generic.c

  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/spinlock.h>
 29#include <linux/stackdepot.h>
 30#include <linux/stacktrace.h>
 31#include <linux/string.h>
 32#include <linux/types.h>
 33#include <linux/vmalloc.h>
 34#include <linux/bug.h>
 35
 36#include "kasan.h"
 37#include "../slab.h"
 38
 39/*
 40 * Initialize Generic KASAN and enable runtime checks.
 41 * This should be called from arch kasan_init() once shadow memory is ready.
 42 */
 43void __init kasan_init_generic(void)
 44{
 45	kasan_enable();
 46
 47	pr_info("KernelAddressSanitizer initialized (generic)\n");
 48}
 49
 50/*
 51 * All functions below always inlined so compiler could
 52 * perform better optimizations in each of __asan_loadX/__assn_storeX
 53 * depending on memory access size X.
 54 */
 55
 56static __always_inline bool memory_is_poisoned_1(const void *addr)
 57{
 58	s8 shadow_value = *(s8 *)kasan_mem_to_shadow(addr);
 59
 60	if (unlikely(shadow_value)) {
 61		s8 last_accessible_byte = (unsigned long)addr & KASAN_GRANULE_MASK;
 62		return unlikely(last_accessible_byte >= shadow_value);
 63	}
 64
 65	return false;
 66}
 67
 68static __always_inline bool memory_is_poisoned_2_4_8(const void *addr,
 69						unsigned long size)
 70{
 71	u8 *shadow_addr = (u8 *)kasan_mem_to_shadow(addr);
 72
 73	/*
 74	 * Access crosses 8(shadow size)-byte boundary. Such access maps
 75	 * into 2 shadow bytes, so we need to check them both.
 76	 */
 77	if (unlikely((((unsigned long)addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
 78		return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
 79
 80	return memory_is_poisoned_1(addr + size - 1);
 81}
 82
 83static __always_inline bool memory_is_poisoned_16(const void *addr)
 84{
 85	u16 *shadow_addr = (u16 *)kasan_mem_to_shadow(addr);
 86
 87	/* Unaligned 16-bytes access maps into 3 shadow bytes. */
 88	if (unlikely(!IS_ALIGNED((unsigned long)addr, KASAN_GRANULE_SIZE)))
 89		return *shadow_addr || memory_is_poisoned_1(addr + 15);
 90
 91	return *shadow_addr;
 92}
 93
 94static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
 95					size_t size)
 96{
 97	while (size) {
 98		if (unlikely(*start))
 99			return (unsigned long)start;
100		start++;
101		size--;
102	}
103
104	return 0;
105}
106
107static __always_inline unsigned long memory_is_nonzero(const void *start,
108						const void *end)
109{
110	unsigned int words;
111	unsigned long ret;
112	unsigned int prefix = (unsigned long)start % 8;
113
114	if (end - start <= 16)
115		return bytes_is_nonzero(start, end - start);
116
117	if (prefix) {
118		prefix = 8 - prefix;
119		ret = bytes_is_nonzero(start, prefix);
120		if (unlikely(ret))
121			return ret;
122		start += prefix;
123	}
124
125	words = (end - start) / 8;
126	while (words) {
127		if (unlikely(*(u64 *)start))
128			return bytes_is_nonzero(start, 8);
129		start += 8;
130		words--;
131	}
132
133	return bytes_is_nonzero(start, (end - start) % 8);
134}
135
136static __always_inline bool memory_is_poisoned_n(const void *addr, size_t size)
137{
138	unsigned long ret;
139
140	ret = memory_is_nonzero(kasan_mem_to_shadow(addr),
141			kasan_mem_to_shadow(addr + size - 1) + 1);
142
143	if (unlikely(ret)) {
144		const void *last_byte = addr + size - 1;
145		s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte);
146		s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;
147
148		if (unlikely(ret != (unsigned long)last_shadow ||
149			     last_accessible_byte >= *last_shadow))
150			return true;
151	}
152	return false;
153}
154
155static __always_inline bool memory_is_poisoned(const void *addr, size_t size)
156{
157	if (__builtin_constant_p(size)) {
158		switch (size) {
159		case 1:
160			return memory_is_poisoned_1(addr);
161		case 2:
162		case 4:
163		case 8:
164			return memory_is_poisoned_2_4_8(addr, size);
165		case 16:
166			return memory_is_poisoned_16(addr);
167		default:
168			BUILD_BUG();
169		}
170	}
171
172	return memory_is_poisoned_n(addr, size);
173}
174
175static __always_inline bool check_region_inline(const void *addr,
176						size_t size, bool write,
177						unsigned long ret_ip)
178{
179	if (!kasan_enabled())
180		return true;
181
182	if (unlikely(size == 0))
183		return true;
184
185	if (unlikely(addr + size < addr))
186		return !kasan_report(addr, size, write, ret_ip);
187
188	if (unlikely(!addr_has_metadata(addr)))
189		return !kasan_report(addr, size, write, ret_ip);
190
191	if (likely(!memory_is_poisoned(addr, size)))
192		return true;
193
194	return !kasan_report(addr, size, write, ret_ip);
195}
196
197bool kasan_check_range(const void *addr, size_t size, bool write,
198					unsigned long ret_ip)
