1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * KFENCE guarded object allocator and fault handling. 4 * 5 * Copyright (C) 2020, Google LLC. 6 */ 7 8 #define pr_fmt(fmt) "kfence: " fmt 9 10 #include <linux/atomic.h> 11 #include <linux/bug.h> 12 #include <linux/debugfs.h> 13 #include <linux/hash.h> 14 #include <linux/irq_work.h> 15 #include <linux/jhash.h> 16 #include <linux/kcsan-checks.h> 17 #include <linux/kfence.h> 18 #include <linux/kmemleak.h> 19 #include <linux/list.h> 20 #include <linux/lockdep.h> 21 #include <linux/log2.h> 22 #include <linux/memblock.h> 23 #include <linux/moduleparam.h> 24 #include <linux/notifier.h> 25 #include <linux/panic_notifier.h> 26 #include <linux/random.h> 27 #include <linux/rcupdate.h> 28 #include <linux/sched/clock.h> 29 #include <linux/seq_file.h> 30 #include <linux/slab.h> 31 #include <linux/spinlock.h> 32 #include <linux/string.h> 33 34 #include <asm/kfence.h> 35 36 #include "kfence.h" 37 38 /* Disables KFENCE on the first warning assuming an irrecoverable error. */ 39 #define KFENCE_WARN_ON(cond) \ 40 ({ \ 41 const bool __cond = WARN_ON(cond); \ 42 if (unlikely(__cond)) { \ 43 WRITE_ONCE(kfence_enabled, false); \ 44 disabled_by_warn = true; \ 45 } \ 46 __cond; \ 47 }) 48 49 /* === Data ================================================================= */ 50 51 static bool kfence_enabled __read_mostly; 52 static bool disabled_by_warn __read_mostly; 53 54 unsigned long kfence_sample_interval __read_mostly = CONFIG_KFENCE_SAMPLE_INTERVAL; 55 EXPORT_SYMBOL_GPL(kfence_sample_interval); /* Export for test modules. */ 56 57 #ifdef MODULE_PARAM_PREFIX 58 #undef MODULE_PARAM_PREFIX 59 #endif 60 #define MODULE_PARAM_PREFIX "kfence." 61 62 static int kfence_enable_late(void); 63 static int param_set_sample_interval(const char *val, const struct kernel_param *kp) 64 { 65 unsigned long num; 66 int ret = kstrtoul(val, 0, &num); 67 68 if (ret < 0) 69 return ret; 70 71 /* Using 0 to indicate KFENCE is disabled. */ 72 if (!num && READ_ONCE(kfence_enabled)) { 73 pr_info("disabled\n"); 74 WRITE_ONCE(kfence_enabled, false); 75 } 76 77 *((unsigned long *)kp->arg) = num; 78 79 if (num && !READ_ONCE(kfence_enabled) && system_state != SYSTEM_BOOTING) 80 return disabled_by_warn ? -EINVAL : kfence_enable_late(); 81 return 0; 82 } 83 84 static int param_get_sample_interval(char *buffer, const struct kernel_param *kp) 85 { 86 if (!READ_ONCE(kfence_enabled)) 87 return sprintf(buffer, "0\n"); 88 89 return param_get_ulong(buffer, kp); 90 } 91 92 static const struct kernel_param_ops sample_interval_param_ops = { 93 .set = param_set_sample_interval, 94 .get = param_get_sample_interval, 95 }; 96 module_param_cb(sample_interval, &sample_interval_param_ops, &kfence_sample_interval, 0600); 97 98 /* Pool usage% threshold when currently covered allocations are skipped. */ 99 static unsigned long kfence_skip_covered_thresh __read_mostly = 75; 100 module_param_named(skip_covered_thresh, kfence_skip_covered_thresh, ulong, 0644); 101 102 /* Allocation burst count: number of excess KFENCE allocations per sample. */ 103 static unsigned int kfence_burst __read_mostly; 104 module_param_named(burst, kfence_burst, uint, 0644); 105 106 /* If true, use a deferrable timer. */ 107 static bool kfence_deferrable __read_mostly = IS_ENABLED(CONFIG_KFENCE_DEFERRABLE); 108 module_param_named(deferrable, kfence_deferrable, bool, 0444); 109 110 /* If true, check all canary bytes on panic. */ 111 static bool kfence_check_on_panic __read_mostly; 112 module_param_named(check_on_panic, kfence_check_on_panic, bool, 0444); 113 114 /* The pool of pages used for guard pages and objects. */ 115 char *__kfence_pool __read_mostly; 116 EXPORT_SYMBOL(__kfence_pool); /* Export for test modules. */ 117 118 /* 119 * Per-object metadata, with one-to-one mapping of object metadata to 120 * backing pages (in __kfence_pool). 121 */ 122 static_assert(CONFIG_KFENCE_NUM_OBJECTS > 0); 123 struct kfence_metadata *kfence_metadata __read_mostly; 124 125 /* 126 * If kfence_metadata is not NULL, it may be accessed by kfence_shutdown_cache(). 127 * So introduce kfence_metadata_init to initialize metadata, and then make 128 * kfence_metadata visible after initialization is successful. This prevents 129 * potential UAF or access to uninitialized metadata. 130 */ 131 static struct kfence_metadata *kfence_metadata_init __read_mostly; 132 133 /* Freelist with available objects. */ 134 static struct list_head kfence_freelist = LIST_HEAD_INIT(kfence_freelist); 135 static DEFINE_RAW_SPINLOCK(kfence_freelist_lock); /* Lock protecting freelist. */ 136 137 /* 138 * The static key to set up a KFENCE allocation; or if static keys are not used 139 * to gate allocations, to avoid a load and compare if KFENCE is disabled. 