mm/kasan/report.c

   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 <kunit/test.h>
  13 #include <linux/bitops.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/init.h>
  16 #include <linux/kernel.h>
  17 #include <linux/lockdep.h>
  18 #include <linux/mm.h>
  19 #include <linux/printk.h>
  20 #include <linux/sched.h>
  21 #include <linux/slab.h>
  22 #include <linux/stackdepot.h>
  23 #include <linux/stacktrace.h>
  24 #include <linux/string.h>
  25 #include <linux/types.h>
  26 #include <linux/vmalloc.h>
  27 #include <linux/kasan.h>
  28 #include <linux/module.h>
  29 #include <linux/sched/task_stack.h>
  30 #include <linux/uaccess.h>
  31 #include <trace/events/error_report.h>
  32
  33 #include <asm/sections.h>
  34
  35 #include "kasan.h"
  36 #include "../slab.h"
  37
  38 static unsigned long kasan_flags;
  39
  40 #define KASAN_BIT_REPORTED      0
  41 #define KASAN_BIT_MULTI_SHOT    1
  42
  43 enum kasan_arg_fault {
  44         KASAN_ARG_FAULT_DEFAULT,
  45         KASAN_ARG_FAULT_REPORT,
  46         KASAN_ARG_FAULT_PANIC,
  47         KASAN_ARG_FAULT_PANIC_ON_WRITE,
  48 };
  49
  50 static enum kasan_arg_fault kasan_arg_fault __ro_after_init = KASAN_ARG_FAULT_DEFAULT;
  51
  52 /* kasan.fault=report/panic */
  53 static int __init early_kasan_fault(char *arg)
  54 {
  55         if (!arg)
  56                 return -EINVAL;
  57
  58         if (!strcmp(arg, "report"))
  59                 kasan_arg_fault = KASAN_ARG_FAULT_REPORT;
  60         else if (!strcmp(arg, "panic"))
  61                 kasan_arg_fault = KASAN_ARG_FAULT_PANIC;
  62         else if (!strcmp(arg, "panic_on_write"))
  63                 kasan_arg_fault = KASAN_ARG_FAULT_PANIC_ON_WRITE;
  64         else
  65                 return -EINVAL;
  66
  67         return 0;
  68 }
  69 early_param("kasan.fault", early_kasan_fault);
  70
  71 static int __init kasan_set_multi_shot(char *str)
  72 {
  73         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  74         return 1;
  75 }
  76 __setup("kasan_multi_shot", kasan_set_multi_shot);
  77
  78 /*
  79  * This function is used to check whether KASAN reports are suppressed for
  80  * software KASAN modes via kasan_disable/enable_current() critical sections.
  81  *
  82  * This is done to avoid:
  83  * 1. False-positive reports when accessing slab metadata,
  84  * 2. Deadlocking when poisoned memory is accessed by the reporting code.
  85  *
  86  * Hardware Tag-Based KASAN instead relies on:
  87  * For #1: Resetting tags via kasan_reset_tag().
  88  * For #2: Suppression of tag checks via CPU, see report_suppress_start/end().
  89  */
  90 static bool report_suppressed_sw(void)
  91 {
  92 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
  93         if (current->kasan_depth)
  94                 return true;
  95 #endif
  96         return false;
  97 }
  98
  99 static void report_suppress_start(void)
 100 {
 101 #ifdef CONFIG_KASAN_HW_TAGS
 102         /*
 103          * Disable preemption for the duration of printing a KASAN report, as
 104          * hw_suppress_tag_checks_start() disables checks on the current CPU.
 105          */
 106         preempt_disable();
 107         hw_suppress_tag_checks_start();
 108 #else
 109         kasan_disable_current();
 110 #endif
 111 }
 112
 113 static void report_suppress_stop(void)
 114 {
 115 #ifdef CONFIG_KASAN_HW_TAGS
 116         hw_suppress_tag_checks_stop();
 117         preempt_enable();
 118 #else
 119         kasan_enable_current();
 120 #endif
 121 }
 122
 123 /*
 124  * Used to avoid reporting more than one KASAN bug unless kasan_multi_shot
 125  * is enabled. Note that KASAN tests effectively enable kasan_multi_shot
 126  * for their duration.
