1 // SPDX-License-Identifier: GPL-2.0
3 * This file contains common generic and tag-based 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>
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License version 2 as
13 * published by the Free Software Foundation.
17 #include <linux/export.h>
18 #include <linux/interrupt.h>
19 #include <linux/init.h>
20 #include <linux/kasan.h>
21 #include <linux/kernel.h>
22 #include <linux/kmemleak.h>
23 #include <linux/linkage.h>
24 #include <linux/memblock.h>
25 #include <linux/memory.h>
27 #include <linux/module.h>
28 #include <linux/printk.h>
29 #include <linux/sched.h>
30 #include <linux/sched/task_stack.h>
31 #include <linux/slab.h>
32 #include <linux/stacktrace.h>
33 #include <linux/string.h>
34 #include <linux/types.h>
35 #include <linux/vmalloc.h>
36 #include <linux/bug.h>
41 static inline int in_irqentry_text(unsigned long ptr
)
43 return (ptr
>= (unsigned long)&__irqentry_text_start
&&
44 ptr
< (unsigned long)&__irqentry_text_end
) ||
45 (ptr
>= (unsigned long)&__softirqentry_text_start
&&
46 ptr
< (unsigned long)&__softirqentry_text_end
);
49 static inline void filter_irq_stacks(struct stack_trace
*trace
)
53 if (!trace
->nr_entries
)
55 for (i
= 0; i
< trace
->nr_entries
; i
++)
56 if (in_irqentry_text(trace
->entries
[i
])) {
57 /* Include the irqentry function into the stack. */
58 trace
->nr_entries
= i
+ 1;
63 static inline depot_stack_handle_t
save_stack(gfp_t flags
)
65 unsigned long entries
[KASAN_STACK_DEPTH
];
66 struct stack_trace trace
= {
69 .max_entries
= KASAN_STACK_DEPTH
,
73 save_stack_trace(&trace
);
74 filter_irq_stacks(&trace
);
75 if (trace
.nr_entries
!= 0 &&
76 trace
.entries
[trace
.nr_entries
-1] == ULONG_MAX
)
79 return depot_save_stack(&trace
, flags
);
82 static inline void set_track(struct kasan_track
*track
, gfp_t flags
)
84 track
->pid
= current
->pid
;
85 track
->stack
= save_stack(flags
);
88 void kasan_enable_current(void)
90 current
->kasan_depth
++;
93 void kasan_disable_current(void)
95 current
->kasan_depth
--;
98 void kasan_check_read(const volatile void *p
, unsigned int size
)
100 check_memory_region((unsigned long)p
, size
, false, _RET_IP_
);
102 EXPORT_SYMBOL(kasan_check_read
);
104 void kasan_check_write(const volatile void *p
, unsigned int size
)
106 check_memory_region((unsigned long)p
, size
, true, _RET_IP_
);
108 EXPORT_SYMBOL(kasan_check_write
);
111 void *memset(void *addr
, int c
, size_t len
)
113 check_memory_region((unsigned long)addr
, len
, true, _RET_IP_
);
115 return __memset(addr
, c
, len
);
119 void *memmove(void *dest
, const void *src
, size_t len
)
121 check_memory_region((unsigned long)src
, len
, false, _RET_IP_
);
122 check_memory_region((unsigned long)dest
, len
, true, _RET_IP_
);
124 return __memmove(dest
, src
, len
);
128 void *memcpy(void *dest
, const void *src
, size_t len
)
130 check_memory_region((unsigned long)src
, len
, false, _RET_IP_
);
131 check_memory_region((unsigned long)dest
, len
, true, _RET_IP_
);
133 return __memcpy(dest
, src
, len
);
137 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
138 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
140 void kasan_poison_shadow(const void *address
, size_t size
, u8 value
)
142 void *shadow_start
, *shadow_end
;
145 * Perform shadow offset calculation based on untagged address, as
146 * some of the callers (e.g. kasan_poison_object_data) pass tagged
147 * addresses to this function.
149 address
= reset_tag(address
);
151 shadow_start
= kasan_mem_to_shadow(address
);
152 shadow_end
= kasan_mem_to_shadow(address
+ size
);
154 __memset(shadow_start
, value
, shadow_end
- shadow_start
);
157 void kasan_unpoison_shadow(const void *address
, size_t size
)
159 u8 tag
= get_tag(address
);
162 * Perform shadow offset calculation based on untagged address, as
163 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged
164 * addresses to this function.
