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 cache
->align
= round_up(cache
->align
, KASAN_SHADOW_SCALE_SIZE
);
303 *flags
|= SLAB_KASAN
;
306 size_t kasan_metadata_size(struct kmem_cache
*cache
)
308 return (cache
->kasan_info
.alloc_meta_offset
?
309 sizeof(struct kasan_alloc_meta
) : 0) +
310 (cache
->kasan_info
.free_meta_offset
?
311 sizeof(struct kasan_free_meta
) : 0);
314 struct kasan_alloc_meta
*get_alloc_info(struct kmem_cache
*cache
,
317 BUILD_BUG_ON(sizeof(struct kasan_alloc_meta
) > 32);
318 return (void *)object
+ cache
->kasan_info
.alloc_meta_offset
;
321 struct kasan_free_meta
*get_free_info(struct kmem_cache
*cache
,
324 BUILD_BUG_ON(sizeof(struct kasan_free_meta
) > 32);
325 return (void *)object
+ cache
->kasan_info
.free_meta_offset
;
328 void kasan_poison_slab(struct page
*page
)
332 for (i
= 0; i
< (1 << compound_order(page
)); i
++)
333 page_kasan_tag_reset(page
+ i
);
334 kasan_poison_shadow(page_address(page
),
335 PAGE_SIZE
<< compound_order(page
),
336 KASAN_KMALLOC_REDZONE
);
339 void kasan_unpoison_object_data(struct kmem_cache
*cache
, void *object
)
341 kasan_unpoison_shadow(object
, cache
->object_size
);
344 void kasan_poison_object_data(struct kmem_cache
*cache
, void *object
)
346 kasan_poison_shadow(object
,
347 round_up(cache
->object_size
, KASAN_SHADOW_SCALE_SIZE
),
348 KASAN_KMALLOC_REDZONE
);
352 * Since it's desirable to only call object contructors once during slab
353 * allocation, we preassign tags to all such objects. Also preassign tags for
354 * SLAB_TYPESAFE_BY_RCU slabs to avoid use-after-free reports.
355 * For SLAB allocator we can't preassign tags randomly since the freelist is
356 * stored as an array of indexes instead of a linked list. Assign tags based
357 * on objects indexes, so that objects that are next to each other get
359 * After a tag is assigned, the object always gets allocated with the same tag.
360 * The reason is that we can't change tags for objects with constructors on
361 * reallocation (even for non-SLAB_TYPESAFE_BY_RCU), because the constructor
362 * code can save the pointer to the object somewhere (e.g. in the object
363 * itself). Then if we retag it, the old saved pointer will become invalid.
365 static u8
assign_tag(struct kmem_cache
*cache
, const void *object
, bool new)
367 if (!cache
->ctor
&& !(cache
->flags
& SLAB_TYPESAFE_BY_RCU
))
368 return new ? KASAN_TAG_KERNEL
: random_tag();
371 return (u8
)obj_to_index(cache
, virt_to_page(object
), (void *)object
);
373 return new ? random_tag() : get_tag(object
);
377 void * __must_check
kasan_init_slab_obj(struct kmem_cache
*cache
,
380 struct kasan_alloc_meta
*alloc_info
;
382 if (!(cache
->flags
& SLAB_KASAN
))
383 return (void *)object
;
385 alloc_info
= get_alloc_info(cache
, object
);
386 __memset(alloc_info
, 0, sizeof(*alloc_info
));
388 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
389 object
= set_tag(object
, assign_tag(cache
, object
, true));
391 return (void *)object
;
394 void * __must_check
kasan_slab_alloc(struct kmem_cache
*cache
, void *object
,
397 return kasan_kmalloc(cache
, object
, cache
->object_size
, flags
);
400 static inline bool shadow_invalid(u8 tag
, s8 shadow_byte
)
402 if (IS_ENABLED(CONFIG_KASAN_GENERIC
))
403 return shadow_byte
< 0 ||
404 shadow_byte
>= KASAN_SHADOW_SCALE_SIZE
;
406 return tag
!= (u8
)shadow_byte
;
