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 <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 #include <trace/events/error_report.h>
  29
  30 #include <asm/sections.h>
  31
  32 #include <kunit/test.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 bool kasan_save_enable_multi_shot(void)
  68 {
  69         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  70 }
  71 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  72
  73 void kasan_restore_multi_shot(bool enabled)
  74 {
  75         if (!enabled)
  76                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  77 }
  78 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  79
  80 static int __init kasan_set_multi_shot(char *str)
  81 {
  82         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  83         return 1;
  84 }
  85 __setup("kasan_multi_shot", kasan_set_multi_shot);
  86
  87 static void print_error_description(struct kasan_access_info *info)
  88 {
  89         pr_err("BUG: KASAN: %s in %pS\n",
  90                 kasan_get_bug_type(info), (void *)info->ip);
  91         if (info->access_size)
  92                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
  93                         info->is_write ? "Write" : "Read", info->access_size,
  94                         info->access_addr, current->comm, task_pid_nr(current));
  95         else
  96                 pr_err("%s at addr %px by task %s/%d\n",
  97                         info->is_write ? "Write" : "Read",
  98                         info->access_addr, current->comm, task_pid_nr(current));
  99 }
 100
 101 static DEFINE_SPINLOCK(report_lock);
 102
 103 static void start_report(unsigned long *flags)
 104 {
 105         /*
 106          * Make sure we don't end up in loop.
 107          */
 108         kasan_disable_current();
 109         spin_lock_irqsave(&report_lock, *flags);
 110         pr_err("==================================================================\n");
 111 }
 112
 113 static void end_report(unsigned long *flags, unsigned long addr)
 114 {
 115         if (!kasan_async_mode_enabled())
 116                 trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
 117         pr_err("==================================================================\n");
 118         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 119         spin_unlock_irqrestore(&report_lock, *flags);
 120         if (!test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 121                 check_panic_on_warn("KASAN");
 122         if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
 123                 panic("kasan.fault=panic set ...\n");
 124         kasan_enable_current();
 125 }
 126
 127 static void print_stack(depot_stack_handle_t stack)
 128 {
 129         unsigned long *entries;
 130         unsigned int nr_entries;
 131
 132         nr_entries = stack_depot_fetch(stack, &entries);
 133         stack_trace_print(entries, nr_entries, 0);
 134 }
 135
 136 static void print_track(struct kasan_track *track, const char *prefix)
 137 {
 138         pr_err("%s by task %u:\n", prefix, track->pid);
 139         if (track->stack) {
 140                 print_stack(track->stack);
 141         } else {
 142                 pr_err("(stack is not available)\n");
 143         }
 144 }
 145
 146 struct page *kasan_addr_to_page(const void *addr)
 147 {
 148         if ((addr >= (void *)PAGE_OFFSET) &&
 149                         (addr < high_memory))
 150                 return virt_to_head_page(addr);
 151         return NULL;
 152 }
 153
 154 static void describe_object_addr(struct kmem_cache *cache, void *object,
 155                                 const void *addr)
 156 {
 157         unsigned long access_addr = (unsigned long)addr;
 158         unsigned long object_addr = (unsigned long)object;
 159         const char *rel_type;
 160         int rel_bytes;
 161
 162         pr_err("The buggy address belongs to the object at %px\n"
 163                " which belongs to the cache %s of size %d\n",
 164                 object, cache->name, cache->object_size);
 165
 166         if (!addr)
 167                 return;
 168
 169         if (access_addr < object_addr) {
 170                 rel_type = "to the left";
 171                 rel_bytes = object_addr - access_addr;
 172         } else if (access_addr >= object_addr + cache->object_size) {
 173                 rel_type = "to the right";
 174                 rel_bytes = access_addr - (object_addr + cache->object_size);
 175         } else {
 176                 rel_type = "inside";
 177                 rel_bytes = access_addr - object_addr;
 178         }
 179
 180         pr_err("The buggy address is located %d bytes %s of\n"
 181                " %d-byte region [%px, %px)\n",
 182                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 183                 (void *)(object_addr + cache->object_size));
