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