kasan: add functions to clear stack poison
[deliverable/linux.git] / mm / kasan / kasan.c
1 /*
2 * This file contains shadow memory manipulation code.
3 *
4 * Copyright (c) 2014 Samsung Electronics Co., Ltd.
5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
6 *
7 * Some code borrowed from https://github.com/xairy/kasan-prototype by
8 * Andrey Konovalov <adech.fo@gmail.com>
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 */
15
16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
17 #define DISABLE_BRANCH_PROFILING
18
19 #include <linux/export.h>
20 #include <linux/init.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>
26 #include <linux/mm.h>
27 #include <linux/module.h>
28 #include <linux/printk.h>
29 #include <linux/sched.h>
30 #include <linux/slab.h>
31 #include <linux/stacktrace.h>
32 #include <linux/string.h>
33 #include <linux/types.h>
34 #include <linux/vmalloc.h>
35 #include <linux/kasan.h>
36
37 #include "kasan.h"
38 #include "../slab.h"
39
40 /*
41 * Poisons the shadow memory for 'size' bytes starting from 'addr'.
42 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE.
43 */
44 static void kasan_poison_shadow(const void *address, size_t size, u8 value)
45 {
46 void *shadow_start, *shadow_end;
47
48 shadow_start = kasan_mem_to_shadow(address);
49 shadow_end = kasan_mem_to_shadow(address + size);
50
51 memset(shadow_start, value, shadow_end - shadow_start);
52 }
53
54 void kasan_unpoison_shadow(const void *address, size_t size)
55 {
56 kasan_poison_shadow(address, size, 0);
57
58 if (size & KASAN_SHADOW_MASK) {
59 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
60 *shadow = size & KASAN_SHADOW_MASK;
61 }
62 }
63
64 static void __kasan_unpoison_stack(struct task_struct *task, void *sp)
65 {
66 void *base = task_stack_page(task);
67 size_t size = sp - base;
68
69 kasan_unpoison_shadow(base, size);
70 }
71
72 /* Unpoison the entire stack for a task. */
73 void kasan_unpoison_task_stack(struct task_struct *task)
74 {
75 __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE);
76 }
77
78 /* Unpoison the stack for the current task beyond a watermark sp value. */
79 asmlinkage void kasan_unpoison_remaining_stack(void *sp)
80 {
81 __kasan_unpoison_stack(current, sp);
82 }
83
84 /*
85 * All functions below always inlined so compiler could
86 * perform better optimizations in each of __asan_loadX/__assn_storeX
87 * depending on memory access size X.
88 */
89
90 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
91 {
92 s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
93
94 if (unlikely(shadow_value)) {
95 s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
96 return unlikely(last_accessible_byte >= shadow_value);
97 }
98
99 return false;
100 }
101
102 static __always_inline bool memory_is_poisoned_2(unsigned long addr)
103 {
104 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
105
106 if (unlikely(*shadow_addr)) {
107 if (memory_is_poisoned_1(addr + 1))
108 return true;
109
110 /*
111 * If single shadow byte covers 2-byte access, we don't
112 * need to do anything more. Otherwise, test the first
113 * shadow byte.
114 */
115 if (likely(((addr + 1) & KASAN_SHADOW_MASK) != 0))
116 return false;
117
118 return unlikely(*(u8 *)shadow_addr);
119 }
120
121 return false;
122 }
123
124 static __always_inline bool memory_is_poisoned_4(unsigned long addr)
125 {
126 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
127
128 if (unlikely(*shadow_addr)) {
129 if (memory_is_poisoned_1(addr + 3))
130 return true;
131
132 /*
133 * If single shadow byte covers 4-byte access, we don't
134 * need to do anything more. Otherwise, test the first
135 * shadow byte.
136 */
137 if (likely(((addr + 3) & KASAN_SHADOW_MASK) >= 3))
138 return false;
139
140 return unlikely(*(u8 *)shadow_addr);
141 }
142
143 return false;
144 }
145
146 static __always_inline bool memory_is_poisoned_8(unsigned long addr)
147 {
148 u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
149
150 if (unlikely(*shadow_addr)) {
151 if (memory_is_poisoned_1(addr + 7))
152 return true;
153
154 /*
155 * If single shadow byte covers 8-byte access, we don't
156 * need to do anything more. Otherwise, test the first
157 * shadow byte.