140 */ 141 DEFINE_STATIC_KEY_FALSE(kfence_allocation_key); 142 143 /* Gates the allocation, ensuring only one succeeds in a given period. */ 144 atomic_t kfence_allocation_gate = ATOMIC_INIT(1); 145 146 /* 147 * A Counting Bloom filter of allocation coverage: limits currently covered 148 * allocations of the same source filling up the pool. 149 * 150 * Assuming a range of 15%-85% unique allocations in the pool at any point in 151 * time, the below parameters provide a probablity of 0.02-0.33 for false 152 * positive hits respectively: 153 * 154 * P(alloc_traces) = (1 - e^(-HNUM * (alloc_traces / SIZE)) ^ HNUM 155 */ 156 #define ALLOC_COVERED_HNUM 2 157 #define ALLOC_COVERED_ORDER (const_ilog2(CONFIG_KFENCE_NUM_OBJECTS) + 2) 158 #define ALLOC_COVERED_SIZE (1 << ALLOC_COVERED_ORDER) 159 #define ALLOC_COVERED_HNEXT(h) hash_32(h, ALLOC_COVERED_ORDER) 160 #define ALLOC_COVERED_MASK (ALLOC_COVERED_SIZE - 1) 161 static atomic_t alloc_covered[ALLOC_COVERED_SIZE]; 162 163 /* Stack depth used to determine uniqueness of an allocation. */ 164 #define UNIQUE_ALLOC_STACK_DEPTH ((size_t)8) 165 166 /* 167 * Randomness for stack hashes, making the same collisions across reboots and 168 * different machines less likely. 169 */ 170 static u32 stack_hash_seed __ro_after_init; 171 172 /* Statistics counters for debugfs. */ 173 enum kfence_counter_id { 174 KFENCE_COUNTER_ALLOCATED, 175 KFENCE_COUNTER_ALLOCS, 176 KFENCE_COUNTER_FREES, 177 KFENCE_COUNTER_ZOMBIES, 178 KFENCE_COUNTER_BUGS, 179 KFENCE_COUNTER_SKIP_INCOMPAT, 180 KFENCE_COUNTER_SKIP_CAPACITY, 181 KFENCE_COUNTER_SKIP_COVERED, 182 KFENCE_COUNTER_COUNT, 183 }; 184 static atomic_long_t counters[KFENCE_COUNTER_COUNT]; 185 static const char *const counter_names[] = { 186 [KFENCE_COUNTER_ALLOCATED] = "currently allocated", 187 [KFENCE_COUNTER_ALLOCS] = "total allocations", 188 [KFENCE_COUNTER_FREES] = "total frees", 189 [KFENCE_COUNTER_ZOMBIES] = "zombie allocations", 190 [KFENCE_COUNTER_BUGS] = "total bugs", 191 [KFENCE_COUNTER_SKIP_INCOMPAT] = "skipped allocations (incompatible)", 192 [KFENCE_COUNTER_SKIP_CAPACITY] = "skipped allocations (capacity)", 193 [KFENCE_COUNTER_SKIP_COVERED] = "skipped allocations (covered)", 194 }; 195 static_assert(ARRAY_SIZE(counter_names) == KFENCE_COUNTER_COUNT); 196 197 /* === Internals ============================================================ */ 198 199 static inline bool should_skip_covered(void) 200 { 201 unsigned long thresh = (CONFIG_KFENCE_NUM_OBJECTS * kfence_skip_covered_thresh) / 100; 202 203 return atomic_long_read(&counters[KFENCE_COUNTER_ALLOCATED]) > thresh; 204 } 205 206 static u32 get_alloc_stack_hash(unsigned long *stack_entries, size_t num_entries) 207 { 208 num_entries = min(num_entries, UNIQUE_ALLOC_STACK_DEPTH); 209 num_entries = filter_irq_stacks(stack_entries, num_entries); 210 return jhash(stack_entries, num_entries * sizeof(stack_entries[0]), stack_hash_seed); 211 } 212 213 /* 214 * Adds (or subtracts) count @val for allocation stack trace hash 215 * @alloc_stack_hash from Counting Bloom filter. 216 */ 217 static void alloc_covered_add(u32 alloc_stack_hash, int val) 218 { 219 int i; 220 221 for (i = 0; i < ALLOC_COVERED_HNUM; i++) { 222 atomic_add(val, &alloc_covered[alloc_stack_hash & ALLOC_COVERED_MASK]); 223 alloc_stack_hash = ALLOC_COVERED_HNEXT(alloc_stack_hash); 224 } 225 } 226 227 /* 228 * Returns true if the allocation stack trace hash @alloc_stack_hash is 229 * currently contained (non-zero count) in Counting Bloom filter. 230 */ 231 static bool alloc_covered_contains(u32 alloc_stack_hash) 232 { 233 int i; 234 235 for (i = 0; i < ALLOC_COVERED_HNUM; i++) { 236 if (!atomic_read(&alloc_covered[alloc_stack_hash & ALLOC_COVERED_MASK])) 237 return false; 238 alloc_stack_hash = ALLOC_COVERED_HNEXT(alloc_stack_hash); 239 } 240 241 return true; 242 } 243 244 static bool kfence_protect(unsigned long addr) 245 { 246 return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), true)); 247 } 248 249 static bool kfence_unprotect(unsigned long addr) 250 { 251 return !KFENCE_WARN_ON(!kfence_protect_page(ALIGN_DOWN(addr, PAGE_SIZE), false)); 252 } 253 254 static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta) 255 { 256 unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2; 257 unsigned long pageaddr = (unsigned long)&__kfence_pool[offset]; 258 259 /* The checks do not affect performance; only called from slow-paths. */ 260 261 /* Only call with a pointer into kfence_metadata. */ 262 if (KFENCE_WARN_ON(meta < kfence_metadata || 263 meta >= kfence_metadata + CONFIG_KFENCE_NUM_OBJECTS)) 264 return 0; 265 266 /* 267 * This metadata object only ever maps to 1 page; verify that the stored 268 * address is in the expected range. 269 */ 270 if (KFENCE_WARN_ON(ALIGN_DOWN(meta->addr, PAGE_SIZE) != pageaddr)) 271 return 0; 272 273 return pageaddr; 274 } 275 276 static inline bool kfence_obj_allocated(const struct kfence_metadata *meta) 277 { 278 enum kfence_object_state state = READ_ONCE(meta->state); 279 280 return state == KFENCE_OBJECT_ALLOCATED || state == KFENCE_OBJECT_RCU_FREEING; 281 } 282 283 /* 284 * Update the object's metadata state, including updating the alloc/free stacks 285 * depending on the state transition. 286 */ 287 static noinline void 288 metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next, 289 unsigned long *stack_entries, size_t num_stack_entries) 290 { 291 struct kfence_track *track = 292 next == KFENCE_OBJECT_ALLOCATED ? &meta->alloc_track : &meta->free_track; 293 294 lockdep_assert_held(&meta->lock); 295 296 /* Stack has been saved when calling rcu, skip. */ 297 if (READ_ONCE(meta->state) == KFENCE_OBJECT_RCU_FREEING) 298 goto out; 299 300 if (stack_entries) { 301 memcpy(track->stack_entries, stack_entries, 302 num_stack_entries * sizeof(stack_entries[0])); 303 } else { 304 /* 305 * Skip over 1 (this) functions; noinline ensures we do not 306 * accidentally skip over the caller by never inlining. 