1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains common generic and tag-based KASAN code. 4 * 5 * Copyright (c) 2014 Samsung Electronics Co., Ltd. 6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 7 * 8 * Some code borrowed from https://github.com/xairy/kasan-prototype by 9 * Andrey Konovalov <andreyknvl@gmail.com> 10 * 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. 14 * 15 */ 16 17 #include <linux/export.h> 18 #include <linux/init.h> 19 #include <linux/kasan.h> 20 #include <linux/kernel.h> 21 #include <linux/kmemleak.h> 22 #include <linux/linkage.h> 23 #include <linux/memblock.h> 24 #include <linux/memory.h> 25 #include <linux/mm.h> 26 #include <linux/module.h> 27 #include <linux/printk.h> 28 #include <linux/sched.h> 29 #include <linux/sched/task_stack.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/bug.h> 36 #include <linux/uaccess.h> 37 38 #include <asm/cacheflush.h> 39 #include <asm/tlbflush.h> 40 41 #include "kasan.h" 42 #include "../slab.h" 43 44 static inline depot_stack_handle_t save_stack(gfp_t flags) 45 { 46 unsigned long entries[KASAN_STACK_DEPTH]; 47 unsigned int nr_entries; 48 49 nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0); 50 nr_entries = filter_irq_stacks(entries, nr_entries); 51 return stack_depot_save(entries, nr_entries, flags); 52 } 53 54 static inline void set_track(struct kasan_track *track, gfp_t flags) 55 { 56 track->pid = current->pid; 57 track->stack = save_stack(flags); 58 } 59 60 void kasan_enable_current(void) 61 { 62 current->kasan_depth++; 63 } 64 65 void kasan_disable_current(void) 66 { 67 current->kasan_depth--; 68 } 69 70 bool __kasan_check_read(const volatile void *p, unsigned int size) 71 { 72 return check_memory_region((unsigned long)p, size, false, _RET_IP_); 73 } 74 EXPORT_SYMBOL(__kasan_check_read); 75 76 bool __kasan_check_write(const volatile void *p, unsigned int size) 77 { 78 return check_memory_region((unsigned long)p, size, true, _RET_IP_); 79 } 80 EXPORT_SYMBOL(__kasan_check_write); 81 82 #undef memset 83 void *memset(void *addr, int c, size_t len) 84 { 85 if (!check_memory_region((unsigned long)addr, len, true, _RET_IP_)) 86 return NULL; 87 88 return __memset(addr, c, len); 89 } 90 91 #ifdef __HAVE_ARCH_MEMMOVE 92 #undef memmove 93 void *memmove(void *dest, const void *src, size_t len) 94 { 95 if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || 96 !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) 97 return NULL; 98 99 return __memmove(dest, src, len); 100 } 101 #endif 102 103 #undef memcpy 104 void *memcpy(void *dest, const void *src, size_t len) 105 { 106 if (!check_memory_region((unsigned long)src, len, false, _RET_IP_) || 107 !check_memory_region((unsigned long)dest, len, true, _RET_IP_)) 108 return NULL; 109 110 return __memcpy(dest, src, len); 111 } 112 113 /* 114 * Poisons the shadow memory for 'size' bytes starting from 'addr'. 115 * Memory addresses should be aligned to KASAN_SHADOW_SCALE_SIZE. 116 */ 117 void kasan_poison_shadow(const void *address, size_t size, u8 value) 118 { 119 void *shadow_start, *shadow_end; 120 121 /* 122 * Perform shadow offset calculation based on untagged address, as 123 * some of the callers (e.g. kasan_poison_object_data) pass tagged 124 * addresses to this function. 125 */ 126 address = reset_tag(address); 127 128 shadow_start = kasan_mem_to_shadow(address); 129 shadow_end = kasan_mem_to_shadow(address + size); 130 131 __memset(shadow_start, value, shadow_end - shadow_start); 132 } 133 134 void kasan_unpoison_shadow(const void *address, size_t size) 135 { 136 u8 tag = get_tag(address); 137 138 /* 139 * Perform shadow offset calculation based on untagged address, as 140 * some of the callers (e.g. kasan_unpoison_object_data) pass tagged 141 * addresses to this function. 