1 /* 2 * This file contains error reporting code. 3 * 4 * Copyright (c) 2014 Samsung Electronics Co., Ltd. 5 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com> 6 * 7 * Some code borrowed from https://github.com/xairy/kasan-prototype by 8 * Andrey Konovalov <andreyknvl@gmail.com> 9 * 10 * This program is free software; you can redistribute it and/or modify 11 * it under the terms of the GNU General Public License version 2 as 12 * published by the Free Software Foundation. 13 * 14 */ 15 16 #include <linux/bitops.h> 17 #include <linux/ftrace.h> 18 #include <linux/init.h> 19 #include <linux/kernel.h> 20 #include <linux/mm.h> 21 #include <linux/printk.h> 22 #include <linux/sched.h> 23 #include <linux/slab.h> 24 #include <linux/stackdepot.h> 25 #include <linux/stacktrace.h> 26 #include <linux/string.h> 27 #include <linux/types.h> 28 #include <linux/kasan.h> 29 #include <linux/module.h> 30 31 #include <asm/sections.h> 32 33 #include "kasan.h" 34 #include "../slab.h" 35 36 /* Shadow layout customization. */ 37 #define SHADOW_BYTES_PER_BLOCK 1 38 #define SHADOW_BLOCKS_PER_ROW 16 39 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK) 40 #define SHADOW_ROWS_AROUND_ADDR 2 41 42 static const void *find_first_bad_addr(const void *addr, size_t size) 43 { 44 u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr); 45 const void *first_bad_addr = addr; 46 47 while (!shadow_val && first_bad_addr < addr + size) { 48 first_bad_addr += KASAN_SHADOW_SCALE_SIZE; 49 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr); 50 } 51 return first_bad_addr; 52 } 53 54 static bool addr_has_shadow(struct kasan_access_info *info) 55 { 56 return (info->access_addr >= 57 kasan_shadow_to_mem((void *)KASAN_SHADOW_START)); 58 } 59 60 static const char *get_shadow_bug_type(struct kasan_access_info *info) 61 { 62 const char *bug_type = "unknown-crash"; 63 u8 *shadow_addr; 64 65 info->first_bad_addr = find_first_bad_addr(info->access_addr, 66 info->access_size); 67 68 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); 69 70 /* 71 * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look 72 * at the next shadow byte to determine the type of the bad access. 73 */ 74 if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1) 75 shadow_addr++; 76 77 switch (*shadow_addr) { 78 case 0 ... KASAN_SHADOW_SCALE_SIZE - 1: 79 /* 80 * In theory it's still possible to see these shadow values 81 * due to a data race in the kernel code. 82 */ 83 bug_type = "out-of-bounds"; 84 break; 85 case KASAN_PAGE_REDZONE: 86 case KASAN_KMALLOC_REDZONE: 87 bug_type = "slab-out-of-bounds"; 88 break; 89 case KASAN_GLOBAL_REDZONE: 90 bug_type = "global-out-of-bounds"; 91 break; 92 case KASAN_STACK_LEFT: 93 case KASAN_STACK_MID: 94 case KASAN_STACK_RIGHT: 95 case KASAN_STACK_PARTIAL: 96 bug_type = "stack-out-of-bounds"; 97 break; 98 case KASAN_FREE_PAGE: 99 case KASAN_KMALLOC_FREE: 100 bug_type = "use-after-free"; 101 break; 102 case KASAN_USE_AFTER_SCOPE: 103 bug_type = "use-after-scope"; 104 break; 105 case KASAN_ALLOCA_LEFT: 106 case KASAN_ALLOCA_RIGHT: 107 bug_type = "alloca-out-of-bounds"; 108 break; 109 } 110 111 return bug_type; 112 } 113 114 static const char *get_wild_bug_type(struct kasan_access_info *info) 115 { 116 const char *bug_type = "unknown-crash"; 117 118 if ((unsigned long)info->access_addr < PAGE_SIZE) 119 bug_type = "null-ptr-deref"; 120 else if ((unsigned long)info->access_addr < TASK_SIZE) 121 bug_type = "user-memory-access"; 122 else 123 bug_type = "wild-memory-access"; 124 125 return bug_type; 126 } 127 128 static const char *get_bug_type(struct kasan_access_info *info) 129 { 130 if (addr_has_shadow(info)) 131 return get_shadow_bug_type(info); 132 return get_wild_bug_type(info); 133 } 134 135 static void print_error_description(struct kasan_access_info *info) 136 { 137 const char *bug_type = get_bug_type(info); 138 139 pr_err("BUG: KASAN: %s in %pS\n", 140 bug_type, (void *)info->ip); 141 pr_err("%s of size %zu at addr %px by task %s/%d\n", 142 info->is_write ? "Write" : "Read", info->access_size, 143 info->access_addr, current->comm, task_pid_nr(current)); 144 } 145 146 static inline bool kernel_or_module_addr(const void *addr) 147 { 148 if (addr >= (void *)_stext && addr < (void *)_end) 149 return true; 150 if (is_module_address((unsigned long)addr)) 151 return true; 152 return false; 153 } 154 155 static inline bool init_task_stack_addr(const void *addr) 156 { 157 return addr >= (void *)&init_thread_union.stack && 158 (addr <= (void *)&init_thread_union.stack + 159 sizeof(init_thread_union.stack)); 160 } 161 162 static DEFINE_SPINLOCK(report_lock); 163 164 static void kasan_start_report(unsigned long *flags) 165 { 166 /* 167 * Make sure we don't end up in loop. 168 */ 169 kasan_disable_current(); 170 spin_lock_irqsave(&report_lock, *flags); 171 pr_err("==================================================================\n"); 172 } 173 174 static void kasan_end_report(unsigned long *flags) 175 { 176 pr_err("==================================================================\n"); 177 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 178 spin_unlock_irqrestore(&report_lock, *flags); 179 if (panic_on_warn) 180 panic("panic_on_warn set ...\n"); 181 kasan_enable_current(); 182 } 183 184 static void print_track(struct kasan_track *track, const char *prefix) 185 { 186 pr_err("%s by task %u:\n", prefix, track->pid); 187 if (track->stack) { 188 struct stack_trace trace; 189 190 depot_fetch_stack(track->stack, &trace); 191 print_stack_trace(&trace, 0); 192 } else { 193 pr_err("(stack is not available)\n"); 194 } 195 } 196 197 static struct page *addr_to_page(const void *addr) 198 { 199 if ((addr >= (void *)PAGE_OFFSET) && 200 (addr < high_memory)) 201 return virt_to_head_page(addr); 202 return NULL; 203 } 204 205 static void describe_object_addr(struct kmem_cache *cache, void *object, 206 const void *addr) 207 { 208 unsigned long access_addr = (unsigned long)addr; 209 unsigned long object_addr = (unsigned long)object; 210 const char *rel_type; 211 int rel_bytes; 212 213 pr_err("The buggy address belongs to the object at %px\n" 214 " which belongs to the cache %s of size %d\n", 215 object, cache->name, cache->object_size); 216 217 if (!addr) 218 return; 219 220 if (access_addr < object_addr) { 221 rel_type = "to the left"; 222 rel_bytes = object_addr - access_addr; 223 } else if (access_addr >= object_addr + cache->object_size) { 224 rel_type = "to the right"; 225 rel_bytes = access_addr - (object_addr + cache->object_size); 226 } else { 227 rel_type = "inside"; 228 rel_bytes = access_addr - object_addr; 229 } 230 231 pr_err("The buggy address is located %d bytes %s of\n" 232 " %d-byte region [%px, %px)\n", 233 rel_bytes, rel_type, cache->object_size, (void *)object_addr, 234 (void *)(object_addr + cache->object_size)); 235 } 236 237 static void describe_object(struct kmem_cache *cache, void *object, 238 const void *addr) 239 { 240 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 241 242 if (cache->flags & SLAB_KASAN) { 243 print_track(&alloc_info->alloc_track, "Allocated"); 244 pr_err("\n"); 245 print_track(&alloc_info->free_track, "Freed"); 246 pr_err("\n"); 247 } 248 249 describe_object_addr(cache, object, addr); 250 } 251 252 static void print_address_description(void *addr) 253 { 254 struct page *page = addr_to_page(addr); 255 256 dump_stack(); 257 pr_err("\n"); 258 259 if (page && PageSlab(page)) { 260 struct kmem_cache *cache = page->slab_cache; 261 void *object = nearest_obj(cache, page, addr); 262 263 describe_object(cache, object, addr); 264 } 265 266 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 267 pr_err("The buggy address belongs to the variable:\n"); 268 pr_err(" %pS\n", addr); 269 } 270 271 if (page) { 272 pr_err("The buggy address belongs to the page:\n"); 273 dump_page(page, "kasan: bad access detected"); 274 } 275 } 276 277 static bool row_is_guilty(const void *row, const void *guilty) 278 { 279 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 280 } 281 282 static int shadow_pointer_offset(const void *row, const void *shadow) 283 { 284 /* The length of ">ff00ff00ff00ff00: " is 285 * 3 + (BITS_PER_LONG/8)*2 chars. 