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