1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains generic KASAN specific 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 12 #include <linux/bitops.h> 13 #include <linux/ftrace.h> 14 #include <linux/init.h> 15 #include <linux/kernel.h> 16 #include <linux/mm.h> 17 #include <linux/printk.h> 18 #include <linux/sched.h> 19 #include <linux/sched/task_stack.h> 20 #include <linux/slab.h> 21 #include <linux/stackdepot.h> 22 #include <linux/stacktrace.h> 23 #include <linux/string.h> 24 #include <linux/types.h> 25 #include <linux/kasan.h> 26 #include <linux/module.h> 27 28 #include <asm/sections.h> 29 30 #include "kasan.h" 31 #include "../slab.h" 32 33 const void *kasan_find_first_bad_addr(const void *addr, size_t size) 34 { 35 const void *p = addr; 36 37 if (!addr_has_metadata(p)) 38 return p; 39 40 while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p))) 41 p += KASAN_GRANULE_SIZE; 42 43 return p; 44 } 45 46 size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache) 47 { 48 size_t size = 0; 49 u8 *shadow; 50 51 /* 52 * Skip the addr_has_metadata check, as this function only operates on 53 * slab memory, which must have metadata. 54 */ 55 56 /* 57 * The loop below returns 0 for freed objects, for which KASAN cannot 58 * calculate the allocation size based on the metadata. 59 */ 60 shadow = (u8 *)kasan_mem_to_shadow(object); 61 while (size < cache->object_size) { 62 if (*shadow == 0) 63 size += KASAN_GRANULE_SIZE; 64 else if (*shadow >= 1 && *shadow <= KASAN_GRANULE_SIZE - 1) 65 return size + *shadow; 66 else 67 return size; 68 shadow++; 69 } 70 71 return cache->object_size; 72 } 73 74 static const char *get_shadow_bug_type(struct kasan_report_info *info) 75 { 76 const char *bug_type = "unknown-crash"; 77 u8 *shadow_addr; 78 79 shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr); 80 81 /* 82 * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look 83 * at the next shadow byte to determine the type of the bad access. 84 */ 85 if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1) 86 shadow_addr++; 87 88 switch (*shadow_addr) { 89 case 0 ... KASAN_GRANULE_SIZE - 1: 90 /* 91 * In theory it's still possible to see these shadow values 92 * due to a data race in the kernel code. 93 */ 94 bug_type = "out-of-bounds"; 95 break; 96 case KASAN_PAGE_REDZONE: 97 case KASAN_SLAB_REDZONE: 98 bug_type = "slab-out-of-bounds"; 99 break; 100 case KASAN_GLOBAL_REDZONE: 101 bug_type = "global-out-of-bounds"; 102 break; 103 case KASAN_STACK_LEFT: 104 case KASAN_STACK_MID: 105 case KASAN_STACK_RIGHT: 106 case KASAN_STACK_PARTIAL: 107 bug_type = "stack-out-of-bounds"; 108 break; 109 case KASAN_PAGE_FREE: 110 bug_type = "use-after-free"; 111 break; 112 case KASAN_SLAB_FREE: 113 case KASAN_SLAB_FREE_META: 114 bug_type = "slab-use-after-free"; 115 break; 116 case KASAN_ALLOCA_LEFT: 117 case KASAN_ALLOCA_RIGHT: 118 bug_type = "alloca-out-of-bounds"; 119 break; 120 case KASAN_VMALLOC_INVALID: 121 bug_type = "vmalloc-out-of-bounds"; 122 break; 123 } 124 125 return bug_type; 126 } 127 128 static const char *get_wild_bug_type(struct kasan_report_info *info) 129 { 130 const char *bug_type = "unknown-crash"; 131 132 if ((unsigned long)info->access_addr < PAGE_SIZE) 133 bug_type = "null-ptr-deref"; 134 else if ((unsigned long)info->access_addr < TASK_SIZE) 135 bug_type = "user-memory-access"; 136 else 137 bug_type = "wild-memory-access"; 138 139 return bug_type; 140 } 141 142 static const char *get_bug_type(struct kasan_report_info *info) 143 { 144 /* 145 * If access_size is a negative number, then it has reason to be 146 * defined as out-of-bounds bug type. 147 * 148 * Casting negative numbers to size_t would indeed turn up as 149 * a large size_t and its value will be larger than ULONG_MAX/2, 150 * so that this can qualify as out-of-bounds. 