 184 }
 185
 186 static void describe_object_stacks(struct kmem_cache *cache, void *object,
 187                                         const void *addr, u8 tag)
 188 {
 189         struct kasan_alloc_meta *alloc_meta;
 190         struct kasan_track *free_track;
 191
 192         alloc_meta = kasan_get_alloc_meta(cache, object);
 193         if (alloc_meta) {
 194                 print_track(&alloc_meta->alloc_track, "Allocated");
 195                 pr_err("\n");
 196         }
 197
 198         free_track = kasan_get_free_track(cache, object, tag);
 199         if (free_track) {
 200                 print_track(free_track, "Freed");
 201                 pr_err("\n");
 202         }
 203
 204 #ifdef CONFIG_KASAN_GENERIC
 205         if (!alloc_meta)
 206                 return;
 207         if (alloc_meta->aux_stack[0]) {
 208                 pr_err("Last potentially related work creation:\n");
 209                 print_stack(alloc_meta->aux_stack[0]);
 210                 pr_err("\n");
 211         }
 212         if (alloc_meta->aux_stack[1]) {
 213                 pr_err("Second to last potentially related work creation:\n");
 214                 print_stack(alloc_meta->aux_stack[1]);
 215                 pr_err("\n");
 216         }
 217 #endif
 218 }
 219
 220 static void describe_object(struct kmem_cache *cache, void *object,
 221                                 const void *addr, u8 tag)
 222 {
 223         if (kasan_stack_collection_enabled())
 224                 describe_object_stacks(cache, object, addr, tag);
 225         describe_object_addr(cache, object, addr);
 226 }
 227
 228 static inline bool kernel_or_module_addr(const void *addr)
 229 {
 230         if (addr >= (void *)_stext && addr < (void *)_end)
 231                 return true;
 232         if (is_module_address((unsigned long)addr))
 233                 return true;
 234         return false;
 235 }
 236
 237 static inline bool init_task_stack_addr(const void *addr)
 238 {
 239         return addr >= (void *)&init_thread_union.stack &&
 240                 (addr <= (void *)&init_thread_union.stack +
 241                         sizeof(init_thread_union.stack));
 242 }
 243
 244 static void print_address_description(void *addr, u8 tag)
 245 {
 246         struct page *page = kasan_addr_to_page(addr);
 247
 248         dump_stack_lvl(KERN_ERR);
 249         pr_err("\n");
 250
 251         if (page && PageSlab(page)) {
 252                 struct kmem_cache *cache = page->slab_cache;
 253                 void *object = nearest_obj(cache, page, addr);
 254
 255                 describe_object(cache, object, addr, tag);
 256         }
 257
 258         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 259                 pr_err("The buggy address belongs to the variable:\n");
 260                 pr_err(" %pS\n", addr);
 261         }
 262
 263         if (page) {
 264                 pr_err("The buggy address belongs to the page:\n");
 265                 dump_page(page, "kasan: bad access detected");
 266         }
 267
 268         kasan_print_address_stack_frame(addr);
 269 }
 270
 271 static bool meta_row_is_guilty(const void *row, const void *addr)
 272 {
 273         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 274 }
 275
 276 static int meta_pointer_offset(const void *row, const void *addr)
 277 {
 278         /*
 279          * Memory state around the buggy address:
 280          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 281          *  ...
 282          *
 283          * The length of ">ff00ff00ff00ff00: " is
 284          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 285          * The length of each granule metadata is 2 bytes
 286          *    plus 1 byte for space.
 287          */
 288         return 3 + (BITS_PER_LONG / 8) * 2 +
 289                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 290 }
 291
 292 static void print_memory_metadata(const void *addr)
 293 {
 294         int i;
 295         void *row;
 296
 297         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 298                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 299
 300         pr_err("Memory state around the buggy address:\n");
 301
 302         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 303                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 304                 char metadata[META_BYTES_PER_ROW];
 305
 306                 snprintf(buffer, sizeof(buffer),
 307                                 (i == 0) ? ">%px: " : " %px: ", row);
 308
 309                 /*
 310                  * We should not pass a shadow pointer to generic
 311                  * function, because generic functions may try to
 312                  * access kasan mapping for the passed address.