142 */ 143 address = reset_tag(address); 144 145 kasan_poison_shadow(address, size, tag); 146 147 if (size & KASAN_SHADOW_MASK) { 148 u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size); 149 150 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 151 *shadow = tag; 152 else 153 *shadow = size & KASAN_SHADOW_MASK; 154 } 155 } 156 157 static void __kasan_unpoison_stack(struct task_struct *task, const void *sp) 158 { 159 void *base = task_stack_page(task); 160 size_t size = sp - base; 161 162 kasan_unpoison_shadow(base, size); 163 } 164 165 /* Unpoison the entire stack for a task. */ 166 void kasan_unpoison_task_stack(struct task_struct *task) 167 { 168 __kasan_unpoison_stack(task, task_stack_page(task) + THREAD_SIZE); 169 } 170 171 /* Unpoison the stack for the current task beyond a watermark sp value. */ 172 asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) 173 { 174 /* 175 * Calculate the task stack base address. Avoid using 'current' 176 * because this function is called by early resume code which hasn't 177 * yet set up the percpu register (%gs). 178 */ 179 void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1)); 180 181 kasan_unpoison_shadow(base, watermark - base); 182 } 183 184 /* 185 * Clear all poison for the region between the current SP and a provided 186 * watermark value, as is sometimes required prior to hand-crafted asm function 187 * returns in the middle of functions. 188 */ 189 void kasan_unpoison_stack_above_sp_to(const void *watermark) 190 { 191 const void *sp = __builtin_frame_address(0); 192 size_t size = watermark - sp; 193 194 if (WARN_ON(sp > watermark)) 195 return; 196 kasan_unpoison_shadow(sp, size); 197 } 198 199 void kasan_alloc_pages(struct page *page, unsigned int order) 200 { 201 u8 tag; 202 unsigned long i; 203 204 if (unlikely(PageHighMem(page))) 205 return; 206 207 tag = random_tag(); 208 for (i = 0; i < (1 << order); i++) 209 page_kasan_tag_set(page + i, tag); 210 kasan_unpoison_shadow(page_address(page), PAGE_SIZE << order); 211 } 212 213 void kasan_free_pages(struct page *page, unsigned int order) 214 { 215 if (likely(!PageHighMem(page))) 216 kasan_poison_shadow(page_address(page), 217 PAGE_SIZE << order, 218 KASAN_FREE_PAGE); 219 } 220 221 /* 222 * Adaptive redzone policy taken from the userspace AddressSanitizer runtime. 223 * For larger allocations larger redzones are used. 224 */ 225 static inline unsigned int optimal_redzone(unsigned int object_size) 226 { 227 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 228 return 0; 229 230 return 231 object_size <= 64 - 16 ? 16 : 232 object_size <= 128 - 32 ? 32 : 233 object_size <= 512 - 64 ? 64 : 234 object_size <= 4096 - 128 ? 128 : 235 object_size <= (1 << 14) - 256 ? 256 : 236 object_size <= (1 << 15) - 512 ? 512 : 237 object_size <= (1 << 16) - 1024 ? 1024 : 2048; 238 } 239 240 void kasan_cache_create(struct kmem_cache *cache, unsigned int *size, 241 slab_flags_t *flags) 242 { 243 unsigned int orig_size = *size; 244 unsigned int redzone_size; 245 int redzone_adjust; 246 247 /* Add alloc meta. */ 248 cache->kasan_info.alloc_meta_offset = *size; 249 *size += sizeof(struct kasan_alloc_meta); 250 251 /* Add free meta. */ 252 if (IS_ENABLED(CONFIG_KASAN_GENERIC) && 253 (cache->flags & SLAB_TYPESAFE_BY_RCU || cache->ctor || 254 cache->object_size < sizeof(struct kasan_free_meta))) { 255 cache->kasan_info.free_meta_offset = *size; 256 *size += sizeof(struct kasan_free_meta); 257 } 258 259 redzone_size = optimal_redzone(cache->object_size); 260 redzone_adjust = redzone_size - (*size - cache->object_size); 261 if (redzone_adjust > 0) 262 *size += redzone_adjust; 263 264 *size = min_t(unsigned int, KMALLOC_MAX_SIZE, 265 max(*size, cache->object_size + redzone_size)); 266 267 /* 268 * If the metadata doesn't fit, don't enable KASAN at all. 269 */ 270 if (*size <= cache->kasan_info.alloc_meta_offset || 271 *size <= cache->kasan_info.free_meta_offset) { 272 cache->kasan_info.alloc_meta_offset = 0; 273 cache->kasan_info.free_meta_offset = 0; 274 *size = orig_size; 275 return; 276 } 277 278 *flags |= SLAB_KASAN; 279 } 280 281 size_t kasan_metadata_size(struct kmem_cache *cache) 282 { 283 return (cache->kasan_info.alloc_meta_offset ? 