1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains common generic and tag-based KASAN error reporting 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/bitops.h> 18 #include <linux/ftrace.h> 19 #include <linux/init.h> 20 #include <linux/kernel.h> 21 #include <linux/mm.h> 22 #include <linux/printk.h> 23 #include <linux/sched.h> 24 #include <linux/slab.h> 25 #include <linux/stackdepot.h> 26 #include <linux/stacktrace.h> 27 #include <linux/string.h> 28 #include <linux/types.h> 29 #include <linux/kasan.h> 30 #include <linux/module.h> 31 #include <linux/sched/task_stack.h> 32 #include <linux/uaccess.h> 33 34 #include <asm/sections.h> 35 36 #include <kunit/test.h> 37 38 #include "kasan.h" 39 #include "../slab.h" 40 41 /* Shadow layout customization. */ 42 #define SHADOW_BYTES_PER_BLOCK 1 43 #define SHADOW_BLOCKS_PER_ROW 16 44 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 45 #define SHADOW_ROWS_AROUND_ADDR 2 46 47 static unsigned long kasan_flags; 48 49 #define KASAN_BIT_REPORTED 0 50 #define KASAN_BIT_MULTI_SHOT 1 51 52 bool kasan_save_enable_multi_shot(void) 53 { 54 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 55 } 56 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 57 58 void kasan_restore_multi_shot(bool enabled) 59 { 60 if (!enabled) 61 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 62 } 63 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 64 65 static int __init kasan_set_multi_shot(char *str) 66 { 67 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 68 return 1; 69 } 70 __setup("kasan_multi_shot", kasan_set_multi_shot); 71 72 static void print_error_description(struct kasan_access_info *info) 73 { 74 pr_err("BUG: KASAN: %s in %pS\n", 75 get_bug_type(info), (void *)info->ip); 76 pr_err("%s of size %zu at addr %px by task %s/%d\n", 77 info->is_write ? "Write" : "Read", info->access_size, 78 info->access_addr, current->comm, task_pid_nr(current)); 79 } 80 81 static DEFINE_SPINLOCK(report_lock); 82 83 static void start_report(unsigned long *flags) 84 { 85 /* 86 * Make sure we don't end up in loop. 87 */ 88 kasan_disable_current(); 89 spin_lock_irqsave(&report_lock, *flags); 90 pr_err("==================================================================\n"); 91 } 92 93 static void end_report(unsigned long *flags) 94 { 95 pr_err("==================================================================\n"); 96 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 97 spin_unlock_irqrestore(&report_lock, *flags); 98 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) { 99 /* 100 * This thread may hit another WARN() in the panic path. 101 * Resetting this prevents additional WARN() from panicking the 102 * system on this thread. Other threads are blocked by the 103 * panic_mutex in panic(). 104 */ 105 panic_on_warn = 0; 106 panic("panic_on_warn set ...\n"); 107 } 108 kasan_enable_current(); 109 } 110 111 static void print_stack(depot_stack_handle_t stack) 112 { 113 unsigned long *entries; 114 unsigned int nr_entries; 115 116 nr_entries = stack_depot_fetch(stack, &entries); 117 stack_trace_print(entries, nr_entries, 0); 118 } 119 120 static void print_track(struct kasan_track *track, const char *prefix) 121 { 122 pr_err("%s by task %u:\n", prefix, track->pid); 123 if (track->stack) { 124 print_stack(track->stack); 125 } else { 126 pr_err("(stack is not available)\n"); 127 } 128 } 129 130 struct page *kasan_addr_to_page(const void *addr) 131 { 132 if ((addr >= (void *)PAGE_OFFSET) && 133 (addr < high_memory)) 134 return virt_to_head_page(addr); 135 return NULL; 136 } 137 138 static void describe_object_addr(struct kmem_cache *cache, void *object, 139 const void *addr) 140 { 141 unsigned long access_addr = (unsigned long)addr; 142 unsigned long object_addr = (unsigned long)object; 143 const char *rel_type; 144 int rel_bytes; 145 146 pr_err("The buggy address belongs to the object at %px\n" 147 " which belongs to the cache %s of size %d\n", 148 object, cache->name, cache->object_size); 149 150 if (!addr) 151 return; 152 153 if (access_addr < object_addr) { 154 rel_type = "to the left"; 155 rel_bytes = object_addr - access_addr; 156 } else if (access_addr >= object_addr + cache->object_size) { 157 rel_type = "to the right"; 158 rel_bytes = access_addr - (object_addr + cache->object_size); 159 } else { 160 