307 */ 308 num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1); 309 } 310 track->num_stack_entries = num_stack_entries; 311 track->pid = task_pid_nr(current); 312 track->cpu = raw_smp_processor_id(); 313 track->ts_nsec = local_clock(); /* Same source as printk timestamps. */ 314 315 out: 316 /* 317 * Pairs with READ_ONCE() in 318 * kfence_shutdown_cache(), 319 * kfence_handle_page_fault(). 320 */ 321 WRITE_ONCE(meta->state, next); 322 } 323 324 #ifdef CONFIG_KMSAN 325 #define check_canary_attributes noinline __no_kmsan_checks 326 #else 327 #define check_canary_attributes inline 328 #endif 329 330 /* Check canary byte at @addr. */ 331 static check_canary_attributes bool check_canary_byte(u8 *addr) 332 { 333 struct kfence_metadata *meta; 334 unsigned long flags; 335 336 if (likely(*addr == KFENCE_CANARY_PATTERN_U8(addr))) 337 return true; 338 339 atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]); 340 341 meta = addr_to_metadata((unsigned long)addr); 342 raw_spin_lock_irqsave(&meta->lock, flags); 343 kfence_report_error((unsigned long)addr, false, NULL, meta, KFENCE_ERROR_CORRUPTION); 344 raw_spin_unlock_irqrestore(&meta->lock, flags); 345 346 return false; 347 } 348 349 static inline void set_canary(const struct kfence_metadata *meta) 350 { 351 const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE); 352 unsigned long addr = pageaddr; 353 354 /* 355 * The canary may be written to part of the object memory, but it does 356 * not affect it. The user should initialize the object before using it. 357 */ 358 for (; addr < meta->addr; addr += sizeof(u64)) 359 *((u64 *)addr) = KFENCE_CANARY_PATTERN_U64; 360 361 addr = ALIGN_DOWN(meta->addr + meta->size, sizeof(u64)); 362 for (; addr - pageaddr < PAGE_SIZE; addr += sizeof(u64)) 363 *((u64 *)addr) = KFENCE_CANARY_PATTERN_U64; 364 } 365 366 static check_canary_attributes void 367 check_canary(const struct kfence_metadata *meta) 368 { 369 const unsigned long pageaddr = ALIGN_DOWN(meta->addr, PAGE_SIZE); 370 unsigned long addr = pageaddr; 371 372 /* 373 * We'll iterate over each canary byte per-side until a corrupted byte 374 * is found. However, we'll still iterate over the canary bytes to the 375 * right of the object even if there was an error in the canary bytes to 376 * the left of the object. Specifically, if check_canary_byte() 377 * generates an error, showing both sides might give more clues as to 378 * what the error is about when displaying which bytes were corrupted. 379 */ 380 381 /* Apply to left of object. */ 382 for (; meta->addr - addr >= sizeof(u64); addr += sizeof(u64)) { 383 if (unlikely(*((u64 *)addr) != KFENCE_CANARY_PATTERN_U64)) 384 break; 385 } 386 387 /* 388 * If the canary is corrupted in a certain 64 bytes, or the canary 389 * memory cannot be completely covered by multiple consecutive 64 bytes, 390 * it needs to be checked one by one. 391 */ 392 for (; addr < meta->addr; addr++) { 393 if (unlikely(!check_canary_byte((u8 *)addr))) 394 break; 395 } 396 397 /* Apply to right of object. */ 398 for (addr = meta->addr + meta->size; addr % sizeof(u64) != 0; addr++) { 399 if (unlikely(!check_canary_byte((u8 *)addr))) 400 return; 401 } 402 for (; addr - pageaddr < PAGE_SIZE; addr += sizeof(u64)) { 403 if (unlikely(*((u64 *)addr) != KFENCE_CANARY_PATTERN_U64)) { 404 405 for (; addr - pageaddr < PAGE_SIZE; addr++) { 406 if (!check_canary_byte((u8 *)addr)) 407 return; 408 } 409 } 410 } 411 } 412 413 static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp, 414 unsigned long *stack_entries, size_t num_stack_entries, 415 u32 alloc_stack_hash) 416 { 417 struct kfence_metadata *meta = NULL; 418 unsigned long flags; 419 struct slab *slab; 420 void *addr; 421 const bool random_right_allocate = get_random_u32_below(2); 422 const bool random_fault = CONFIG_KFENCE_STRESS_TEST_FAULTS && 423 !get_random_u32_below(CONFIG_KFENCE_STRESS_TEST_FAULTS); 424 425 /* Try to obtain a free object. */ 426 raw_spin_lock_irqsave(&kfence_freelist_lock, flags); 427 if (!list_empty(&kfence_freelist)) { 428 meta = list_entry(kfence_freelist.next, struct kfence_metadata, list); 429 list_del_init(&meta->list); 430 } 431 raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags); 432 if (!meta) { 433 atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_CAPACITY]); 434 return NULL; 435 } 436 437 if (unlikely(!raw_spin_trylock_irqsave(&meta->lock, flags))) { 438 /* 439 * This is extremely unlikely -- we are reporting on a 440 * use-after-free, which locked meta->lock, and the reporting 441 * code via printk calls kmalloc() which ends up in 442 * kfence_alloc() and tries to grab the same object that we're 443 * reporting on. While it has never been observed, lockdep does 444 * report that there is a possibility of deadlock. Fix it by 445 * using trylock and bailing out gracefully. 