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 <adech.fo@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 } 106 107 return bug_type; 108 } 109 110 static const char *get_wild_bug_type(struct kasan_access_info *info) 111 { 112 const char *bug_type = "unknown-crash"; 113 114 if ((unsigned long)info->access_addr < PAGE_SIZE) 115 bug_type = "null-ptr-deref"; 116 else if ((unsigned long)info->access_addr < TASK_SIZE) 117 bug_type = "user-memory-access"; 118 else 119 bug_type = "wild-memory-access"; 120 121 return bug_type; 122 } 123 124 static const char *get_bug_type(struct kasan_access_info *info) 125 { 126 if (addr_has_shadow(info)) 127 return get_shadow_bug_type(info); 128 return get_wild_bug_type(info); 129 } 130 131 static void print_error_description(struct kasan_access_info *info) 132 { 133 const char *bug_type = get_bug_type(info); 134 135 pr_err("BUG: KASAN: %s in %pS\n", 136 bug_type, (void *)info->ip); 137 pr_err("%s of size %zu at addr %p by task %s/%d\n", 138 info->is_write ? "Write" : "Read", info->access_size, 139 info->access_addr, current->comm, task_pid_nr(current)); 140 } 141 142 static inline bool kernel_or_module_addr(const void *addr) 143 { 144 if (addr >= (void *)_stext && addr < (void *)_end) 145 return true; 146 if (is_module_address((unsigned long)addr)) 147 return true; 148 return false; 149 } 150 151 static inline bool init_task_stack_addr(const void *addr) 152 { 153 return addr >= (void *)&init_thread_union.stack && 154 (addr <= (void *)&init_thread_union.stack + 155 sizeof(init_thread_union.stack)); 156 } 157 158 static DEFINE_SPINLOCK(report_lock); 159 160 static void kasan_start_report(unsigned long *flags) 161 { 162 /* 163 * Make sure we don't end up in loop. 164 */ 165 kasan_disable_current(); 166 spin_lock_irqsave(&report_lock, *flags); 167 pr_err("==================================================================\n"); 168 } 169 170 static void kasan_end_report(unsigned long *flags) 171 { 172 pr_err("==================================================================\n"); 173 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 174 spin_unlock_irqrestore(&report_lock, *flags); 175 if (panic_on_warn) 176 panic("panic_on_warn set ...\n"); 177 kasan_enable_current(); 178 } 179 180 static void print_track(struct kasan_track *track, const char *prefix) 181 { 182 pr_err("%s by task %u:\n", prefix, track->pid); 183 if (track->stack) { 184 struct stack_trace trace; 185 186 depot_fetch_stack(track->stack, &trace); 187 print_stack_trace(&trace, 0); 188 } else { 189 pr_err("(stack is not available)\n"); 190 } 191 } 192 193 static struct page *addr_to_page(const void *addr) 194 { 195 if ((addr >= (void *)PAGE_OFFSET) && 196 (addr < high_memory)) 197 return virt_to_head_page(addr); 198 return NULL; 199 } 200 201 static void describe_object_addr(struct kmem_cache *cache, void *object, 202 const void *addr) 203 { 204 unsigned long access_addr = (unsigned long)addr; 205 unsigned long object_addr = (unsigned long)object; 206 const char *rel_type; 207 int rel_bytes; 208 209 pr_err("The buggy address belongs to the object at %p\n" 210 " which belongs to the cache %s of size %d\n", 211 object, cache->name, cache->object_size); 212 213 if (!addr) 214 return; 215 216 if (access_addr < object_addr) { 217 rel_type = "to the left"; 218 rel_bytes = object_addr - access_addr; 219 } else if (access_addr >= object_addr + cache->object_size) { 220 rel_type = "to the right"; 221 rel_bytes = access_addr - (object_addr + cache->object_size); 222 } else { 223 rel_type = "inside"; 224 rel_bytes = access_addr - object_addr; 225 } 226 227 pr_err("The buggy address is located %d bytes %s of\n" 228 " %d-byte region [%p, %p)\n", 229 rel_bytes, rel_type, cache->object_size, (void *)object_addr, 230 (void *)(object_addr + cache->object_size)); 231 } 232 233 static void describe_object(struct kmem_cache *cache, void *object, 234 const void *addr) 235 { 236 struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object); 237 238 if (cache->flags & SLAB_KASAN) { 239 print_track(&alloc_info->alloc_track, "Allocated"); 240 pr_err("\n"); 241 print_track(&alloc_info->free_track, "Freed"); 242 pr_err("\n"); 243 } 244 245 describe_object_addr(cache, object, addr); 246 } 247 248 static void print_address_description(void *addr) 249 { 250 struct page *page = addr_to_page(addr); 251 252 dump_stack(); 253 pr_err("\n"); 254 255 if (page && PageSlab(page)) { 256 struct kmem_cache *cache = page->slab_cache; 257 void *object = nearest_obj(cache, page, addr); 258 259 describe_object(cache, object, addr); 260 } 261 262 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 263 pr_err("The buggy address belongs to the variable:\n"); 264 pr_err(" %pS\n", addr); 265 } 266 267 if (page) { 268 pr_err("The buggy address belongs to the page:\n"); 269 dump_page(page, "kasan: bad access detected"); 270 } 271 } 272 273 static bool row_is_guilty(const void *row, const void *guilty) 274 { 275 return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW); 276 } 277 278 static int shadow_pointer_offset(const void *row, const void *shadow) 279 { 280 /* The length of ">ff00ff00ff00ff00: " is 281 * 3 + (BITS_PER_LONG/8)*2 chars. 