199{
200	return check_region_inline(addr, size, write, ret_ip);
201}
202
203bool kasan_byte_accessible(const void *addr)
204{
205	s8 shadow_byte;
206
207	if (!kasan_enabled())
208		return true;
209
210	shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
211
212	return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
213}
214
215void kasan_cache_shrink(struct kmem_cache *cache)
216{
217	kasan_quarantine_remove_cache(cache);
218}
219
220void kasan_cache_shutdown(struct kmem_cache *cache)
221{
222	if (!__kmem_cache_empty(cache))
223		kasan_quarantine_remove_cache(cache);
224}
225
226static void register_global(struct kasan_global *global)
227{
228	size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
229
230	kasan_unpoison(global->beg, global->size, false);
231
232	kasan_poison(global->beg + aligned_size,
233		     global->size_with_redzone - aligned_size,
234		     KASAN_GLOBAL_REDZONE, false);
235}
236
237void __asan_register_globals(void *ptr, ssize_t size)
238{
239	int i;
240	struct kasan_global *globals = ptr;
241
242	for (i = 0; i < size; i++)
243		register_global(&globals[i]);
244}
245EXPORT_SYMBOL(__asan_register_globals);
246
247void __asan_unregister_globals(void *ptr, ssize_t size)
248{
249}
250EXPORT_SYMBOL(__asan_unregister_globals);
251
252#define DEFINE_ASAN_LOAD_STORE(size)					\
253	void __asan_load##size(void *addr)				\
254	{								\
255		check_region_inline(addr, size, false, _RET_IP_);	\
256	}								\
257	EXPORT_SYMBOL(__asan_load##size);				\
258	__alias(__asan_load##size)					\
259	void __asan_load##size##_noabort(void *);			\
260	EXPORT_SYMBOL(__asan_load##size##_noabort);			\
261	void __asan_store##size(void *addr)				\
262	{								\
263		check_region_inline(addr, size, true, _RET_IP_);	\
264	}								\
265	EXPORT_SYMBOL(__asan_store##size);				\
266	__alias(__asan_store##size)					\
267	void __asan_store##size##_noabort(void *);			\
268	EXPORT_SYMBOL(__asan_store##size##_noabort)
269
270DEFINE_ASAN_LOAD_STORE(1);
271DEFINE_ASAN_LOAD_STORE(2);
272DEFINE_ASAN_LOAD_STORE(4);
273DEFINE_ASAN_LOAD_STORE(8);
274DEFINE_ASAN_LOAD_STORE(16);
275
276void __asan_loadN(void *addr, ssize_t size)
277{
278	kasan_check_range(addr, size, false, _RET_IP_);
279}
280EXPORT_SYMBOL(__asan_loadN);
281
282__alias(__asan_loadN)
283void __asan_loadN_noabort(void *, ssize_t);
284EXPORT_SYMBOL(__asan_loadN_noabort);
285
286void __asan_storeN(void *addr, ssize_t size)
287{
288	kasan_check_range(addr, size, true, _RET_IP_);
289}
290EXPORT_SYMBOL(__asan_storeN);
291
292__alias(__asan_storeN)
293void __asan_storeN_noabort(void *, ssize_t);
294EXPORT_SYMBOL(__asan_storeN_noabort);
295
296/* to shut up compiler complaints */
297void __asan_handle_no_return(void) {}
298EXPORT_SYMBOL(__asan_handle_no_return);
299
300/* Emitted by compiler to poison alloca()ed objects. */
301void __asan_alloca_poison(void *addr, ssize_t size)
302{
303	size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
304	size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
305			rounded_up_size;
306	size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
307
308	const void *left_redzone = (const void *)(addr -
309			KASAN_ALLOCA_REDZONE_SIZE);
310	const void *right_redzone = (const void *)(addr + rounded_up_size);
311
312	WARN_ON(!IS_ALIGNED((unsigned long)addr, KASAN_ALLOCA_REDZONE_SIZE));
313
314	kasan_unpoison((const void *)(addr + rounded_down_size),
315			size - rounded_down_size, false);
316	kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
317		     KASAN_ALLOCA_LEFT, false);
318	kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
319		     KASAN_ALLOCA_RIGHT, false);
320}
321EXPORT_SYMBOL(__asan_alloca_poison);
322
323/* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
324void __asan_allocas_unpoison(void *stack_top, ssize_t stack_bottom)
325{
326	if (unlikely(!stack_top || stack_top > (void *)stack_bottom))
327		return;
328
329	kasan_unpoison(stack_top, (void *)stack_bottom - stack_top, false);
330}
331EXPORT_SYMBOL(__asan_allocas_unpoison);
332
333/* Emitted by the compiler to [un]poison local variables. */
334#define DEFINE_ASAN_SET_SHADOW(byte) \
335	void __asan_set_shadow_##byte(const void *addr, ssize_t size)	\
336	{								\
337		__memset((void *)addr, 0x##byte, size);			\
338	}								\
339	EXPORT_SYMBOL(__asan_set_shadow_##byte)
340
341DEFINE_ASAN_SET_SHADOW(00);
342DEFINE_ASAN_SET_SHADOW(f1);
343DEFINE_ASAN_SET_SHADOW(f2);
344DEFINE_ASAN_SET_SHADOW(f3);
345DEFINE_ASAN_SET_SHADOW(f5);
346DEFINE_ASAN_SET_SHADOW(f8);
347
348/*
349 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
350 * For larger allocations larger redzones are used.