286 */ 287 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 288 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 289 } 290 291 static void print_shadow_for_address(const void *addr) 292 { 293 int i; 294 const void *shadow = kasan_mem_to_shadow(addr); 295 const void *shadow_row; 296 297 shadow_row = (void *)round_down((unsigned long)shadow, 298 SHADOW_BYTES_PER_ROW) 299 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 300 301 pr_err("Memory state around the buggy address:\n"); 302 303 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 304 const void *kaddr = kasan_shadow_to_mem(shadow_row); 305 char buffer[4 + (BITS_PER_LONG/8)*2]; 306 char shadow_buf[SHADOW_BYTES_PER_ROW]; 307 308 snprintf(buffer, sizeof(buffer), 309 (i == 0) ? ">%px: " : " %px: ", kaddr); 310 /* 311 * We should not pass a shadow pointer to generic 312 * function, because generic functions may try to 313 * access kasan mapping for the passed address. 314 */ 315 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 316 print_hex_dump(KERN_ERR, buffer, 317 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 318 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 319 320 if (row_is_guilty(shadow_row, shadow)) 321 pr_err("%*c\n", 322 shadow_pointer_offset(shadow_row, shadow), 323 '^'); 324 325 shadow_row += SHADOW_BYTES_PER_ROW; 326 } 327 } 328 329 void kasan_report_invalid_free(void *object, unsigned long ip) 330 { 331 unsigned long flags; 332 333 kasan_start_report(&flags); 334 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); 335 pr_err("\n"); 336 print_address_description(object); 337 pr_err("\n"); 338 print_shadow_for_address(object); 339 kasan_end_report(&flags); 340 } 341 342 static void kasan_report_error(struct kasan_access_info *info) 343 { 344 unsigned long flags; 345 346 kasan_start_report(&flags); 347 348 print_error_description(info); 349 pr_err("\n"); 350 351 if (!addr_has_shadow(info)) { 352 dump_stack(); 353 } else { 354 print_address_description((void *)info->access_addr); 355 pr_err("\n"); 356 print_shadow_for_address(info->first_bad_addr); 357 } 358 359 kasan_end_report(&flags); 360 } 361 362 static unsigned long kasan_flags; 363 364 #define KASAN_BIT_REPORTED 0 365 #define KASAN_BIT_MULTI_SHOT 1 366 367 bool kasan_save_enable_multi_shot(void) 368 { 369 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 370 } 371 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 372 373 void kasan_restore_multi_shot(bool enabled) 374 { 375 if (!enabled) 376 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 377 } 378 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 379 380 static int __init kasan_set_multi_shot(char *str) 381 { 382 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 383 return 1; 384 } 385 __setup("kasan_multi_shot", kasan_set_multi_shot); 386 387 static inline bool kasan_report_enabled(void) 388 { 389 if (current->kasan_depth) 390 return false; 391 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 392 return true; 393 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 394 } 395 396 void kasan_report(unsigned long addr, size_t size, 397 bool is_write, unsigned long ip) 398 { 399 struct kasan_access_info info; 400 401 if (likely(!kasan_report_enabled())) 402 return; 403 404 disable_trace_on_warning(); 405 406 info.access_addr = (void *)addr; 407 info.first_bad_addr = (void *)addr; 408 info.access_size = size; 409 info.is_write = is_write; 410 info.ip = ip; 411 412 kasan_report_error(&info); 413 } 414 415 416 #define DEFINE_ASAN_REPORT_LOAD(size) \ 417 void __asan_report_load##size##_noabort(unsigned long addr) \ 418 { \ 419 kasan_report(addr, size, false, _RET_IP_); \ 420 } \ 421 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 422 423 #define DEFINE_ASAN_REPORT_STORE(size) \ 424 void __asan_report_store##size##_noabort(unsigned long addr) \ 425 { \ 426 kasan_report(addr, size, true, _RET_IP_); \ 427 } \ 428 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 429 430 DEFINE_ASAN_REPORT_LOAD(1); 431 DEFINE_ASAN_REPORT_LOAD(2); 432 DEFINE_ASAN_REPORT_LOAD(4); 433 DEFINE_ASAN_REPORT_LOAD(8); 434 DEFINE_ASAN_REPORT_LOAD(16); 435 DEFINE_ASAN_REPORT_STORE(1); 436 DEFINE_ASAN_REPORT_STORE(2); 437 DEFINE_ASAN_REPORT_STORE(4); 438 DEFINE_ASAN_REPORT_STORE(8); 439 DEFINE_ASAN_REPORT_STORE(16); 440 441 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 442 { 443 kasan_report(addr, size, false, _RET_IP_); 444 } 445 EXPORT_SYMBOL(__asan_report_load_n_noabort); 446 447 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 448 { 449 kasan_report(addr, size, true, _RET_IP_); 450 } 451 EXPORT_SYMBOL(__asan_report_store_n_noabort); 452