166 address
= reset_tag(address
);
168 kasan_poison_shadow(address
, size
, tag
);
170 if (size
& KASAN_SHADOW_MASK
) {
171 u8
*shadow
= (u8
*)kasan_mem_to_shadow(address
+ size
);
173 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
176 *shadow
= size
& KASAN_SHADOW_MASK
;
180 static void __kasan_unpoison_stack(struct task_struct
*task
, const void *sp
)
182 void *base
= task_stack_page(task
);
183 size_t size
= sp
- base
;
185 kasan_unpoison_shadow(base
, size
);
188 /* Unpoison the entire stack for a task. */
189 void kasan_unpoison_task_stack(struct task_struct
*task
)
191 __kasan_unpoison_stack(task
, task_stack_page(task
) + THREAD_SIZE
);
194 /* Unpoison the stack for the current task beyond a watermark sp value. */
195 asmlinkage
void kasan_unpoison_task_stack_below(const void *watermark
)
198 * Calculate the task stack base address. Avoid using 'current'
199 * because this function is called by early resume code which hasn't
200 * yet set up the percpu register (%gs).
202 void *base
= (void *)((unsigned long)watermark
& ~(THREAD_SIZE
- 1));
204 kasan_unpoison_shadow(base
, watermark
- base
);
208 * Clear all poison for the region between the current SP and a provided
209 * watermark value, as is sometimes required prior to hand-crafted asm function
210 * returns in the middle of functions.
212 void kasan_unpoison_stack_above_sp_to(const void *watermark
)
214 const void *sp
= __builtin_frame_address(0);
215 size_t size
= watermark
- sp
;
217 if (WARN_ON(sp
> watermark
))
219 kasan_unpoison_shadow(sp
, size
);
222 void kasan_alloc_pages(struct page
*page
, unsigned int order
)
227 if (unlikely(PageHighMem(page
)))
231 for (i
= 0; i
< (1 << order
); i
++)
232 page_kasan_tag_set(page
+ i
, tag
);
233 kasan_unpoison_shadow(page_address(page
), PAGE_SIZE
<< order
);
236 void kasan_free_pages(struct page
*page
, unsigned int order
)
238 if (likely(!PageHighMem(page
)))
239 kasan_poison_shadow(page_address(page
),
245 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime.
246 * For larger allocations larger redzones are used.
248 static inline unsigned int optimal_redzone(unsigned int object_size
)
250 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
254 object_size
<= 64 - 16 ? 16 :
255 object_size
<= 128 - 32 ? 32 :
256 object_size
<= 512 - 64 ? 64 :
257 object_size
<= 4096 - 128 ? 128 :
258 object_size
<= (1 << 14) - 256 ? 256 :
259 object_size
<= (1 << 15) - 512 ? 512 :
260 object_size
<= (1 << 16) - 1024 ? 1024 : 2048;
263 void kasan_cache_create(struct kmem_cache
*cache
, unsigned int *size
,
266 unsigned int orig_size
= *size
;
267 unsigned int redzone_size
;
270 /* Add alloc meta. */
271 cache
->kasan_info
.alloc_meta_offset
= *size
;
272 *size
+= sizeof(struct kasan_alloc_meta
);
275 if (IS_ENABLED(CONFIG_KASAN_GENERIC
) &&
276 (cache
->flags
& SLAB_TYPESAFE_BY_RCU
|| cache
->ctor
||
277 cache
->object_size
< sizeof(struct kasan_free_meta
))) {
278 cache
->kasan_info
.free_meta_offset
= *size
;
279 *size
+= sizeof(struct kasan_free_meta
);
282 redzone_size
= optimal_redzone(cache
->object_size
);
283 redzone_adjust
= redzone_size
- (*size
- cache
->object_size
);
284 if (redzone_adjust
> 0)
285 *size
+= redzone_adjust
;
287 *size
= min_t(unsigned int, KMALLOC_MAX_SIZE
,
288 max(*size
, cache
->object_size
+ redzone_size
));
291 * If the metadata doesn't fit, don't enable KASAN at all.
293 if (*size
<= cache
->kasan_info
.alloc_meta_offset
||
294 *size
<= cache
->kasan_info
.free_meta_offset
) {
295 cache
->kasan_info
.alloc_meta_offset
= 0;
296 cache
->kasan_info
.free_meta_offset
= 0;
301 *flags
|= SLAB_KASAN
;
304 size_t kasan_metadata_size(struct kmem_cache
*cache
)
306 return (cache
->kasan_info
.alloc_meta_offset
?