 127  */
 128 static bool report_enabled(void)
 129 {
 130         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 131                 return true;
 132         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 133 }
 134
 135 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) || IS_ENABLED(CONFIG_KASAN_MODULE_TEST)
 136
 137 bool kasan_save_enable_multi_shot(void)
 138 {
 139         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 140 }
 141 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
 142
 143 void kasan_restore_multi_shot(bool enabled)
 144 {
 145         if (!enabled)
 146                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 147 }
 148 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
 149
 150 #endif
 151
 152 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 153
 154 /*
 155  * Whether the KASAN KUnit test suite is currently being executed.
 156  * Updated in kasan_test.c.
 157  */
 158 static bool kasan_kunit_executing;
 159
 160 void kasan_kunit_test_suite_start(void)
 161 {
 162         WRITE_ONCE(kasan_kunit_executing, true);
 163 }
 164 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_start);
 165
 166 void kasan_kunit_test_suite_end(void)
 167 {
 168         WRITE_ONCE(kasan_kunit_executing, false);
 169 }
 170 EXPORT_SYMBOL_GPL(kasan_kunit_test_suite_end);
 171
 172 static bool kasan_kunit_test_suite_executing(void)
 173 {
 174         return READ_ONCE(kasan_kunit_executing);
 175 }
 176
 177 #else /* CONFIG_KASAN_KUNIT_TEST */
 178
 179 static inline bool kasan_kunit_test_suite_executing(void) { return false; }
 180
 181 #endif /* CONFIG_KASAN_KUNIT_TEST */
 182
 183 #if IS_ENABLED(CONFIG_KUNIT)
 184
 185 static void fail_non_kasan_kunit_test(void)
 186 {
 187         struct kunit *test;
 188
 189         if (kasan_kunit_test_suite_executing())
 190                 return;
 191
 192         test = current->kunit_test;
 193         if (test)
 194                 kunit_set_failure(test);
 195 }
 196
 197 #else /* CONFIG_KUNIT */
 198
 199 static inline void fail_non_kasan_kunit_test(void) { }
 200
 201 #endif /* CONFIG_KUNIT */
 202
 203 static DEFINE_SPINLOCK(report_lock);
 204
 205 static void start_report(unsigned long *flags, bool sync)
 206 {
 207         fail_non_kasan_kunit_test();
 208         /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
 209         disable_trace_on_warning();
 210         /* Do not allow LOCKDEP mangling KASAN reports. */
 211         lockdep_off();
 212         /* Make sure we don't end up in loop. */
 213         report_suppress_start();
 214         spin_lock_irqsave(&report_lock, *flags);
 215         pr_err("==================================================================\n");
 216 }
 217
 218 static void end_report(unsigned long *flags, const void *addr, bool is_write)
 219 {
 220         if (addr)
 221                 trace_error_report_end(ERROR_DETECTOR_KASAN,
 222                                        (unsigned long)addr);
 223         pr_err("==================================================================\n");
 224         spin_unlock_irqrestore(&report_lock, *flags);
 225         if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 226                 check_panic_on_warn("KASAN");
 227         switch (kasan_arg_fault) {
 228         case KASAN_ARG_FAULT_DEFAULT:
 229         case KASAN_ARG_FAULT_REPORT:
 230                 break;
 231         case KASAN_ARG_FAULT_PANIC:
 232                 panic("kasan.fault=panic set ...\n");
 233                 break;
 234         case KASAN_ARG_FAULT_PANIC_ON_WRITE:
 235                 if (is_write)