151 */ 152 if (info->access_addr + info->access_size < info->access_addr) 153 return "out-of-bounds"; 154 155 if (addr_has_metadata(info->access_addr)) 156 return get_shadow_bug_type(info); 157 return get_wild_bug_type(info); 158 } 159 160 void kasan_complete_mode_report_info(struct kasan_report_info *info) 161 { 162 struct kasan_alloc_meta *alloc_meta; 163 struct kasan_free_meta *free_meta; 164 165 if (!info->bug_type) 166 info->bug_type = get_bug_type(info); 167 168 if (!info->cache || !info->object) 169 return; 170 171 alloc_meta = kasan_get_alloc_meta(info->cache, info->object); 172 if (alloc_meta) 173 memcpy(&info->alloc_track, &alloc_meta->alloc_track, 174 sizeof(info->alloc_track)); 175 176 if (*(u8 *)kasan_mem_to_shadow(info->object) == KASAN_SLAB_FREE_META) { 177 /* Free meta must be present with KASAN_SLAB_FREE_META. */ 178 free_meta = kasan_get_free_meta(info->cache, info->object); 179 memcpy(&info->free_track, &free_meta->free_track, 180 sizeof(info->free_track)); 181 } 182 } 183 184 void kasan_metadata_fetch_row(char *buffer, void *row) 185 { 186 memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW); 187 } 188 189 void kasan_print_aux_stacks(struct kmem_cache *cache, const void *object) 190 { 191 struct kasan_alloc_meta *alloc_meta; 192 193 alloc_meta = kasan_get_alloc_meta(cache, object); 194 if (!alloc_meta) 195 return; 196 197 if (alloc_meta->aux_stack[0]) { 198 pr_err("Last potentially related work creation:\n"); 199 stack_depot_print(alloc_meta->aux_stack[0]); 200 pr_err("\n"); 201 } 202 if (alloc_meta->aux_stack[1]) { 203 pr_err("Second to last potentially related work creation:\n"); 204 stack_depot_print(alloc_meta->aux_stack[1]); 205 pr_err("\n"); 206 } 207 } 208 209 #ifdef CONFIG_KASAN_STACK 210 static bool __must_check tokenize_frame_descr(const char **frame_descr, 211 char *token, size_t max_tok_len, 212 unsigned long *value) 213 { 214 const char *sep = strchr(*frame_descr, ' '); 215 216 if (sep == NULL) 217 sep = *frame_descr + strlen(*frame_descr); 218 219 if (token != NULL) { 220 const size_t tok_len = sep - *frame_descr; 221 222 if (tok_len + 1 > max_tok_len) { 223 pr_err("internal error: frame description too long: %s\n", 224 *frame_descr); 225 return false; 226 } 227 228 /* Copy token (+ 1 byte for '\0'). */ 229 strscpy(token, *frame_descr, tok_len + 1); 230 } 231 232 /* Advance frame_descr past separator. */ 233 *frame_descr = sep + 1; 234 235 if (value != NULL && kstrtoul(token, 10, value)) { 236 pr_err("internal error: not a valid number: %s\n", token); 237 return false; 238 } 239 240 return true; 241 } 242 243 static void print_decoded_frame_descr(const char *frame_descr) 244 { 245 /* 246 * We need to parse the following string: 247 * "n alloc_1 alloc_2 ... alloc_n" 248 * where alloc_i looks like 249 * "offset size len name" 250 * or "offset size len name:line". 