307 sizeof(struct kasan_alloc_meta
) : 0) +
308 (cache
->kasan_info
.free_meta_offset
?
309 sizeof(struct kasan_free_meta
) : 0);
312 struct kasan_alloc_meta
*get_alloc_info(struct kmem_cache
*cache
,
315 BUILD_BUG_ON(sizeof(struct kasan_alloc_meta
) > 32);
316 return (void *)object
+ cache
->kasan_info
.alloc_meta_offset
;
319 struct kasan_free_meta
*get_free_info(struct kmem_cache
*cache
,
322 BUILD_BUG_ON(sizeof(struct kasan_free_meta
) > 32);
323 return (void *)object
+ cache
->kasan_info
.free_meta_offset
;
326 void kasan_poison_slab(struct page
*page
)
330 for (i
= 0; i
< (1 << compound_order(page
)); i
++)
331 page_kasan_tag_reset(page
+ i
);
332 kasan_poison_shadow(page_address(page
),
333 PAGE_SIZE
<< compound_order(page
),
334 KASAN_KMALLOC_REDZONE
);
337 void kasan_unpoison_object_data(struct kmem_cache
*cache
, void *object
)
339 kasan_unpoison_shadow(object
, cache
->object_size
);
342 void kasan_poison_object_data(struct kmem_cache
*cache
, void *object
)
344 kasan_poison_shadow(object
,
345 round_up(cache
->object_size
, KASAN_SHADOW_SCALE_SIZE
),
346 KASAN_KMALLOC_REDZONE
);
350 * This function assigns a tag to an object considering the following:
351 * 1. A cache might have a constructor, which might save a pointer to a slab
352 * object somewhere (e.g. in the object itself). We preassign a tag for
353 * each object in caches with constructors during slab creation and reuse
354 * the same tag each time a particular object is allocated.
355 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be
356 * accessed after being freed. We preassign tags for objects in these
358 * 3. For SLAB allocator we can't preassign tags randomly since the freelist
359 * is stored as an array of indexes instead of a linked list. Assign tags
360 * based on objects indexes, so that objects that are next to each other
361 * get different tags.
363 static u8
assign_tag(struct kmem_cache
*cache
, const void *object
,
364 bool init
, bool krealloc
)
366 /* Reuse the same tag for krealloc'ed objects. */
368 return get_tag(object
);
371 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU
372 * set, assign a tag when the object is being allocated (init == false).
374 if (!cache
->ctor
&& !(cache
->flags
& SLAB_TYPESAFE_BY_RCU
))
375 return init
? KASAN_TAG_KERNEL
: random_tag();
377 /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */
379 /* For SLAB assign tags based on the object index in the freelist. */
380 return (u8
)obj_to_index(cache
, virt_to_page(object
), (void *)object
);
383 * For SLUB assign a random tag during slab creation, otherwise reuse
384 * the already assigned tag.
386 return init
? random_tag() : get_tag(object
);
390 void * __must_check
kasan_init_slab_obj(struct kmem_cache
*cache
,
393 struct kasan_alloc_meta
*alloc_info
;
395 if (!(cache
->flags
& SLAB_KASAN
))
396 return (void *)object
;
398 alloc_info
= get_alloc_info(cache
, object
);
399 __memset(alloc_info
, 0, sizeof(*alloc_info
));
401 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
402 object
= set_tag(object
,
403 assign_tag(cache
, object
, true, false));
405 return (void *)object
;
408 void * __must_check
kasan_slab_alloc(struct kmem_cache
*cache
, void *object
,
411 return kasan_kmalloc(cache
, object
, cache
->object_size
, flags
);
414 static inline bool shadow_invalid(u8 tag
, s8 shadow_byte
)
416 if (IS_ENABLED(CONFIG_KASAN_GENERIC
))
417 return shadow_byte
< 0 ||
418 shadow_byte
>= KASAN_SHADOW_SCALE_SIZE
;
420 return tag
!= (u8
)shadow_byte