 236                         panic("kasan.fault=panic_on_write set ...\n");
 237                 break;
 238         }
 239         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 240         lockdep_on();
 241         report_suppress_stop();
 242 }
 243
 244 static void print_error_description(struct kasan_report_info *info)
 245 {
 246         pr_err("BUG: KASAN: %s in %pS\n", info->bug_type, (void *)info->ip);
 247
 248         if (info->type != KASAN_REPORT_ACCESS) {
 249                 pr_err("Free of addr %px by task %s/%d\n",
 250                         info->access_addr, current->comm, task_pid_nr(current));
 251                 return;
 252         }
 253
 254         if (info->access_size)
 255                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
 256                         info->is_write ? "Write" : "Read", info->access_size,
 257                         info->access_addr, current->comm, task_pid_nr(current));
 258         else
 259                 pr_err("%s at addr %px by task %s/%d\n",
 260                         info->is_write ? "Write" : "Read",
 261                         info->access_addr, current->comm, task_pid_nr(current));
 262 }
 263
 264 static void print_track(struct kasan_track *track, const char *prefix)
 265 {
 266 #ifdef CONFIG_KASAN_EXTRA_INFO
 267         u64 ts_nsec = track->timestamp;
 268         unsigned long rem_usec;
 269
 270         ts_nsec <<= 9;
 271         rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000;
 272
 273         pr_err("%s by task %u on cpu %d at %lu.%06lus:\n",
 274                         prefix, track->pid, track->cpu,
 275                         (unsigned long)ts_nsec, rem_usec);
 276 #else
 277         pr_err("%s by task %u:\n", prefix, track->pid);
 278 #endif /* CONFIG_KASAN_EXTRA_INFO */
 279         if (track->stack)
 280                 stack_depot_print(track->stack);
 281         else
 282                 pr_err("(stack is not available)\n");
 283 }
 284
 285 static inline struct page *addr_to_page(const void *addr)
 286 {
 287         if (virt_addr_valid(addr))
 288                 return virt_to_head_page(addr);
 289         return NULL;
 290 }
 291
 292 static void describe_object_addr(const void *addr, struct kasan_report_info *info)
 293 {
 294         unsigned long access_addr = (unsigned long)addr;
 295         unsigned long object_addr = (unsigned long)info->object;
 296         const char *rel_type, *region_state = "";
 297         int rel_bytes;
 298
 299         pr_err("The buggy address belongs to the object at %px\n"
 300                " which belongs to the cache %s of size %d\n",
 301                 info->object, info->cache->name, info->cache->object_size);
 302
 303         if (access_addr < object_addr) {
 304                 rel_type = "to the left";
 305                 rel_bytes = object_addr - access_addr;
 306         } else if (access_addr >= object_addr + info->alloc_size) {
 307                 rel_type = "to the right";
 308                 rel_bytes = access_addr - (object_addr + info->alloc_size);
 309         } else {
 310                 rel_type = "inside";
 311                 rel_bytes = access_addr - object_addr;
 312         }
 313
 314         /*
 315          * Tag-Based modes use the stack ring to infer the bug type, but the
 316          * memory region state description is generated based on the metadata.
 317          * Thus, defining the region state as below can contradict the metadata.
 318          * Fixing this requires further improvements, so only infer the state
 319          * for the Generic mode.