409 static bool __kasan_slab_free(struct kmem_cache
*cache
, void *object
,
410 unsigned long ip
, bool quarantine
)
415 unsigned long rounded_up_size
;
417 tag
= get_tag(object
);
418 tagged_object
= object
;
419 object
= reset_tag(object
);
421 if (unlikely(nearest_obj(cache
, virt_to_head_page(object
), object
) !=
423 kasan_report_invalid_free(tagged_object
, ip
);
427 /* RCU slabs could be legally used after free within the RCU period */
428 if (unlikely(cache
->flags
& SLAB_TYPESAFE_BY_RCU
))
431 shadow_byte
= READ_ONCE(*(s8
*)kasan_mem_to_shadow(object
));
432 if (shadow_invalid(tag
, shadow_byte
)) {
433 kasan_report_invalid_free(tagged_object
, ip
);
437 rounded_up_size
= round_up(cache
->object_size
, KASAN_SHADOW_SCALE_SIZE
);
438 kasan_poison_shadow(object
, rounded_up_size
, KASAN_KMALLOC_FREE
);
440 if ((IS_ENABLED(CONFIG_KASAN_GENERIC
) && !quarantine
) ||
441 unlikely(!(cache
->flags
& SLAB_KASAN
)))
444 set_track(&get_alloc_info(cache
, object
)->free_track
, GFP_NOWAIT
);
445 quarantine_put(get_free_info(cache
, object
), cache
);
447 return IS_ENABLED(CONFIG_KASAN_GENERIC
);
450 bool kasan_slab_free(struct kmem_cache
*cache
, void *object
, unsigned long ip
)
452 return __kasan_slab_free(cache
, object
, ip
, true);
455 void * __must_check
kasan_kmalloc(struct kmem_cache
*cache
, const void *object
,
456 size_t size
, gfp_t flags
)
458 unsigned long redzone_start
;
459 unsigned long redzone_end
;
462 if (gfpflags_allow_blocking(flags
))
465 if (unlikely(object
== NULL
))
468 redzone_start
= round_up((unsigned long)(object
+ size
),
469 KASAN_SHADOW_SCALE_SIZE
);
470 redzone_end
= round_up((unsigned long)object
+ cache
->object_size
,
471 KASAN_SHADOW_SCALE_SIZE
);
473 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS
))
474 tag
= assign_tag(cache
, object
, false);
476 /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */
477 kasan_unpoison_shadow(set_tag(object
, tag
), size
);
478 kasan_poison_shadow((void *)redzone_start
, redzone_end
- redzone_start
,
479 KASAN_KMALLOC_REDZONE
);
481 if (cache
->flags
& SLAB_KASAN
)
482 set_track(&get_alloc_info(cache
, object
)->alloc_track
, flags
);
484 return set_tag(object
, tag
);
486 EXPORT_SYMBOL(kasan_kmalloc
);
488 void * __must_check
kasan_kmalloc_large(const void *ptr
, size_t size
,
492 unsigned long redzone_start
;
493 unsigned long redzone_end
;
495 if (gfpflags_allow_blocking(flags
))
498 if (unlikely(ptr
== NULL
))
501 page
= virt_to_page(ptr
);
502 redzone_start
= round_up((unsigned long)(ptr
+ size
),
503 KASAN_SHADOW_SCALE_SIZE
);
504 redzone_end
= (unsigned long)ptr
+ (PAGE_SIZE
<< compound_order(page
));
506 kasan_unpoison_shadow(ptr
, size
);
507 kasan_poison_shadow((void *)redzone_start
, redzone_end
- redzone_start
,
513 void * __must_check
kasan_krealloc(const void *object
, size_t size
, gfp_t flags
)
517 if (unlikely(object
== ZERO_SIZE_PTR
))
518 return (void *)object
;
520 page
= virt_to_head_page(object
);
522 if (unlikely(!PageSlab(page
)))
523 return kasan_kmalloc_large(object
, size
, flags
);
525 return kasan_kmalloc(page
->slab_cache
, object
, size
, flags
);
528 void kasan_poison_kfree(void *ptr
, unsigned long ip
)
532 page
= virt_to_head_page(ptr
);
534 if (unlikely(!PageSlab(page
))) {
535 if (ptr
!= page_address(page
)) {
536 kasan_report_invalid_free(ptr
, ip
);
539 kasan_poison_shadow(ptr
, PAGE_SIZE
<< compound_order(page
),
