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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/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>
29
30#include "kasan.h"
31#include "../slab.h"
32
33struct slab *kasan_addr_to_slab(const void *addr)
34{
35 if (virt_addr_valid(addr))
36 return virt_to_slab(addr);
37 return NULL;
38}
39
40depot_stack_handle_t kasan_save_stack(gfp_t flags, bool can_alloc)
41{
42 unsigned long entries[KASAN_STACK_DEPTH];
43 unsigned int nr_entries;
44
45 nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
46 return __stack_depot_save(entries, nr_entries, 0, flags, can_alloc);
47}
48
49void kasan_set_track(struct kasan_track *track, gfp_t flags)
50{
51 track->pid = current->pid;
52 track->stack = kasan_save_stack(flags, true);
53}
54
55#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
56void kasan_enable_current(void)
57{
58 current->kasan_depth++;
59}
60EXPORT_SYMBOL(kasan_enable_current);
61
62void kasan_disable_current(void)
63{
64 current->kasan_depth--;
65}
66EXPORT_SYMBOL(kasan_disable_current);
67
68#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
69
70void __kasan_unpoison_range(const void *address, size_t size)
71{
72 kasan_unpoison(address, size, false);
73}
74
75#ifdef CONFIG_KASAN_STACK
76/* Unpoison the entire stack for a task. */
77void kasan_unpoison_task_stack(struct task_struct *task)
78{
79 void *base = task_stack_page(task);
80
81 kasan_unpoison(base, THREAD_SIZE, false);
82}
83
84/* Unpoison the stack for the current task beyond a watermark sp value. */
85asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
86{
87 /*
88 * Calculate the task stack base address. Avoid using 'current'
89 * because this function is called by early resume code which hasn't
90 * yet set up the percpu register (%gs).
91 */
92 void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1));
93
94 kasan_unpoison(base, watermark - base, false);
95}
96#endif /* CONFIG_KASAN_STACK */
97
98void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init)
99{
100 u8 tag;
101 unsigned long i;
102
103 if (unlikely(PageHighMem(page)))
104 return;
105
106 tag = kasan_random_tag();
107 kasan_unpoison(set_tag(page_address(page), tag),
108 PAGE_SIZE << order, init);
109 for (i = 0; i < (1 << order); i++)
110 page_kasan_tag_set(page + i, tag);
111}
112
113void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
114{
115 if (likely(!PageHighMem(page)))
116 kasan_poison(page_address(page), PAGE_SIZE << order,
117 KASAN_PAGE_FREE, init);
118}
119
120void __kasan_cache_create_kmalloc(struct kmem_cache *cache)
121{
122 cache->kasan_info.is_kmalloc = true;
123}
124
125void __kasan_poison_slab(struct slab *slab)
126{
127 struct page *page = slab_page(slab);
128 unsigned long i;
129
130 for (i = 0; i < compound_nr(page); i++)
131 page_kasan_tag_reset(page + i);
132 kasan_poison(page_address(page), page_size(page),
133 KASAN_SLAB_REDZONE, false);
134}
135
136void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
137{
138 kasan_unpoison(object, cache->object_size, false);
139}
140
141void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
142{
143 kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
144 KASAN_SLAB_REDZONE, false);
145}
146
147/*
148 * This function assigns a tag to an object considering the following:
149 * 1. A cache might have a constructor, which might save a pointer to a slab
150 * object somewhere (e.g. in the object itself). We preassign a tag for
151 * each object in caches with constructors during slab creation and reuse
152 * the same tag each time a particular object is allocated.
153 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
154 * accessed after being freed. We preassign tags for objects in these
155 * caches as well.
156 * 3. For SLAB allocator we can't preassign tags randomly since the freelist
157 * is stored as an array of indexes instead of a linked list. Assign tags
158 * based on objects indexes, so that objects that are next to each other
159 * get different tags.
160 */
161static inline u8 assign_tag(struct kmem_cache *cache,
162 const void *object, bool init)
163{
164 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
165 return 0xff;
166
167 /*
168 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
169 * set, assign a tag when the object is being allocated (init == false).
170 */
171 if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU))
172 return init ? KASAN_TAG_KERNEL : kasan_random_tag();
173
174 /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
175#ifdef CONFIG_SLAB
176 /* For SLAB assign tags based on the object index in the freelist. */
177 return (u8)obj_to_index(cache, virt_to_slab(object), (void *)object);
178#else
179 /*
180 * For SLUB assign a random tag during slab creation, otherwise reuse
181 * the already assigned tag.
