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