rel_type = "inside"; 161 rel_bytes = access_addr - object_addr; 162 } 163 164 pr_err("The buggy address is located %d bytes %s of\n" 165 " %d-byte region [%px, %px)\n", 166 rel_bytes, rel_type, cache->object_size, (void *)object_addr, 167 (void *)(object_addr + cache->object_size)); 168 } 169 170 static void describe_object(struct kmem_cache *cache, void *object, 171 const void *addr, u8 tag) 172 { 173 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 174 175 if (cache->flags & SLAB_KASAN) { 176 struct kasan_track *free_track; 177 178 print_track(&alloc_info->alloc_track, "Allocated"); 179 pr_err("\n"); 180 free_track = kasan_get_free_track(cache, object, tag); 181 if (free_track) { 182 print_track(free_track, "Freed"); 183 pr_err("\n"); 184 } 185 186 #ifdef CONFIG_KASAN_GENERIC 187 if (alloc_info->aux_stack[0]) { 188 pr_err("Last call_rcu():\n"); 189 print_stack(alloc_info->aux_stack[0]); 190 pr_err("\n"); 191 } 192 if (alloc_info->aux_stack[1]) { 193 pr_err("Second to last call_rcu():\n"); 194 print_stack(alloc_info->aux_stack[1]); 195 pr_err("\n"); 196 } 197 #endif 198 } 199 200 describe_object_addr(cache, object, addr); 201 } 202 203 static inline bool kernel_or_module_addr(const void *addr) 204 { 205 if (addr >= (void *)_stext && addr < (void *)_end) 206 return true; 207 if (is_module_address((unsigned long)addr)) 208 return true; 209 return false; 210 } 211 212 static inline bool init_task_stack_addr(const void *addr) 213 { 214 return addr >= (void *)&init_thread_union.stack && 215 (addr <= (void *)&init_thread_union.stack + 216 sizeof(init_thread_union.stack)); 217 } 218 219 static bool __must_check tokenize_frame_descr(const char **frame_descr, 220 char *token, size_t max_tok_len, 221 unsigned long *value) 222 { 223 const char *sep = strchr(*frame_descr, ' '); 224 225 if (sep == NULL) 226 sep = *frame_descr + strlen(*frame_descr); 227 228 if (token != NULL) { 229 const size_t tok_len = sep - *frame_descr; 230 231 if (tok_len + 1 > max_tok_len) { 232 pr_err("KASAN internal error: frame description too long: %s\n", 233 *frame_descr); 234 return false; 235 } 236 237 /* Copy token (+ 1 byte for '\0'). */ 238 strlcpy(token, *frame_descr, tok_len + 1); 239 } 240 241 /* Advance frame_descr past separator. */ 242 *frame_descr = sep + 1; 243 244 if (value != NULL && kstrtoul(token, 10, value)) { 245 pr_err("KASAN internal error: not a valid number: %s\n", token); 246 return false; 247 } 248 249 return true; 250 } 251 252 static void print_decoded_frame_descr(const char *frame_descr) 253 { 254 /* 255 * We need to parse the following string: 256 * "n alloc_1 alloc_2 ... alloc_n" 257 * where alloc_i looks like 258 * "offset size len name" 259 * or "offset size len name:line". 260 */ 261 262 char token[64]; 263 unsigned long num_objects; 264 265 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 266 &num_objects)) 267 return; 268 269 pr_err("\n"); 270 pr_err("this frame has %lu %s:\n", num_objects, 271 num_objects == 1 ? "object" : "objects"); 272 273 while (num_objects--) { 274 unsigned long offset; 275 unsigned long size; 276 277 /* access offset */ 278 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 279 &offset)) 280 return; 281 /* access size */ 282 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 283 &size)) 284 return; 285 /* name length (unused) */ 286 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL)) 287 return; 288 /* object name */ 289 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 290 NULL)) 291 return; 292 293 /* Strip line number; without filename it's not very helpful. */ 294 strreplace(token, ':', '\0'); 295 296 /* Finally, print object information. */ 297 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token); 298 } 299 } 300 301 static bool __must_check get_address_stack_frame_info(const void *addr, 302 unsigned long *offset, 303 const char **frame_descr, 304 const void **frame_pc) 305 { 306 unsigned long aligned_addr; 307 unsigned long mem_ptr; 308 const u8 *shadow_bottom; 309 const u8 *shadow_ptr; 310 const unsigned long *frame; 311 312 BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP)); 313 314 /* 315 * NOTE: We currently only support printing frame information for 316 * accesses to the task's own stack. 