182 */
183 return init ? kasan_random_tag() : get_tag(object);
184#endif
185}
186
187void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
188 const void *object)
189{
190 /* Initialize per-object metadata if it is present. */
191 if (kasan_requires_meta())
192 kasan_init_object_meta(cache, object);
193
194 /* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
195 object = set_tag(object, assign_tag(cache, object, true));
196
197 return (void *)object;
198}
199
200static inline bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
201 unsigned long ip, bool quarantine, bool init)
202{
203 void *tagged_object;
204
205 if (!kasan_arch_is_ready())
206 return false;
207
208 tagged_object = object;
209 object = kasan_reset_tag(object);
210
211 if (is_kfence_address(object))
212 return false;
213
214 if (unlikely(nearest_obj(cache, virt_to_slab(object), object) !=
215 object)) {
216 kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_INVALID_FREE);
217 return true;
218 }
219
220 /* RCU slabs could be legally used after free within the RCU period */
221 if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU))
222 return false;
223
224 if (!kasan_byte_accessible(tagged_object)) {
225 kasan_report_invalid_free(tagged_object, ip, KASAN_REPORT_DOUBLE_FREE);
226 return true;
227 }
228
229 kasan_poison(object, round_up(cache->object_size, KASAN_GRANULE_SIZE),
230 KASAN_SLAB_FREE, init);
231
232 if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
233 return false;
234
235 if (kasan_stack_collection_enabled())
236 kasan_save_free_info(cache, tagged_object);
237
238 return kasan_quarantine_put(cache, object);
239}
240
241bool __kasan_slab_free(struct kmem_cache *cache, void *object,
242 unsigned long ip, bool init)
243{
244 return ____kasan_slab_free(cache, object, ip, true, init);
245}
246
247static inline bool ____kasan_kfree_large(void *ptr, unsigned long ip)
248{
249 if (!kasan_arch_is_ready())
250 return false;
251
252 if (ptr != page_address(virt_to_head_page(ptr))) {
253 kasan_report_invalid_free(ptr, ip, KASAN_REPORT_INVALID_FREE);
254 return true;
255 }
256
257 if (!kasan_byte_accessible(ptr)) {
258 kasan_report_invalid_free(ptr, ip, KASAN_REPORT_DOUBLE_FREE);
259 return true;
260 }
261
262 /*
263 * The object will be poisoned by kasan_poison_pages() or
264 * kasan_slab_free_mempool().
265 */
266
267 return false;
268}
269
270void __kasan_kfree_large(void *ptr, unsigned long ip)
271{
272 ____kasan_kfree_large(ptr, ip);
273}
274
275void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
276{
277 struct folio *folio;
278
279 folio = virt_to_folio(ptr);
280
281 /*
282 * Even though this function is only called for kmem_cache_alloc and
283 * kmalloc backed mempool allocations, those allocations can still be
284 * !PageSlab() when the size provided to kmalloc is larger than
285 * KMALLOC_MAX_SIZE, and kmalloc falls back onto page_alloc.
286 */
287 if (unlikely(!folio_test_slab(folio))) {
288 if (____kasan_kfree_large(ptr, ip))
289 return;
290 kasan_poison(ptr, folio_size(folio), KASAN_PAGE_FREE, false);
291 } else {
292 struct slab *slab = folio_slab(folio);
293
294 ____kasan_slab_free(slab->slab_cache, ptr, ip, false, false);
295 }
296}
297
298void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
299 void *object, gfp_t flags, bool init)
300{
301 u8 tag;
302 void *tagged_object;
303
304 if (gfpflags_allow_blocking(flags))
305 kasan_quarantine_reduce();
306
307 if (unlikely(object == NULL))
308 return NULL;
309
310 if (is_kfence_address(object))
311 return (void *)object;
312
313 /*
314 * Generate and assign random tag for tag-based modes.
315 * Tag is ignored in set_tag() for the generic mode.
316 */
317 tag = assign_tag(cache, object, false);
318 tagged_object = set_tag(object, tag);
319
320 /*
321 * Unpoison the whole object.
322 * For kmalloc() allocations, kasan_kmalloc() will do precise poisoning.