284 sizeof(struct kasan_alloc_meta) : 0) + 285 (cache->kasan_info.free_meta_offset ? 286 sizeof(struct kasan_free_meta) : 0); 287 } 288 289 struct kasan_alloc_meta *get_alloc_info(struct kmem_cache *cache, 290 const void *object) 291 { 292 return (void *)object + cache->kasan_info.alloc_meta_offset; 293 } 294 295 struct kasan_free_meta *get_free_info(struct kmem_cache *cache, 296 const void *object) 297 { 298 BUILD_BUG_ON(sizeof(struct kasan_free_meta) > 32); 299 return (void *)object + cache->kasan_info.free_meta_offset; 300 } 301 302 303 static void kasan_set_free_info(struct kmem_cache *cache, 304 void *object, u8 tag) 305 { 306 struct kasan_alloc_meta *alloc_meta; 307 u8 idx = 0; 308 309 alloc_meta = get_alloc_info(cache, object); 310 311 #ifdef CONFIG_KASAN_SW_TAGS_IDENTIFY 312 idx = alloc_meta->free_track_idx; 313 alloc_meta->free_pointer_tag[idx] = tag; 314 alloc_meta->free_track_idx = (idx + 1) % KASAN_NR_FREE_STACKS; 315 #endif 316 317 set_track(&alloc_meta->free_track[idx], GFP_NOWAIT); 318 } 319 320 void kasan_poison_slab(struct page *page) 321 { 322 unsigned long i; 323 324 for (i = 0; i < compound_nr(page); i++) 325 page_kasan_tag_reset(page + i); 326 kasan_poison_shadow(page_address(page), page_size(page), 327 KASAN_KMALLOC_REDZONE); 328 } 329 330 void kasan_unpoison_object_data(struct kmem_cache *cache, void *object) 331 { 332 kasan_unpoison_shadow(object, cache->object_size); 333 } 334 335 void kasan_poison_object_data(struct kmem_cache *cache, void *object) 336 { 337 kasan_poison_shadow(object, 338 round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE), 339 KASAN_KMALLOC_REDZONE); 340 } 341 342 /* 343 * This function assigns a tag to an object considering the following: 344 * 1. A cache might have a constructor, which might save a pointer to a slab 345 * object somewhere (e.g. in the object itself). We preassign a tag for 346 * each object in caches with constructors during slab creation and reuse 347 * the same tag each time a particular object is allocated. 348 * 2. A cache might be SLAB_TYPESAFE_BY_RCU, which means objects can be 349 * accessed after being freed. We preassign tags for objects in these 350 * caches as well. 351 * 3. For SLAB allocator we can't preassign tags randomly since the freelist 352 * is stored as an array of indexes instead of a linked list. Assign tags 353 * based on objects indexes, so that objects that are next to each other 354 * get different tags. 355 */ 356 static u8 assign_tag(struct kmem_cache *cache, const void *object, 357 bool init, bool keep_tag) 358 { 359 /* 360 * 1. When an object is kmalloc()'ed, two hooks are called: 361 * kasan_slab_alloc() and kasan_kmalloc(). We assign the 362 * tag only in the first one. 363 * 2. We reuse the same tag for krealloc'ed objects. 364 */ 365 if (keep_tag) 366 return get_tag(object); 367 368 /* 369 * If the cache neither has a constructor nor has SLAB_TYPESAFE_BY_RCU 370 * set, assign a tag when the object is being allocated (init == false). 371 */ 372 if (!cache->ctor && !