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 static struct page *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 void describe_object(struct kmem_cache *cache, void *object, 155 const void *addr) 156 { 157 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 158 159 if (cache->flags & SLAB_KASAN) { 160 print_track(&alloc_info->alloc_track, "Allocated"); 161 pr_err("\n"); 162 print_track(&alloc_info->free_track, "Freed"); 163 pr_err("\n"); 164 } 165 166 describe_object_addr(cache, object, addr); 167 } 168 169 static inline bool kernel_or_module_addr(const void *addr) 170 { 171 if (addr >= (void *)_stext && addr < (void *)_end) 172 return true; 173 if (is_module_address((unsigned long)addr)) 174 return true; 175 return false; 176 } 177 178 static inline bool init_task_stack_addr(const void *addr) 179 { 180 return addr >= (void *)&init_thread_union.stack && 181 (addr <= (void *)&init_thread_union.stack + 182 sizeof(init_thread_union.stack)); 183 } 184 185 static bool __must_check tokenize_frame_descr(const char **frame_descr, 186 char *token, size_t max_tok_len, 187 unsigned long *value) 188 { 189 const char *sep = strchr(*frame_descr, ' '); 190 191 if (sep == NULL) 192 sep = *frame_descr + strlen(*frame_descr); 193 194 if (token != NULL) { 195 const size_t tok_len = sep - *frame_descr; 196 197 if (tok_len + 1 > max_tok_len) { 198 pr_err("KASAN internal error: frame description too long: %s\n", 199 *frame_descr); 200 return false; 201 } 202 203 /* Copy token (+ 1 byte for '\0'). */ 204 strlcpy(token, *frame_descr, tok_len + 1); 205 } 206 207 /* Advance frame_descr past separator. */ 208 *frame_descr = sep + 1; 209 210 if (value != NULL && kstrtoul(token, 10, value)) { 211 pr_err("KASAN internal error: not a valid number: %s\n", token); 212 return false; 213 } 214 215 return true; 216 } 217 218 static void print_decoded_frame_descr(const char *frame_descr) 219 { 220 /* 221 * We need to parse the following string: 222 * "n alloc_1 alloc_2 ... alloc_n" 223 * where alloc_i looks like 224 * "offset size len name" 225 * or "offset size len name:line". 226 */ 227 228 char token[64]; 229 unsigned long num_objects; 230 231 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 232 &num_objects)) 233 return; 234 235 pr_err("\n"); 236 pr_err("this frame has %lu %s:\n", num_objects, 237 num_objects == 1 ? "object" : "objects"); 238 239 while (num_objects--) { 240 unsigned long offset; 241 unsigned long size; 242 243 /* access offset */ 244 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 245 &offset)) 246 return; 247 /* access size */ 248 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 249 &size)) 250 return; 251 /* name length (unused) */ 252 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL)) 253 return; 254 /* object name */ 255 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 256 NULL)) 257 return; 258 259 /* Strip line number; without filename it's not very helpful. */ 260 strreplace(token, ':', '\0'); 261 262 /* Finally, print object information. */ 263 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token); 264 } 265 } 266 267 static bool __must_check get_address_stack_frame_info(const void *addr, 268 unsigned long *offset, 269 const char **frame_descr, 270 const void **frame_pc) 271 { 272 unsigned long aligned_addr; 273 unsigned long mem_ptr; 274 const u8 *shadow_bottom; 275 const u8 *shadow_ptr; 276 const unsigned long *frame; 277 278 BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP)); 279 280 /* 281 * NOTE: We currently only support printing frame information for 282 * accesses to the task's own stack. 283 */ 284 if (!object_is_on_stack(addr)) 285 return false; 286 287 aligned_addr = round_down((unsigned long)addr, sizeof(long)); 288 mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE); 289 shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr); 290 shadow_bottom = kasan_mem_to_shadow(end_of_stack(current)); 291 292 while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) { 293 shadow_ptr--; 294 mem_ptr -= KASAN_SHADOW_SCALE_SIZE; 295 } 296 297 while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) { 298 shadow_ptr--; 299 mem_ptr -= KASAN_SHADOW_SCALE_SIZE; 300 } 301 302 if (shadow_ptr < shadow_bottom) 303 return false; 304 305 frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE); 306 if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) { 307 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n", 308 frame[0]); 309 return false; 310 } 311 312 *offset = (unsigned long)addr - (unsigned long)frame; 313 *frame_descr = (const char *)frame[1]; 314 *frame_pc = (void *)frame[2]; 315 316 return true; 317 } 318 319 static void print_address_stack_frame(const void *addr) 320 { 321 unsigned long offset; 322 const char *frame_descr; 323 const void *frame_pc; 324 325 if (IS_ENABLED(CONFIG_KASAN_SW_TAGS)) 326 return; 327 328 if (!get_address_stack_frame_info(addr, &offset, &frame_descr, 329 &frame_pc)) 330 return; 331 332 /* 333 * get_address_stack_frame_info only returns true if the given addr is 334 * on the current task's stack. 