446 */ 447 raw_spin_lock_irqsave(&kfence_freelist_lock, flags); 448 /* Put the object back on the freelist. */ 449 list_add_tail(&meta->list, &kfence_freelist); 450 raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags); 451 452 return NULL; 453 } 454 455 meta->addr = metadata_to_pageaddr(meta); 456 /* Unprotect if we're reusing this page. */ 457 if (meta->state == KFENCE_OBJECT_FREED) 458 kfence_unprotect(meta->addr); 459 460 /* 461 * Note: for allocations made before RNG initialization, will always 462 * return zero. We still benefit from enabling KFENCE as early as 463 * possible, even when the RNG is not yet available, as this will allow 464 * KFENCE to detect bugs due to earlier allocations. The only downside 465 * is that the out-of-bounds accesses detected are deterministic for 466 * such allocations. 467 */ 468 if (random_right_allocate) { 469 /* Allocate on the "right" side, re-calculate address. */ 470 meta->addr += PAGE_SIZE - size; 471 meta->addr = ALIGN_DOWN(meta->addr, cache->align); 472 } 473 474 addr = (void *)meta->addr; 475 476 /* Update remaining metadata. */ 477 metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED, stack_entries, num_stack_entries); 478 /* Pairs with READ_ONCE() in kfence_shutdown_cache(). */ 479 WRITE_ONCE(meta->cache, cache); 480 meta->size = size; 481 meta->alloc_stack_hash = alloc_stack_hash; 482 raw_spin_unlock_irqrestore(&meta->lock, flags); 483 484 alloc_covered_add(alloc_stack_hash, 1); 485 486 /* Set required slab fields. */ 487 slab = virt_to_slab((void *)meta->addr); 488 slab->slab_cache = cache; 489 slab->objects = 1; 490 491 /* Memory initialization. */ 492 set_canary(meta); 493 494 /* 495 * We check slab_want_init_on_alloc() ourselves, rather than letting 496 * SL*B do the initialization, as otherwise we might overwrite KFENCE's 497 * redzone. 498 */ 499 if (unlikely(slab_want_init_on_alloc(gfp, cache))) 500 memzero_explicit(addr, size); 501 if (cache->ctor) 502 cache->ctor(addr); 503 504 if (random_fault) 505 kfence_protect(meta->addr); /* Random "faults" by protecting the object. */ 506 507 atomic_long_inc(&counters[KFENCE_COUNTER_ALLOCATED]); 508 atomic_long_inc(&counters[KFENCE_COUNTER_ALLOCS]); 509 510 return addr; 511 } 512 513 static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool zombie) 514 { 515 struct kcsan_scoped_access assert_page_exclusive; 516 unsigned long flags; 517 bool init; 518 519 raw_spin_lock_irqsave(&meta->lock, flags); 520 521 if (!kfence_obj_allocated(meta) || meta->addr != (unsigned long)addr) { 522 /* Invalid or double-free, bail out. */ 523 atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]); 524 kfence_report_error((unsigned long)addr, false, NULL, meta, 525 KFENCE_ERROR_INVALID_FREE); 526 raw_spin_unlock_irqrestore(&meta->lock, flags); 527 return; 528 } 529 530 /* Detect racy use-after-free, or incorrect reallocation of this page by KFENCE. */ 531 kcsan_begin_scoped_access((void *)ALIGN_DOWN((unsigned long)addr, PAGE_SIZE), PAGE_SIZE, 532 KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ASSERT, 533 &assert_page_exclusive); 534 535 if (CONFIG_KFENCE_STRESS_TEST_FAULTS) 536 kfence_unprotect((unsigned long)addr); /* To check canary bytes. */ 537 538 /* Restore page protection if there was an OOB access. */ 539 if (meta->unprotected_page) { 540 memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE); 541 kfence_protect(meta->unprotected_page); 542 meta->unprotected_page = 0; 543 } 544 545 /* Mark the object as freed. */ 546 metadata_update_state(meta, KFENCE_OBJECT_FREED, NULL, 0); 547 init = slab_want_init_on_free(meta->cache); 548 raw_spin_unlock_irqrestore(&meta->lock, flags); 549 550 alloc_covered_add(meta->alloc_stack_hash, -1); 551 552 /* Check canary bytes for memory corruption. */ 553 check_canary(meta); 554 555 /* 556 * Clear memory if init-on-free is set. While we protect the page, the 557 * data is still there, and after a use-after-free is detected, we 558 * unprotect the page, so the data is still accessible. 559 */ 560 if (!zombie && unlikely(init)) 561 memzero_explicit(addr, meta->size); 562 563 /* Protect to detect use-after-frees. */ 564 kfence_protect((unsigned long)addr); 565 566 kcsan_end_scoped_access(&assert_page_exclusive); 567 if (!zombie) { 568 /* Add it to the tail of the freelist for reuse. */ 569 raw_spin_lock_irqsave(&kfence_freelist_lock, flags); 570 KFENCE_WARN_ON(!list_empty(&meta->list)); 571 list_add_tail(&meta->list, &kfence_freelist); 572 raw_spin_unlock_irqrestore(&kfence_freelist_lock, flags); 573 574 atomic_long_dec(&counters[KFENCE_COUNTER_ALLOCATED]); 575 atomic_long_inc(&counters[KFENCE_COUNTER_FREES]); 576 } else { 577 /* See kfence_shutdown_cache(). */ 578 atomic_long_inc(&counters[KFENCE_COUNTER_ZOMBIES]); 579 } 580 } 581 582 static void rcu_guarded_free(struct rcu_head *h) 583 { 584 struct kfence_metadata *meta = container_of(h, struct kfence_metadata, rcu_head); 585 586 kfence_guarded_free((void *)meta->addr, meta, false); 587 } 588 589 /* 590 * Initialization of the KFENCE pool after its allocation. 591 * Returns 0 on success; otherwise returns the address up to 592 * which partial initialization succeeded. 