1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This file contains common 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 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/slab.h> 20 #include <linux/stackdepot.h> 21 #include <linux/stacktrace.h> 22 #include <linux/string.h> 23 #include <linux/types.h> 24 #include <linux/kasan.h> 25 #include <linux/module.h> 26 #include <linux/sched/task_stack.h> 27 #include <linux/uaccess.h> 28 29 #include <asm/sections.h> 30 31 #include <kunit/test.h> 32 33 #include "kasan.h" 34 #include "../slab.h" 35 36 static unsigned long kasan_flags; 37 38 #define KASAN_BIT_REPORTED 0 39 #define KASAN_BIT_MULTI_SHOT 1 40 41 bool kasan_save_enable_multi_shot(void) 42 { 43 return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 44 } 45 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); 46 47 void kasan_restore_multi_shot(bool enabled) 48 { 49 if (!enabled) 50 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 51 } 52 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); 53 54 static int __init kasan_set_multi_shot(char *str) 55 { 56 set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); 57 return 1; 58 } 59 __setup("kasan_multi_shot", kasan_set_multi_shot); 60 61 static void print_error_description(struct kasan_access_info *info) 62 { 63 pr_err("BUG: KASAN: %s in %pS\n", 64 get_bug_type(info), (void *)info->ip); 65 if (info->access_size) 66 pr_err("%s of size %zu at addr %px by task %s/%d\n", 67 info->is_write ? "Write" : "Read", info->access_size, 68 info->access_addr, current->comm, task_pid_nr(current)); 69 else 70 pr_err("%s at addr %px by task %s/%d\n", 71 info->is_write ? "Write" : "Read", 72 info->access_addr, current->comm, task_pid_nr(current)); 73 } 74 75 static DEFINE_SPINLOCK(report_lock); 76 77 static void start_report(unsigned long *flags) 78 { 79 /* 80 * Make sure we don't end up in loop. 81 */ 82 kasan_disable_current(); 83 spin_lock_irqsave(&report_lock, *flags); 84 pr_err("==================================================================\n"); 85 } 86 87 static void end_report(unsigned long *flags) 88 { 89 pr_err("==================================================================\n"); 90 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); 91 spin_unlock_irqrestore(&report_lock, *flags); 92 if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) { 93 /* 94 * This thread may hit another WARN() in the panic path. 95 * Resetting this prevents additional WARN() from panicking the 96 * system on this thread. Other threads are blocked by the 97 * panic_mutex in panic(). 98 */ 99 panic_on_warn = 0; 100 panic("panic_on_warn set ...\n"); 101 } 102 #ifdef CONFIG_KASAN_HW_TAGS 103 if (kasan_flag_panic) 104 panic("kasan.fault=panic set ...\n"); 105 #endif 106 kasan_enable_current(); 107 } 108 109 static void print_stack(depot_stack_handle_t stack) 110 { 111 unsigned long *entries; 112 unsigned int nr_entries; 113 114 nr_entries = stack_depot_fetch(stack, &entries); 115 stack_trace_print(entries, nr_entries, 0); 116 } 117 118 static void print_track(struct kasan_track *track, const char *prefix) 119 { 120 pr_err("%s by task %u:\n", prefix, track->pid); 121 if (track->stack) { 122 print_stack(track->stack); 123 } else { 124 pr_err("(stack is not available)\n"); 125 } 126 } 127 128 struct page *kasan_addr_to_page(const void *addr) 129 { 130 if ((addr >= (void *)PAGE_OFFSET) && 131 (addr < high_memory)) 132 return virt_to_head_page(addr); 133 return NULL; 134 } 135 136 static void describe_object_addr(struct kmem_cache *cache, void *object, 137 const void *addr) 138 { 139 unsigned long access_addr = (unsigned long)addr; 140 unsigned long object_addr = (unsigned long)object; 141 const char *rel_type; 142 int rel_bytes; 143 144 pr_err("The buggy address belongs to the object at %px\n" 145 " which belongs to the cache %s of size %d\n", 146 object, cache->name, cache->object_size); 147 148 if (!addr) 149 return; 150 151 if (access_addr < object_addr) { 152 rel_type = "to the left"; 153 rel_bytes = object_addr - access_addr; 154 } else if (access_addr >= object_addr + cache->object_size) { 155 rel_type = "to the right"; 156 rel_bytes = access_addr - (object_addr + cache->object_size); 157 } else { 158 rel_type = "inside"; 159 rel_bytes = access_addr - object_addr; 160 } 161 162 pr_err("The buggy address is located %d bytes %s of\n" 163 " %d-byte region [%px, %px)\n", 164 