1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains core generic 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/interrupt.h>
14#include <linux/init.h>
15#include <linux/kasan.h>
16#include <linux/kernel.h>
17#include <linux/kfence.h>
18#include <linux/kmemleak.h>
19#include <linux/linkage.h>
20#include <linux/memblock.h>
21#include <linux/memory.h>
22#include <linux/mm.h>
23#include <linux/module.h>
24#include <linux/printk.h>
25#include <linux/sched.h>
26#include <linux/sched/task_stack.h>
27#include <linux/slab.h>
28#include <linux/stacktrace.h>
29#include <linux/string.h>
30#include <linux/types.h>
31#include <linux/vmalloc.h>
32#include <linux/bug.h>
33
34#include "kasan.h"
35#include "../slab.h"
36
37/*
38 * All functions below always inlined so compiler could
39 * perform better optimizations in each of __asan_loadX/__assn_storeX
40 * depending on memory access size X.
41 */
42
43static __always_inline bool memory_is_poisoned_1(const void *addr)
44{
45 s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr);
46
47 if (unlikely(shadow_value)) {
48 s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK;
49 return unlikely(last_accessible_byte >= shadow_value);
50 }
51
52 return false;
53}
54
55static __always_inline bool memory_is_poisoned_2_4_8(const void *addr,
56 unsigned long size)
57{
58 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr);
59
60 /*
61 * Access crosses 8(shadow size)-byte boundary. Such access maps
62 * into 2 shadow bytes, so we need to check them both.
63 */
64 if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
65 return *shadow_addr || memory_is_poisoned_1(addr: addr + size - 1);
66
67 return memory_is_poisoned_1(addr: addr + size - 1);
68}
69
70static __always_inline bool memory_is_poisoned_16(const void *addr)
71{
72 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr);
73
74 /* Unaligned 16-bytes access maps into 3 shadow bytes. */
75 if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE)))
76 return *shadow_addr || memory_is_poisoned_1(addr: addr + 15);
77
78 return *shadow_addr;
79}
80
81static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
82 size_t size)
83{
84 while (size) {
85 if (unlikely(*start))
86 return (unsigned long)start;
87 start++;
88 size--;
89 }
90
91 return 0;
92}
93
94static __always_inline unsigned long memory_is_nonzero(const void *start,
95 const void *end)
96{
97 unsigned int words;
98 unsigned long ret;
99 unsigned int prefix = (unsigned long)start % 8;
100
101 if (end - start <= 16)
102 return bytes_is_nonzero(start, size: end - start);
103
104 if (prefix) {
105 prefix = 8 - prefix;
106 ret = bytes_is_nonzero(start, size: prefix);
107 if (unlikely(ret))
108 return ret;
109 start += prefix;
110 }
111
112 words = (end - start) / 8;
113 while (words) {
114 if (unlikely(*(u64 *)start))
115 return bytes_is_nonzero(start, size: 8);
116 start += 8;
117 words--;
118 }
119
120 return bytes_is_nonzero(start, size: (end - start) % 8);
121}
122
123static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)
124{
125 unsigned long ret;
126
127 ret = memory_is_nonzero(start: kasan_mem_to_shadow(addr),
128 end: kasan_mem_to_shadow(addr + size - 1) + 1);
129
130 if (unlikely(ret)) {
131 const void *last_byte = addr + size - 1;
132 s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte);
133 s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;
134
135 if (unlikely(ret != (unsigned long)last_shadow ||
136 last_accessible_byte >= *last_shadow))
137 return true;
138 }
139 return false;
140}
141
142static __always_inline bool memory_is_poisoned(const void *addr, size_t size)
143{