317 */ 318 if (!object_is_on_stack(addr)) 319 return false; 320 321 aligned_addr = round_down((unsigned long)addr, sizeof(long)); 322 mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE); 323 shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr); 324 shadow_bottom = kasan_mem_to_shadow(end_of_stack(current)); 325 326 while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) { 327 shadow_ptr--; 328 mem_ptr -= KASAN_SHADOW_SCALE_SIZE; 329 } 330 331 while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) { 332 shadow_ptr--; 333 mem_ptr -= KASAN_SHADOW_SCALE_SIZE; 334 } 335 336 if (shadow_ptr < shadow_bottom) 337 return false; 338 339 frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE); 340 if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) { 341 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n", 342 frame[0]); 343 return false; 344 } 345 346 *offset = (unsigned long)addr - (unsigned long)frame; 347 *frame_descr = (const char *)frame[1]; 348 *frame_pc = (void *)frame[2]; 349 350 return true; 351 } 352 353 static void print_address_stack_frame(const void *addr) 354 { 355 unsigned long offset; 356 const char *frame_descr; 357 const void *frame_pc; 358 359 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 360 return; 361 362 if (!get_address_stack_frame_info(addr, &offset, &frame_descr, 363 &frame_pc)) 364 return; 365 366 /* 367 * get_address_stack_frame_info only returns true if the given addr is 368 * on the current task's stack. 369 */ 370 pr_err("\n"); 371 pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n", 372 addr, current->comm, task_pid_nr(current), offset); 373 pr_err(" %pS\n", frame_pc); 374 375 if (!frame_descr) 376 return; 377 378 print_decoded_frame_descr(frame_descr); 379 } 380 381 static void print_address_description(void *addr, u8 tag) 382 { 383 struct page *page = kasan_addr_to_page(addr); 384 385 dump_stack(); 386 pr_err("\n"); 387 388 if (page && PageSlab(page)) { 389 struct kmem_cache *cache = page->slab_cache; 390 void *object = nearest_obj(cache, page, addr); 391 392 describe_object(cache, object, addr, tag); 393 } 394 395 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 396 pr_err("The buggy address belongs to the variable:\n"); 397 pr_err(" %pS\n", addr); 398 } 399 400 if (page) { 401 pr_err("The buggy address belongs to the page:\n"); 402 dump_page(page, "kasan: bad access detected"); 403 } 404 405 print_address_stack_frame(addr); 406 } 407 408 static bool row_is_guilty(const void *row, const void *guilty) 409 { 410 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 411 } 412 413 static int shadow_pointer_offset(const void *row, const void *shadow) 414 { 415 /* The length of ">ff00ff00ff00ff00: " is 416 * 3 + (BITS_PER_LONG/8)*2 chars. 417 */ 418 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 419 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 420 } 421 422 static void print_shadow_for_address(const void *addr) 423 { 424 int i; 425 const void *shadow = kasan_mem_to_shadow(addr); 426 const void *shadow_row; 427 428 shadow_row = (void *)round_down((unsigned long)shadow, 429 SHADOW_BYTES_PER_ROW) 430 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 431 432 pr_err("Memory state around the buggy address:\n"); 433 434 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 435 const void *kaddr = kasan_shadow_to_mem(shadow_row); 436 char buffer[4 + (BITS_PER_LONG/8)*2]; 437 char shadow_buf[SHADOW_BYTES_PER_ROW]; 438 439 snprintf(buffer, sizeof(buffer), 440 (i == 0) ? ">%px: " : " %px: ", kaddr); 441 /* 442 * We should not pass a shadow pointer to generic 443 * function, because generic functions may try to 444 * access kasan mapping for the passed address. 445 */ 446 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 447 print_hex_dump(KERN_ERR, buffer, 448 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 449 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 450 451 if (row_is_guilty(shadow_row, shadow)) 452 pr_err("%*c\n", 453 shadow_pointer_offset(shadow_row, shadow), 454 '^'); 455 456 shadow_row += SHADOW_BYTES_PER_ROW; 457 } 458 } 459 460 static bool report_enabled(void) 461 { 462 if (current->kasan_depth) 463 return false; 464 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 465 return true; 466 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 467 } 468 469 #if IS_ENABLED(CONFIG_KUNIT) 470 static void