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
 35struct 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
 42depot_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
 51void 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 >> 3;
 59#endif /* CONFIG_KASAN_EXTRA_INFO */
 60	track->pid = current->pid;
 61	track->stack = stack;
 62}
 63
 64void 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)
 73void kasan_enable_current(void)
 74{
 75	current->kasan_depth++;
 76}
 77EXPORT_SYMBOL(kasan_enable_current);
 78
 79void kasan_disable_current(void)
 80{
 81	current->kasan_depth--;
 82}
 83EXPORT_SYMBOL(kasan_disable_current);
 84
 85#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
 86
 87void __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. */
 97void 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. */
105asmlinkage 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
118bool __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
138void __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
145void __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
156void __kasan_unpoison_new_object(struct kmem_cache *cache, void *object)
157{
158	kasan_unpoison(object, cache->object_size, false);
159}
160
161void __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 */
177static 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
198void * __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
211static 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
245bool __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
276static 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
294void __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
301static 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
315void * __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
343static 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
374void * __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}
392EXPORT_SYMBOL(__kasan_kmalloc);
393
394static 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
415void * __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
431void * __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
462bool __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
485void __kasan_mempool_unpoison_pages(struct page *page, unsigned int order,
486				    unsigned long ip)
487{
488	__kasan_unpoison_pages(page, order, false);
489}
490
491bool __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
514void __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, size, flags);
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
542bool __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}