;
423 static bool __kasan_slab_free(struct kmem_cache
*cache
, void *object
,
424 unsigned long ip
, bool quarantine
)
429 unsigned long rounded_up_size
;
431 tag
= get_tag(object
);
432 tagged_object
= object
;
433 object
= reset_tag(object
);
435 if (unlikely(nearest_obj(cache
, virt_to_head_page(object
), object
) !=
437 kasan_report_invalid_free(tagged_object
, ip
);
441 /* RCU slabs could be legally used after free within the RCU period */
442 if (unlikely(cache
->flags
& SLAB_TYPESAFE_BY_RCU
))
445 shadow_byte
= READ_ONCE(*(s8
*)kasan_mem_to_shadow(object
));
446 if (shadow_invalid(tag
, shadow_byte
)) {
447 kasan_report_invalid_free(tagged_object
, ip
);
451 rounded_up_size
= round_up(cache
->object_size
, KASAN_SHADOW_SCALE_SIZE
);
452 kasan_poison_shadow(object
, rounded_up_size
, KASAN_KMALLOC_FREE
);
454 if ((IS_ENABLED(CONFIG_KASAN_GENERIC
) && !quarantine
) ||
455 unlikely(!(cache
->flags
& SLAB_KASAN
)))
458 set_track(&get_alloc_info(cache
, object
)->free_track
, GFP_NOWAIT
);
459 quarantine_put(get_free_info(cache
, object
), cache
);
461 return IS_ENABLED(CONFIG_KASAN_GENERIC
);
464 bool kasan_slab_free(struct kmem_cache
*cache
, void *object
, unsigned long ip
)
466 return __kasan_slab_free(cache
, object
, ip
, true);
469 static void *__kasan_kmalloc(struct kmem_cache
*cache
, const void *object
,
470 size_t size
, gfp_t flags
, bool krealloc
)
472 unsigned long redzone_start
;
473 unsigned long redzone_end
;
476 if (gfpflags_allow_blocking(flags
))
479 if (unlikely(object
== NULL
))
482 redzone_start
= round_up((unsigned long)(object
+ size
),
483 KASAN_SHADOW_SCALE_SIZE
);
484 redzone_end
= round_up((unsigned long)object
+ cache
->object_size
,
485 KASAN_SHADOW_SCALE_SIZE
);
487 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
488 tag
= assign_tag(cache
, object
, false, krealloc
);
490 /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
491 kasan_unpoison_shadow(set_tag(object
, tag
), size
);
492 kasan_poison_shadow((void *)redzone_start
, redzone_end
- redzone_start
,
493 KASAN_KMALLOC_REDZONE
);
495 if (cache
->flags
& SLAB_KASAN
)
496 set_track(&get_alloc_info(cache
, object
)->alloc_track
, flags
);
498 return set_tag(object
, tag
);
501 void * __must_check
kasan_kmalloc(struct kmem_cache
*cache
, const void *object
,
502 size_t size
, gfp_t flags
)
504 return __kasan_kmalloc(cache
, object
, size
, flags
, false);
506 EXPORT_SYMBOL(kasan_kmalloc
);
508 void * __must_check
kasan_kmalloc_large(const void *ptr
, size_t size
,
512 unsigned long redzone_start
;
513 unsigned long redzone_end
;
515 if (gfpflags_allow_blocking(flags
))
518 if (unlikely(ptr
== NULL
))
521 page
= virt_to_page(ptr
);
522 redzone_start
= round_up((unsigned long)(ptr
+ size
),
523 KASAN_SHADOW_SCALE_SIZE
);
524 redzone_end
= (unsigned long)ptr
+ (PAGE_SIZE
<< compound_order(page
));
526 kasan_unpoison_shadow(ptr
, size
);
527 kasan_poison_shadow((void *)redzone_start
, redzone_end
- redzone_start
,
533 void * __must_check
kasan_krealloc(const void *object
, size_t size
, gfp_t flags
)
537 if (unlikely(object
== ZERO_SIZE_PTR
))
538 return (void *)object
;
540 page
= virt_to_head_page(object
);
542 if (unlikely(!PageSlab(page
)))
543 return kasan_kmalloc_large(object
, size
, flags
);
545 return __kasan_kmalloc(page
->slab_cache
, object
, size
,
549 void kasan_poison_kfree(void *ptr
, unsigned long ip
)
553 page
= virt_to_head_page(ptr
);
555 if (unlikely(!PageSlab(page
))) {
556 if (ptr
!= page_address(page
)) {