351 */
352static inline unsigned int optimal_redzone(unsigned int object_size)
353{
354	return
355		object_size <= 64        - 16   ? 16 :
356		object_size <= 128       - 32   ? 32 :
357		object_size <= 512       - 64   ? 64 :
358		object_size <= 4096      - 128  ? 128 :
359		object_size <= (1 << 14) - 256  ? 256 :
360		object_size <= (1 << 15) - 512  ? 512 :
361		object_size <= (1 << 16) - 1024 ? 1024 : 2048;
362}
363
364void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
365			  slab_flags_t *flags)
366{
367	unsigned int ok_size;
368	unsigned int optimal_size;
369	unsigned int rem_free_meta_size;
370	unsigned int orig_alloc_meta_offset;
371
372	if (!kasan_requires_meta())
373		return;
374
375	/*
376	 * SLAB_KASAN is used to mark caches that are sanitized by KASAN and
377	 * that thus have per-object metadata. Currently, this flag is used in
378	 * slab_ksize() to account for per-object metadata when calculating the
379	 * size of the accessible memory within the object. Additionally, we use
380	 * SLAB_NO_MERGE to prevent merging of caches with per-object metadata.
381	 */
382	*flags |= SLAB_KASAN | SLAB_NO_MERGE;
383
384	ok_size = *size;
385
386	/* Add alloc meta into the redzone. */
387	cache->kasan_info.alloc_meta_offset = *size;
388	*size += sizeof(struct kasan_alloc_meta);
389
390	/* If alloc meta doesn't fit, don't add it. */
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	ok_size = *size;
398	orig_alloc_meta_offset = cache->kasan_info.alloc_meta_offset;
399
400	/*
401	 * Store free meta in the redzone when it's not possible to store
402	 * it in the object. This is the case when:
403	 * 1. Object is SLAB_TYPESAFE_BY_RCU, which means that it can
404	 *    be touched after it was freed, or
405	 * 2. Object has a constructor, which means it's expected to
406	 *    retain its content until the next allocation, or
407	 * 3. It is from a kmalloc cache which enables the debug option
408	 *    to store original size.
409	 */
410	if ((cache->flags & SLAB_TYPESAFE_BY_RCU) || cache->ctor ||
411	     slub_debug_orig_size(cache)) {
412		cache->kasan_info.free_meta_offset = *size;
413		*size += sizeof(struct kasan_free_meta);
414		goto free_meta_added;
415	}
416
417	/*
418	 * Otherwise, if the object is large enough to contain free meta,
419	 * store it within the object.
420	 */
421	if (sizeof(struct kasan_free_meta) <= cache->object_size) {
422		/* cache->kasan_info.free_meta_offset = 0 is implied. */
423		goto free_meta_added;
424	}
425
426	/*
427	 * For smaller objects, store the beginning of free meta within the
428	 * object and the end in the redzone. And thus shift the location of
429	 * alloc meta to free up space for free meta.
430	 * This is only possible when slub_debug is disabled, as otherwise
431	 * the end of free meta will overlap with slub_debug metadata.
432	 */
433	if (!__slub_debug_enabled()) {
434		rem_free_meta_size = sizeof(struct kasan_free_meta) -
435							cache->object_size;
436		*size += rem_free_meta_size;
437		if (cache->kasan_info.alloc_meta_offset != 0)
438			cache->kasan_info.alloc_meta_offset += rem_free_meta_size;
439		goto free_meta_added;
440	}
441
442	/*
443	 * If the object is small and slub_debug is enabled, store free meta
444	 * in the redzone after alloc meta.