kasan_update_kunit_status(struct kunit *cur_test) 471 { 472 struct kunit_resource *resource; 473 struct kunit_kasan_expectation *kasan_data; 474 475 resource = kunit_find_named_resource(cur_test, "kasan_data"); 476 477 if (!resource) { 478 kunit_set_failure(cur_test); 479 return; 480 } 481 482 kasan_data = (struct kunit_kasan_expectation *)resource->data; 483 kasan_data->report_found = true; 484 kunit_put_resource(resource); 485 } 486 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 487 488 void kasan_report_invalid_free(void *object, unsigned long ip) 489 { 490 unsigned long flags; 491 u8 tag = get_tag(object); 492 493 object = reset_tag(object); 494 495 #if IS_ENABLED(CONFIG_KUNIT) 496 if (current->kunit_test) 497 kasan_update_kunit_status(current->kunit_test); 498 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 499 500 start_report(&flags); 501 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); 502 print_tags(tag, object); 503 pr_err("\n"); 504 print_address_description(object, tag); 505 pr_err("\n"); 506 print_shadow_for_address(object); 507 end_report(&flags); 508 } 509 510 static void __kasan_report(unsigned long addr, size_t size, bool is_write, 511 unsigned long ip) 512 { 513 struct kasan_access_info info; 514 void *tagged_addr; 515 void *untagged_addr; 516 unsigned long flags; 517 518 #if IS_ENABLED(CONFIG_KUNIT) 519 if (current->kunit_test) 520 kasan_update_kunit_status(current->kunit_test); 521 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 522 523 disable_trace_on_warning(); 524 525 tagged_addr = (void *)addr; 526 untagged_addr = reset_tag(tagged_addr); 527 528 info.access_addr = tagged_addr; 529 if (addr_has_shadow(untagged_addr)) 530 info.first_bad_addr = find_first_bad_addr(tagged_addr, size); 531 else 532 info.first_bad_addr = untagged_addr; 533 info.access_size = size; 534 info.is_write = is_write; 535 info.ip = ip; 536 537 start_report(&flags); 538 539 print_error_description(&info); 540 if (addr_has_shadow(untagged_addr)) 541 print_tags(get_tag(tagged_addr), info.first_bad_addr); 542 pr_err("\n"); 543 544 if (addr_has_shadow(untagged_addr)) { 545 print_address_description(untagged_addr, get_tag(tagged_addr)); 546 pr_err("\n"); 547 print_shadow_for_address(info.first_bad_addr); 548 } else { 549 dump_stack(); 550 } 551 552 end_report(&flags); 553 } 554 555 bool kasan_report(unsigned long addr, size_t size, bool is_write, 556 unsigned long ip) 557 { 558 unsigned long flags = user_access_save(); 559 bool ret = false; 560 561 if (likely(report_enabled())) { 562 __kasan_report(addr, size, is_write, ip); 563 ret = true; 564 } 565 566 user_access_restore(flags); 567 568 return ret; 569 } 570 571 #ifdef CONFIG_KASAN_INLINE 572 /* 573 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high 574 * canonical half of the address space) cause out-of-bounds shadow memory reads 575 * before the actual access. For addresses in the low canonical half of the 576 * address space, as well as most non-canonical addresses, that out-of-bounds 577 * shadow memory access lands in the non-canonical part of the address space. 578 * Help the user figure out what the original bogus pointer was. 579 */ 580 void kasan_non_canonical_hook(unsigned long addr) 581 { 582 unsigned long orig_addr; 583 const char *bug_type; 584 585 if (addr < KASAN_SHADOW_OFFSET) 586 return; 587 588 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT; 589 /* 590 * For faults near the shadow address for NULL, we can be fairly certain 591 * that this is a KASAN shadow memory access. 592 * For faults that correspond to shadow for low canonical addresses, we 593 * can still be pretty sure - that shadow region is a fairly narrow 594 * chunk of the non-canonical address space. 595 * But faults that look like shadow for non-canonical addresses are a 596 * really large chunk of the address space. In that case, we still 597 * print the decoded address, but make it clear that this is not 598 * necessarily what's actually going on. 599 */ 600 if (orig_addr < PAGE_SIZE) 601 bug_type = "null-ptr-deref"; 602 else if (orig_addr < TASK_SIZE) 603 bug_type = "probably user-memory-access"; 604 else 605 bug_type = "maybe wild-memory-access"; 606 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type, 607 orig_addr, orig_addr + KASAN_SHADOW_MASK); 608 } 609 #endif 610