158 */
159 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
160 return false;
161
162 return unlikely(*(u8 *)shadow_addr);
163 }
164
165 return false;
166 }
167
168 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
169 {
170 u32 *shadow_addr = (u32 *)kasan_mem_to_shadow((void *)addr);
171
172 if (unlikely(*shadow_addr)) {
173 u16 shadow_first_bytes = *(u16 *)shadow_addr;
174
175 if (unlikely(shadow_first_bytes))
176 return true;
177
178 /*
179 * If two shadow bytes covers 16-byte access, we don't
180 * need to do anything more. Otherwise, test the last
181 * shadow byte.
182 */
183 if (likely(IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
184 return false;
185
186 return memory_is_poisoned_1(addr + 15);
187 }
188
189 return false;
190 }
191
192 static __always_inline unsigned long bytes_is_zero(const u8 *start,
193 size_t size)
194 {
195 while (size) {
196 if (unlikely(*start))
197 return (unsigned long)start;
198 start++;
199 size--;
200 }
201
202 return 0;
203 }
204
205 static __always_inline unsigned long memory_is_zero(const void *start,
206 const void *end)
207 {
208 unsigned int words;
209 unsigned long ret;
210 unsigned int prefix = (unsigned long)start % 8;
211
212 if (end - start <= 16)
213 return bytes_is_zero(start, end - start);
214
215 if (prefix) {
216 prefix = 8 - prefix;
217 ret = bytes_is_zero(start, prefix);
218 if (unlikely(ret))
219 return ret;
220 start += prefix;
221 }
222
223 words = (end - start) / 8;
224 while (words) {
225 if (unlikely(*(u64 *)start))
226 return bytes_is_zero(start, 8);
227 start += 8;
228 words--;
229 }
230
231 return bytes_is_zero(start, (end - start) % 8);
232 }
233
234 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
235 size_t size)
236 {
237 unsigned long ret;
238
239 ret = memory_is_zero(kasan_mem_to_shadow((void *)addr),
240 kasan_mem_to_shadow((void *)addr + size - 1) + 1);
241
242 if (unlikely(ret)) {
243 unsigned long last_byte = addr + size - 1;
244 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
245
246 if (unlikely(ret != (unsigned long)last_shadow ||
247 ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
248 return true;
249 }
250 return false;
251 }
252
253 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
254 {
255 if (__builtin_constant_p(size)) {
256 switch (size) {
257 case 1:
258 return memory_is_poisoned_1(addr);
259 case 2:
260 return memory_is_poisoned_2(addr);
261 case 4:
262 return memory_is_poisoned_4(addr);
263 case 8:
264 return memory_is_poisoned_8(addr);
265 case 16:
266 return memory_is_poisoned_16(addr);
267 default:
268 BUILD_BUG();
269 }
270 }
271
272 return memory_is_poisoned_n(addr, size);
273 }
274
275
276 static __always_inline void check_memory_region(unsigned long addr,
277 size_t size, bool write)
278 {
279 if (unlikely(size == 0))
280 return;
281
282 if (unlikely((void *)addr <
283 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
284 kasan_report(addr, size, write, _RET_IP_);
285 return;
286 }
287
288 if (likely(!memory_is_poisoned(addr, size)))
289 return;
290
291 kasan_report(addr, size, write, _RET_IP_);
292 }
293
294 void __asan_loadN(unsigned long addr, size_t size);
295 void __asan_storeN(unsigned long addr, size_t size);
296
297 #undef memset
298 void *memset(void *addr, int c, size_t len)
299 {
300 __asan_storeN((unsigned long)addr, len);
301
302 return __memset(addr, c, len);
303 }
304
305 #undef memmove
306 void *memmove(void *dest, const void *src, size_t len)
307 {
308 __asan_loadN((unsigned long)src, len);
309 __asan_storeN((unsigned long)dest, len);
310
311 return __memmove(dest, src, len);