593 */ 594 static unsigned long kfence_init_pool(void) 595 { 596 unsigned long addr; 597 struct page *pages; 598 int i; 599 600 if (!arch_kfence_init_pool()) 601 return (unsigned long)__kfence_pool; 602 603 addr = (unsigned long)__kfence_pool; 604 pages = virt_to_page(__kfence_pool); 605 606 /* 607 * Set up object pages: they must have PG_slab set, to avoid freeing 608 * these as real pages. 609 * 610 * We also want to avoid inserting kfence_free() in the kfree() 611 * fast-path in SLUB, and therefore need to ensure kfree() correctly 612 * enters __slab_free() slow-path. 613 */ 614 for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { 615 struct slab *slab = page_slab(nth_page(pages, i)); 616 617 if (!i || (i % 2)) 618 continue; 619 620 __folio_set_slab(slab_folio(slab)); 621 #ifdef CONFIG_MEMCG 622 slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | 623 MEMCG_DATA_OBJEXTS; 624 #endif 625 } 626 627 /* 628 * Protect the first 2 pages. The first page is mostly unnecessary, and 629 * merely serves as an extended guard page. However, adding one 630 * additional page in the beginning gives us an even number of pages, 631 * which simplifies the mapping of address to metadata index. 632 */ 633 for (i = 0; i < 2; i++) { 634 if (unlikely(!kfence_protect(addr))) 635 return addr; 636 637 addr += PAGE_SIZE; 638 } 639 640 for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { 641 struct kfence_metadata *meta = &kfence_metadata_init[i]; 642 643 /* Initialize metadata. */ 644 INIT_LIST_HEAD(&meta->list); 645 raw_spin_lock_init(&meta->lock); 646 meta->state = KFENCE_OBJECT_UNUSED; 647 meta->addr = addr; /* Initialize for validation in metadata_to_pageaddr(). */ 648 list_add_tail(&meta->list, &kfence_freelist); 649 650 /* Protect the right redzone. */ 651 if (unlikely(!kfence_protect(addr + PAGE_SIZE))) 652 goto reset_slab; 653 654 addr += 2 * PAGE_SIZE; 655 } 656 657 /* 658 * Make kfence_metadata visible only when initialization is successful. 659 * Otherwise, if the initialization fails and kfence_metadata is freed, 660 * it may cause UAF in kfence_shutdown_cache(). 661 */ 662 smp_store_release(&kfence_metadata, kfence_metadata_init); 663 return 0; 664 665 reset_slab: 666 for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { 667 struct slab *slab = page_slab(nth_page(pages, i)); 668 669 if (!i || (i % 2)) 670 continue; 671 #ifdef CONFIG_MEMCG 672 slab->obj_exts = 0; 673 #endif 674 __folio_clear_slab(slab_folio(slab)); 675 } 676 677 return addr; 678 } 679 680 static bool __init kfence_init_pool_early(void) 681 { 682 unsigned long addr; 683 684 if (!__kfence_pool) 685 return false; 686 687 addr = kfence_init_pool(); 688 689 if (!addr) { 690 /* 691 * The pool is live and will never be deallocated from this point on. 692 * Ignore the pool object from the kmemleak phys object tree, as it would 693 * otherwise overlap with allocations returned by kfence_alloc(), which 694 * are registered with kmemleak through the slab post-alloc hook. 695 */ 696 kmemleak_ignore_phys(__pa(__kfence_pool)); 697 return true; 698 } 699 700 /* 701 * Only release unprotected pages, and do not try to go back and change 702 * page attributes due to risk of failing to do so as well. If changing 703 * page attributes for some pages fails, it is very likely that it also 704 * fails for the first page, and therefore expect addr==__kfence_pool in 705 * most failure cases. 706 */ 707 memblock_free_late(__pa(addr), KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool)); 708 __kfence_pool = NULL; 709 710 memblock_free_late(__pa(kfence_metadata_init), KFENCE_METADATA_SIZE); 711 kfence_metadata_init = NULL; 712 713 return false; 714 } 715 716 /* === DebugFS Interface ==================================================== */ 717 718 static int stats_show(struct seq_file *seq, void *v) 719 { 720 int i; 721 722 seq_printf(seq, "enabled: %i\n", READ_ONCE(kfence_enabled)); 723 for (i = 0; i < KFENCE_COUNTER_COUNT; i++) 724 seq_printf(seq, "%s: %ld\n", counter_names[i], atomic_long_read(&counters[i])); 725 726 return 0; 727 } 728 DEFINE_SHOW_ATTRIBUTE(stats); 729 730 /* 731 * debugfs seq_file operations for /sys/kernel/debug/kfence/objects. 732 * start_object() and next_object() return the object index + 1, because NULL is used 733 * to stop iteration. 734 */ 735 static void *start_object(struct seq_file *seq, loff_t *pos) 736 { 737 if (*pos < CONFIG_KFENCE_NUM_OBJECTS) 738 return (void *)((long)*pos + 1); 739 return NULL; 740 } 741 742 static void stop_object(struct seq_file *seq, void *v) 743 { 744 } 745 746 static void *next_object(struct seq_file *seq, void *v, loff_t *pos) 747 { 748 ++*pos; 749 if (*pos < CONFIG_KFENCE_NUM_OBJECTS) 750 return (void *)((long)*pos + 1); 751 return NULL; 752 } 753 754 static int show_object(struct seq_file *seq, void *v) 755 { 756 struct kfence_metadata *meta = &kfence_metadata[(long)v - 1]; 757 unsigned long flags; 758 759 raw_spin_lock_irqsave(&meta->lock, flags); 760 kfence_print_object(seq, meta); 761 raw_spin_unlock_irqrestore(&meta->lock, flags); 762 seq_puts(seq, "---------------------------------\n"); 763 764 return 0; 765 } 766 767 static const struct seq_operations objects_sops = { 768 .start = start_object, 769 .next = next_object, 770 .stop = stop_object, 771 .show = show_object, 772 }; 773 DEFINE_SEQ_ATTRIBUTE(objects); 774 775 static int kfence_debugfs_init(void) 776 { 777 