 320          */
 321         if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
 322                 if (strcmp(info->bug_type, "slab-out-of-bounds") == 0)
 323                         region_state = "allocated ";
 324                 else if (strcmp(info->bug_type, "slab-use-after-free") == 0)
 325                         region_state = "freed ";
 326         }
 327
 328         pr_err("The buggy address is located %d bytes %s of\n"
 329                " %s%zu-byte region [%px, %px)\n",
 330                rel_bytes, rel_type, region_state, info->alloc_size,
 331                (void *)object_addr, (void *)(object_addr + info->alloc_size));
 332 }
 333
 334 static void describe_object_stacks(struct kasan_report_info *info)
 335 {
 336         if (info->alloc_track.stack) {
 337                 print_track(&info->alloc_track, "Allocated");
 338                 pr_err("\n");
 339         }
 340
 341         if (info->free_track.stack) {
 342                 print_track(&info->free_track, "Freed");
 343                 pr_err("\n");
 344         }
 345
 346         kasan_print_aux_stacks(info->cache, info->object);
 347 }
 348
 349 static void describe_object(const void *addr, struct kasan_report_info *info)
 350 {
 351         if (kasan_stack_collection_enabled())
 352                 describe_object_stacks(info);
 353         describe_object_addr(addr, info);
 354 }
 355
 356 static inline bool kernel_or_module_addr(const void *addr)
 357 {
 358         if (is_kernel((unsigned long)addr))
 359                 return true;
 360         if (is_module_address((unsigned long)addr))
 361                 return true;
 362         return false;
 363 }
 364
 365 static inline bool init_task_stack_addr(const void *addr)
 366 {
 367         return addr >= (void *)&init_thread_union.stack &&
 368                 (addr <= (void *)&init_thread_union.stack +
 369                         sizeof(init_thread_union.stack));
 370 }
 371
 372 static void print_address_description(void *addr, u8 tag,
 373                                       struct kasan_report_info *info)
 374 {
 375         struct page *page = addr_to_page(addr);
 376
 377         dump_stack_lvl(KERN_ERR);
 378         pr_err("\n");
 379
 380         if (info->cache && info->object) {
 381                 describe_object(addr, info);
 382                 pr_err("\n");
 383         }
 384
 385         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 386                 pr_err("The buggy address belongs to the variable:\n");
 387                 pr_err(" %pS\n", addr);
 388                 pr_err("\n");
 389         }
 390
 391         if (object_is_on_stack(addr)) {
 392                 /*
 393                  * Currently, KASAN supports printing frame information only
 394                  * for accesses to the task's own stack.
 395                  */
 396                 kasan_print_address_stack_frame(addr);
 397                 pr_err("\n");
 398         }
 399
 400         if (is_vmalloc_addr(addr)) {
 401                 struct vm_struct *va = find_vm_area(addr);
 402
 403                 if (va) {
 404                         pr_err("The buggy address belongs to the virtual mapping at\n"
 405                                " [%px, %px) created by:\n"
 406                                " %pS\n",
 407                                va->addr, va->addr + va->size, va->caller);
 408                         pr_err("\n");
 409
 410                         page = vmalloc_to_page(addr);
 411                 }
 412         }
 413
 414         if (page) {
 415                 pr_err("The buggy address belongs to the physical page:\n");
 416                 dump_page(page, "kasan: bad access detected");
 417                 pr_err("\n");
 418         }
 419 }
 420
 421 static bool meta_row_is_guilty(const void *row, const void *addr)
 422 {
 423         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 424 }
 425
 426 static int meta_pointer_offset(const void *row, const void *addr)
 427 {
 428         /*
 429          * Memory state around the buggy address:
 430          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 431          *  ...
 432          *
 433          * The length of ">ff00ff00ff00ff00: " is
 434          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 435          * The length of each granule metadata is 2 bytes
 436          *    plus 1 byte for space.
 437          */
 438         return 3 + (BITS_PER_LONG / 8) * 2 +
 439                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 440 }
 441
 442 static void print_memory_metadata(const void *addr)
 443 {
 444         int i;
 445         void *row;
 446
 447         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 448                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 449
 450         pr_err("Memory state around the buggy address:\n");
 451
 452         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 453                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 454                 char metadata[META_BYTES_PER_ROW];
 455
 456                 snprintf(buffer, sizeof(buffer),
 457                                 (i == 0) ? ">%px: " : " %px: ", row);
 458
 459                 /*
 460                  * We should not pass a shadow pointer to generic
 461                  * function, because generic functions may try to
 462                  * access kasan mapping for the passed address.