323 */
324 kasan_unpoison(tagged_object, cache->object_size, init);
325
326 /* Save alloc info (if possible) for non-kmalloc() allocations. */
327 if (kasan_stack_collection_enabled() && !cache->kasan_info.is_kmalloc)
328 kasan_save_alloc_info(cache, tagged_object, flags);
329
330 return tagged_object;
331}
332
333static inline void *____kasan_kmalloc(struct kmem_cache *cache,
334 const void *object, size_t size, gfp_t flags)
335{
336 unsigned long redzone_start;
337 unsigned long redzone_end;
338
339 if (gfpflags_allow_blocking(flags))
340 kasan_quarantine_reduce();
341
342 if (unlikely(object == NULL))
343 return NULL;
344
345 if (is_kfence_address(kasan_reset_tag(object)))
346 return (void *)object;
347
348 /*
349 * The object has already been unpoisoned by kasan_slab_alloc() for
350 * kmalloc() or by kasan_krealloc() for krealloc().
351 */
352
353 /*
354 * The redzone has byte-level precision for the generic mode.
355 * Partially poison the last object granule to cover the unaligned
356 * part of the redzone.
357 */
358 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
359 kasan_poison_last_granule((void *)object, size);
360
361 /* Poison the aligned part of the redzone. */
362 redzone_start = round_up((unsigned long)(object + size),
363 KASAN_GRANULE_SIZE);
364 redzone_end = round_up((unsigned long)(object + cache->object_size),
365 KASAN_GRANULE_SIZE);
366 kasan_poison((void *)redzone_start, redzone_end - redzone_start,
367 KASAN_SLAB_REDZONE, false);
368
369 /*
370 * Save alloc info (if possible) for kmalloc() allocations.
371 * This also rewrites the alloc info when called from kasan_krealloc().
372 */
373 if (kasan_stack_collection_enabled() && cache->kasan_info.is_kmalloc)
374 kasan_save_alloc_info(cache, (void *)object, flags);
375
376 /* Keep the tag that was set by kasan_slab_alloc(). */
377 return (void *)object;
378}
379
380void * __must_check __kasan_kmalloc(struct kmem_cache *cache, const void *object,
381 size_t size, gfp_t flags)
382{
383 return ____kasan_kmalloc(cache, object, size, flags);
384}
385EXPORT_SYMBOL(__kasan_kmalloc);
386
387void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
388 gfp_t flags)
389{
390 unsigned long redzone_start;
391 unsigned long redzone_end;
392
393 if (gfpflags_allow_blocking(flags))
394 kasan_quarantine_reduce();
395
396 if (unlikely(ptr == NULL))
397 return NULL;
398
399 /*
400 * The object has already been unpoisoned by kasan_unpoison_pages() for
401 * alloc_pages() or by kasan_krealloc() for krealloc().
402 */
403
404 /*
405 * The redzone has byte-level precision for the generic mode.
406 * Partially poison the last object granule to cover the unaligned
407 * part of the redzone.
408 */
409 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
410 kasan_poison_last_granule(ptr, size);
411
412 /* Poison the aligned part of the redzone. */
413 redzone_start = round_up((unsigned long)(ptr + size),
414 KASAN_GRANULE_SIZE);
415 redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
416 kasan_poison((void *)redzone_start, redzone_end - redzone_start,
417 KASAN_PAGE_REDZONE, false);
418
419 return (void *)ptr;
420}
421
422void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flags)
423{
424 struct slab *slab;
425
426 if (unlikely(object == ZERO_SIZE_PTR))
427 return (void *)object;
428
429 /*
430 * Unpoison the object's data.
431 * Part of it might already have been unpoisoned, but it's unknown
432 * how big that part is.
433 */
434 kasan_unpoison(object, size, false);
435
436 slab = virt_to_slab(object);
437
438 /* Piggy-back on kmalloc() instrumentation to poison the redzone. */
439 if (unlikely(!slab))
440 return __kasan_kmalloc_large(object, size, flags);
441 else
442 return ____kasan_kmalloc(slab->slab_cache, object, size, flags);
443}
444
445bool __kasan_check_byte(const void *address, unsigned long ip)
446{
447 if (!kasan_byte_accessible(address)) {
448 kasan_report((unsigned long)address, 1, false, ip);
449 return false;
450 }
451 return true;
452}