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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file contains KASAN runtime code that manages shadow memory for
4 * generic and software tag-based KASAN modes.
5 *
6 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
7 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
8 *
9 * Some code borrowed from https://github.com/xairy/kasan-prototype by
10 * Andrey Konovalov <andreyknvl@gmail.com>
11 */
12
13#include <linux/init.h>
14#include <linux/kasan.h>
15#include <linux/kernel.h>
16#include <linux/kfence.h>
17#include <linux/kmemleak.h>
18#include <linux/memory.h>
19#include <linux/mm.h>
20#include <linux/string.h>
21#include <linux/types.h>
22#include <linux/vmalloc.h>
23
24#include <asm/cacheflush.h>
25#include <asm/tlbflush.h>
26
27#include "kasan.h"
28
29bool __kasan_check_read(const volatile void *p, unsigned int size)
30{
31 return kasan_check_range((void *)p, size, false, _RET_IP_);
32}
33EXPORT_SYMBOL(__kasan_check_read);
34
35bool __kasan_check_write(const volatile void *p, unsigned int size)
36{
37 return kasan_check_range((void *)p, size, true, _RET_IP_);
38}
39EXPORT_SYMBOL(__kasan_check_write);
40
41#if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY)
42/*
43 * CONFIG_GENERIC_ENTRY relies on compiler emitted mem*() calls to not be
44 * instrumented. KASAN enabled toolchains should emit __asan_mem*() functions
45 * for the sites they want to instrument.
46 *
47 * If we have a compiler that can instrument meminstrinsics, never override
48 * these, so that non-instrumented files can safely consider them as builtins.
49 */
50#undef memset
51void *memset(void *addr, int c, size_t len)
52{
53 if (!kasan_check_range(addr, len, true, _RET_IP_))
54 return NULL;
55
56 return __memset(addr, c, len);
57}
58
59#ifdef __HAVE_ARCH_MEMMOVE
60#undef memmove
61void *memmove(void *dest, const void *src, size_t len)
62{
63 if (!kasan_check_range(src, len, false, _RET_IP_) ||
64 !kasan_check_range(dest, len, true, _RET_IP_))
65 return NULL;
66
67 return __memmove(dest, src, len);
68}
69#endif
70
71#undef memcpy
72void *memcpy(void *dest, const void *src, size_t len)
73{
74 if (!kasan_check_range(src, len, false, _RET_IP_) ||
75 !kasan_check_range(dest, len, true, _RET_IP_))
76 return NULL;
77
78 return __memcpy(dest, src, len);
79}
80#endif
81
82void *__asan_memset(void *addr, int c, ssize_t len)
83{
84 if (!kasan_check_range(addr, len, true, _RET_IP_))
85 return NULL;
86
87 return __memset(addr, c, len);
88}
89EXPORT_SYMBOL(__asan_memset);
90
91#ifdef __HAVE_ARCH_MEMMOVE
92void *__asan_memmove(void *dest, const void *src, ssize_t len)
93{
94 if (!kasan_check_range(src, len, false, _RET_IP_) ||
95 !kasan_check_range(dest, len, true, _RET_IP_))
96 return NULL;
97
98 return __memmove(dest, src, len);
99}
100EXPORT_SYMBOL(__asan_memmove);
101#endif
102
103void *__asan_memcpy(void *dest, const void *src, ssize_t len)
104{
105 if (!kasan_check_range(src, len, false, _RET_IP_) ||
106 !kasan_check_range(dest, len, true, _RET_IP_))
107 return NULL;
108
109 return __memcpy(dest, src, len);
110}
111EXPORT_SYMBOL(__asan_memcpy);
112
113#ifdef CONFIG_KASAN_SW_TAGS
114void *__hwasan_memset(void *addr, int c, ssize_t len) __alias(__asan_memset);
115EXPORT_SYMBOL(__hwasan_memset);
116#ifdef __HAVE_ARCH_MEMMOVE
117void *__hwasan_memmove(void *dest, const void *src, ssize_t len) __alias(__asan_memmove);
118EXPORT_SYMBOL(__hwasan_memmove);
119#endif
120void *__hwasan_memcpy(void *dest, const void *src, ssize_t len) __alias(__asan_memcpy);
121EXPORT_SYMBOL(__hwasan_memcpy);
122#endif
123
124void kasan_poison(const void *addr, size_t size, u8 value, bool init)
125{
126 void *shadow_start, *shadow_end;
127
128 if (!kasan_arch_is_ready())
129 return;
130
131 /*
132 * Perform shadow offset calculation based on untagged address, as
133 * some of the callers (e.g. kasan_poison_new_object) pass tagged
134 * addresses to this function.
