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 (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
 121                 /*
 122                  * This thread may hit another WARN() in the panic path.
 123                  * Resetting this prevents additional WARN() from panicking the
 124                  * system on this thread.  Other threads are blocked by the
 125                  * panic_mutex in panic().
 126                  */
 127                 panic_on_warn = 0;
 128                 panic("panic_on_warn set ...\n");
 129         }
 130         if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
 131                 panic("kasan.fault=panic set ...\n");
 132         kasan_enable_current();
 133 }
 134
 135 static void print_stack(depot_stack_handle_t stack)
 136 {
 137         unsigned long *entries;
 138         unsigned int nr_entries;
 139
 140         nr_entries = stack_depot_fetch(stack, &entries);
 141         stack_trace_print(entries, nr_entries, 0);
 142 }
 143
 144 static void print_track(struct kasan_track *track, const char *prefix)
 145 {
 146         pr_err("%s by task %u:\n", prefix, track->pid);
 147         if (track->stack) {
 148                 print_stack(track->stack);
 149         } else {
 150                 pr_err("(stack is not available)\n");
 151         }
 152 }
 153
 154 struct page *kasan_addr_to_page(const void *addr)
 155 {
 156         if ((addr >= (void *)PAGE_OFFSET) &&
 157                         (addr < high_memory))
 158                 return virt_to_head_page(addr);
 159         return NULL;
 160 }
 161
 162 static void describe_object_addr(struct kmem_cache *cache, void *object,
 163                                 const void *addr)
 164 {
 165         unsigned long access_addr = (unsigned long)addr;
 166         unsigned long object_addr = (unsigned long)object;
 167         const char *rel_type;
 168         int rel_bytes;
 169
 170         pr_err("The buggy address belongs to the object at %px\n"
 171                " which belongs to the cache %s of size %d\n",
 172                 object, cache->name, cache->object_size);
 173
 174         if (!addr)
 175                 return;
 176
 177         if (access_addr < object_addr) {
 178                 rel_type = "to the left";
 179                 rel_bytes = object_addr - access_addr;
 180         } else if (access_addr >= object_addr + cache->object_size) {
 181                 rel_type = "to the right";
 182                 rel_bytes = access_addr - (object_addr + cache->object_size);
 183         } else {
 184                 rel_type = "inside";
 185                 rel_bytes = access_addr - object_addr;
 186         }
 187
 188         pr_err("The buggy address is located %d bytes %s of\n"
 189                " %d-byte region [%px, %px)\n",
 190                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 191                 (void *)(object_addr + cache->object_size));
 192 }
 193
 194 static void describe_object_stacks(struct kmem_cache *cache, void *object,
 195                                         const void *addr, u8 tag)
 196 {
 197         struct kasan_alloc_meta *alloc_meta;
 198         struct kasan_track *free_track;
 199
 200         alloc_meta = kasan_get_alloc_meta(cache, object);
 201         if (alloc_meta) {
 202                 print_track(&alloc_meta->alloc_track, "Allocated");
 203                 pr_err("\n");
 204         }
 205
 206         free_track = kasan_get_free_track(cache, object, tag);
 207         if (free_track) {
 208                 print_track(free_track, "Freed");
 209                 pr_err("\n");
 210         }
 211
 212 #ifdef CONFIG_KASAN_GENERIC
 213         if (!alloc_meta)
 214                 return;
 215         if (alloc_meta->aux_stack[0]) {
 216                 pr_err("Last potentially related work creation:\n");
 217                 print_stack(alloc_meta->aux_stack[0]);
 218                 pr_err("\n");
 219         }
 220         if (alloc_meta->aux_stack[1]) {
 221                 pr_err("Second to last potentially related work creation:\n");
 222                 print_stack(alloc_meta->aux_stack[1]);
 223                 pr_err("\n");
 224         }
 225 #endif
 226 }
 227
 228 static void describe_object(struct kmem_cache *cache, void *object,
 229                                 const void *addr, u8 tag)
 230 {
 231         if (kasan_stack_collection_enabled())
 232                 describe_object_stacks(cache, object, addr, tag);
 233         describe_object_addr(cache, object, addr);
 234 }
 235
 236 static inline bool kernel_or_module_addr(const void *addr)
 237 {
 238         if (addr >= (void *)_stext && addr < (void *)_end)
 239                 return true;
 240         if (is_module_address((unsigned long)addr))
 241                 return true;
 242         return false;
 243 }
 244
 245 static inline bool init_task_stack_addr(const void *addr)
