1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains core generic 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/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>
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/stackdepot.h>
29 #include <linux/stacktrace.h>
30 #include <linux/string.h>
31 #include <linux/types.h>
32 #include <linux/vmalloc.h>
33 #include <linux/bug.h>
39 * All functions below always inlined so compiler could
40 * perform better optimizations in each of __asan_loadX/__assn_storeX
41 * depending on memory access size X.
44 static __always_inline bool memory_is_poisoned_1(const void *addr)
46 s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr);
48 if (unlikely(shadow_value)) {
49 s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK;
50 return unlikely(last_accessible_byte >= shadow_value);
56 static __always_inline bool memory_is_poisoned_2_4_8(const void *addr,
59 u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr);
62 * Access crosses 8(shadow size)-byte boundary. Such access maps
63 * into 2 shadow bytes, so we need to check them both.
65 if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
66 return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
68 return memory_is_poisoned_1(addr + size - 1);
71 static __always_inline bool memory_is_poisoned_16(const void *addr)
73 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr);
75 /* Unaligned 16-bytes access maps into 3 shadow bytes. */
76 if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE)))
77 return *shadow_addr || memory_is_poisoned_1(addr + 15);
82 static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
87 return (unsigned long)start;
95 static __always_inline unsigned long memory_is_nonzero(const void *start,
100 unsigned int prefix = (unsigned long)start % 8;
102 if (end - start <= 16)
103 return bytes_is_nonzero(start, end - start);
107 ret = bytes_is_nonzero(start, prefix);
113 words = (end - start) / 8;
115 if (unlikely(*(u64 *)start))
116 return bytes_is_nonzero(start, 8);
121 return bytes_is_nonzero(start, (end - start) % 8);
124 static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)
128 ret = memory_is_nonzero(kasan_mem_to_shadow(addr),
129 kasan_mem_to_shadow(addr + size - 1) + 1);
132 const void *last_byte = addr + size - 1;
133 s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte);
134 s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;
136 if (unlikely(ret != (unsigned long)last_shadow ||
137 last_accessible_byte >= *last_shadow))
143 static __always_inline bool memory_is_poisoned(const void *addr, size_t size)
145 if (__builtin_constant_p(size)) {
148 return memory_is_poisoned_1(addr);
152 return memory_is_poisoned_2_4_8(addr, size);
154 return memory_is_poisoned_16(addr);
160 return memory_is_poisoned_n(addr, size);
163 static __always_inline bool check_region_inline(const void *addr,
164 size_t size, bool write,
165 unsigned long ret_ip)
167 if (!kasan_arch_is_ready())
170 if (unlikely(size == 0))
173 if (unlikely(addr + size < addr))
174 return !kasan_report(addr, size, write, ret_ip);
176 if (unlikely(!addr_has_metadata(addr)))
177 return !kasan_report(addr, size, write, ret_ip);
179 if (likely(!memory_is_poisoned(addr, size)))
182 return !kasan_report(addr, size, write, ret_ip);
185 bool kasan_check_range(const void *addr, size_t size, bool write,
186 unsigned long ret_ip)
188 return check_region_inline(addr, size, write, ret_ip);
191 bool kasan_byte_accessible(const void *addr)
195 if (!kasan_arch_is_ready())
198 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
200 return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
203 void kasan_cache_shrink(struct kmem_cache *cache)
205 kasan_quarantine_remove_cache(cache);
208 void kasan_cache_shutdown(struct kmem_cache *cache)
210 if (!__kmem_cache_empty(cache))
211 kasan_quarantine_remove_cache(cache);
214 static void register_global(struct kasan_global *global)
216 size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
218 kasan_unpoison(global->beg, global->size, false);
220 kasan_poison(global->beg + aligned_size,
221 global->size_with_redzone - aligned_size,
222 KASAN_GLOBAL_REDZONE, false);
225 void __asan_register_globals(void *ptr, ssize_t size)
228 struct kasan_global *globals = ptr;
230 for (i = 0; i < size; i++)
231 register_global(&globals[i]);
233 EXPORT_SYMBOL(__asan_register_globals);
235 void __asan_unregister_globals(void *ptr, ssize_t size)