135 */
136 addr = kasan_reset_tag(addr);
137
138 if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
139 return;
140 if (WARN_ON(size & KASAN_GRANULE_MASK))
141 return;
142
143 shadow_start = kasan_mem_to_shadow(addr);
144 shadow_end = kasan_mem_to_shadow(addr + size);
145
146 __memset(shadow_start, value, shadow_end - shadow_start);
147}
148EXPORT_SYMBOL_GPL(kasan_poison);
149
150#ifdef CONFIG_KASAN_GENERIC
151void kasan_poison_last_granule(const void *addr, size_t size)
152{
153 if (!kasan_arch_is_ready())
154 return;
155
156 if (size & KASAN_GRANULE_MASK) {
157 u8 *shadow = (u8 *)kasan_mem_to_shadow(addr + size);
158 *shadow = size & KASAN_GRANULE_MASK;
159 }
160}
161#endif
162
163void kasan_unpoison(const void *addr, size_t size, bool init)
164{
165 u8 tag = get_tag(addr);
166
167 /*
168 * Perform shadow offset calculation based on untagged address, as
169 * some of the callers (e.g. kasan_unpoison_new_object) pass tagged
170 * addresses to this function.
171 */
172 addr = kasan_reset_tag(addr);
173
174 if (WARN_ON((unsigned long)addr & KASAN_GRANULE_MASK))
175 return;
176
177 /* Unpoison all granules that cover the object. */
178 kasan_poison(addr, round_up(size, KASAN_GRANULE_SIZE), tag, false);
179
180 /* Partially poison the last granule for the generic mode. */
181 if (IS_ENABLED(CONFIG_KASAN_GENERIC))
182 kasan_poison_last_granule(addr, size);
183}
184
185#ifdef CONFIG_MEMORY_HOTPLUG
186static bool shadow_mapped(unsigned long addr)
187{
188 pgd_t *pgd = pgd_offset_k(addr);
189 p4d_t *p4d;
190 pud_t *pud;
191 pmd_t *pmd;
192 pte_t *pte;
193
194 if (pgd_none(*pgd))
195 return false;
196 p4d = p4d_offset(pgd, addr);
197 if (p4d_none(*p4d))
198 return false;
199 pud = pud_offset(p4d, addr);
200 if (pud_none(*pud))
201 return false;
202
203 /*
204 * We can't use pud_large() or pud_huge(), the first one is
205 * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse
206 * pud_bad(), if pud is bad then it's bad because it's huge.
207 */
208 if (pud_bad(*pud))
209 return true;
210 pmd = pmd_offset(pud, addr);
211 if (pmd_none(*pmd))
212 return false;
213
214 if (pmd_bad(*pmd))
215 return true;
216 pte = pte_offset_kernel(pmd, addr);
217 return !pte_none(ptep_get(pte));
218}
219
220static int __meminit kasan_mem_notifier(struct notifier_block *nb,
221 unsigned long action, void *data)
222{
223 struct memory_notify *mem_data = data;
224 unsigned long nr_shadow_pages, start_kaddr, shadow_start;
225 unsigned long shadow_end, shadow_size;
226
227 nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
228 start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
229 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
230 shadow_size = nr_shadow_pages << PAGE_SHIFT;
231 shadow_end = shadow_start + shadow_size;
232
233 if (WARN_ON(mem_data->nr_pages % KASAN_GRANULE_SIZE) ||
234 WARN_ON(start_kaddr % KASAN_MEMORY_PER_SHADOW_PAGE))
235 return NOTIFY_BAD;
236
237 switch (action) {
238 case MEM_GOING_ONLINE: {
239 void *ret;
240
241 /*
242 * If shadow is mapped already than it must have been mapped
243 * during the boot. This could happen if we onlining previously
244 * offlined memory.