144 if (__builtin_constant_p(size)) {
145 switch (size) {
146 case 1:
147 return memory_is_poisoned_1(addr);
148 case 2:
149 case 4:
150 case 8:
151 return memory_is_poisoned_2_4_8(addr, size);
152 case 16:
153 return memory_is_poisoned_16(addr);
154 default:
155 BUILD_BUG();
156 }
157 }
158
159 return memory_is_poisoned_n(addr, size);
160}
161
162static __always_inline bool check_region_inline(const void *addr,
163 size_t size, bool write,
164 unsigned long ret_ip)
165{
166 if (!kasan_arch_is_ready())
167 return true;
168
169 if (unlikely(size == 0))
170 return true;
171
172 if (unlikely(addr + size < addr))
173 return !kasan_report(addr, size, is_write: write, ip: ret_ip);
174
175 if (unlikely(!addr_has_metadata(addr)))
176 return !kasan_report(addr, size, is_write: write, ip: ret_ip);
177
178 if (likely(!memory_is_poisoned(addr, size)))
179 return true;
180
181 return !kasan_report(addr, size, is_write: write, ip: ret_ip);
182}
183
184bool kasan_check_range(const void *addr, size_t size, bool write,
185 unsigned long ret_ip)
186{
187 return check_region_inline(addr, size, write, ret_ip);
188}
189
190bool kasan_byte_accessible(const void *addr)
191{
192 s8 shadow_byte;
193
194 if (!kasan_arch_is_ready())
195 return true;
196
197 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
198
199 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
200}
201
202void kasan_cache_shrink(struct kmem_cache *cache)
203{
204 kasan_quarantine_remove_cache(cache);
205}
206
207void kasan_cache_shutdown(struct kmem_cache *cache)
208{
209 if (!__kmem_cache_empty(cache))
210 kasan_quarantine_remove_cache(cache);
211}
212
213static void register_global(struct kasan_global *global)
214{
215 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
216
217 kasan_unpoison(addr: global->beg, size: global->size, init: false);
218
219 kasan_poison(addr: global->beg + aligned_size,
220 size: global->size_with_redzone - aligned_size,
221 value: KASAN_GLOBAL_REDZONE, init: false);
222}
223
224void __asan_register_globals(void *ptr, ssize_t size)
225{
226 int i;
227 struct kasan_global *globals = ptr;
228
229 for (i = 0; i < size; i++)
230 register_global(global: &globals[i]);
231}
232EXPORT_SYMBOL(__asan_register_globals);
233
234void __asan_unregister_globals(void *ptr, ssize_t size)
235{
236}
237EXPORT_SYMBOL(__asan_unregister_globals);
238
239#define DEFINE_ASAN_LOAD_STORE(size) \
240 void __asan_load##size(void *addr) \
241 { \
242 check_region_inline(addr, size, false, _RET_IP_); \
243 } \
244 EXPORT_SYMBOL(__asan_load##size); \
245 __alias(__asan_load##size) \
246 void __asan_load##size##_noabort(void *); \
247 EXPORT_SYMBOL(__asan_load##size##_noabort); \
248 void __asan_store##size(void *addr) \
249 { \
250 check_region_inline(addr, size, true, _RET_IP_); \
251 } \
252 EXPORT_SYMBOL(__asan_store##size); \
253 __alias(__asan_store##size) \
254 void __asan_store##size##_noabort(void *); \
255 EXPORT_SYMBOL(__asan_store##size##_noabort)
256
257DEFINE_ASAN_LOAD_STORE(1);
258DEFINE_ASAN_LOAD_STORE(2);
259DEFINE_ASAN_LOAD_STORE(4);
260DEFINE_ASAN_LOAD_STORE(8);
261DEFINE_ASAN_LOAD_STORE(16);
262
263void __asan_loadN(void *addr, ssize_t size)
264{
265 kasan_check_range(addr, size, write: false, _RET_IP_);
266}
267EXPORT_SYMBOL(__asan_loadN);
268
269__alias(__asan_loadN)
270void __asan_loadN_noabort(void *, ssize_t);
271EXPORT_SYMBOL(__asan_loadN_noabort);
272
273void __asan_storeN(void *addr, ssize_t size)
274{
275 kasan_check_range(addr, size, write: true, _RET_IP_);
276}
277EXPORT_SYMBOL(__asan_storeN);
278
279__alias(__asan_storeN)
280void __asan_storeN_noabort(void *, ssize_t);
281EXPORT_SYMBOL(__asan_storeN_noabort);
