive.
280 	 */
281 	if (still_accessible)
282 		return false;
283 
284 	poison_slab_object(cache, object, init);
285 
286 	if (no_quarantine)
287 		return false;
288 
289 	/*
290 	 * If the object is put into quarantine, do not let slab put the object
291 	 * onto the freelist for now. The object's metadata is kept until the
292 	 * object gets evicted from quarantine.
293 	 */
294 	if (kasan_quarantine_put(cache, object))
295 		return true;
296 
297 	/*
298 	 * Note: Keep per-object metadata to allow KASAN print stack traces for
299 	 * use-after-free-before-realloc bugs.
300 	 */
301 
302 	/* Let slab put the object onto the freelist. */
303 	return false;
304 }
305 
check_page_allocation(void * ptr,unsigned long ip)306 static inline bool check_page_allocation(void *ptr, unsigned long ip)
307 {
308 	if (!kasan_enabled())
309 		return false;
310 
311 	if (ptr != page_address(virt_to_head_page(ptr))) {
312 		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
313 		return true;
314 	}
315 
316 	if (!kasan_byte_accessible(ptr)) {
317 		kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE);
318 		return true;
319 	}
320 
321 	return false;
322 }
323 
__kasan_kfree_large(void * ptr,unsigned long ip)324 void __kasan_kfree_large(void *ptr, unsigned long ip)
325 {
326 	check_page_allocation(ptr, ip);
327 
328 	/* The object will be poisoned by kasan_poison_pages(). */
329 }
330 
unpoison_slab_object(struct kmem_cache * cache,void * object,gfp_t flags,bool init)331 static inline void unpoison_slab_object(struct kmem_cache *cache, void *object,
332 					gfp_t flags, bool init)
333 {
334 	/*
335 	 * Unpoison the whole object. For kmalloc() allocations,
336 	 * poison_kmalloc_redzone() will do precise poisoning.
337 	 */
338 	kasan_unpoison(object, cache->object_size, init);
339 
340 	/* Save alloc info (if possible) for non-kmalloc() allocations. */
341 	if (kasan_stack_collection_enabled() && !is_kmalloc_cache(cache))
342 		kasan_save_alloc_info(cache, object, flags);
343 }
344 
__kasan_slab_alloc(struct kmem_cache * cache,void * object,gfp_t flags,bool init)345 void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
346 					void *object, gfp_t flags, bool init)
347 {
348 	u8 tag;
349 	void *tagged_object;
350 
351 	if (gfpflags_allow_blocking(flags))
352 		kasan_quarantine_reduce();
353 
354 	if (unlikely(object == NULL))
355 		return NULL;
356 
357 	if (is_kfence_address(object))
358 		return (void *)object;
359 
360 	/*
361 	 * Generate and assign random tag for tag-based modes.
362 	 * Tag is ignored in set_tag() for the generic mode.
363 	 */
364 	tag = assign_tag(cache, object, false);
365 	tagged_object = set_tag(object, tag);
366 
367 	/* Unpoison the object and save alloc info for non-kmalloc() allocations. */
368 	unpoison_slab_object(cache, tagged_object, flags, init);
369 
370 	return tagged_object;
371 }
372 
poison_kmalloc_redzone(struct kmem_cache * cache,const void * object,size_t size,gfp_t flags)373 static inline void poison_kmalloc_redzone(struct kmem_cache *cache,
374 				const void *object, size_t size, gfp_t flags)
375 {
376 	unsigned long redzone_start;
377 	unsigned long redzone_end;
378 
379 	/*
380 	 * The redzone has byte-level precision for the generic mode.
381 	 * Partially poison the last object granule to cover the unaligned
382 	 * part of the redzone.
383 	 */
384 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
385 		kasan_poison_last_granule((void *)object, size);
386 
387 	/* Poison the aligned part of the redzone. */
388 	redzone_start = round_up((unsigned long)(object + size),
389 				KASAN_GRANULE_SIZE);
390 	redzone_end = round_up((unsigned long)(object + cache->object_size),
391 				KASAN_GRANULE_SIZE);
392 	kasan_poison((void *)redzone_start, redzone_end - redzone_start,
393 			   KASAN_SLAB_REDZONE, false);
394 
395 	/*
396 	 * Save alloc info (if possible) for kmalloc() allocations.
397 	 * This also rewrites the alloc info when called from kasan_krealloc().
398 	 */
399 	if (kasan_stack_collection_enabled() && is_kmalloc_cache(cache))
400 		kasan_save_alloc_info(cache, (void *)object, flags);
401 
402 }
403 
__kasan_kmalloc(struct kmem_cache * cache,const void * object,size_t size,gfp_t flags)404 void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
405 					size_t size, gfp_t flags)
406 {
407 	if (gfpflags_allow_blocking(flags))
408 		kasan_quarantine_reduce();
409 
410 	if (unlikely(object == NULL))
411 		return NULL;
412 
413 	if (is_kfence_address(object))
414 		return (void *)object;
415 
416 	/* The object has already been unpoisoned by kasan_slab_alloc(). */
417 	poison_kmalloc_redzone(cache, object, size, flags);
418 
419 	/* Keep the tag that was set by kasan_slab_alloc(). */
420 	return (void *)object;
421 }
422 EXPORT_SYMBOL(__kasan_kmalloc);
423 
poison_kmalloc_large_redzone(const void * ptr,size_t size,gfp_t flags)424 static inline void poison_kmalloc_large_redzone(const void *ptr, size_t size,
425 						gfp_t flags)
426 {
427 	unsigned long redzone_start;
428 	unsigned long redzone_end;
429 
430 	/*
431 	 * The redzone has byte-level precision for the generic mode.