245 */
246 if (shadow_mapped(shadow_start))
247 return NOTIFY_OK;
248
249 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
250 shadow_end, GFP_KERNEL,
251 PAGE_KERNEL, VM_NO_GUARD,
252 pfn_to_nid(mem_data->start_pfn),
253 __builtin_return_address(0));
254 if (!ret)
255 return NOTIFY_BAD;
256
257 kmemleak_ignore(ret);
258 return NOTIFY_OK;
259 }
260 case MEM_CANCEL_ONLINE:
261 case MEM_OFFLINE: {
262 struct vm_struct *vm;
263
264 /*
265 * shadow_start was either mapped during boot by kasan_init()
266 * or during memory online by __vmalloc_node_range().
267 * In the latter case we can use vfree() to free shadow.
268 * Non-NULL result of the find_vm_area() will tell us if
269 * that was the second case.
270 *
271 * Currently it's not possible to free shadow mapped
272 * during boot by kasan_init(). It's because the code
273 * to do that hasn't been written yet. So we'll just
274 * leak the memory.
275 */
276 vm = find_vm_area((void *)shadow_start);
277 if (vm)
278 vfree((void *)shadow_start);
279 }
280 }
281
282 return NOTIFY_OK;
283}
284
285static int __init kasan_memhotplug_init(void)
286{
287 hotplug_memory_notifier(kasan_mem_notifier, DEFAULT_CALLBACK_PRI);
288
289 return 0;
290}
291
292core_initcall(kasan_memhotplug_init);
293#endif
294
295#ifdef CONFIG_KASAN_VMALLOC
296
297void __init __weak kasan_populate_early_vm_area_shadow(void *start,
298 unsigned long size)
299{
300}
301
302static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
303 void *unused)
304{
305 unsigned long page;
306 pte_t pte;
307
308 if (likely(!pte_none(ptep_get(ptep))))
309 return 0;
310
311 page = __get_free_page(GFP_KERNEL);
312 if (!page)
313 return -ENOMEM;
314
315 __memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE);
316 pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL);
317
318 spin_lock(&init_mm.page_table_lock);
319 if (likely(pte_none(ptep_get(ptep)))) {
320 set_pte_at(&init_mm, addr, ptep, pte);
321 page = 0;
322 }
323 spin_unlock(&init_mm.page_table_lock);
324 if (page)
325 free_page(page);
326 return 0;
327}
328
329int kasan_populate_vmalloc(unsigned long addr, unsigned long size)
330{
331 unsigned long shadow_start, shadow_end;
332 int ret;
333
334 if (!kasan_arch_is_ready())
335 return 0;
336
337 if (!is_vmalloc_or_module_addr((void *)addr))
338 return 0;
339
340 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr);
341 shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size);
342
343 /*
344 * User Mode Linux maps enough shadow memory for all of virtual memory
345 * at boot, so doesn't need to allocate more on vmalloc, just clear it.
346 *
347 * The remaining CONFIG_UML checks in this file exist for the same
348 * reason.
349 */
350 if (IS_ENABLED(CONFIG_UML)) {
351 __memset((void *)shadow_start, KASAN_VMALLOC_INVALID, shadow_end - shadow_start);
352 return 0;
353 }
354
355 shadow_start = PAGE_ALIGN_DOWN(shadow_start);
356 shadow_end = PAGE_ALIGN(shadow_end);
357
358 ret = apply_to_page_range(&init_mm, shadow_start,
359 shadow_end - shadow_start,
360 kasan_populate_vmalloc_pte, NULL);
361 if (ret)
362 return ret;
363
364 flush_cache_vmap(shadow_start, shadow_end);
365
366 /*
367 * We need to be careful about inter-cpu effects here. Consider:
368 *
369 * CPU#0 CPU#1
370 * WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ;
371 * p[99] = 1;
372 *
373 * With compiler instrumentation, that ends up looking like this:
374 *
375 * CPU#0 CPU#1
376 * // vmalloc() allocates memory
377 * // let a = area->addr
378 * // we reach kasan_populate_vmalloc
379 * // and call kasan_unpoison:
380 * STORE shadow(a), unpoison_val
381 * ...
382 * STORE shadow(a+99), unpoison_val x = LOAD p
383 * // rest of vmalloc process <data dependency>
384 * STORE p, a LOAD shadow(x+99)
385 *
386 * If there is no barrier between the end of unpoisoning the shadow
387 * and the store of the result to p, the stores could be committed
388 * in a different order by CPU#0, and CPU#1 could erroneously observe
389 * poison in the shadow.