282
283/* to shut up compiler complaints */
284void __asan_handle_no_return(void) {}
285EXPORT_SYMBOL(__asan_handle_no_return);
286
287/* Emitted by compiler to poison alloca()ed objects. */
288void __asan_alloca_poison(void *addr, ssize_t size)
289{
290 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
291 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
292 rounded_up_size;
293 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
294
295 const void *left_redzone = (const void *)(addr -
296 KASAN_ALLOCA_REDZONE_SIZE);
297 const void *right_redzone = (const void *)(addr + rounded_up_size);
298
299 WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE));
300
301 kasan_unpoison(addr: (const void *)(addr + rounded_down_size),
302 size: size - rounded_down_size, init: false);
303 kasan_poison(addr: left_redzone, size: KASAN_ALLOCA_REDZONE_SIZE,
304 value: KASAN_ALLOCA_LEFT, init: false);
305 kasan_poison(addr: right_redzone, size: padding_size + KASAN_ALLOCA_REDZONE_SIZE,
306 value: KASAN_ALLOCA_RIGHT, init: false);
307}
308EXPORT_SYMBOL(__asan_alloca_poison);
309
310/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
311void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom)
312{
313 if (unlikely(!stack_top || stack_top > (void *)stack_bottom))
314 return;
315
316 kasan_unpoison(addr: stack_top, size: (void *)stack_bottom - stack_top, init: false);
317}
318EXPORT_SYMBOL(__asan_allocas_unpoison);
319
320/* Emitted by the compiler to [un]poison local variables. */
321#define DEFINE_ASAN_SET_SHADOW(byte) \
322 void __asan_set_shadow_##byte(const void *addr, ssize_t size) \
323 { \
324 __memset((void *)addr, 0x##byte, size); \
325 } \
326 EXPORT_SYMBOL(__asan_set_shadow_##byte)
327
328DEFINE_ASAN_SET_SHADOW(00);
329DEFINE_ASAN_SET_SHADOW(f1);
330DEFINE_ASAN_SET_SHADOW(f2);
331DEFINE_ASAN_SET_SHADOW(f3);
332DEFINE_ASAN_SET_SHADOW(f5);
333DEFINE_ASAN_SET_SHADOW(f8);
334
335/* Only allow cache merging when no per-object metadata is present. */
336slab_flags_t kasan_never_merge(void)
337{
338 if (!kasan_requires_meta())
339 return 0;
340 return SLAB_KASAN;
341}
342
343/*
344 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
345 * For larger allocations larger redzones are used.
346 */
347static inline unsigned int optimal_redzone(unsigned int object_size)
348{
349 return
350 object_size <= 64 - 16 ? 16 :
351 object_size <= 128 - 32 ? 32 :
352 object_size <= 512 - 64 ? 64 :
353 object_size <= 4096 - 128 ? 128 :
354 object_size <= (1 << 14) - 256 ? 256 :
355 object_size <= (1 << 15) - 512 ? 512 :
356 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
357}
358
359void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
360 slab_flags_t *flags)
361{
362 unsigned int ok_size;
363 unsigned int optimal_size;
364
365 if (!kasan_requires_meta())
366 return;
367
368 /*
369 * SLAB_KASAN is used to mark caches that are sanitized by KASAN
370 * and that thus have per-object metadata.
371 * Currently this flag is used in two places:
372 * 1. In slab_ksize() to account for per-object metadata when
373 * calculating the size of the accessible memory within the object.
374 * 2. In slab_common.c via kasan_never_merge() to prevent merging of
375 * caches with per-object metadata.
376 */
377 *flags |= SLAB_KASAN;
378
379 ok_size = *size;
380
381 /* Add alloc meta into redzone. */
382 cache->kasan_info.alloc_meta_offset = *size;
383 *size += sizeof(struct kasan_alloc_meta);
384
385 /*
386 * If alloc meta doesn't fit, don't add it.
387 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
388 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
389 * larger sizes.
