1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains common KASAN code.
5 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
8 * Some code borrowed from https://github.com/xairy/kasan-prototype by
9 * Andrey Konovalov <andreyknvl@gmail.com>
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>
20 #include <linux/module.h>
21 #include <linux/printk.h>
22 #include <linux/sched.h>
23 #include <linux/sched/task_stack.h>
24 #include <linux/slab.h>
25 #include <linux/stacktrace.h>
26 #include <linux/string.h>
27 #include <linux/types.h>
28 #include <linux/bug.h>
33 depot_stack_handle_t kasan_save_stack(gfp_t flags)
35 unsigned long entries[KASAN_STACK_DEPTH];
36 unsigned int nr_entries;
38 nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
39 nr_entries = filter_irq_stacks(entries, nr_entries);
40 return stack_depot_save(entries, nr_entries, flags);
43 void kasan_set_track(struct kasan_track *track, gfp_t flags)
45 track->pid = current->pid;
46 track->stack = kasan_save_stack(flags);
49 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
50 void kasan_enable_current(void)
52 current->kasan_depth++;
55 void kasan_disable_current(void)
57 current->kasan_depth--;
59 #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
61 void __kasan_unpoison_range(const void *address, size_t size)
63 unpoison_range(address, size);
66 #if CONFIG_KASAN_STACK
67 /* Unpoison the entire stack for a task. */
68 void kasan_unpoison_task_stack(struct task_struct *task)
70 void *base = task_stack_page(task);
72 unpoison_range(base, THREAD_SIZE);
75 /* Unpoison the stack for the current task beyond a watermark sp value. */
76 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
79 * Calculate the task stack base address. Avoid using 'current'
80 * because this function is called by early resume code which hasn't
81 * yet set up the percpu register (%gs).
83 void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
85 unpoison_range(base, watermark - base);
87 #endif /* CONFIG_KASAN_STACK */
90 * Only allow cache merging when stack collection is disabled and no metadata
93 slab_flags_t __kasan_never_merge(void)
95 if (kasan_stack_collection_enabled())
100 void __kasan_alloc_pages(struct page *page, unsigned int order)
105 if (unlikely(PageHighMem(page)))
109 for (i = 0; i < (1 << order); i++)
110 page_kasan_tag_set(page + i, tag);
111 unpoison_range(page_address(page), PAGE_SIZE << order);
114 void __kasan_free_pages(struct page *page, unsigned int order)
116 if (likely(!PageHighMem(page)))
117 poison_range(page_address(page),
123 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
124 * For larger allocations larger redzones are used.
126 static inline unsigned int optimal_redzone(unsigned int object_size)
129 object_size <= 64 - 16 ? 16 :
130 object_size <= 128 - 32 ? 32 :
131 object_size <= 512 - 64 ? 64 :
132 object_size <= 4096 - 128 ? 128 :
133 object_size <= (1 << 14) - 256 ? 256 :
134 object_size <= (1 << 15) - 512 ? 512 :
135 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
138 void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
141 unsigned int ok_size;
142 unsigned int optimal_size;
145 * SLAB_KASAN is used to mark caches as ones that are sanitized by
146 * KASAN. Currently this flag is used in two places:
147 * 1. In slab_ksize() when calculating the size of the accessible
148 * memory within the object.
149 * 2. In slab_common.c to prevent merging of sanitized caches.
151 *flags |= SLAB_KASAN;
153 if (!kasan_stack_collection_enabled())
158 /* Add alloc meta into redzone. */
159 cache->kasan_info.alloc_meta_offset = *size;
160 *size += sizeof(struct kasan_alloc_meta);
163 * If alloc meta doesn't fit, don't add it.