312 }
313
314 #undef memcpy
315 void *memcpy(void *dest, const void *src, size_t len)
316 {
317 __asan_loadN((unsigned long)src, len);
318 __asan_storeN((unsigned long)dest, len);
319
320 return __memcpy(dest, src, len);
321 }
322
323 void kasan_alloc_pages(struct page *page, unsigned int order)
324 {
325 if (likely(!PageHighMem(page)))
326 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order);
327 }
328
329 void kasan_free_pages(struct page *page, unsigned int order)
330 {
331 if (likely(!PageHighMem(page)))
332 kasan_poison_shadow(page_address(page),
333 PAGE_SIZE << order,
334 KASAN_FREE_PAGE);
335 }
336
337 void kasan_poison_slab(struct page *page)
338 {
339 kasan_poison_shadow(page_address(page),
340 PAGE_SIZE << compound_order(page),
341 KASAN_KMALLOC_REDZONE);
342 }
343
344 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
345 {
346 kasan_unpoison_shadow(object, cache->object_size);
347 }
348
349 void kasan_poison_object_data(struct kmem_cache *cache, void *object)
350 {
351 kasan_poison_shadow(object,
352 round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE),
353 KASAN_KMALLOC_REDZONE);
354 }
355
356 void kasan_slab_alloc(struct kmem_cache *cache, void *object)
357 {
358 kasan_kmalloc(cache, object, cache->object_size);
359 }
360
361 void kasan_slab_free(struct kmem_cache *cache, void *object)
362 {
363 unsigned long size = cache->object_size;
364 unsigned long rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
365
366 /* RCU slabs could be legally used after free within the RCU period */
367 if (unlikely(cache->flags & SLAB_DESTROY_BY_RCU))
368 return;
369
370 kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE);
371 }
372
373 void kasan_kmalloc(struct kmem_cache *cache, const void *object, size_t size)
374 {
375 unsigned long redzone_start;
376 unsigned long redzone_end;
377
378 if (unlikely(object == NULL))
379 return;
380
381 redzone_start = round_up((unsigned long)(object + size),
382 KASAN_SHADOW_SCALE_SIZE);
383 redzone_end = round_up((unsigned long)object + cache->object_size,
384 KASAN_SHADOW_SCALE_SIZE);
385
386 kasan_unpoison_shadow(object, size);
387 kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
388 KASAN_KMALLOC_REDZONE);
389 }
390 EXPORT_SYMBOL(kasan_kmalloc);
391
392 void kasan_kmalloc_large(const void *ptr, size_t size)
393 {
394 struct page *page;
395 unsigned long redzone_start;
396 unsigned long redzone_end;
397
398 if (unlikely(ptr == NULL))
399 return;
400
401 page = virt_to_page(ptr);
402 redzone_start = round_up((unsigned long)(ptr + size),
403 KASAN_SHADOW_SCALE_SIZE);
404 redzone_end = (unsigned long)ptr + (PAGE_SIZE << compound_order(page));
405
406 kasan_unpoison_shadow(ptr, size);
407 kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start,
408 KASAN_PAGE_REDZONE);
409 }
410
411 void kasan_krealloc(const void *object, size_t size)
412 {
413 struct page *page;
414
415 if (unlikely(object == ZERO_SIZE_PTR))
416 return;
417
418 page = virt_to_head_page(object);
419
420 if (unlikely(!PageSlab(page)))
421 kasan_kmalloc_large(object, size);
422 else
423 kasan_kmalloc(page->slab_cache, object, size);
424 }
425
426 void kasan_kfree(void *ptr)
427 {
428 struct page *page;
429
430 page = virt_to_head_page(ptr);
431
432 if (unlikely(!PageSlab(page)))
433 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
434 KASAN_FREE_PAGE);
435 else
436 kasan_slab_free(page->slab_cache, ptr);
437 }
438
439 void kasan_kfree_large(const void *ptr)
440 {
441 struct page *page = virt_to_page(ptr);
442
443 kasan_poison_shadow(ptr, PAGE_SIZE << compound_order(page),
444 KASAN_FREE_PAGE);
