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