 313                  */
 314                 kasan_metadata_fetch_row(&metadata[0], row);
 315
 316                 print_hex_dump(KERN_ERR, buffer,
 317                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 318                         metadata, META_BYTES_PER_ROW, 0);
 319
 320                 if (meta_row_is_guilty(row, addr))
 321                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 322
 323                 row += META_MEM_BYTES_PER_ROW;
 324         }
 325 }
 326
 327 static bool report_enabled(void)
 328 {
 329 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 330         if (current->kasan_depth)
 331                 return false;
 332 #endif
 333         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 334                 return true;
 335         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 336 }
 337
 338 #if IS_ENABLED(CONFIG_KUNIT)
 339 static void kasan_update_kunit_status(struct kunit *cur_test)
 340 {
 341         struct kunit_resource *resource;
 342         struct kunit_kasan_expectation *kasan_data;
 343
 344         resource = kunit_find_named_resource(cur_test, "kasan_data");
 345
 346         if (!resource) {
 347                 kunit_set_failure(cur_test);
 348                 return;
 349         }
 350
 351         kasan_data = (struct kunit_kasan_expectation *)resource->data;
 352         WRITE_ONCE(kasan_data->report_found, true);
 353         kunit_put_resource(resource);
 354 }
 355 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 356
 357 void kasan_report_invalid_free(void *object, unsigned long ip)
 358 {
 359         unsigned long flags;
 360         u8 tag = get_tag(object);
 361
 362         object = kasan_reset_tag(object);
 363
 364 #if IS_ENABLED(CONFIG_KUNIT)
 365         if (current->kunit_test)
 366                 kasan_update_kunit_status(current->kunit_test);
 367 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 368
 369         start_report(&flags);
 370         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 371         kasan_print_tags(tag, object);
 372         pr_err("\n");
 373         print_address_description(object, tag);
 374         pr_err("\n");
 375         print_memory_metadata(object);
 376         end_report(&flags, (unsigned long)object);
 377 }
 378
 379 #ifdef CONFIG_KASAN_HW_TAGS
 380 void kasan_report_async(void)
 381 {
 382         unsigned long flags;
 383
 384 #if IS_ENABLED(CONFIG_KUNIT)
 385         if (current->kunit_test)
 386                 kasan_update_kunit_status(current->kunit_test);
 387 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 388
 389         start_report(&flags);
 390         pr_err("BUG: KASAN: invalid-access\n");
 391         pr_err("Asynchronous mode enabled: no access details available\n");
 392         pr_err("\n");
 393         dump_stack_lvl(KERN_ERR);
 394         end_report(&flags, 0);
 395 }
 396 #endif /* CONFIG_KASAN_HW_TAGS */
 397
 398 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 399                                 unsigned long ip)
 400 {
 401         struct kasan_access_info info;
 402         void *tagged_addr;
 403         void *untagged_addr;
 404         unsigned long flags;
 405
 406 #if IS_ENABLED(CONFIG_KUNIT)
 407         if (current->kunit_test)
 408                 kasan_update_kunit_status(current->kunit_test);
 409 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 410
 411         disable_trace_on_warning();
 412
 413         tagged_addr = (void *)addr;
 414         untagged_addr = kasan_reset_tag(tagged_addr);
 415
 416         info.access_addr = tagged_addr;
 417         if (addr_has_metadata(untagged_addr))
 418                 info.first_bad_addr =
 419                         kasan_find_first_bad_addr(tagged_addr, size);
 420         else
 421                 info.first_bad_addr = untagged_addr;
 422         info.access_size = size;
 423         info.is_write = is_write;
 424         info.ip = ip;
 425
 426         start_report(&flags);
 427
 428         print_error_description(&info);
 429         if (addr_has_metadata(untagged_addr))
 430                 kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
 431         pr_err("\n");
 432
 433         if (addr_has_metadata(untagged_addr)) {
 434                 print_address_description(untagged_addr, get_tag(tagged_addr));
 435                 pr_err("\n");
 436                 print_memory_metadata(info.first_bad_addr);
 437         } else {
 438                 dump_stack_lvl(KERN_ERR);
 439         }
 440
 441         end_report(&flags, addr);
 442 }
 443
 444 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 445                         unsigned long ip)
 446 {
 447         unsigned long flags = user_access_save();
 448         bool ret = false;
 449
 450         if (likely(report_enabled())) {
 451                 __kasan_report(addr, size, is_write, ip);
 452                 ret = true;
 453         }
 454
 455         user_access_restore(flags);
 456
 457         return ret;
 458 }
 459
 460 #ifdef CONFIG_KASAN_INLINE
 461 /*
 462  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 463  * canonical half of the address space) cause out-of-bounds shadow memory reads
 464  * before the actual access. For addresses in the low canonical half of the
 465  * address space, as well as most non-canonical addresses, that out-of-bounds
 466  * shadow memory access lands in the non-canonical part of the address space.
 467  * Help the user figure out what the original bogus pointer was.
 468  */
 469 void kasan_non_canonical_hook(unsigned long addr)
 470 {
 471         unsigned long orig_addr;
 472         const char *bug_type;
 473
 474         if (addr < KASAN_SHADOW_OFFSET)
 475                 return;
 476
 477         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 478         /*
 479          * For faults near the shadow address for NULL, we can be fairly certain
 480          * that this is a KASAN shadow memory access.
 481          * For faults that correspond to shadow for low canonical addresses, we
 482          * can still be pretty sure - that shadow region is a fairly narrow
 483          * chunk of the non-canonical address space.
 484          * But faults that look like shadow for non-canonical addresses are a
 485          * really large chunk of the address space. In that case, we still
 486          * print the decoded address, but make it clear that this is not
 487          * necessarily what's actually going on.
 488          */
 489         if (orig_addr < PAGE_SIZE)
 490                 bug_type = "null-ptr-deref";
 491         else if (orig_addr < TASK_SIZE)
 492                 bug_type = "probably user-memory-access";
 493         else
 494                 bug_type = "maybe wild-memory-access";
 495         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 496                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 497 }
 498 #endif