 463                  */
 464                 kasan_metadata_fetch_row(&metadata[0], row);
 465
 466                 print_hex_dump(KERN_ERR, buffer,
 467                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 468                         metadata, META_BYTES_PER_ROW, 0);
 469
 470                 if (meta_row_is_guilty(row, addr))
 471                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 472
 473                 row += META_MEM_BYTES_PER_ROW;
 474         }
 475 }
 476
 477 static void print_report(struct kasan_report_info *info)
 478 {
 479         void *addr = kasan_reset_tag((void *)info->access_addr);
 480         u8 tag = get_tag((void *)info->access_addr);
 481
 482         print_error_description(info);
 483         if (addr_has_metadata(addr))
 484                 kasan_print_tags(tag, info->first_bad_addr);
 485         pr_err("\n");
 486
 487         if (addr_has_metadata(addr)) {
 488                 print_address_description(addr, tag, info);
 489                 print_memory_metadata(info->first_bad_addr);
 490         } else {
 491                 dump_stack_lvl(KERN_ERR);
 492         }
 493 }
 494
 495 static void complete_report_info(struct kasan_report_info *info)
 496 {
 497         void *addr = kasan_reset_tag((void *)info->access_addr);
 498         struct slab *slab;
 499
 500         if (info->type == KASAN_REPORT_ACCESS)
 501                 info->first_bad_addr = kasan_find_first_bad_addr(
 502                                         (void *)info->access_addr, info->access_size);
 503         else
 504                 info->first_bad_addr = addr;
 505
 506         slab = kasan_addr_to_slab(addr);
 507         if (slab) {
 508                 info->cache = slab->slab_cache;
 509                 info->object = nearest_obj(info->cache, slab, addr);
 510
 511                 /* Try to determine allocation size based on the metadata. */
 512                 info->alloc_size = kasan_get_alloc_size(info->object, info->cache);
 513                 /* Fallback to the object size if failed. */
 514                 if (!info->alloc_size)
 515                         info->alloc_size = info->cache->object_size;
 516         } else
 517                 info->cache = info->object = NULL;
 518
 519         switch (info->type) {
 520         case KASAN_REPORT_INVALID_FREE:
 521                 info->bug_type = "invalid-free";
 522                 break;
 523         case KASAN_REPORT_DOUBLE_FREE:
 524                 info->bug_type = "double-free";
 525                 break;
 526         default:
 527                 /* bug_type filled in by kasan_complete_mode_report_info. */
 528                 break;
 529         }
 530
 531         /* Fill in mode-specific report info fields. */
 532         kasan_complete_mode_report_info(info);
 533 }
 534
 535 void kasan_report_invalid_free(void *ptr, unsigned long ip, enum kasan_report_type type)
 536 {
 537         unsigned long flags;
 538         struct kasan_report_info info;
 539
 540         /*
 541          * Do not check report_suppressed_sw(), as an invalid-free cannot be
 542          * caused by accessing poisoned memory and thus should not be suppressed
 543          * by kasan_disable/enable_current() critical sections.
 544          *
 545          * Note that for Hardware Tag-Based KASAN, kasan_report_invalid_free()
 546          * is triggered by explicit tag checks and not by the ones performed by
 547          * the CPU. Thus, reporting invalid-free is not suppressed as well.
 548          */
 549         if (unlikely(!report_enabled()))
 550                 return;
 551
 552         start_report(&flags, true);
 553
 554         __memset(&info, 0, sizeof(info));
 555         info.type = type;
 556         info.access_addr = ptr;
 557         info.access_size = 0;
 558         info.is_write = false;
 559         info.ip = ip;
 560
 561         complete_report_info(&info);
 562
 563         print_report(&info);
 564
 565         /*
 566          * Invalid free is considered a "write" since the allocator's metadata
 567          * updates involves writes.
 568          */
 569         end_report(&flags, ptr, true);
 570 }
 571
 572 /*
 573  * kasan_report() is the only reporting function that uses
 574  * user_access_save/restore(): kasan_report_invalid_free() cannot be called
 575  * from a UACCESS region, and kasan_report_async() is not used on x86.