390 *
391 * We need some sort of barrier between the stores.
392 *
393 * In the vmalloc() case, this is provided by a smp_wmb() in
394 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in
395 * get_vm_area() and friends, the caller gets shadow allocated but
396 * doesn't have any pages mapped into the virtual address space that
397 * has been reserved. Mapping those pages in will involve taking and
398 * releasing a page-table lock, which will provide the barrier.
399 */
400
401 return 0;
402}
403
404static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr,
405 void *unused)
406{
407 unsigned long page;
408
409 page = (unsigned long)__va(pte_pfn(ptep_get(ptep)) << PAGE_SHIFT);
410
411 spin_lock(&init_mm.page_table_lock);
412
413 if (likely(!pte_none(ptep_get(ptep)))) {
414 pte_clear(&init_mm, addr, ptep);
415 free_page(page);
416 }
417 spin_unlock(&init_mm.page_table_lock);
418
419 return 0;
420}
421
422/*
423 * Release the backing for the vmalloc region [start, end), which
424 * lies within the free region [free_region_start, free_region_end).
425 *
426 * This can be run lazily, long after the region was freed. It runs
427 * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap
428 * infrastructure.
429 *
430 * How does this work?
431 * -------------------
432 *
433 * We have a region that is page aligned, labeled as A.
434 * That might not map onto the shadow in a way that is page-aligned:
435 *
436 * start end
437 * v v
438 * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc
439 * -------- -------- -------- -------- --------
440 * | | | | |
441 * | | | /-------/ |
442 * \-------\|/------/ |/---------------/
443 * ||| ||
444 * |??AAAAAA|AAAAAAAA|AA??????| < shadow
445 * (1) (2) (3)
446 *
447 * First we align the start upwards and the end downwards, so that the
448 * shadow of the region aligns with shadow page boundaries. In the
449 * example, this gives us the shadow page (2). This is the shadow entirely
450 * covered by this allocation.
451 *
452 * Then we have the tricky bits. We want to know if we can free the
453 * partially covered shadow pages - (1) and (3) in the example. For this,
454 * we are given the start and end of the free region that contains this
455 * allocation. Extending our previous example, we could have:
456 *
457 * free_region_start free_region_end
458 * | start end |
459 * v v v v
460 * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc
461 * -------- -------- -------- -------- --------
462 * | | | | |
463 * | | | /-------/ |
464 * \-------\|/------/ |/---------------/
465 * ||| ||
466 * |FFAAAAAA|AAAAAAAA|AAF?????| < shadow
467 * (1) (2) (3)
468 *
469 * Once again, we align the start of the free region up, and the end of
470 * the free region down so that the shadow is page aligned. So we can free
471 * page (1) - we know no allocation currently uses anything in that page,
472 * because all of it is in the vmalloc free region. But we cannot free
473 * page (3), because we can't be sure that the rest of it is unused.
474 *
475 * We only consider pages that contain part of the original region for
476 * freeing: we don't try to free other pages from the free region or we'd
477 * end up trying to free huge chunks of virtual address space.
478 *
479 * Concurrency
480 * -----------
481 *
482 * How do we know that we're not freeing a page that is simultaneously
483 * being used for a fresh allocation in kasan_populate_vmalloc(_pte)?
484 *
485 * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running
486 * at the same time. While we run under free_vmap_area_lock, the population
487 * code does not.
488 *
489 * free_vmap_area_lock instead operates to ensure that the larger range
490 * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and
491 * the per-cpu region-finding algorithm both run under free_vmap_area_lock,
492 * no space identified as free will become used while we are running. This
493 * means that so long as we are careful with alignment and only free shadow
494 * pages entirely covered by the free region, we will not run in to any
495 * trouble - any simultaneous allocations will be for disjoint regions.