432 	 * Partially poison the last object granule to cover the unaligned
433 	 * part of the redzone.
434 	 */
435 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
436 		kasan_poison_last_granule(ptr, size);
437 
438 	/* Poison the aligned part of the redzone. */
439 	redzone_start = round_up((unsigned long)(ptr + size), KASAN_GRANULE_SIZE);
440 	redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
441 	kasan_poison((void *)redzone_start, redzone_end - redzone_start,
442 		     KASAN_PAGE_REDZONE, false);
443 }
444 
__kasan_kmalloc_large(const void * ptr,size_t size,gfp_t flags)445 void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
446 						gfp_t flags)
447 {
448 	if (gfpflags_allow_blocking(flags))
449 		kasan_quarantine_reduce();
450 
451 	if (unlikely(ptr == NULL))
452 		return NULL;
453 
454 	/* The object has already been unpoisoned by kasan_unpoison_pages(). */
455 	poison_kmalloc_large_redzone(ptr, size, flags);
456 
457 	/* Keep the tag that was set by alloc_pages(). */
458 	return (void *)ptr;
459 }
460 
__kasan_krealloc(const void * object,size_t size,gfp_t flags)461 void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
462 {
463 	struct slab *slab;
464 
465 	if (gfpflags_allow_blocking(flags))
466 		kasan_quarantine_reduce();
467 
468 	if (unlikely(object == ZERO_SIZE_PTR))
469 		return (void *)object;
470 
471 	if (is_kfence_address(object))
472 		return (void *)object;
473 
474 	/*
475 	 * Unpoison the object's data.
476 	 * Part of it might already have been unpoisoned, but it's unknown
477 	 * how big that part is.
478 	 */
479 	kasan_unpoison(object, size, false);
480 
481 	slab = virt_to_slab(object);
482 
483 	/* Piggy-back on kmalloc() instrumentation to poison the redzone. */
484 	if (unlikely(!slab))
485 		poison_kmalloc_large_redzone(object, size, flags);
486 	else
487 		poison_kmalloc_redzone(slab->slab_cache, object, size, flags);
488 
489 	return (void *)object;
490 }
491 
__kasan_mempool_poison_pages(struct page * page,unsigned int order,unsigned long ip)492 bool __kasan_mempool_poison_pages(struct page *page, unsigned int order,
493 				  unsigned long ip)
494 {
495 	unsigned long *ptr;
496 
497 	if (unlikely(PageHighMem(page)))
498 		return true;
499 
500 	/* Bail out if allocation was excluded due to sampling. */
501 	if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
502 	    page_kasan_tag(page) == KASAN_TAG_KERNEL)
503 		return true;
504 
505 	ptr = page_address(page);
506 
507 	if (check_page_allocation(ptr, ip))
508 		return false;
509 
510 	kasan_poison(ptr, PAGE_SIZE << order, KASAN_PAGE_FREE, false);
511 
512 	return true;
513 }
514 
__kasan_mempool_unpoison_pages(struct page * page,unsigned int order,unsigned long ip)515 void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
516 				    unsigned long ip)
517 {
518 	__kasan_unpoison_pages(page, order, false);
519 }
520 
__kasan_mempool_poison_object(void * ptr,unsigned long ip)521 bool __kasan_mempool_poison_object(void *ptr, unsigned long ip)
522 {
523 	struct folio *folio = virt_to_folio(ptr);
524 	struct slab *slab;
525 
526 	/*
527 	 * This function can be called for large kmalloc allocation that get
528 	 * their memory from page_alloc. Thus, the folio might not be a slab.
529 	 */
530 	if (unlikely(!folio_test_slab(folio))) {
531 		if (check_page_allocation(ptr, ip))
532 			return false;
533 		kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
534 		return true;
535 	}
536 
537 	if (is_kfence_address(ptr))
538 		return true;
539 
540 	slab = folio_slab(folio);
541 
542 	if (check_slab_allocation(slab->slab_cache, ptr, ip))
543 		return false;
544 
545 	poison_slab_object(slab->slab_cache, ptr, false);
546 	return true;
547 }
548 
__kasan_mempool_unpoison_object(void * ptr,size_t size,unsigned long ip)549 void __kasan_mempool_unpoison_object(void *ptr, size_t size, unsigned long ip)
550 {
551 	struct slab *slab;
552 	gfp_t flags = 0; /* Might be executing under a lock. */
553 
554 	slab = virt_to_slab(ptr);
555 
556 	/*
557 	 * This function can be called for large kmalloc allocation that get
558 	 * their memory from page_alloc.
559 	 */
560 	if (unlikely(!slab)) {
561 		kasan_unpoison(ptr, size, false);
562 		poison_kmalloc_large_redzone(ptr, size, flags);
563 		return;
564 	}
565 
566 	if (is_kfence_address(ptr))
567 		return;
568 
569 	/* Unpoison the object and save alloc info for non-kmalloc() allocations. */
570 	unpoison_slab_object(slab->slab_cache, ptr, flags, false);
571 
572 	/* Poison the redzone and save alloc info for kmalloc() allocations. */
573 	if (is_kmalloc_cache(slab->slab_cache))
574 		poison_kmalloc_redzone(slab->slab_cache, ptr, size, flags);
575 }
576 
__kasan_check_byte(const void * address,unsigned long ip)577 bool __kasan_check_byte(const void *address, unsigned long ip)
578 {
579 	if (!kasan_byte_accessible(address)) {
580 		kasan_report(address, 1, false, ip);
581 		return false;
582 	}
583 	return true;
584 }
585