282 */ 283 return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 + 284 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1; 285 } 286 287 static void print_shadow_for_address(const void *addr) 288 { 289 int i; 290 const void *shadow = kasan_mem_to_shadow(addr); 291 const void *shadow_row; 292 293 shadow_row = (void *)round_down((unsigned long)shadow, 294 SHADOW_BYTES_PER_ROW) 295 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW; 296 297 pr_err("Memory state around the buggy address:\n"); 298 299 for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) { 300 const void *kaddr = kasan_shadow_to_mem(shadow_row); 301 char buffer[4 + (BITS_PER_LONG/8)*2]; 302 char shadow_buf[SHADOW_BYTES_PER_ROW]; 303 304 snprintf(buffer, sizeof(buffer), 305 (i == 0) ? ">%p: " : " %p: ", kaddr); 306 /* 307 * We should not pass a shadow pointer to generic 308 * function, because generic functions may try to 309 * access kasan mapping for the passed address. 310 */ 311 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW); 312 print_hex_dump(KERN_ERR, buffer, 313 DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1, 314 shadow_buf, SHADOW_BYTES_PER_ROW, 0); 315 316 if (row_is_guilty(shadow_row, shadow)) 317 pr_err("%*c\n", 318 shadow_pointer_offset(shadow_row, shadow), 319 '^'); 320 321 shadow_row += SHADOW_BYTES_PER_ROW; 322 } 323 } 324 325 void kasan_report_double_free(struct kmem_cache *cache, void *object, 326 void *ip) 327 { 328 unsigned long flags; 329 330 kasan_start_report(&flags); 331 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", ip); 332 pr_err("\n"); 333 print_address_description(object); 334 pr_err("\n"); 335 print_shadow_for_address(object); 336 kasan_end_report(&flags); 337 } 338 339 static void kasan_report_error(struct kasan_access_info *info) 340 { 341 unsigned long flags; 342 343 kasan_start_report(&flags); 344 345 print_error_description(info); 346 pr_err("\n"); 347 348 if (!addr_has_shadow(info)) { 349 dump_stack(); 350 } else { 351 print_address_description((void *)info->access_addr); 352 pr_err("\n"); 353 print_shadow_for_address(info->first_bad_addr); 354 } 355 356 kasan_end_report(&flags); 357 } 358 359 static unsigned long kasan_flags; 360 361 #define KASAN_BIT_REPORTED 0 362 #define KASAN_BIT_MULTI_SHOT 1 363 364 bool kasan_save_enable_multi_shot(void) 365 { 366 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 367 } 368 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 369 370 void kasan_restore_multi_shot(bool enabled) 371 { 372 if (!enabled) 373 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 374 } 375 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 376 377 static int __init kasan_set_multi_shot(char *str) 378 { 379 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 380 return 1; 381 } 382 __setup("kasan_multi_shot", kasan_set_multi_shot); 383 384 static inline bool kasan_report_enabled(void) 385 { 386 if (current->kasan_depth) 387 return false; 388 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 389 return true; 390 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 391 } 392 393 void kasan_report(unsigned long addr, size_t size, 394 bool is_write, unsigned long ip) 395 { 396 struct kasan_access_info info; 397 398 if (likely(!kasan_report_enabled())) 399 return; 400 401 disable_trace_on_warning(); 402 403 info.access_addr = (void *)addr; 404 info.access_size = size; 405 info.is_write = is_write; 406 info.ip = ip; 407 408 kasan_report_error(&info); 409 } 410 411 412 #define DEFINE_ASAN_REPORT_LOAD(size) \ 413 void __asan_report_load##size##_noabort(unsigned long addr) \ 414 { \ 415 kasan_report(addr, size, false, _RET_IP_); \ 416 } \ 417 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 418 419 #define DEFINE_ASAN_REPORT_STORE(size) \ 420 void __asan_report_store##size##_noabort(unsigned long addr) \ 421 { \ 422 kasan_report(addr, size, true, _RET_IP_); \ 423 } \ 424 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 425 426 DEFINE_ASAN_REPORT_LOAD(1); 427 DEFINE_ASAN_REPORT_LOAD(2); 428 DEFINE_ASAN_REPORT_LOAD(4); 429 DEFINE_ASAN_REPORT_LOAD(8); 430 DEFINE_ASAN_REPORT_LOAD(16); 431 DEFINE_ASAN_REPORT_STORE(1); 432 DEFINE_ASAN_REPORT_STORE(2); 433 DEFINE_ASAN_REPORT_STORE(4); 434 DEFINE_ASAN_REPORT_STORE(8); 435 DEFINE_ASAN_REPORT_STORE(16); 436 437 void __asan_report_load_n_noabort(unsigned long addr, size_t size) 438 { 439 kasan_report(addr, size, false, _RET_IP_); 440 } 441 EXPORT_SYMBOL(__asan_report_load_n_noabort); 442 443 void __asan_report_store_n_noabort(unsigned long addr, size_t size) 444 { 445 kasan_report(addr, size, true, _RET_IP_); 446 } 447 EXPORT_SYMBOL(__asan_report_store_n_noabort); 448