335 */ 336 pr_err("\n"); 337 pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n", 338 addr, current->comm, task_pid_nr(current), offset); 339 pr_err(" %pS\n", frame_pc); 340 341 if (!frame_descr) 342 return; 343 344 print_decoded_frame_descr(frame_descr); 345 } 346 347 static void print_address_description(void *addr) 348 { 349 struct page *page = addr_to_page(addr); 350 351 dump_stack(); 352 pr_err("\n"); 353 354 if (page && PageSlab(page)) { 355 struct kmem_cache *cache = page->slab_cache; 356 void *object = nearest_obj(cache, page, addr); 357 358 describe_object(cache, object, addr); 359 } 360 361 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 362 pr_err("The buggy address belongs to the variable:\n"); 363 pr_err(" %pS\n", addr); 364 } 365 366 if (page) { 367 pr_err("The buggy address belongs to the page:\n"); 368 dump_page(page, "kasan: bad access detected"); 369 } 370 371 print_address_stack_frame(addr); 372 } 373 374 static bool row_is_guilty(const void *row, const void *guilty) 375 { 376 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 377 } 378 379 static int shadow_pointer_offset(const void *row, const void *shadow) 380 { 381 /* The length of ">ff00ff00ff00ff00: " is 382 * 3 + (BITS_PER_LONG/8)*2 chars. 383 */ 384 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 385 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 386 } 387 388 static void print_shadow_for_address(const void *addr) 389 { 390 int i; 391 const void *shadow = kasan_mem_to_shadow(addr); 392 const void *shadow_row; 393 394 shadow_row = (void *)round_down((unsigned long)shadow, 395 SHADOW_BYTES_PER_ROW) 396 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 397 398 pr_err("Memory state around the buggy address:\n"); 399 400 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 401 const void *kaddr = kasan_shadow_to_mem(shadow_row); 402 char buffer[4 + (BITS_PER_LONG/8)*2]; 403 char shadow_buf[SHADOW_BYTES_PER_ROW]; 404 405 snprintf(buffer, sizeof(buffer), 406 (i == 0) ? ">%px: " : " %px: ", kaddr); 407 /* 408 * We should not pass a shadow pointer to generic 409 * function, because generic functions may try to 410 * access kasan mapping for the passed address. 411 */ 412 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 413 print_hex_dump(KERN_ERR, buffer, 414 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 415 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 416 417 if (row_is_guilty(shadow_row, shadow)) 418 pr_err("%*c\n", 419 shadow_pointer_offset(shadow_row, shadow), 420 '^'); 421 422 shadow_row += SHADOW_BYTES_PER_ROW; 423 } 424 } 425 426 static bool report_enabled(void) 427 { 428 if (current->kasan_depth) 429 return false; 430 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 431 return true; 432 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 433 } 434 435 void kasan_report_invalid_free(void *object, unsigned long ip) 436 { 437 unsigned long flags; 438 439 start_report(&flags); 440 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); 441 print_tags(get_tag(object), reset_tag(object)); 442 object = reset_tag(object); 443 pr_err("\n"); 444 print_address_description(object); 445 pr_err("\n"); 446 print_shadow_for_address(object); 447 end_report(&flags); 448 } 449 450 void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) 451 { 452 struct kasan_access_info info; 453 void *tagged_addr; 454 void *untagged_addr; 455 unsigned long flags; 456 457 if (likely(!report_enabled())) 458 return; 459 460 disable_trace_on_warning(); 461 462 tagged_addr = (void *)addr; 463 untagged_addr = reset_tag(tagged_addr); 464 465 info.access_addr = tagged_addr; 466 if (addr_has_shadow(untagged_addr)) 467 info.first_bad_addr = find_first_bad_addr(tagged_addr, size); 468 else 469 info.first_bad_addr = untagged_addr; 470 info.access_size = size; 471 info.is_write = is_write; 472 info.ip = ip; 473 474 start_report(&flags); 475 476 print_error_description(&info); 477 if (addr_has_shadow(untagged_addr)) 478 print_tags(get_tag(tagged_addr), info.first_bad_addr); 479 pr_err("\n"); 480 481 if (addr_has_shadow(untagged_addr)) { 482 print_address_description(untagged_addr); 483 pr_err("\n"); 484 print_shadow_for_address(info.first_bad_addr); 485 } else { 486 dump_stack(); 487 } 488 489 end_report(&flags); 490 } 491