238 EXPORT_SYMBOL(__asan_unregister_globals);
240 #define DEFINE_ASAN_LOAD_STORE(size) \
241 void __asan_load##size(void *addr) \
243 check_region_inline(addr, size, false, _RET_IP_); \
245 EXPORT_SYMBOL(__asan_load##size); \
246 __alias(__asan_load##size) \
247 void __asan_load##size##_noabort(void *); \
248 EXPORT_SYMBOL(__asan_load##size##_noabort); \
249 void __asan_store##size(void *addr) \
251 check_region_inline(addr, size, true, _RET_IP_); \
253 EXPORT_SYMBOL(__asan_store##size); \
254 __alias(__asan_store##size) \
255 void __asan_store##size##_noabort(void *); \
256 EXPORT_SYMBOL(__asan_store##size##_noabort)
258 DEFINE_ASAN_LOAD_STORE(1);
259 DEFINE_ASAN_LOAD_STORE(2);
260 DEFINE_ASAN_LOAD_STORE(4);
261 DEFINE_ASAN_LOAD_STORE(8);
262 DEFINE_ASAN_LOAD_STORE(16);
264 void __asan_loadN(void *addr, ssize_t size)
266 kasan_check_range(addr, size, false, _RET_IP_);
268 EXPORT_SYMBOL(__asan_loadN);
270 __alias(__asan_loadN)
271 void __asan_loadN_noabort(void *, ssize_t);
272 EXPORT_SYMBOL(__asan_loadN_noabort);
274 void __asan_storeN(void *addr, ssize_t size)
276 kasan_check_range(addr, size, true, _RET_IP_);
278 EXPORT_SYMBOL(__asan_storeN);
280 __alias(__asan_storeN)
281 void __asan_storeN_noabort(void *, ssize_t);
282 EXPORT_SYMBOL(__asan_storeN_noabort);
284 /* to shut up compiler complaints */
285 void __asan_handle_no_return(void) {}
286 EXPORT_SYMBOL(__asan_handle_no_return);
288 /* Emitted by compiler to poison alloca()ed objects. */
289 void __asan_alloca_poison(void *addr, ssize_t size)
291 size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
292 size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
294 size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
296 const void *left_redzone = (const void *)(addr -
297 KASAN_ALLOCA_REDZONE_SIZE);
298 const void *right_redzone = (const void *)(addr + rounded_up_size);
300 WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE));
302 kasan_unpoison((const void *)(addr + rounded_down_size),
303 size - rounded_down_size, false);
304 kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
305 KASAN_ALLOCA_LEFT, false);
306 kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
307 KASAN_ALLOCA_RIGHT, false);
309 EXPORT_SYMBOL(__asan_alloca_poison);
311 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
312 void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom)
314 if (unlikely(!stack_top || stack_top > (void *)stack_bottom))
317 kasan_unpoison(stack_top, (void *)stack_bottom - stack_top, false);
319 EXPORT_SYMBOL(__asan_allocas_unpoison);
321 /* Emitted by the compiler to [un]poison local variables. */
322 #define DEFINE_ASAN_SET_SHADOW(byte) \
323 void __asan_set_shadow_##byte(const void *addr, ssize_t size) \
325 __memset((void *)addr, 0x##byte, size); \
327 EXPORT_SYMBOL(__asan_set_shadow_##byte)
329 DEFINE_ASAN_SET_SHADOW(00);
330 DEFINE_ASAN_SET_SHADOW(f1);
331 DEFINE_ASAN_SET_SHADOW(f2);
332 DEFINE_ASAN_SET_SHADOW(f3);
333 DEFINE_ASAN_SET_SHADOW(f5);
334 DEFINE_ASAN_SET_SHADOW(f8);
336 /* Only allow cache merging when no per-object metadata is present. */
337 slab_flags_t kasan_never_merge(void)
339 if (!kasan_requires_meta())
345 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
346 * For larger allocations larger redzones are used.
348 static inline unsigned int optimal_redzone(unsigned int object_size)
351 object_size <= 64 - 16 ? 16 :
352 object_size <= 128 - 32 ? 32 :
353 object_size <= 512 - 64 ? 64 :
354 object_size <= 4096 - 128 ? 128 :
355 object_size <= (1 << 14) - 256 ? 256 :
356 object_size <= (1 << 15) - 512 ? 512 :
357 object_size <= (1 << 16) - 1024 ? 1024 : 2048;
360 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
363 unsigned int ok_size;
364 unsigned int optimal_size;
365 unsigned int rem_free_meta_size;
366 unsigned int orig_alloc_meta_offset;
368 if (!kasan_requires_meta())
372 * SLAB_KASAN is used to mark caches that are sanitized by KASAN
373 * and that thus have per-object metadata.
374 * Currently this flag is used in two places:
375 * 1. In slab_ksize() to account for per-object metadata when
376 * calculating the size of the accessible memory within the object.
377 * 2. In slab_common.c via kasan_never_merge() to prevent merging of
378 * caches with per-object metadata.
380 *flags |= SLAB_KASAN;
384 /* Add alloc meta into redzone. */
385 cache->kasan_info.alloc_meta_offset = *size;
386 *size += sizeof(struct kasan_alloc_meta);
389 * If alloc meta doesn't fit, don't add it.
