xref: /openbmc/linux/mm/kasan/generic.c (revision 05c56e7b)
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(const void * addr)43 static __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 
memory_is_poisoned_2_4_8(const void * addr,unsigned long size)55 static __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 + size - 1);
66 
67 	return memory_is_poisoned_1(addr + size - 1);
68 }
69 
memory_is_poisoned_16(const void * addr)70 static __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 + 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(const void * addr,size_t size)123 static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)
124 {
125 	unsigned long ret;
126 
127 	ret = memory_is_nonzero(kasan_mem_to_shadow(addr),
128 			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 
memory_is_poisoned(const void * addr,size_t size)142 static __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 
check_region_inline(const void * addr,size_t size,bool write,unsigned long ret_ip)162 static __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, write, ret_ip);
174 
175 	if (unlikely(!addr_has_metadata(addr)))
176 		return !kasan_report(addr, size, write, ret_ip);
177 
178 	if (likely(!memory_is_poisoned(addr, size)))
179 		return true;
180 
181 	return !kasan_report(addr, size, write, ret_ip);
182 }
183 
kasan_check_range(const void * addr,size_t size,bool write,unsigned long ret_ip)184 bool 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 
kasan_byte_accessible(const void * addr)190 bool 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 
kasan_cache_shrink(struct kmem_cache * cache)202 void kasan_cache_shrink(struct kmem_cache *cache)
203 {
204 	kasan_quarantine_remove_cache(cache);
205 }
206 
kasan_cache_shutdown(struct kmem_cache * cache)207 void kasan_cache_shutdown(struct kmem_cache *cache)
208 {
209 	if (!__kmem_cache_empty(cache))
210 		kasan_quarantine_remove_cache(cache);
211 }
212 
register_global(struct kasan_global * global)213 static void register_global(struct kasan_global *global)
214 {
215 	size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
216 
217 	kasan_unpoison(global->beg, global->size, false);
218 
219 	kasan_poison(global->beg + aligned_size,
220 		     global->size_with_redzone - aligned_size,
221 		     KASAN_GLOBAL_REDZONE, false);
222 }
223 
__asan_register_globals(void * ptr,ssize_t size)224 void __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(&globals[i]);
231 }
232 EXPORT_SYMBOL(__asan_register_globals);
233 
__asan_unregister_globals(void * ptr,ssize_t size)234 void __asan_unregister_globals(void *ptr, ssize_t size)
235 {
236 }
237 EXPORT_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 
257 DEFINE_ASAN_LOAD_STORE(1);
258 DEFINE_ASAN_LOAD_STORE(2);
259 DEFINE_ASAN_LOAD_STORE(4);
260 DEFINE_ASAN_LOAD_STORE(8);
261 DEFINE_ASAN_LOAD_STORE(16);
262 
__asan_loadN(void * addr,ssize_t size)263 void __asan_loadN(void *addr, ssize_t size)
264 {
265 	kasan_check_range(addr, size, false, _RET_IP_);
266 }
267 EXPORT_SYMBOL(__asan_loadN);
268 
269 __alias(__asan_loadN)
270 void __asan_loadN_noabort(void *, ssize_t);
271 EXPORT_SYMBOL(__asan_loadN_noabort);
272 
__asan_storeN(void * addr,ssize_t size)273 void __asan_storeN(void *addr, ssize_t size)
274 {
275 	kasan_check_range(addr, size, true, _RET_IP_);
276 }
277 EXPORT_SYMBOL(__asan_storeN);
278 
279 __alias(__asan_storeN)
280 void __asan_storeN_noabort(void *, ssize_t);
281 EXPORT_SYMBOL(__asan_storeN_noabort);
282 
283 /* to shut up compiler complaints */
__asan_handle_no_return(void)284 void __asan_handle_no_return(void) {}
285 EXPORT_SYMBOL(__asan_handle_no_return);
286 
287 /* Emitted by compiler to poison alloca()ed objects. */
__asan_alloca_poison(void * addr,ssize_t size)288 void __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((const void *)(addr + rounded_down_size),
302 			size - rounded_down_size, false);
303 	kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
304 		     KASAN_ALLOCA_LEFT, false);
305 	kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
306 		     KASAN_ALLOCA_RIGHT, false);
307 }
308 EXPORT_SYMBOL(__asan_alloca_poison);
309 
310 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
__asan_allocas_unpoison(void * stack_top,ssize_t stack_bottom)311 void __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(stack_top, (void *)stack_bottom - stack_top, false);
317 }
318 EXPORT_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 
328 DEFINE_ASAN_SET_SHADOW(00);
329 DEFINE_ASAN_SET_SHADOW(f1);
330 DEFINE_ASAN_SET_SHADOW(f2);
331 DEFINE_ASAN_SET_SHADOW(f3);
332 DEFINE_ASAN_SET_SHADOW(f5);
333 DEFINE_ASAN_SET_SHADOW(f8);
334 
335 /* Only allow cache merging when no per-object metadata is present. */
kasan_never_merge(void)336 slab_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  */
optimal_redzone(unsigned int object_size)347 static 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 
kasan_cache_create(struct kmem_cache * cache,unsigned int * size,slab_flags_t * flags)359 void 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(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 
kasan_get_alloc_meta(struct kmem_cache * cache,const void * object)431 struct 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 
kasan_get_free_meta(struct kmem_cache * cache,const void * object)439 struct 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 
kasan_init_object_meta(struct kmem_cache * cache,const void * object)448 void 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 
kasan_metadata_size(struct kmem_cache * cache,bool in_object)457 size_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 
__kasan_record_aux_stack(void * addr,bool can_alloc)475 static 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, 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(0, can_alloc);
493 }
494 
kasan_record_aux_stack(void * addr)495 void kasan_record_aux_stack(void *addr)
496 {
497 	return __kasan_record_aux_stack(addr, true);
498 }
499 
kasan_record_aux_stack_noalloc(void * addr)500 void kasan_record_aux_stack_noalloc(void *addr)
501 {
502 	return __kasan_record_aux_stack(addr, false);
503 }
504 
kasan_save_alloc_info(struct kmem_cache * cache,void * object,gfp_t flags)505 void 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(&alloc_meta->alloc_track, flags);
512 }
513 
kasan_save_free_info(struct kmem_cache * cache,void * object)514 void 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(&free_meta->free_track, 0);
523 	/* The object was freed and has free track set. */
524 	*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;
525 }
526