164 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
165 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
168 if (*size > KMALLOC_MAX_SIZE) {
169 cache->kasan_info.alloc_meta_offset = 0;
171 /* Continue, since free meta might still fit. */
174 /* Only the generic mode uses free meta or flexible redzones. */
175 if (!IS_ENABLED(CONFIG_KASAN_GENERIC)) {
176 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
181 * Add free meta into redzone when it's not possible to store
182 * it in the object. This is the case when:
183 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
184 * be touched after it was freed, or
185 * 2. Object has a constructor, which means it's expected to
186 * retain its content until the next allocation, or
187 * 3. Object is too small.
188 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
190 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
191 cache->object_size < sizeof(struct kasan_free_meta)) {
194 cache->kasan_info.free_meta_offset = *size;
195 *size += sizeof(struct kasan_free_meta);
197 /* If free meta doesn't fit, don't add it. */
198 if (*size > KMALLOC_MAX_SIZE) {
199 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
204 /* Calculate size with optimal redzone. */
205 optimal_size = cache->object_size + optimal_redzone(cache->object_size);
206 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
207 if (optimal_size > KMALLOC_MAX_SIZE)
208 optimal_size = KMALLOC_MAX_SIZE;
209 /* Use optimal size if the size with added metas is not large enough. */
210 if (*size < optimal_size)
211 *size = optimal_size;
214 size_t __kasan_metadata_size(struct kmem_cache *cache)
216 if (!kasan_stack_collection_enabled())
218 return (cache->kasan_info.alloc_meta_offset ?
219 sizeof(struct kasan_alloc_meta) : 0) +
220 (cache->kasan_info.free_meta_offset ?
221 sizeof(struct kasan_free_meta) : 0);
224 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
227 if (!cache->kasan_info.alloc_meta_offset)
229 return kasan_reset_tag(object) + cache->kasan_info.alloc_meta_offset;
232 #ifdef CONFIG_KASAN_GENERIC
233 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
236 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
237 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
239 return kasan_reset_tag(object) + cache->kasan_info.free_meta_offset;
243 void __kasan_poison_slab(struct page *page)
247 for (i = 0; i < compound_nr(page); i++)
248 page_kasan_tag_reset(page + i);
249 poison_range(page_address(page), page_size(page),
250 KASAN_KMALLOC_REDZONE);
253 void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
255 unpoison_range(object, cache->object_size);
258 void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
260 poison_range(object, cache->object_size, KASAN_KMALLOC_REDZONE);
264 * This function assigns a tag to an object considering the following:
265 * 1. A cache might have a constructor, which might save a pointer to a slab
266 * object somewhere (e.g. in the object itself). We preassign a tag for
267 * each object in caches with constructors during slab creation and reuse
268 * the same tag each time a particular object is allocated.
269 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
270 * accessed after being freed. We preassign tags for objects in these
272 * 3. For SLAB allocator we can't preassign tags randomly since the freelist
273 * is stored as an array of indexes instead of a linked list. Assign tags
274 * based on objects indexes, so that objects that are next to each other
275 * get different tags.
277 static u8 assign_tag(struct kmem_cache *cache, const void *object,
278 bool init, bool keep_tag)
280 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
284 * 1. When an object is kmalloc()'ed, two hooks are called:
285 * kasan_slab_alloc() and kasan_kmalloc(). We assign the
286 * tag only in the first one.
287 * 2. We reuse the same tag for krealloc'ed objects.
290 return get_tag(object);
293 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
294 * set, assign a tag when the object is being allocated (init == false).
296 if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
297 return init ? KASAN_TAG_KERNEL : random_tag();
299 /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
301 /* For SLAB assign tags based on the object index in the freelist. */
302 return (u8)obj_to_index(cache, virt_to_page(object), (void *)object);
305 * For SLUB assign a random tag during slab creation, otherwise reuse
306 * the already assigned tag.