557 kasan_report_invalid_free(ptr
, ip
);
560 kasan_poison_shadow(ptr
, PAGE_SIZE
<< compound_order(page
),
563 __kasan_slab_free(page
->slab_cache
, ptr
, ip
, false);
567 void kasan_kfree_large(void *ptr
, unsigned long ip
)
569 if (ptr
!= page_address(virt_to_head_page(ptr
)))
570 kasan_report_invalid_free(ptr
, ip
);
571 /* The object will be poisoned by page_alloc. */
574 int kasan_module_alloc(void *addr
, size_t size
)
579 unsigned long shadow_start
;
581 shadow_start
= (unsigned long)kasan_mem_to_shadow(addr
);
582 scaled_size
= (size
+ KASAN_SHADOW_MASK
) >> KASAN_SHADOW_SCALE_SHIFT
;
583 shadow_size
= round_up(scaled_size
, PAGE_SIZE
);
585 if (WARN_ON(!PAGE_ALIGNED(shadow_start
)))
588 ret
= __vmalloc_node_range(shadow_size
, 1, shadow_start
,
589 shadow_start
+ shadow_size
,
591 PAGE_KERNEL
, VM_NO_GUARD
, NUMA_NO_NODE
,
592 __builtin_return_address(0));
595 __memset(ret
, KASAN_SHADOW_INIT
, shadow_size
);
596 find_vm_area(addr
)->flags
|= VM_KASAN
;
597 kmemleak_ignore(ret
);
604 void kasan_free_shadow(const struct vm_struct
*vm
)
606 if (vm
->flags
& VM_KASAN
)
607 vfree(kasan_mem_to_shadow(vm
->addr
));
610 #ifdef CONFIG_MEMORY_HOTPLUG
611 static bool shadow_mapped(unsigned long addr
)
613 pgd_t
*pgd
= pgd_offset_k(addr
);
621 p4d
= p4d_offset(pgd
, addr
);
624 pud
= pud_offset(p4d
, addr
);
629 * We can't use pud_large() or pud_huge(), the first one is
630 * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse
631 * pud_bad(), if pud is bad then it's bad because it's huge.
635 pmd
= pmd_offset(pud
, addr
);
641 pte
= pte_offset_kernel(pmd
, addr
);
642 return !pte_none(*pte
);
645 static int __meminit
kasan_mem_notifier(struct notifier_block
*nb
,
646 unsigned long action
, void *data
)
648 struct memory_notify
*mem_data
= data
;
649 unsigned long nr_shadow_pages
, start_kaddr
, shadow_start
;
650 unsigned long shadow_end
, shadow_size
;
652 nr_shadow_pages
= mem_data
->nr_pages
>> KASAN_SHADOW_SCALE_SHIFT
;
653 start_kaddr
= (unsigned long)pfn_to_kaddr(mem_data
->start_pfn
);
654 shadow_start
= (unsigned long)kasan_mem_to_shadow((void *)start_kaddr
);
655 shadow_size
= nr_shadow_pages
<< PAGE_SHIFT
;
656 shadow_end
= shadow_start
+ shadow_size
;
658 if (WARN_ON(mem_data
->nr_pages
% KASAN_SHADOW_SCALE_SIZE
) ||
659 WARN_ON(start_kaddr
% (KASAN_SHADOW_SCALE_SIZE
<< PAGE_SHIFT
)))
663 case MEM_GOING_ONLINE
: {
667 * If shadow is mapped already than it must have been mapped
668 * during the boot. This could happen if we onlining previously
671 if (shadow_mapped(shadow_start
))
674 ret
= __vmalloc_node_range(shadow_size
, PAGE_SIZE
, shadow_start
,
675 shadow_end
, GFP_KERNEL
,
676 PAGE_KERNEL
, VM_NO_GUARD
,
677 pfn_to_nid(mem_data
->start_pfn
),
678 __builtin_return_address(0));
682 kmemleak_ignore(ret
);
685 case MEM_CANCEL_ONLINE
:
687 struct vm_struct
*vm
;
690 * shadow_start was either mapped during boot by kasan_init()
691 * or during memory online by __vmalloc_node_range().
692 * In the latter case we can use vfree() to free shadow.
693 * Non-NULL result of the find_vm_area() will tell us if
694 * that was the second case.
696 * Currently it's not possible to free shadow mapped
697 * during boot by kasan_init(). It's because the code
698 * to do that hasn't been written yet. So we'll just
701 vm
= find_vm_area((void *)shadow_start
);
703 vfree((void *)shadow_start
);
710 static int __init
kasan_memhotplug_init(void)
712 hotplug_memory_notifier(kasan_mem_notifier
, 0);
717 core_initcall(kasan_memhotplug_init
);