 576  */
 577 bool kasan_report(const void *addr, size_t size, bool is_write,
 578                         unsigned long ip)
 579 {
 580         bool ret = true;
 581         unsigned long ua_flags = user_access_save();
 582         unsigned long irq_flags;
 583         struct kasan_report_info info;
 584
 585         if (unlikely(report_suppressed_sw()) || unlikely(!report_enabled())) {
 586                 ret = false;
 587                 goto out;
 588         }
 589
 590         start_report(&irq_flags, true);
 591
 592         __memset(&info, 0, sizeof(info));
 593         info.type = KASAN_REPORT_ACCESS;
 594         info.access_addr = addr;
 595         info.access_size = size;
 596         info.is_write = is_write;
 597         info.ip = ip;
 598
 599         complete_report_info(&info);
 600
 601         print_report(&info);
 602
 603         end_report(&irq_flags, (void *)addr, is_write);
 604
 605 out:
 606         user_access_restore(ua_flags);
 607
 608         return ret;
 609 }
 610
 611 #ifdef CONFIG_KASAN_HW_TAGS
 612 void kasan_report_async(void)
 613 {
 614         unsigned long flags;
 615
 616         /*
 617          * Do not check report_suppressed_sw(), as
 618          * kasan_disable/enable_current() critical sections do not affect
 619          * Hardware Tag-Based KASAN.
 620          */
 621         if (unlikely(!report_enabled()))
 622                 return;
 623
 624         start_report(&flags, false);
 625         pr_err("BUG: KASAN: invalid-access\n");
 626         pr_err("Asynchronous fault: no details available\n");
 627         pr_err("\n");
 628         dump_stack_lvl(KERN_ERR);
 629         /*
 630          * Conservatively set is_write=true, because no details are available.
 631          * In this mode, kasan.fault=panic_on_write is like kasan.fault=panic.
 632          */
 633         end_report(&flags, NULL, true);
 634 }
 635 #endif /* CONFIG_KASAN_HW_TAGS */
 636
 637 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 638 /*
 639  * With compiler-based KASAN modes, accesses to bogus pointers (outside of the
 640  * mapped kernel address space regions) cause faults when KASAN tries to check
 641  * the shadow memory before the actual memory access. This results in cryptic
 642  * GPF reports, which are hard for users to interpret. This hook helps users to
 643  * figure out what the original bogus pointer was.
 644  */
 645 void kasan_non_canonical_hook(unsigned long addr)
 646 {
 647         unsigned long orig_addr;
 648         const char *bug_type;
 649
 650         /*
 651          * All addresses that came as a result of the memory-to-shadow mapping
 652          * (even for bogus pointers) must be >= KASAN_SHADOW_OFFSET.
 653          */
 654         if (addr < KASAN_SHADOW_OFFSET)
 655                 return;
 656
 657         orig_addr = (unsigned long)kasan_shadow_to_mem((void *)addr);
 658
 659         /*
 660          * For faults near the shadow address for NULL, we can be fairly certain
 661          * that this is a KASAN shadow memory access.
 662          * For faults that correspond to the shadow for low or high canonical
 663          * addresses, we can still be pretty sure: these shadow regions are a
 664          * fairly narrow chunk of the address space.
 665          * But the shadow for non-canonical addresses is a really large chunk
 666          * of the address space. For this case, we still print the decoded
 667          * address, but make it clear that this is not necessarily what's
 668          * actually going on.
 669          */
 670         if (orig_addr < PAGE_SIZE)
 671                 bug_type = "null-ptr-deref";
 672         else if (orig_addr < TASK_SIZE)
 673                 bug_type = "probably user-memory-access";
 674         else if (addr_in_shadow((void *)addr))
 675                 bug_type = "probably wild-memory-access";
 676         else
 677                 bug_type = "maybe wild-memory-access";
 678         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 679                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 680 }
 681 #endif