(cache->flags & SLAB_TYPESAFE_BY_RCU)) 373 return init ? KASAN_TAG_KERNEL : random_tag(); 374 375 /* For caches that either have a constructor or SLAB_TYPESAFE_BY_RCU: */ 376 #ifdef CONFIG_SLAB 377 /* For SLAB assign tags based on the object index in the freelist. */ 378 return (u8)obj_to_index(cache, virt_to_page(object), (void *)object); 379 #else 380 /* 381 * For SLUB assign a random tag during slab creation, otherwise reuse 382 * the already assigned tag. 383 */ 384 return init ? random_tag() : get_tag(object); 385 #endif 386 } 387 388 void * __must_check kasan_init_slab_obj(struct kmem_cache *cache, 389 const void *object) 390 { 391 struct kasan_alloc_meta *alloc_info; 392 393 if (!(cache->flags & SLAB_KASAN)) 394 return (void *)object; 395 396 alloc_info = get_alloc_info(cache, object); 397 __memset(alloc_info, 0, sizeof(*alloc_info)); 398 399 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 400 object = set_tag(object, 401 assign_tag(cache, object, true, false)); 402 403 return (void *)object; 404 } 405 406 static inline bool shadow_invalid(u8 tag, s8 shadow_byte) 407 { 408 if (IS_ENABLED(CONFIG_KASAN_GENERIC)) 409 return shadow_byte < 0 || 410 shadow_byte >= KASAN_SHADOW_SCALE_SIZE; 411 412 /* else CONFIG_KASAN_SW_TAGS: */ 413 if ((u8)shadow_byte == KASAN_TAG_INVALID) 414 return true; 415 if ((tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte)) 416 return true; 417 418 return false; 419 } 420 421 static bool __kasan_slab_free(struct kmem_cache *cache, void *object, 422 unsigned long ip, bool quarantine) 423 { 424 s8 shadow_byte; 425 u8 tag; 426 void *tagged_object; 427 unsigned long rounded_up_size; 428 429 tag = get_tag(object); 430 tagged_object = object; 431 object = reset_tag(object); 432 433 if (unlikely(nearest_obj(cache, virt_to_head_page(object), object) != 434 object)) { 435 kasan_report_invalid_free(tagged_object, ip); 436 return true; 437 } 438 439 /* RCU slabs could be legally used after free within the RCU period */ 440 if (unlikely(cache->flags & SLAB_TYPESAFE_BY_RCU)) 441 return false; 442 443 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(object)); 444 if (shadow_invalid(tag, shadow_byte)) { 445 kasan_report_invalid_free(tagged_object, ip); 446 return true; 447 } 448 449 rounded_up_size = round_up(cache->object_size, KASAN_SHADOW_SCALE_SIZE); 450 kasan_poison_shadow(object, rounded_up_size, KASAN_KMALLOC_FREE); 451 452 if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) || 453 unlikely(!(cache->flags & SLAB_KASAN))) 454 return false; 455 456 kasan_set_free_info(cache, object, tag); 457 458 quarantine_put(get_free_info(cache, object), cache); 459 460 return IS_ENABLED(CONFIG_KASAN_GENERIC); 461 } 462 463 bool kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip) 464 { 465 return __kasan_slab_free(cache, object, ip, true); 466 } 467 468 static void *__kasan_kmalloc(struct kmem_cache *cache, const void *object, 469 size_t size, gfp_t flags, bool keep_tag) 470 { 471 unsigned long redzone_start; 472 unsigned long redzone_end; 473 u8 tag = 0xff; 474 475 if (gfpflags_allow_blocking(flags)) 476 quarantine_reduce(); 477 478 if (unlikely(object == NULL)) 479 return NULL; 480 481 redzone_start = round_up((unsigned long)(object + size), 482 KASAN_SHADOW_SCALE_SIZE); 483 redzone_end = round_up((unsigned long)object + cache->object_size, 484 KASAN_SHADOW_SCALE_SIZE); 485 486 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 487 tag = assign_tag(cache, object, false, keep_tag); 488 489 /* Tag is ignored in set_tag without CONFIG_KASAN_SW_TAGS */ 490 kasan_unpoison_shadow(set_tag(object, tag), size); 491 kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start, 492 KASAN_KMALLOC_REDZONE); 493 494 if (cache->flags & SLAB_KASAN) 495 set_track(&get_alloc_info(cache, object)->alloc_track, flags); 496 497 return set_tag(object, tag); 498 } 499 500 void * __must_check kasan_slab_alloc(struct