445 }
446
447 int kasan_module_alloc(void *addr, size_t size)
448 {
449 void *ret;
450 size_t shadow_size;
451 unsigned long shadow_start;
452
453 shadow_start = (unsigned long)kasan_mem_to_shadow(addr);
454 shadow_size = round_up(size >> KASAN_SHADOW_SCALE_SHIFT,
455 PAGE_SIZE);
456
457 if (WARN_ON(!PAGE_ALIGNED(shadow_start)))
458 return -EINVAL;
459
460 ret = __vmalloc_node_range(shadow_size, 1, shadow_start,
461 shadow_start + shadow_size,
462 GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
463 PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE,
464 __builtin_return_address(0));
465
466 if (ret) {
467 find_vm_area(addr)->flags |= VM_KASAN;
468 kmemleak_ignore(ret);
469 return 0;
470 }
471
472 return -ENOMEM;
473 }
474
475 void kasan_free_shadow(const struct vm_struct *vm)
476 {
477 if (vm->flags & VM_KASAN)
478 vfree(kasan_mem_to_shadow(vm->addr));
479 }
480
481 static void register_global(struct kasan_global *global)
482 {
483 size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
484
485 kasan_unpoison_shadow(global->beg, global->size);
486
487 kasan_poison_shadow(global->beg + aligned_size,
488 global->size_with_redzone - aligned_size,
489 KASAN_GLOBAL_REDZONE);
490 }
491
492 void __asan_register_globals(struct kasan_global *globals, size_t size)
493 {
494 int i;
495
496 for (i = 0; i < size; i++)
497 register_global(&globals[i]);
498 }
499 EXPORT_SYMBOL(__asan_register_globals);
500
501 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
502 {
503 }
504 EXPORT_SYMBOL(__asan_unregister_globals);
505
506 #define DEFINE_ASAN_LOAD_STORE(size) \
507 void __asan_load##size(unsigned long addr) \
508 { \
509 check_memory_region(addr, size, false); \
510 } \
511 EXPORT_SYMBOL(__asan_load##size); \
512 __alias(__asan_load##size) \
513 void __asan_load##size##_noabort(unsigned long); \
514 EXPORT_SYMBOL(__asan_load##size##_noabort); \
515 void __asan_store##size(unsigned long addr) \
516 { \
517 check_memory_region(addr, size, true); \
518 } \
519 EXPORT_SYMBOL(__asan_store##size); \
520 __alias(__asan_store##size) \
521 void __asan_store##size##_noabort(unsigned long); \
522 EXPORT_SYMBOL(__asan_store##size##_noabort)
523
524 DEFINE_ASAN_LOAD_STORE(1);
525 DEFINE_ASAN_LOAD_STORE(2);
526 DEFINE_ASAN_LOAD_STORE(4);
527 DEFINE_ASAN_LOAD_STORE(8);
528 DEFINE_ASAN_LOAD_STORE(16);
529
530 void __asan_loadN(unsigned long addr, size_t size)
531 {
532 check_memory_region(addr, size, false);
533 }
534 EXPORT_SYMBOL(__asan_loadN);
535
536 __alias(__asan_loadN)
537 void __asan_loadN_noabort(unsigned long, size_t);
538 EXPORT_SYMBOL(__asan_loadN_noabort);
539
540 void __asan_storeN(unsigned long addr, size_t size)
541 {
542 check_memory_region(addr, size, true);
543 }
544 EXPORT_SYMBOL(__asan_storeN);
545
546 __alias(__asan_storeN)
547 void __asan_storeN_noabort(unsigned long, size_t);
548 EXPORT_SYMBOL(__asan_storeN_noabort);
549
550 /* to shut up compiler complaints */
551 void __asan_handle_no_return(void) {}
552 EXPORT_SYMBOL(__asan_handle_no_return);
553
554 #ifdef CONFIG_MEMORY_HOTPLUG
555 static int kasan_mem_notifier(struct notifier_block *nb,
556 unsigned long action, void *data)
557 {
558 return (action == MEM_GOING_ONLINE) ? NOTIFY_BAD : NOTIFY_OK;
559 }
560
561 static int __init kasan_memhotplug_init(void)
562 {
563 pr_err("WARNING: KASAN doesn't support memory hot-add\n");
564 pr_err("Memory hot-add will be disabled\n");
565
566 hotplug_memory_notifier(kasan_mem_notifier, 0);
567
568 return 0;
569 }
570
571 module_init(kasan_memhotplug_init);
572 #endif
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