rel_bytes, rel_type, cache->object_size, (void *)object_addr, 165 (void *)(object_addr + cache->object_size)); 166 } 167 168 static void describe_object_stacks(struct kmem_cache *cache, void *object, 169 const void *addr, u8 tag) 170 { 171 struct kasan_alloc_meta *alloc_meta; 172 struct kasan_track *free_track; 173 174 alloc_meta = kasan_get_alloc_meta(cache, object); 175 if (alloc_meta) { 176 print_track(&alloc_meta->alloc_track, "Allocated"); 177 pr_err("\n"); 178 } 179 180 free_track = kasan_get_free_track(cache, object, tag); 181 if (free_track) { 182 print_track(free_track, "Freed"); 183 pr_err("\n"); 184 } 185 186 #ifdef CONFIG_KASAN_GENERIC 187 if (!alloc_meta) 188 return; 189 if (alloc_meta->aux_stack[0]) { 190 pr_err("Last potentially related work creation:\n"); 191 print_stack(alloc_meta->aux_stack[0]); 192 pr_err("\n"); 193 } 194 if (alloc_meta->aux_stack[1]) { 195 pr_err("Second to last potentially related work creation:\n"); 196 print_stack(alloc_meta->aux_stack[1]); 197 pr_err("\n"); 198 } 199 #endif 200 } 201 202 static void describe_object(struct kmem_cache *cache, void *object, 203 const void *addr, u8 tag) 204 { 205 if (kasan_stack_collection_enabled()) 206 describe_object_stacks(cache, object, addr, tag); 207 describe_object_addr(cache, object, addr); 208 } 209 210 static inline bool kernel_or_module_addr(const void *addr) 211 { 212 if (addr >= (void *)_stext && addr < (void *)_end) 213 return true; 214 if (is_module_address((unsigned long)addr)) 215 return true; 216 return false; 217 } 218 219 static inline bool init_task_stack_addr(const void *addr) 220 { 221 return addr >= (void *)&init_thread_union.stack && 222 (addr <= (void *)&init_thread_union.stack + 223 sizeof(init_thread_union.stack)); 224 } 225 226 static void print_address_description(void *addr, u8 tag) 227 { 228 struct page *page = kasan_addr_to_page(addr); 229 230 dump_stack(); 231 pr_err("\n"); 232 233 if (page && PageSlab(page)) { 234 struct kmem_cache *cache = page->slab_cache; 235 void *object = nearest_obj(cache, page, addr); 236 237 describe_object(cache, object, addr, tag); 238 } 239 240 if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) { 241 pr_err("The buggy address belongs to the variable:\n"); 242 pr_err(" %pS\n", addr); 243 } 244 245 if (page) { 246 pr_err("The buggy address belongs to the page:\n"); 247 dump_page(page, "kasan: bad access detected"); 248 } 249 250 print_address_stack_frame(addr); 251 } 252 253 static bool meta_row_is_guilty(const void *row, const void *addr) 254 { 255 return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW); 256 } 257 258 static int meta_pointer_offset(const void *row, const void *addr) 259 { 260 /* 261 * Memory state around the buggy address: 262 * ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe 263 * ... 264 * 265 * The length of ">ff00ff00ff00ff00: " is 266 * 3 + (BITS_PER_LONG / 8) * 2 chars. 267 * The length of each granule metadata is 2 bytes 268 * plus 1 byte for space. 269 */ 270 return 3 + (BITS_PER_LONG / 8) * 2 + 271 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1; 272 } 273 274 static void print_memory_metadata(const void *addr) 275 { 276 int i; 277 void *row; 278 279 row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW) 280 - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW; 281 282 pr_err("Memory state around the buggy address:\n"); 283 284 for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) { 285 char buffer[4 + (BITS_PER_LONG / 8) * 2]; 286 char metadata[META_BYTES_PER_ROW]; 287 288 snprintf(buffer, sizeof(buffer), 289 (i == 0) ? ">%px: " : " %px: ", row); 290 291 /* 292 * We should not pass a shadow pointer to generic 293 * function, because generic functions may try to 294 * access kasan mapping for the passed address. 