 246 {
 247         return addr >= (void *)&init_thread_union.stack &&
 248                 (addr <= (void *)&init_thread_union.stack +
 249                         sizeof(init_thread_union.stack));
 250 }
 251
 252 static void print_address_description(void *addr, u8 tag)
 253 {
 254         struct page *page = kasan_addr_to_page(addr);
 255
 256         dump_stack_lvl(KERN_ERR);
 257         pr_err("\n");
 258
 259         if (page && PageSlab(page)) {
 260                 struct kmem_cache *cache = page->slab_cache;
 261                 void *object = nearest_obj(cache, page, addr);
 262
 263                 describe_object(cache, object, addr, tag);
 264         }
 265
 266         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 267                 pr_err("The buggy address belongs to the variable:\n");
 268                 pr_err(" %pS\n", addr);
 269         }
 270
 271         if (page) {
 272                 pr_err("The buggy address belongs to the page:\n");
 273                 dump_page(page, "kasan: bad access detected");
 274         }
 275
 276         kasan_print_address_stack_frame(addr);
 277 }
 278
 279 static bool meta_row_is_guilty(const void *row, const void *addr)
 280 {
 281         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 282 }
 283
 284 static int meta_pointer_offset(const void *row, const void *addr)
 285 {
 286         /*
 287          * Memory state around the buggy address:
 288          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 289          *  ...
 290          *
 291          * The length of ">ff00ff00ff00ff00: " is
 292          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 293          * The length of each granule metadata is 2 bytes
 294          *    plus 1 byte for space.
 295          */
 296         return 3 + (BITS_PER_LONG / 8) * 2 +
 297                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 298 }
 299
 300 static void print_memory_metadata(const void *addr)
 301 {
 302         int i;
 303         void *row;
 304
 305         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 306                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 307
 308         pr_err("Memory state around the buggy address:\n");
 309
 310         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 311                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 312                 char metadata[META_BYTES_PER_ROW];
 313
 314                 snprintf(buffer, sizeof(buffer),
 315                                 (i == 0) ? ">%px: " : " %px: ", row);
 316
 317                 /*
 318                  * We should not pass a shadow pointer to generic
 319                  * function, because generic functions may try to
 320                  * access kasan mapping for the passed address.
 321                  */
 322                 kasan_metadata_fetch_row(&metadata[0], row);
 323
 324                 print_hex_dump(KERN_ERR, buffer,
 325                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 326                         metadata, META_BYTES_PER_ROW, 0);
 327
 328                 if (meta_row_is_guilty(row, addr))
 329                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 330
 331                 row += META_MEM_BYTES_PER_ROW;
 332         }
 333 }
 334
 335 static bool report_enabled(void)
 336 {
 337 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 338         if (current->kasan_depth)
 339                 return false;
 340 #endif
 341         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 342                 return true;
 343         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 344 }
 345
 346 #if IS_ENABLED(CONFIG_KUNIT)
 347 static void kasan_update_kunit_status(struct kunit *cur_test)
 348 {
 349         struct kunit_resource *resource;
 350         struct kunit_kasan_expectation *kasan_data;
 351
 352         resource = kunit_find_named_resource(cur_test, "kasan_data");
 353
 354         if (!resource) {
 355                 kunit_set_failure(cur_test);
 356                 return;
 357         }
 358
 359         kasan_data = (struct kunit_kasan_expectation *)resource->data;
 360         WRITE_ONCE(kasan_data->report_found, true);
 361         kunit_put_resource(resource);
 362 }
 363 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 364
 365 void kasan_report_invalid_free(void *object, unsigned long ip)
 366 {
 367         unsigned long flags;
 368         u8 tag = get_tag(object);
 369
 370         object = kasan_reset_tag(object);
 371
 372 #if IS_ENABLED(CONFIG_KUNIT)
 373         if (current->kunit_test)
 374                 kasan_update_kunit_status(current->kunit_test);
 375 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 376
 377         start_report(&flags);
 378         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 379         kasan_print_tags(tag, object);