496 */
497void kasan_release_vmalloc(unsigned long start, unsigned long end,
498 unsigned long free_region_start,
499 unsigned long free_region_end)
500{
501 void *shadow_start, *shadow_end;
502 unsigned long region_start, region_end;
503 unsigned long size;
504
505 if (!kasan_arch_is_ready())
506 return;
507
508 region_start = ALIGN(start, KASAN_MEMORY_PER_SHADOW_PAGE);
509 region_end = ALIGN_DOWN(end, KASAN_MEMORY_PER_SHADOW_PAGE);
510
511 free_region_start = ALIGN(free_region_start, KASAN_MEMORY_PER_SHADOW_PAGE);
512
513 if (start != region_start &&
514 free_region_start < region_start)
515 region_start -= KASAN_MEMORY_PER_SHADOW_PAGE;
516
517 free_region_end = ALIGN_DOWN(free_region_end, KASAN_MEMORY_PER_SHADOW_PAGE);
518
519 if (end != region_end &&
520 free_region_end > region_end)
521 region_end += KASAN_MEMORY_PER_SHADOW_PAGE;
522
523 shadow_start = kasan_mem_to_shadow((void *)region_start);
524 shadow_end = kasan_mem_to_shadow((void *)region_end);
525
526 if (shadow_end > shadow_start) {
527 size = shadow_end - shadow_start;
528 if (IS_ENABLED(CONFIG_UML)) {
529 __memset(shadow_start, KASAN_SHADOW_INIT, shadow_end - shadow_start);
530 return;
531 }
532 apply_to_existing_page_range(&init_mm,
533 (unsigned long)shadow_start,
534 size, kasan_depopulate_vmalloc_pte,
535 NULL);
536 flush_tlb_kernel_range((unsigned long)shadow_start,
537 (unsigned long)shadow_end);
538 }
539}
540
541void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
542 kasan_vmalloc_flags_t flags)
543{
544 /*
545 * Software KASAN modes unpoison both VM_ALLOC and non-VM_ALLOC
546 * mappings, so the KASAN_VMALLOC_VM_ALLOC flag is ignored.
547 * Software KASAN modes can't optimize zeroing memory by combining it
548 * with setting memory tags, so the KASAN_VMALLOC_INIT flag is ignored.
549 */
550
551 if (!kasan_arch_is_ready())
552 return (void *)start;
553
554 if (!is_vmalloc_or_module_addr(start))
555 return (void *)start;
556
557 /*
558 * Don't tag executable memory with the tag-based mode.
559 * The kernel doesn't tolerate having the PC register tagged.
560 */
561 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) &&
562 !(flags & KASAN_VMALLOC_PROT_NORMAL))
563 return (void *)start;
564
565 start = set_tag(start, kasan_random_tag());
566 kasan_unpoison(start, size, false);
567 return (void *)start;
568}
569
570/*
571 * Poison the shadow for a vmalloc region. Called as part of the
572 * freeing process at the time the region is freed.
573 */
574void __kasan_poison_vmalloc(const void *start, unsigned long size)
575{
576 if (!kasan_arch_is_ready())
577 return;
578
579 if (!is_vmalloc_or_module_addr(start))
580 return;
581
582 size = round_up(size, KASAN_GRANULE_SIZE);
583 kasan_poison(start, size, KASAN_VMALLOC_INVALID, false);
584}
585
586#else /* CONFIG_KASAN_VMALLOC */
587
588int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask)
589{
590 void *ret;
591 size_t scaled_size;
592 size_t shadow_size;
593 unsigned long shadow_start;
594
595 shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
596 scaled_size = (size + KASAN_GRANULE_SIZE - 1) >>
597 KASAN_SHADOW_SCALE_SHIFT;
598 shadow_size = round_up(scaled_size, PAGE_SIZE);
599
600 if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
601 return -EINVAL;
602
603 if (IS_ENABLED(CONFIG_UML)) {
604 __memset((void *)shadow_start, KASAN_SHADOW_INIT, shadow_size);
605 return 0;
606 }
607
608 ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
609 shadow_start + shadow_size,
610 GFP_KERNEL,
611 PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
612 __builtin_return_address(0));
613
614 if (ret) {
615 struct vm_struct *vm = find_vm_area(addr);
616 __memset(ret, KASAN_SHADOW_INIT, shadow_size);
617 vm->flags |= VM_KASAN;
618 kmemleak_ignore(ret);
619
620 if (vm->flags & VM_DEFER_KMEMLEAK)
621 kmemleak_vmalloc(vm, size, gfp_mask);
622
623 return 0;
624 }
625
626 return -ENOMEM;
627}
628
629void kasan_free_module_shadow(const struct vm_struct *vm)
630{
631 if (IS_ENABLED(CONFIG_UML))
632 return;
633
634 if (vm->flags & VM_KASAN)
635 vfree(kasan_mem_to_shadow(vm->addr));
636}
637
638#endif