295 */ 296 metadata_fetch_row(&metadata[0], row); 297 298 print_hex_dump(KERN_ERR, buffer, 299 DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1, 300 metadata, META_BYTES_PER_ROW, 0); 301 302 if (meta_row_is_guilty(row, addr)) 303 pr_err("%*c\n", meta_pointer_offset(row, addr), '^'); 304 305 row += META_MEM_BYTES_PER_ROW; 306 } 307 } 308 309 static bool report_enabled(void) 310 { 311 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS) 312 if (current->kasan_depth) 313 return false; 314 #endif 315 if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) 316 return true; 317 return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); 318 } 319 320 #if IS_ENABLED(CONFIG_KUNIT) 321 static void kasan_update_kunit_status(struct kunit *cur_test) 322 { 323 struct kunit_resource *resource; 324 struct kunit_kasan_expectation *kasan_data; 325 326 resource = kunit_find_named_resource(cur_test, "kasan_data"); 327 328 if (!resource) { 329 kunit_set_failure(cur_test); 330 return; 331 } 332 333 kasan_data = (struct kunit_kasan_expectation *)resource->data; 334 kasan_data->report_found = true; 335 kunit_put_resource(resource); 336 } 337 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 338 339 void kasan_report_invalid_free(void *object, unsigned long ip) 340 { 341 unsigned long flags; 342 u8 tag = get_tag(object); 343 344 object = kasan_reset_tag(object); 345 346 #if IS_ENABLED(CONFIG_KUNIT) 347 if (current->kunit_test) 348 kasan_update_kunit_status(current->kunit_test); 349 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 350 351 start_report(&flags); 352 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip); 353 print_tags(tag, object); 354 pr_err("\n"); 355 print_address_description(object, tag); 356 pr_err("\n"); 357 print_memory_metadata(object); 358 end_report(&flags); 359 } 360 361 static void __kasan_report(unsigned long addr, size_t size, bool is_write, 362 unsigned long ip) 363 { 364 struct kasan_access_info info; 365 void *tagged_addr; 366 void *untagged_addr; 367 unsigned long flags; 368 369 #if IS_ENABLED(CONFIG_KUNIT) 370 if (current->kunit_test) 371 kasan_update_kunit_status(current->kunit_test); 372 #endif /* IS_ENABLED(CONFIG_KUNIT) */ 373 374 disable_trace_on_warning(); 375 376 tagged_addr = (void *)addr; 377 untagged_addr = kasan_reset_tag(tagged_addr); 378 379 info.access_addr = tagged_addr; 380 if (addr_has_metadata(untagged_addr)) 381 info.first_bad_addr = find_first_bad_addr(tagged_addr, size); 382 else 383 info.first_bad_addr = untagged_addr; 384 info.access_size = size; 385 info.is_write = is_write; 386 info.ip = ip; 387 388 start_report(&flags); 389 390 print_error_description(&info); 391 if (addr_has_metadata(untagged_addr)) 392 print_tags(get_tag(tagged_addr), info.first_bad_addr); 393 pr_err("\n"); 394 395 if (addr_has_metadata(untagged_addr)) { 396 print_address_description(untagged_addr, get_tag(tagged_addr)); 397 pr_err("\n"); 398 print_memory_metadata(info.first_bad_addr); 399 } else { 400 dump_stack(); 401 } 402 403 end_report(&flags); 404 } 405 406 bool kasan_report(unsigned long addr, size_t size, bool is_write, 407 unsigned long ip) 408 { 409 unsigned long flags = user_access_save(); 410 bool ret = false; 411 412 if (likely(report_enabled())) { 413 __kasan_report(addr, size, is_write, ip); 414 ret = true; 415 } 416 417 user_access_restore(flags); 418 419 return ret; 420 } 421 422 #ifdef CONFIG_KASAN_INLINE 423 /* 424 * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high 425 * canonical half of the address space) cause out-of-bounds shadow memory reads 426 * before the actual access. For addresses in the low canonical half of the 427 * address space, as well as most non-canonical addresses, that out-of-bounds 428 * shadow memory access lands in the non-canonical part of the address space. 429 * Help the user figure out what the original bogus pointer was. 430 */ 431 void kasan_non_canonical_hook(unsigned long addr) 432 { 433 unsigned long orig_addr; 434 const char *bug_type; 435 436 if (addr < KASAN_SHADOW_OFFSET) 437 return; 438 439 orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT; 440 /* 441 * For faults near the shadow address for NULL, we can be fairly certain 442 * that this is a KASAN shadow memory access. 443 * For faults that correspond to shadow for low canonical addresses, we 444 * can still be pretty sure - that shadow region is a fairly narrow 445 * chunk of the non-canonical address space. 446 * But faults that look like shadow for non-canonical addresses are a 447 * really large chunk of the address space. In that case, we still 448 * print the decoded address, but make it clear that this is not 449 * necessarily what's actually going on. 450 */ 451 if (orig_addr < PAGE_SIZE) 452 bug_type = "null-ptr-deref"; 453 else if (orig_addr < TASK_SIZE) 454 bug_type = "probably user-memory-access"; 455 else 456 bug_type = "maybe wild-memory-access"; 457 pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type, 458 orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1); 459 } 460 #endif 461