kmem_cache *cache, void *object, 501 gfp_t flags) 502 { 503 return __kasan_kmalloc(cache, object, cache->object_size, flags, false); 504 } 505 506 void * __must_check kasan_kmalloc(struct kmem_cache *cache, const void *object, 507 size_t size, gfp_t flags) 508 { 509 return __kasan_kmalloc(cache, object, size, flags, true); 510 } 511 EXPORT_SYMBOL(kasan_kmalloc); 512 513 void * __must_check kasan_kmalloc_large(const void *ptr, size_t size, 514 gfp_t flags) 515 { 516 struct page *page; 517 unsigned long redzone_start; 518 unsigned long redzone_end; 519 520 if (gfpflags_allow_blocking(flags)) 521 quarantine_reduce(); 522 523 if (unlikely(ptr == NULL)) 524 return NULL; 525 526 page = virt_to_page(ptr); 527 redzone_start = round_up((unsigned long)(ptr + size), 528 KASAN_SHADOW_SCALE_SIZE); 529 redzone_end = (unsigned long)ptr + page_size(page); 530 531 kasan_unpoison_shadow(ptr, size); 532 kasan_poison_shadow((void *)redzone_start, redzone_end - redzone_start, 533 KASAN_PAGE_REDZONE); 534 535 return (void *)ptr; 536 } 537 538 void * __must_check kasan_krealloc(const void *object, size_t size, gfp_t flags) 539 { 540 struct page *page; 541 542 if (unlikely(object == ZERO_SIZE_PTR)) 543 return (void *)object; 544 545 page = virt_to_head_page(object); 546 547 if (unlikely(!PageSlab(page))) 548 return kasan_kmalloc_large(object, size, flags); 549 else 550 return __kasan_kmalloc(page->slab_cache, object, size, 551 flags, true); 552 } 553 554 void kasan_poison_kfree(void *ptr, unsigned long ip) 555 { 556 struct page *page; 557 558 page = virt_to_head_page(ptr); 559 560 if (unlikely(!PageSlab(page))) { 561 if (ptr != page_address(page)) { 562 kasan_report_invalid_free(ptr, ip); 563 return; 564 } 565 kasan_poison_shadow(ptr, page_size(page), KASAN_FREE_PAGE); 566 } else { 567 __kasan_slab_free(page->slab_cache, ptr, ip, false); 568 } 569 } 570 571 void kasan_kfree_large(void *ptr, unsigned long ip) 572 { 573 if (ptr != page_address(virt_to_head_page(ptr))) 574 kasan_report_invalid_free(ptr, ip); 575 /* The object will be poisoned by page_alloc. */ 576 } 577 578 #ifndef CONFIG_KASAN_VMALLOC 579 int kasan_module_alloc(void *addr, size_t size) 580 { 581 void *ret; 582 size_t scaled_size; 583 size_t shadow_size; 584 unsigned long shadow_start; 585 586 shadow_start = (unsigned long)kasan_mem_to_shadow(addr); 587 scaled_size = (size + KASAN_SHADOW_MASK) >> KASAN_SHADOW_SCALE_SHIFT; 588 shadow_size = round_up(scaled_size, PAGE_SIZE); 589 590 if (WARN_ON(!PAGE_ALIGNED(shadow_start))) 591 return -EINVAL; 592 593 ret = __vmalloc_node_range(shadow_size, 1, shadow_start, 594 shadow_start + shadow_size, 595 GFP_KERNEL, 596 PAGE_KERNEL, VM_NO_GUARD, NUMA_NO_NODE, 597 __builtin_return_address(0)); 598 599 if (ret) { 600 __memset(ret, KASAN_SHADOW_INIT, shadow_size); 601 find_vm_area(addr)->flags |= VM_KASAN; 602 kmemleak_ignore(ret); 603 return 0; 604 } 605 606 return -ENOMEM; 607 } 608 609 void kasan_free_shadow(const struct vm_struct *vm) 610 { 611 if (vm->flags & VM_KASAN) 612 vfree(kasan_mem_to_shadow(vm->addr)); 613 } 614 #endif 615 616 extern void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); 617 extern bool report_enabled(void); 618 619 bool kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) 620 { 621 unsigned long flags = user_access_save(); 622 bool ret = false; 623 624 if (likely(report_enabled())) { 625 __kasan_report(addr, size, is_write, ip); 626 ret = true; 627 } 628 629 user_access_restore(flags); 630 631 return ret; 632 } 633 634 #ifdef CONFIG_MEMORY_HOTPLUG 635 static bool shadow_mapped(unsigned long addr) 636 { 637 pgd_t *pgd = pgd_offset_k(addr); 638 p4d_t *p4d; 639 pud_t *pud; 640 pmd_t *pmd; 641 pte_t *pte; 642 643 if (pgd_none(*pgd)) 644 return