 380         pr_err("\n");
 381         print_address_description(object, tag);
 382         pr_err("\n");
 383         print_memory_metadata(object);
 384         end_report(&flags, (unsigned long)object);
 385 }
 386
 387 #ifdef CONFIG_KASAN_HW_TAGS
 388 void kasan_report_async(void)
 389 {
 390         unsigned long flags;
 391
 392 #if IS_ENABLED(CONFIG_KUNIT)
 393         if (current->kunit_test)
 394                 kasan_update_kunit_status(current->kunit_test);
 395 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 396
 397         start_report(&flags);
 398         pr_err("BUG: KASAN: invalid-access\n");
 399         pr_err("Asynchronous mode enabled: no access details available\n");
 400         pr_err("\n");
 401         dump_stack_lvl(KERN_ERR);
 402         end_report(&flags, 0);
 403 }
 404 #endif /* CONFIG_KASAN_HW_TAGS */
 405
 406 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 407                                 unsigned long ip)
 408 {
 409         struct kasan_access_info info;
 410         void *tagged_addr;
 411         void *untagged_addr;
 412         unsigned long flags;
 413
 414 #if IS_ENABLED(CONFIG_KUNIT)
 415         if (current->kunit_test)
 416                 kasan_update_kunit_status(current->kunit_test);
 417 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 418
 419         disable_trace_on_warning();
 420
 421         tagged_addr = (void *)addr;
 422         untagged_addr = kasan_reset_tag(tagged_addr);
 423
 424         info.access_addr = tagged_addr;
 425         if (addr_has_metadata(untagged_addr))
 426                 info.first_bad_addr =
 427                         kasan_find_first_bad_addr(tagged_addr, size);
 428         else
 429                 info.first_bad_addr = untagged_addr;
 430         info.access_size = size;
 431         info.is_write = is_write;
 432         info.ip = ip;
 433
 434         start_report(&flags);
 435
 436         print_error_description(&info);
 437         if (addr_has_metadata(untagged_addr))
 438                 kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
 439         pr_err("\n");
 440
 441         if (addr_has_metadata(untagged_addr)) {
 442                 print_address_description(untagged_addr, get_tag(tagged_addr));
 443                 pr_err("\n");
 444                 print_memory_metadata(info.first_bad_addr);
 445         } else {
 446                 dump_stack_lvl(KERN_ERR);
 447         }
 448
 449         end_report(&flags, addr);
 450 }
 451
 452 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 453                         unsigned long ip)
 454 {
 455         unsigned long flags = user_access_save();
 456         bool ret = false;
 457
 458         if (likely(report_enabled())) {
 459                 __kasan_report(addr, size, is_write, ip);
 460                 ret = true;
 461         }
 462
 463         user_access_restore(flags);
 464
 465         return ret;
 466 }
 467
 468 #ifdef CONFIG_KASAN_INLINE
 469 /*
 470  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 471  * canonical half of the address space) cause out-of-bounds shadow memory reads
 472  * before the actual access. For addresses in the low canonical half of the
 473  * address space, as well as most non-canonical addresses, that out-of-bounds
 474  * shadow memory access lands in the non-canonical part of the address space.
 475  * Help the user figure out what the original bogus pointer was.
 476  */
 477 void kasan_non_canonical_hook(unsigned long addr)
 478 {
 479         unsigned long orig_addr;
 480         const char *bug_type;
 481
 482         if (addr < KASAN_SHADOW_OFFSET)
 483                 return;
 484
 485         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 486         /*
 487          * For faults near the shadow address for NULL, we can be fairly certain
 488          * that this is a KASAN shadow memory access.
 489          * For faults that correspond to shadow for low canonical addresses, we
 490          * can still be pretty sure - that shadow region is a fairly narrow
 491          * chunk of the non-canonical address space.
 492          * But faults that look like shadow for non-canonical addresses are a
 493          * really large chunk of the address space. In that case, we still
 494          * print the decoded address, but make it clear that this is not
 495          * necessarily what's actually going on.
 496          */
 497         if (orig_addr < PAGE_SIZE)
 498                 bug_type = "null-ptr-deref";
 499         else if (orig_addr < TASK_SIZE)
 500                 bug_type = "probably user-memory-access";
 501         else
 502                 bug_type = "maybe wild-memory-access";
 503         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 504                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 505 }
 506 #endif