struct dentry *kfence_dir; 778 779 if (!READ_ONCE(kfence_enabled)) 780 return 0; 781 782 kfence_dir = debugfs_create_dir("kfence", NULL); 783 debugfs_create_file("stats", 0444, kfence_dir, NULL, &stats_fops); 784 debugfs_create_file("objects", 0400, kfence_dir, NULL, &objects_fops); 785 return 0; 786 } 787 788 late_initcall(kfence_debugfs_init); 789 790 /* === Panic Notifier ====================================================== */ 791 792 static void kfence_check_all_canary(void) 793 { 794 int i; 795 796 for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { 797 struct kfence_metadata *meta = &kfence_metadata[i]; 798 799 if (kfence_obj_allocated(meta)) 800 check_canary(meta); 801 } 802 } 803 804 static int kfence_check_canary_callback(struct notifier_block *nb, 805 unsigned long reason, void *arg) 806 { 807 kfence_check_all_canary(); 808 return NOTIFY_OK; 809 } 810 811 static struct notifier_block kfence_check_canary_notifier = { 812 .notifier_call = kfence_check_canary_callback, 813 }; 814 815 /* === Allocation Gate Timer ================================================ */ 816 817 static struct delayed_work kfence_timer; 818 819 #ifdef CONFIG_KFENCE_STATIC_KEYS 820 /* Wait queue to wake up allocation-gate timer task. */ 821 static DECLARE_WAIT_QUEUE_HEAD(allocation_wait); 822 823 static void wake_up_kfence_timer(struct irq_work *work) 824 { 825 wake_up(&allocation_wait); 826 } 827 static DEFINE_IRQ_WORK(wake_up_kfence_timer_work, wake_up_kfence_timer); 828 #endif 829 830 /* 831 * Set up delayed work, which will enable and disable the static key. We need to 832 * use a work queue (rather than a simple timer), since enabling and disabling a 833 * static key cannot be done from an interrupt. 834 * 835 * Note: Toggling a static branch currently causes IPIs, and here we'll end up 836 * with a total of 2 IPIs to all CPUs. If this ends up a problem in future (with 837 * more aggressive sampling intervals), we could get away with a variant that 838 * avoids IPIs, at the cost of not immediately capturing allocations if the 839 * instructions remain cached. 840 */ 841 static void toggle_allocation_gate(struct work_struct *work) 842 { 843 if (!READ_ONCE(kfence_enabled)) 844 return; 845 846 atomic_set(&kfence_allocation_gate, -kfence_burst); 847 #ifdef CONFIG_KFENCE_STATIC_KEYS 848 /* Enable static key, and await allocation to happen. */ 849 static_branch_enable(&kfence_allocation_key); 850 851 wait_event_idle(allocation_wait, atomic_read(&kfence_allocation_gate) > 0); 852 853 /* Disable static key and reset timer. */ 854 static_branch_disable(&kfence_allocation_key); 855 #endif 856 queue_delayed_work(system_unbound_wq, &kfence_timer, 857 msecs_to_jiffies(kfence_sample_interval)); 858 } 859 860 /* === Public interface ===================================================== */ 861 862 void __init kfence_alloc_pool_and_metadata(void) 863 { 864 if (!kfence_sample_interval) 865 return; 866 867 /* 868 * If the pool has already been initialized by arch, there is no need to 869 * re-allocate the memory pool. 870 */ 871 if (!__kfence_pool) 872 __kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); 873 874 if (!__kfence_pool) { 875 pr_err("failed to allocate pool\n"); 876 return; 877 } 878 879 /* The memory allocated by memblock has been zeroed out. */ 880 kfence_metadata_init = memblock_alloc(KFENCE_METADATA_SIZE, PAGE_SIZE); 881 if (!kfence_metadata_init) { 882 pr_err("failed to allocate metadata\n"); 883 memblock_free(__kfence_pool, KFENCE_POOL_SIZE); 884 __kfence_pool = NULL; 885 } 886 } 887 888 static void kfence_init_enable(void) 889 { 890 if (!IS_ENABLED(CONFIG_KFENCE_STATIC_KEYS)) 891 static_branch_enable(&kfence_allocation_key); 892 893 if (kfence_deferrable) 894 INIT_DEFERRABLE_WORK(&kfence_timer, toggle_allocation_gate); 895 else 896 INIT_DELAYED_WORK(&kfence_timer, toggle_allocation_gate); 897 898 if (kfence_check_on_panic) 899 atomic_notifier_chain_register(&panic_notifier_list, &kfence_check_canary_notifier); 900 901 WRITE_ONCE(kfence_enabled, true); 902 queue_delayed_work(system_unbound_wq, &kfence_timer, 0); 903 904 pr_info("initialized - using %lu bytes for %d objects at 0x%p-0x%p\n", KFENCE_POOL_SIZE, 905 CONFIG_KFENCE_NUM_OBJECTS, (void *)__kfence_pool, 906 (void *)(__kfence_pool + KFENCE_POOL_SIZE)); 907 } 908 909 void __init kfence_init(void) 910 { 911 stack_hash_seed = get_random_u32(); 912 913 /* Setting kfence_sample_interval to 0 on boot disables KFENCE. */ 914 if (!kfence_sample_interval) 915 return; 916 917 if (!kfence_init_pool_early()) { 918 pr_err("%s failed\n", __func__); 919 return; 920 } 921 922 kfence_init_enable(); 923 } 924 925 static int kfence_init_late(void) 926 { 927 const unsigned long nr_pages_pool = KFENCE_POOL_SIZE / PAGE_SIZE; 928 const unsigned long nr_pages_meta = KFENCE_METADATA_SIZE / PAGE_SIZE; 929 unsigned long addr = (unsigned long)__kfence_pool; 930 unsigned long free_size = KFENCE_POOL_SIZE; 931 int err = -ENOMEM; 932 933 #ifdef CONFIG_CONTIG_ALLOC 934 struct page *pages; 935 936 pages = alloc_contig_pages(nr_pages_pool, GFP_KERNEL, first_online_node, 937 NULL); 938 if (!pages) 939 return -ENOMEM; 940 941 __kfence_pool = page_to_virt(pages); 942 pages = alloc_contig_pages(nr_pages_meta, GFP_KERNEL, first_online_node, 943 NULL); 944 if (pages) 945 kfence_metadata_init = page_to_virt(pages); 946 #else 947 if (nr_pages_pool > MAX_ORDER_NR_PAGES || 948 nr_pages_meta > MAX_ORDER_NR_PAGES) { 949 pr_warn("KFENCE_NUM_OBJECTS too large for buddy allocator\n"); 950 return -EINVAL; 951 } 952 953 __kfence_pool = alloc_pages_exact(KFENCE_POOL_SIZE, GFP_KERNEL); 954 if (!