390 * This can only happen with SLAB, as it has KMALLOC_MAX_SIZE equal
391 * to KMALLOC_MAX_CACHE_SIZE and doesn't fall back to page_alloc for
394 if (*size > KMALLOC_MAX_SIZE) {
395 cache->kasan_info.alloc_meta_offset = 0;
397 /* Continue, since free meta might still fit. */
401 orig_alloc_meta_offset = cache->kasan_info.alloc_meta_offset;
404 * Add free meta into redzone when it's not possible to store
405 * it in the object. This is the case when:
406 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
407 * be touched after it was freed, or
408 * 2. Object has a constructor, which means it's expected to
409 * retain its content until the next allocation, or
410 * 3. Object is too small and SLUB DEBUG is enabled. Avoid
411 * free meta that exceeds the object size corrupts the
412 * SLUB DEBUG metadata.
413 * Otherwise cache->kasan_info.free_meta_offset = 0 is implied.
414 * If the object is smaller than the free meta and SLUB DEBUG
415 * is not enabled, it is still possible to store part of the
416 * free meta in the object.
418 if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor) {
419 cache->kasan_info.free_meta_offset = *size;
420 *size += sizeof(struct kasan_free_meta);
421 } else if (cache->object_size < sizeof(struct kasan_free_meta)) {
422 if (__slub_debug_enabled()) {
423 cache->kasan_info.free_meta_offset = *size;
424 *size += sizeof(struct kasan_free_meta);
426 rem_free_meta_size = sizeof(struct kasan_free_meta) -
428 *size += rem_free_meta_size;
429 if (cache->kasan_info.alloc_meta_offset != 0)
430 cache->kasan_info.alloc_meta_offset += rem_free_meta_size;
434 /* If free meta doesn't fit, don't add it. */
435 if (*size > KMALLOC_MAX_SIZE) {
436 cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
437 cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;
441 /* Calculate size with optimal redzone. */
442 optimal_size = cache->object_size + optimal_redzone(cache->object_size);
443 /* Limit it with KMALLOC_MAX_SIZE (relevant for SLAB only). */
444 if (optimal_size > KMALLOC_MAX_SIZE)
445 optimal_size = KMALLOC_MAX_SIZE;
446 /* Use optimal size if the size with added metas is not large enough. */
447 if (*size < optimal_size)
448 *size = optimal_size;
451 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
454 if (!cache->kasan_info.alloc_meta_offset)
456 return (void *)object + cache->kasan_info.alloc_meta_offset;
459 struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
462 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
463 if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
465 return (void *)object + cache->kasan_info.free_meta_offset;
468 void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
470 struct kasan_alloc_meta *alloc_meta;
471 struct kasan_free_meta *free_meta;
473 alloc_meta = kasan_get_alloc_meta(cache, object);
475 __memset(alloc_meta, 0, sizeof(*alloc_meta));
476 free_meta = kasan_get_free_meta(cache, object);
478 __memset(free_meta, 0, sizeof(*free_meta));
481 size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
483 struct kasan_cache *info = &cache->kasan_info;
485 if (!kasan_requires_meta())
489 return (info->free_meta_offset ?
490 0 : sizeof(struct kasan_free_meta));
492 return (info->alloc_meta_offset ?
493 sizeof(struct kasan_alloc_meta) : 0) +
494 ((info->free_meta_offset &&
495 info->free_meta_offset != KASAN_NO_FREE_META) ?
496 sizeof(struct kasan_free_meta) : 0);
499 static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags)
501 struct slab *slab = kasan_addr_to_slab(addr);
502 struct kmem_cache *cache;
503 struct kasan_alloc_meta *alloc_meta;
506 if (is_kfence_address(addr) || !slab)
509 cache = slab->slab_cache;
510 object = nearest_obj(cache, slab, addr);
511 alloc_meta = kasan_get_alloc_meta(cache, object);
515 stack_depot_put(alloc_meta->aux_stack[1]);
516 alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
517 alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags);
520 void kasan_record_aux_stack(void *addr)
522 return __kasan_record_aux_stack(addr,
523 STACK_DEPOT_FLAG_CAN_ALLOC | STACK_DEPOT_FLAG_GET);
526 void kasan_record_aux_stack_noalloc(void *addr)
528 return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_GET);
531 void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
533 struct kasan_alloc_meta *alloc_meta;
535 alloc_meta = kasan_get_alloc_meta(cache, object);
539 /* Evict previous stack traces (might exist for krealloc). */
540 stack_depot_put(alloc_meta->alloc_track.stack);
541 stack_depot_put(alloc_meta->aux_stack[0]);
542 stack_depot_put(alloc_meta->aux_stack[1]);
543 __memset(alloc_meta, 0, sizeof(*alloc_meta));
545 kasan_set_track(&alloc_meta->alloc_track, flags);
548 void kasan_save_free_info(struct kmem_cache *cache, void *object)
550 struct kasan_free_meta *free_meta;
552 free_meta = kasan_get_free_meta(cache, object);
556 kasan_set_track(&free_meta->free_track, 0);
557 /* The object was freed and has free track set. */
558 *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;