445	 */
446	cache->kasan_info.free_meta_offset = *size;
447	*size += sizeof(struct kasan_free_meta);
448
449free_meta_added:
450	/* If free meta doesn't fit, don't add it. */
451	if (*size > KMALLOC_MAX_SIZE) {
452		cache->kasan_info.free_meta_offset = KASAN_NO_FREE_META;
453		cache->kasan_info.alloc_meta_offset = orig_alloc_meta_offset;
454		*size = ok_size;
455	}
456
457	/* Calculate size with optimal redzone. */
458	optimal_size = cache->object_size + optimal_redzone(cache->object_size);
459	/* Limit it with KMALLOC_MAX_SIZE. */
460	if (optimal_size > KMALLOC_MAX_SIZE)
461		optimal_size = KMALLOC_MAX_SIZE;
462	/* Use optimal size if the size with added metas is not large enough. */
463	if (*size < optimal_size)
464		*size = optimal_size;
465}
466
467struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
468					      const void *object)
469{
470	if (!cache->kasan_info.alloc_meta_offset)
471		return NULL;
472	return (void *)object + cache->kasan_info.alloc_meta_offset;
473}
474
475struct kasan_free_meta *kasan_get_free_meta(struct kmem_cache *cache,
476					    const void *object)
477{
478	BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32);
479	if (cache->kasan_info.free_meta_offset == KASAN_NO_FREE_META)
480		return NULL;
481	return (void *)object + cache->kasan_info.free_meta_offset;
482}
483
484void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
485{
486	struct kasan_alloc_meta *alloc_meta;
487
488	alloc_meta = kasan_get_alloc_meta(cache, object);
489	if (alloc_meta) {
490		/* Zero out alloc meta to mark it as invalid. */
491		__memset(alloc_meta, 0, sizeof(*alloc_meta));
492	}
493
494	/*
495	 * Explicitly marking free meta as invalid is not required: the shadow
496	 * value for the first 8 bytes of a newly allocated object is not
497	 * KASAN_SLAB_FREE_META.
498	 */
499}
500
501static void release_alloc_meta(struct kasan_alloc_meta *meta)
502{
503	/* Zero out alloc meta to mark it as invalid. */
504	__memset(meta, 0, sizeof(*meta));
505}
506
507static void release_free_meta(const void *object, struct kasan_free_meta *meta)
508{
509	/* Check if free meta is valid. */
510	if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
511		return;
512
513	/* Mark free meta as invalid. */
514	*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE;
515}
516
517size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object)
518{
519	struct kasan_cache *info = &cache->kasan_info;
520
521	if (!kasan_requires_meta())
522		return 0;
523
524	if (in_object)
525		return (info->free_meta_offset ?
526			0 : sizeof(struct kasan_free_meta));
527	else
528		return (info->alloc_meta_offset ?
529			sizeof(struct kasan_alloc_meta) : 0) +
530			((info->free_meta_offset &&
531			info->free_meta_offset != KASAN_NO_FREE_META) ?
532			sizeof(struct kasan_free_meta) : 0);
533}
534
535/*
536 * This function avoids dynamic memory allocations and thus can be called from
537 * contexts that do not allow allocating memory.
538 */
539void kasan_record_aux_stack(void *addr)
540{
541	struct slab *slab = kasan_addr_to_slab(addr);
542	struct kmem_cache *cache;
543	struct kasan_alloc_meta *alloc_meta;
544	void *object;
545
546	if (is_kfence_address(addr) || !slab)
547		return;
548
549	cache = slab->slab_cache;
550	object = nearest_obj(cache, slab, addr);
551	alloc_meta = kasan_get_alloc_meta(cache, object);
552	if (!alloc_meta)
553		return;
554
555	alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
556	alloc_meta->aux_stack[0] = kasan_save_stack(0, 0);
557}
558
559void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
560{
561	struct kasan_alloc_meta *alloc_meta;
562
563	alloc_meta = kasan_get_alloc_meta(cache, object);
564	if (!alloc_meta)
565		return;
566
567	/* Invalidate previous stack traces (might exist for krealloc or mempool). */
568	release_alloc_meta(alloc_meta);
569
570	kasan_save_track(&alloc_meta->alloc_track, flags);
571}
572
573void kasan_save_free_info(struct kmem_cache *cache, void *object)
574{
575	struct kasan_free_meta *free_meta;
576
577	free_meta = kasan_get_free_meta(cache, object);
578	if (!free_meta)
579		return;
580
581	/* Invalidate previous stack trace (might exist for mempool). */
582	release_free_meta(object, free_meta);
583
584	kasan_save_track(&free_meta->free_track, 0);
585
586	/* Mark free meta as valid. */
587	*(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE_META;
588}