__kfence_pool) 955 return -ENOMEM; 956 957 kfence_metadata_init = alloc_pages_exact(KFENCE_METADATA_SIZE, GFP_KERNEL); 958 #endif 959 960 if (!kfence_metadata_init) 961 goto free_pool; 962 963 memzero_explicit(kfence_metadata_init, KFENCE_METADATA_SIZE); 964 addr = kfence_init_pool(); 965 if (!addr) { 966 kfence_init_enable(); 967 kfence_debugfs_init(); 968 return 0; 969 } 970 971 pr_err("%s failed\n", __func__); 972 free_size = KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool); 973 err = -EBUSY; 974 975 #ifdef CONFIG_CONTIG_ALLOC 976 free_contig_range(page_to_pfn(virt_to_page((void *)kfence_metadata_init)), 977 nr_pages_meta); 978 free_pool: 979 free_contig_range(page_to_pfn(virt_to_page((void *)addr)), 980 free_size / PAGE_SIZE); 981 #else 982 free_pages_exact((void *)kfence_metadata_init, KFENCE_METADATA_SIZE); 983 free_pool: 984 free_pages_exact((void *)addr, free_size); 985 #endif 986 987 kfence_metadata_init = NULL; 988 __kfence_pool = NULL; 989 return err; 990 } 991 992 static int kfence_enable_late(void) 993 { 994 if (!__kfence_pool) 995 return kfence_init_late(); 996 997 WRITE_ONCE(kfence_enabled, true); 998 queue_delayed_work(system_unbound_wq, &kfence_timer, 0); 999 pr_info("re-enabled\n"); 1000 return 0; 1001 } 1002 1003 void kfence_shutdown_cache(struct kmem_cache *s) 1004 { 1005 unsigned long flags; 1006 struct kfence_metadata *meta; 1007 int i; 1008 1009 /* Pairs with release in kfence_init_pool(). */ 1010 if (!smp_load_acquire(&kfence_metadata)) 1011 return; 1012 1013 for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { 1014 bool in_use; 1015 1016 meta = &kfence_metadata[i]; 1017 1018 /* 1019 * If we observe some inconsistent cache and state pair where we 1020 * should have returned false here, cache destruction is racing 1021 * with either kmem_cache_alloc() or kmem_cache_free(). Taking 1022 * the lock will not help, as different critical section 1023 * serialization will have the same outcome. 1024 */ 1025 if (READ_ONCE(meta->cache) != s || !kfence_obj_allocated(meta)) 1026 continue; 1027 1028 raw_spin_lock_irqsave(&meta->lock, flags); 1029 in_use = meta->cache == s && kfence_obj_allocated(meta); 1030 raw_spin_unlock_irqrestore(&meta->lock, flags); 1031 1032 if (in_use) { 1033 /* 1034 * This cache still has allocations, and we should not 1035 * release them back into the freelist so they can still 1036 * safely be used and retain the kernel's default 1037 * behaviour of keeping the allocations alive (leak the 1038 * cache); however, they effectively become "zombie 1039 * allocations" as the KFENCE objects are the only ones 1040 * still in use and the owning cache is being destroyed. 1041 * 1042 * We mark them freed, so that any subsequent use shows 1043 * more useful error messages that will include stack 1044 * traces of the user of the object, the original 1045 * allocation, and caller to shutdown_cache(). 1046 */ 1047 kfence_guarded_free((void *)meta->addr, meta, /*zombie=*/true); 1048 } 1049 } 1050 1051 for (i = 0; i < CONFIG_KFENCE_NUM_OBJECTS; i++) { 1052 meta = &kfence_metadata[i]; 1053 1054 /* See above. */ 1055 if (READ_ONCE(meta->cache) != s || READ_ONCE(meta->state) != KFENCE_OBJECT_FREED) 1056 continue; 1057 1058 raw_spin_lock_irqsave(&meta->lock, flags); 1059 if (meta->cache == s && meta->state == KFENCE_OBJECT_FREED) 1060 meta->cache = NULL; 1061 raw_spin_unlock_irqrestore(&meta->lock, flags); 1062 } 1063 } 1064 1065 void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) 1066 { 1067 unsigned long stack_entries[KFENCE_STACK_DEPTH]; 1068 size_t num_stack_entries; 1069 u32 alloc_stack_hash; 1070 int allocation_gate; 1071 1072 /* 1073 * Perform size check before switching kfence_allocation_gate, so that 1074 * we don't disable KFENCE without making an allocation. 1075 */ 1076 if (size > PAGE_SIZE) { 1077 atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]); 1078 return NULL; 1079 } 1080 1081 /* 1082 * Skip allocations from non-default zones, including DMA. We cannot 1083 * guarantee that pages in the KFENCE pool will have the requested 1084 * properties (e.g. reside in DMAable memory). 1085 */ 1086 if ((flags & GFP_ZONEMASK) || 1087 (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32))) { 1088 atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_INCOMPAT]); 1089 return NULL; 1090 } 1091 1092 /* 1093 * Skip allocations for this slab, if KFENCE has been disabled for 1094 * this slab. 1095 */ 1096 if (s->flags & SLAB_SKIP_KFENCE) 1097 return NULL; 1098 1099 allocation_gate = atomic_inc_return(&kfence_allocation_gate); 1100 if (allocation_gate > 1) 1101 return NULL; 1102 #ifdef CONFIG_KFENCE_STATIC_KEYS 1103 /* 1104 * waitqueue_active() is fully ordered after the update of 1105 * kfence_allocation_gate per atomic_inc_return(). 