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