390 */
391 if (*size > KMALLOC_MAX_SIZE) {
392 cache->kasan_info.alloc_meta_offset = 0;
393 *size = ok_size;
394 /* Continue, since free meta might still fit. */
395 }
396
397 /*
398 * Add free meta into redzone when it's not possible to store
399 * it in the object. This is the case when:
400 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
401 * be touched after it was freed, or
402 * 2. Object has a constructor, which means it's expected to
403 * retain its content until the next allocation, or
404 * 3. Object is too small.
405 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
406 */
407 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
408 cache->object_size < sizeof(struct kasan_free_meta)) {
409 ok_size = *size;
410
411 cache->kasan_info.free_meta_offset = *size;
412 *size += sizeof(struct kasan_free_meta);
413
414 /* If free meta doesn't fit, don't add it. */
415 if (*size > KMALLOC_MAX_SIZE) {
416 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
417 *size = ok_size;
418 }
419 }
420
421 /* Calculate size with optimal redzone. */
422 optimal_size = cache->object_size + optimal_redzone(object_size: cache->object_size);
423 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
424 if (optimal_size > KMALLOC_MAX_SIZE)
425 optimal_size = KMALLOC_MAX_SIZE;
426 /* Use optimal size if the size with added metas is not large enough. */
427 if (*size < optimal_size)
428 *size = optimal_size;
429}
430
431struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
432 const void *object)
433{
434 if (!cache->kasan_info.alloc_meta_offset)
435 return NULL;
436 return (void *)object + cache->kasan_info.alloc_meta_offset;
437}
438
439struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
440 const void *object)
441{
442 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
443 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
444 return NULL;
445 return (void *)object + cache->kasan_info.free_meta_offset;
446}
447
448void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
449{
450 struct kasan_alloc_meta *alloc_meta;
451
452 alloc_meta = kasan_get_alloc_meta(cache, object);
453 if (alloc_meta)
454 __memset(alloc_meta, 0, sizeof(*alloc_meta));
455}
456
457size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
458{
459 struct kasan_cache *info = &cache->kasan_info;
460
461 if (!kasan_requires_meta())
462 return 0;
463
464 if (in_object)
465 return (info->free_meta_offset ?
466 0 : sizeof(struct kasan_free_meta));
467 else
468 return (info->alloc_meta_offset ?
469 sizeof(struct kasan_alloc_meta) : 0) +
470 ((info->free_meta_offset &&
471 info->free_meta_offset != KASAN_NO_FREE_META) ?
472 sizeof(struct kasan_free_meta) : 0);
473}
474
475static void __kasan_record_aux_stack(void *addr, bool can_alloc)
476{
477 struct slab *slab = kasan_addr_to_slab(addr);
478 struct kmem_cache *cache;
479 struct kasan_alloc_meta *alloc_meta;
480 void *object;
481
482 if (is_kfence_address(addr) || !slab)
483 return;
484
485 cache = slab->slab_cache;
486 object = nearest_obj(cache, slab, x: addr);
487 alloc_meta = kasan_get_alloc_meta(cache, object);
488 if (!alloc_meta)
489 return;
490
491 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
492 alloc_meta->aux_stack[0] = kasan_save_stack(flags: 0, can_alloc);
493}
494
495void kasan_record_aux_stack(void *addr)
496{
497 return __kasan_record_aux_stack(addr, can_alloc: true);
498}
499
500void kasan_record_aux_stack_noalloc(void *addr)
501{
502 return __kasan_record_aux_stack(addr, can_alloc: false);
503}
504
505void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
506{
507 struct kasan_alloc_meta *alloc_meta;
508
509 alloc_meta = kasan_get_alloc_meta(cache, object);
510 if (alloc_meta)
511 kasan_set_track(track: &alloc_meta->alloc_track, flags);
512}
513
514void kasan_save_free_info(struct kmem_cache *cache, void *object)
515{
516 struct kasan_free_meta *free_meta;
517
518 free_meta = kasan_get_free_meta(cache, object);
519 if (!free_meta)
520 return;
521
522 kasan_set_track(track: &free_meta->free_track, flags: 0);
523 /* The object was freed and has free track set. */
524 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;
525}
526

source code of linux/mm/kasan/generic.c