false; 645 p4d = p4d_offset(pgd, addr); 646 if (p4d_none(*p4d)) 647 return false; 648 pud = pud_offset(p4d, addr); 649 if (pud_none(*pud)) 650 return false; 651 652 /* 653 * We can't use pud_large() or pud_huge(), the first one is 654 * arch-specific, the last one depends on HUGETLB_PAGE. So let's abuse 655 * pud_bad(), if pud is bad then it's bad because it's huge. 656 */ 657 if (pud_bad(*pud)) 658 return true; 659 pmd = pmd_offset(pud, addr); 660 if (pmd_none(*pmd)) 661 return false; 662 663 if (pmd_bad(*pmd)) 664 return true; 665 pte = pte_offset_kernel(pmd, addr); 666 return !pte_none(*pte); 667 } 668 669 static int __meminit kasan_mem_notifier(struct notifier_block *nb, 670 unsigned long action, void *data) 671 { 672 struct memory_notify *mem_data = data; 673 unsigned long nr_shadow_pages, start_kaddr, shadow_start; 674 unsigned long shadow_end, shadow_size; 675 676 nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT; 677 start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn); 678 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr); 679 shadow_size = nr_shadow_pages << PAGE_SHIFT; 680 shadow_end = shadow_start + shadow_size; 681 682 if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) || 683 WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT))) 684 return NOTIFY_BAD; 685 686 switch (action) { 687 case MEM_GOING_ONLINE: { 688 void *ret; 689 690 /* 691 * If shadow is mapped already than it must have been mapped 692 * during the boot. This could happen if we onlining previously 693 * offlined memory. 694 */ 695 if (shadow_mapped(shadow_start)) 696 return NOTIFY_OK; 697 698 ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start, 699 shadow_end, GFP_KERNEL, 700 PAGE_KERNEL, VM_NO_GUARD, 701 pfn_to_nid(mem_data->start_pfn), 702 __builtin_return_address(0)); 703 if (!ret) 704 return NOTIFY_BAD; 705 706 kmemleak_ignore(ret); 707 return NOTIFY_OK; 708 } 709 case MEM_CANCEL_ONLINE: 710 case MEM_OFFLINE: { 711 struct vm_struct *vm; 712 713 /* 714 * shadow_start was either mapped during boot by kasan_init() 715 * or during memory online by __vmalloc_node_range(). 716 * In the latter case we can use vfree() to free shadow. 717 * Non-NULL result of the find_vm_area() will tell us if 718 * that was the second case. 719 * 720 * Currently it's not possible to free shadow mapped 721 * during boot by kasan_init(). It's because the code 722 * to do that hasn't been written yet. So we'll just 723 * leak the memory. 724 */ 725 vm = find_vm_area((void *)shadow_start); 726 if (vm) 727 vfree((void *)shadow_start); 728 } 729 } 730 731 return NOTIFY_OK; 732 } 733 734 static int __init kasan_memhotplug_init(void) 735 { 736 hotplug_memory_notifier(kasan_mem_notifier, 0); 737 738 return 0; 739 } 740 741 core_initcall(kasan_memhotplug_init); 742 #endif 743 744 #ifdef CONFIG_KASAN_VMALLOC 745 static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr, 746 void *unused) 747 { 748 unsigned long page; 749 pte_t pte; 750 751 if (likely(!pte_none(*ptep))) 752 return 0; 753 754 page = __get_free_page(GFP_KERNEL); 755 if (!page) 756 return -ENOMEM; 757 758 memset((void *)page, KASAN_VMALLOC_INVALID, PAGE_SIZE); 759 pte = pfn_pte(PFN_DOWN(__pa(page)), PAGE_KERNEL); 760 761 spin_lock(&init_mm.page_table_lock); 762 if (likely(pte_none(*ptep))) { 763 set_pte_at(&init_mm, addr, ptep, pte); 764 page = 0; 765 } 766 spin_unlock(&init_mm.page_table_lock); 767 if (page) 768 free_page(page); 769 return 0; 770 } 771 772 int kasan_populate_vmalloc(unsigned long addr, unsigned long size) 773 { 774 unsigned long shadow_start, shadow_end; 775 int ret; 776 777 if (!is_vmalloc_or_module_addr((void *)addr)) 778 return 0; 779 780 shadow_start = (unsigned long)kasan_mem_to_shadow((void *)addr); 781 shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE); 782 shadow_end = (unsigned long)kasan_mem_to_shadow((void *)addr + size); 783 shadow_end = ALIGN(shadow_end, PAGE_SIZE); 784 785 ret = apply_to_page_range(&init_mm, shadow_start, 786 shadow_end - shadow_start, 787 kasan_populate_vmalloc_pte, NULL); 788 if (ret) 789 return ret; 790 791 flush_cache_vmap(shadow_start, shadow_end); 792 793 /* 794 * We need to be careful about inter-cpu effects here. Consider: 795 * 796 * CPU#0 CPU#1 797 * WRITE_ONCE(p, vmalloc(100)); while (x = READ_ONCE(p)) ; 798 * p[99] = 1; 799 * 800 * With compiler instrumentation, that ends up looking like this: 801 * 802 * CPU#0 CPU#1 803 * // vmalloc() allocates memory 804 * // let a = area->addr 805 * // we reach kasan_populate_vmalloc 806 * // and call kasan_unpoison_shadow: 807 * STORE shadow(a), unpoison_val 808 * ... 809 * STORE shadow(a+99), unpoison_val x = LOAD p 810 * // rest of vmalloc process <data dependency> 811 * STORE p, a LOAD shadow(x+99) 812 * 813 * If there is no barrier between the end of unpoisioning the shadow 814 * and the store of the result to p, the stores could be committed 815 * in a different order by CPU#0, and CPU#1 could erroneously observe 816 * poison in the shadow. 817 * 818 * We need some sort of barrier between the stores. 819 * 820 * In the vmalloc() case, this is provided by a smp_wmb() in 821 * clear_vm_uninitialized_flag(). In the per-cpu allocator and in 822 * get_vm_area() and friends, the caller gets shadow allocated but 823 * doesn't have any pages mapped into the virtual address space that 824 * has been reserved. Mapping those pages in will involve taking and 825 * releasing a page-table lock, which will provide the barrier. 826 */ 827 828 return 0; 829 } 830 831 /* 832 * Poison the shadow for a vmalloc region. Called as part of the 833 * freeing process at the time the region is freed. 834 */ 835 void kasan_poison_vmalloc(const void *start, unsigned long size) 836 { 837 if (!is_vmalloc_or_module_addr(start)) 838 return; 839 840 size = round_up(size, KASAN_SHADOW_SCALE_SIZE); 841 kasan_poison_shadow(start, size, KASAN_VMALLOC_INVALID); 842 } 843 844 void kasan_unpoison_vmalloc(const void *start, unsigned long size) 845 { 846 if (!is_vmalloc_or_module_addr(start)) 847 return; 848 849 kasan_unpoison_shadow(start, size); 850 } 851 852 static int kasan_depopulate_vmalloc_pte(pte_t *ptep, unsigned long addr, 853 void *unused) 854 { 855 unsigned long page; 856 857 page = (unsigned long)__va(pte_pfn(*ptep) << PAGE_SHIFT); 858 859 spin_lock(&init_mm.page_table_lock); 860 861 if (likely(!pte_none(*ptep))) { 862 pte_clear(&init_mm, addr, ptep); 863 free_page(page); 864 } 865 spin_unlock(&init_mm.page_table_lock); 866 867 return 0; 868 } 869 870 /* 871 * Release the backing for the vmalloc region [start, end), which 872 * lies within the free region [free_region_start, free_region_end). 873 * 874 * This can be run lazily, long after the region was freed. It runs 875 * under vmap_area_lock, so it's not safe to interact with the vmalloc/vmap 876 * infrastructure. 877 * 878 * How does this work? 879 * ------------------- 880 * 881 * We have a region that is page aligned, labelled as A. 882 * That might not map onto the shadow in a way that is page-aligned: 883 * 884 * start end 885 * v v 886 * |????????|????????|AAAAAAAA|AA....AA|AAAAAAAA|????????| < vmalloc 887 * -------- -------- -------- -------- -------- 888 * | | | | | 889 * | | | /-------/ | 890 * \-------\|/------/ |/---------------/ 891 * ||| || 892 * |??AAAAAA|AAAAAAAA|AA??????| < shadow 893 * (1) (2) (3) 894 * 895 * First we align the start upwards and the end downwards, so that the 896 * shadow of the region aligns with shadow page boundaries. In the 897 * example, this gives us the shadow page (2). This is the shadow entirely 898 * covered by this allocation. 