542 __kasan_slab_free(page
->slab_cache
, ptr
, ip
, false);
546 void kasan_kfree_large(void *ptr
, unsigned long ip
)
548 if (ptr
!= page_address(virt_to_head_page(ptr
)))
549 kasan_report_invalid_free(ptr
, ip
);
550 /* The object will be poisoned by page_alloc. */
553 int kasan_module_alloc(void *addr
, size_t size
)
558 unsigned long shadow_start
;
560 shadow_start
= (unsigned long)kasan_mem_to_shadow(addr
);
561 scaled_size
= (size
+ KASAN_SHADOW_MASK
) >> KASAN_SHADOW_SCALE_SHIFT
;
562 shadow_size
= round_up(scaled_size
, PAGE_SIZE
);
564 if (WARN_ON(!PAGE_ALIGNED(shadow_start
)))
567 ret
= __vmalloc_node_range(shadow_size
, 1, shadow_start
,
568 shadow_start
+ shadow_size
,
570 PAGE_KERNEL
, VM_NO_GUARD
, NUMA_NO_NODE
,
571 __builtin_return_address(0));
574 __memset(ret
, KASAN_SHADOW_INIT
, shadow_size
);
575 find_vm_area(addr
)->flags
|= VM_KASAN
;
576 kmemleak_ignore(ret
);
583 void kasan_free_shadow(const struct vm_struct
*vm
)
585 if (vm
->flags
& VM_KASAN
)
586 vfree(kasan_mem_to_shadow(vm
->addr
));
589 #ifdef CONFIG_MEMORY_HOTPLUG
590 static bool shadow_mapped(unsigned long addr
)
592 pgd_t
*pgd
= pgd_offset_k(addr
);
600 p4d
= p4d_offset(pgd
, addr
);
603 pud
= pud_offset(p4d
, addr
);
608 * We can't use pud_large() or pud_huge(), the first one is
609 * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse
610 * pud_bad(), if pud is bad then it's bad because it's huge.
614 pmd
= pmd_offset(pud
, addr
);
620 pte
= pte_offset_kernel(pmd
, addr
);
621 return !pte_none(*pte
);
624 static int __meminit
kasan_mem_notifier(struct notifier_block
*nb
,
625 unsigned long action
, void *data
)
627 struct memory_notify
*mem_data
= data
;
628 unsigned long nr_shadow_pages
, start_kaddr
, shadow_start
;
629 unsigned long shadow_end
, shadow_size
;
631 nr_shadow_pages
= mem_data
->nr_pages
>> KASAN_SHADOW_SCALE_SHIFT
;
632 start_kaddr
= (unsigned long)pfn_to_kaddr(mem_data
->start_pfn
);
633 shadow_start
= (unsigned long)kasan_mem_to_shadow((void *)start_kaddr
);
634 shadow_size
= nr_shadow_pages
<< PAGE_SHIFT
;
635 shadow_end
= shadow_start
+ shadow_size
;
637 if (WARN_ON(mem_data
->nr_pages
% KASAN_SHADOW_SCALE_SIZE
) ||
638 WARN_ON(start_kaddr
% (KASAN_SHADOW_SCALE_SIZE
<< PAGE_SHIFT
)))
642 case MEM_GOING_ONLINE
: {
646 * If shadow is mapped already than it must have been mapped
647 * during the boot. This could happen if we onlining previously
650 if (shadow_mapped(shadow_start
))
653 ret
= __vmalloc_node_range(shadow_size
, PAGE_SIZE
, shadow_start
,
654 shadow_end
, GFP_KERNEL
,
655 PAGE_KERNEL
, VM_NO_GUARD
,
656 pfn_to_nid(mem_data
->start_pfn
),
657 __builtin_return_address(0));
661 kmemleak_ignore(ret
);
664 case MEM_CANCEL_ONLINE
:
666 struct vm_struct
*vm
;
669 * shadow_start was either mapped during boot by kasan_init()
670 * or during memory online by __vmalloc_node_range().
671 * In the latter case we can use vfree() to free shadow.
672 * Non-NULL result of the find_vm_area() will tell us if
673 * that was the second case.
675 * Currently it's not possible to free shadow mapped
676 * during boot by kasan_init(). It's because the code
677 * to do that hasn't been written yet. So we'll just
680 vm
= find_vm_area((void *)shadow_start
);
682 vfree((void *)shadow_start
);
689 static int __init
kasan_memhotplug_init(void)
691 hotplug_memory_notifier(kasan_mem_notifier
, 0);
696 core_initcall(kasan_memhotplug_init
);