251 */ 252 253 char token[64]; 254 unsigned long num_objects; 255 256 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 257 &num_objects)) 258 return; 259 260 pr_err("\n"); 261 pr_err("This frame has %lu %s:\n", num_objects, 262 num_objects == 1 ? "object" : "objects"); 263 264 while (num_objects--) { 265 unsigned long offset; 266 unsigned long size; 267 268 /* access offset */ 269 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 270 &offset)) 271 return; 272 /* access size */ 273 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 274 &size)) 275 return; 276 /* name length (unused) */ 277 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL)) 278 return; 279 /* object name */ 280 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token), 281 NULL)) 282 return; 283 284 /* Strip line number; without filename it's not very helpful. */ 285 strreplace(token, ':', '\0'); 286 287 /* Finally, print object information. */ 288 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token); 289 } 290 } 291 292 /* Returns true only if the address is on the current task's stack. */ 293 static 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 aligned_addr = round_down((unsigned long)addr, sizeof(long)); 307 mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE); 308 shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr); 309 shadow_bottom = kasan_mem_to_shadow(end_of_stack(current)); 310 311 while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) { 312 shadow_ptr--; 313 mem_ptr -= KASAN_GRANULE_SIZE; 314 } 315 316 while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) { 317 shadow_ptr--; 318 mem_ptr -= KASAN_GRANULE_SIZE; 319 } 320 321 if (shadow_ptr < shadow_bottom) 322 return false; 323 324 frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE); 325 if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) { 326 pr_err("internal error: frame has invalid marker: %lu\n", 327 frame[0]); 328 return false; 329 } 330 331 *offset = (unsigned long)addr - (unsigned long)frame; 332 *frame_descr = (const char *)frame[1]; 333 *frame_pc = (void *)frame[2]; 334 335 return true; 336 } 337 338 void kasan_print_address_stack_frame(const void *addr) 339 { 340 unsigned long offset; 341 const char *frame_descr; 342 const void *frame_pc; 343 344 if (WARN_ON(!object_is_on_stack(addr))) 345 return; 346 347 pr_err("The buggy address belongs to stack of task %s/%d\n", 348 current->comm, task_pid_nr(current)); 349 350 if (!get_address_stack_frame_info(addr, &offset, &frame_descr, 351 &frame_pc)) 352 return; 353 354 pr_err(" and is located at offset %lu in frame:\n", offset); 355 pr_err(" %pS\n", frame_pc); 356 357 if (!frame_descr) 358 return; 359 360 print_decoded_frame_descr(frame_descr); 361 } 362 #endif /* CONFIG_KASAN_STACK */ 363 364 #define DEFINE_ASAN_REPORT_LOAD(size) \ 365 void __asan_report_load##size##_noabort(void *addr) \ 366 { \ 367 kasan_report(addr, size, false, _RET_IP_); \ 368 } \ 369 EXPORT_SYMBOL(__asan_report_load##size##_noabort) 370 371 #define DEFINE_ASAN_REPORT_STORE(size) \ 372 void __asan_report_store##size##_noabort(void *addr) \ 373 { \ 374 kasan_report(addr, size, true, _RET_IP_); \ 375 } \ 376 EXPORT_SYMBOL(__asan_report_store##size##_noabort) 377 378 DEFINE_ASAN_REPORT_LOAD(1); 379 DEFINE_ASAN_REPORT_LOAD(2); 380 DEFINE_ASAN_REPORT_LOAD(4); 381 DEFINE_ASAN_REPORT_LOAD(8); 382 DEFINE_ASAN_REPORT_LOAD(16); 383 DEFINE_ASAN_REPORT_STORE(1); 384 DEFINE_ASAN_REPORT_STORE(2); 385 DEFINE_ASAN_REPORT_STORE(4); 386 DEFINE_ASAN_REPORT_STORE(8); 387 DEFINE_ASAN_REPORT_STORE(16); 388 389 void __asan_report_load_n_noabort(void *addr, ssize_t size) 390 { 391 kasan_report(addr, size, false, _RET_IP_); 392 } 393 EXPORT_SYMBOL(__asan_report_load_n_noabort); 394 395 void __asan_report_store_n_noabort(void *addr, ssize_t size) 396 { 397 kasan_report(addr, size, true, _RET_IP_); 398 } 399 EXPORT_SYMBOL(__asan_report_store_n_noabort); 400