1106 */ 1107 if (allocation_gate == 1 && waitqueue_active(&allocation_wait)) { 1108 /* 1109 * Calling wake_up() here may deadlock when allocations happen 1110 * from within timer code. Use an irq_work to defer it. 1111 */ 1112 irq_work_queue(&wake_up_kfence_timer_work); 1113 } 1114 #endif 1115 1116 if (!READ_ONCE(kfence_enabled)) 1117 return NULL; 1118 1119 num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 0); 1120 1121 /* 1122 * Do expensive check for coverage of allocation in slow-path after 1123 * allocation_gate has already become non-zero, even though it might 1124 * mean not making any allocation within a given sample interval. 1125 * 1126 * This ensures reasonable allocation coverage when the pool is almost 1127 * full, including avoiding long-lived allocations of the same source 1128 * filling up the pool (e.g. pagecache allocations). 1129 */ 1130 alloc_stack_hash = get_alloc_stack_hash(stack_entries, num_stack_entries); 1131 if (should_skip_covered() && alloc_covered_contains(alloc_stack_hash)) { 1132 atomic_long_inc(&counters[KFENCE_COUNTER_SKIP_COVERED]); 1133 return NULL; 1134 } 1135 1136 return kfence_guarded_alloc(s, size, flags, stack_entries, num_stack_entries, 1137 alloc_stack_hash); 1138 } 1139 1140 size_t kfence_ksize(const void *addr) 1141 { 1142 const struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr); 1143 1144 /* 1145 * Read locklessly -- if there is a race with __kfence_alloc(), this is 1146 * either a use-after-free or invalid access. 1147 */ 1148 return meta ? meta->size : 0; 1149 } 1150 1151 void *kfence_object_start(const void *addr) 1152 { 1153 const struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr); 1154 1155 /* 1156 * Read locklessly -- if there is a race with __kfence_alloc(), this is 1157 * either a use-after-free or invalid access. 1158 */ 1159 return meta ? (void *)meta->addr : NULL; 1160 } 1161 1162 void __kfence_free(void *addr) 1163 { 1164 struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr); 1165 1166 #ifdef CONFIG_MEMCG 1167 KFENCE_WARN_ON(meta->obj_exts.objcg); 1168 #endif 1169 /* 1170 * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing 1171 * the object, as the object page may be recycled for other-typed 1172 * objects once it has been freed. meta->cache may be NULL if the cache 1173 * was destroyed. 1174 * Save the stack trace here so that reports show where the user freed 1175 * the object. 1176 */ 1177 if (unlikely(meta->cache && (meta->cache->flags & SLAB_TYPESAFE_BY_RCU))) { 1178 unsigned long flags; 1179 1180 raw_spin_lock_irqsave(&meta->lock, flags); 1181 metadata_update_state(meta, KFENCE_OBJECT_RCU_FREEING, NULL, 0); 1182 raw_spin_unlock_irqrestore(&meta->lock, flags); 1183 call_rcu(&meta->rcu_head, rcu_guarded_free); 1184 } else { 1185 kfence_guarded_free(addr, meta, false); 1186 } 1187 } 1188 1189 bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs *regs) 1190 { 1191 const int page_index = (addr - (unsigned long)__kfence_pool) / PAGE_SIZE; 1192 struct kfence_metadata *to_report = NULL; 1193 enum kfence_error_type error_type; 1194 unsigned long flags; 1195 1196 if (!is_kfence_address((void *)addr)) 1197 return false; 1198 1199 if (!READ_ONCE(kfence_enabled)) /* If disabled at runtime ... */ 1200 return kfence_unprotect(addr); /* ... unprotect and proceed. */ 1201 1202 atomic_long_inc(&counters[KFENCE_COUNTER_BUGS]); 1203 1204 if (page_index % 2) { 1205 /* This is a redzone, report a buffer overflow. */ 1206 struct kfence_metadata *meta; 1207 int distance = 0; 1208 1209 meta = addr_to_metadata(addr - PAGE_SIZE); 1210 if (meta && kfence_obj_allocated(meta)) { 1211 to_report = meta; 1212 /* Data race ok; distance calculation approximate. */ 1213 distance = addr - data_race(meta->addr + meta->size); 1214 } 1215 1216 meta = addr_to_metadata(addr + PAGE_SIZE); 1217 if (meta && kfence_obj_allocated(meta)) { 1218 /* Data race ok; distance calculation approximate. */ 1219 if (!to_report || distance > data_race(meta->addr) - addr) 1220 to_report = meta; 1221 } 1222 1223 if (!to_report) 1224 goto out; 1225 1226 raw_spin_lock_irqsave(&to_report->lock, flags); 1227 to_report->unprotected_page = addr; 1228 error_type = KFENCE_ERROR_OOB; 1229 1230 /* 1231 * If the object was freed before we took the look we can still 1232 * report this as an OOB -- the report will simply show the 1233 * stacktrace of the free as well. 1234 */ 1235 } else { 1236 to_report = addr_to_metadata(addr); 1237 if (!to_report) 1238 goto out; 1239 1240 raw_spin_lock_irqsave(&to_report->lock, flags); 1241 error_type = KFENCE_ERROR_UAF; 1242 /* 1243 * We may race with __kfence_alloc(), and it is possible that a 1244 * freed object may be reallocated. We simply report this as a 1245 * use-after-free, with the stack trace showing the place where 1246 * the object was re-allocated. 1247 */ 1248 } 1249 1250 out: 1251 if (to_report) { 1252 kfence_report_error(addr, is_write, regs, to_report, error_type); 1253 raw_spin_unlock_irqrestore(&to_report->lock, flags); 1254 } else { 1255 /* This may be a UAF or OOB access, but we can't be sure. */ 1256 kfence_report_error(addr, is_write, regs, NULL, KFENCE_ERROR_INVALID); 1257 } 1258 1259 return kfence_unprotect(addr); /* Unprotect and let access proceed. */ 1260 } 1261