308 return init ? random_tag() : get_tag(object);
312 void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
315 struct kasan_alloc_meta *alloc_meta;
317 if (kasan_stack_collection_enabled()) {
318 alloc_meta = kasan_get_alloc_meta(cache, object);
320 __memset(alloc_meta, 0, sizeof(*alloc_meta));
323 /* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
324 object = set_tag(object, assign_tag(cache, object, true, false));
326 return (void *)object;
329 static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
330 unsigned long ip, bool quarantine)
335 tag = get_tag(object);
336 tagged_object = object;
337 object = kasan_reset_tag(object);
339 if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) !=
341 kasan_report_invalid_free(tagged_object, ip);
345 /* RCU slabs could be legally used after free within the RCU period */
346 if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
349 if (check_invalid_free(tagged_object)) {
350 kasan_report_invalid_free(tagged_object, ip);
354 poison_range(object, cache->object_size, KASAN_KMALLOC_FREE);
356 if (!kasan_stack_collection_enabled())
359 if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
362 kasan_set_free_info(cache, object, tag);
364 return quarantine_put(cache, object);
367 bool __kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
369 return ____kasan_slab_free(cache, object, ip, true);
372 void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
376 page = virt_to_head_page(ptr);
379 * Even though this function is only called for kmem_cache_alloc and
380 * kmalloc backed mempool allocations, those allocations can still be
381 * !PageSlab() when the size provided to kmalloc is larger than
382 * KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
384 if (unlikely(!PageSlab(page))) {
385 if (ptr != page_address(page)) {
386 kasan_report_invalid_free(ptr, ip);
389 poison_range(ptr, page_size(page), KASAN_FREE_PAGE);
391 ____kasan_slab_free(page->slab_cache, ptr, ip, false);
395 static void set_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
397 struct kasan_alloc_meta *alloc_meta;
399 alloc_meta = kasan_get_alloc_meta(cache, object);
401 kasan_set_track(&alloc_meta->alloc_track, flags);
404 static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
405 size_t size, gfp_t flags, bool keep_tag)
407 unsigned long redzone_start;
408 unsigned long redzone_end;
411 if (gfpflags_allow_blocking(flags))
414 if (unlikely(object == NULL))
417 redzone_start = round_up((unsigned long)(object + size),
419 redzone_end = round_up((unsigned long)object + cache->object_size,
421 tag = assign_tag(cache, object, false, keep_tag);
423 /* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */
424 unpoison_range(set_tag(object, tag), size);
425 poison_range((void *)redzone_start, redzone_end - redzone_start,
426 KASAN_KMALLOC_REDZONE);
428 if (kasan_stack_collection_enabled())
429 set_alloc_info(cache, (void *)object, flags);
431 return set_tag(object, tag);
434 void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
435 void *object, gfp_t flags)
437 return ____kasan_kmalloc(cache, object, cache->object_size, flags, false);
440 void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
441 size_t size, gfp_t flags)
443 return ____kasan_kmalloc(cache, object, size, flags, true);
445 EXPORT_SYMBOL(__kasan_kmalloc);
447 void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
451 unsigned long redzone_start;
452 unsigned long redzone_end;
454 if (gfpflags_allow_blocking(flags))
457 if (unlikely(ptr == NULL))
460 page = virt_to_page(ptr);
461 redzone_start = round_up((unsigned long)(ptr + size),
463 redzone_end = (unsigned long)ptr + page_size(page);
465 unpoison_range(ptr, size);
466 poison_range((void *)redzone_start, redzone_end - redzone_start,
472 void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
476 if (unlikely(object == ZERO_SIZE_PTR))
477 return (void *)object;
479 page = virt_to_head_page(object);
481 if (unlikely(!PageSlab(page)))
482 return __kasan_kmalloc_large(object, size, flags);
484 return ____kasan_kmalloc(page->slab_cache, object, size,
488 void __kasan_kfree_large(void *ptr, unsigned long ip)
490 if (ptr != page_address(virt_to_head_page(ptr)))
491 kasan_report_invalid_free(ptr, ip);
492 /* The object will be poisoned by kasan_free_pages(). */