899 * 900 * Then we have the tricky bits. We want to know if we can free the 901 * partially covered shadow pages - (1) and (3) in the example. For this, 902 * we are given the start and end of the free region that contains this 903 * allocation. Extending our previous example, we could have: 904 * 905 * free_region_start free_region_end 906 * | start end | 907 * v v v v 908 * |FFFFFFFF|FFFFFFFF|AAAAAAAA|AA....AA|AAAAAAAA|FFFFFFFF| < vmalloc 909 * -------- -------- -------- -------- -------- 910 * | | | | | 911 * | | | /-------/ | 912 * \-------\|/------/ |/---------------/ 913 * ||| || 914 * |FFAAAAAA|AAAAAAAA|AAF?????| < shadow 915 * (1) (2) (3) 916 * 917 * Once again, we align the start of the free region up, and the end of 918 * the free region down so that the shadow is page aligned. So we can free 919 * page (1) - we know no allocation currently uses anything in that page, 920 * because all of it is in the vmalloc free region. But we cannot free 921 * page (3), because we can't be sure that the rest of it is unused. 922 * 923 * We only consider pages that contain part of the original region for 924 * freeing: we don't try to free other pages from the free region or we'd 925 * end up trying to free huge chunks of virtual address space. 926 * 927 * Concurrency 928 * ----------- 929 * 930 * How do we know that we're not freeing a page that is simultaneously 931 * being used for a fresh allocation in kasan_populate_vmalloc(_pte)? 932 * 933 * We _can_ have kasan_release_vmalloc and kasan_populate_vmalloc running 934 * at the same time. While we run under free_vmap_area_lock, the population 935 * code does not. 936 * 937 * free_vmap_area_lock instead operates to ensure that the larger range 938 * [free_region_start, free_region_end) is safe: because __alloc_vmap_area and 939 * the per-cpu region-finding algorithm both run under free_vmap_area_lock, 940 * no space identified as free will become used while we are running. This 941 * means that so long as we are careful with alignment and only free shadow 942 * pages entirely covered by the free region, we will not run in to any 943 * trouble - any simultaneous allocations will be for disjoint regions. 944 */ 945 void kasan_release_vmalloc(unsigned long start, unsigned long end, 946 unsigned long free_region_start, 947 unsigned long free_region_end) 948 { 949 void *shadow_start, *shadow_end; 950 unsigned long region_start, region_end; 951 unsigned long size; 952 953 region_start = ALIGN(start, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE); 954 region_end = ALIGN_DOWN(end, PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE); 955 956 free_region_start = ALIGN(free_region_start, 957 PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE); 958 959 if (start != region_start && 960 free_region_start < region_start) 961 region_start -= PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE; 962 963 free_region_end = ALIGN_DOWN(free_region_end, 964 PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE); 965 966 if (end != region_end && 967 free_region_end > region_end) 968 region_end += PAGE_SIZE * KASAN_SHADOW_SCALE_SIZE; 969 970 shadow_start = kasan_mem_to_shadow((void *)region_start); 971 shadow_end = kasan_mem_to_shadow((void *)region_end); 972 973 if (shadow_end > shadow_start) { 974 size = shadow_end - shadow_start; 975 apply_to_existing_page_range(&init_mm, 976 (unsigned long)shadow_start, 977 size, kasan_depopulate_vmalloc_pte, 978 NULL); 979 flush_tlb_kernel_range((unsigned long)shadow_start, 980 (unsigned long)shadow_end); 981 } 982 } 983 #endif 984