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 bool kasan_save_enable_multi_shot(void)
  43 {
  44         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  45 }
  46 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  47
  48 void kasan_restore_multi_shot(bool enabled)
  49 {
  50         if (!enabled)
  51                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  52 }
  53 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  54
  55 static int __init kasan_set_multi_shot(char *str)
  56 {
  57         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  58         return 1;
  59 }
  60 __setup("kasan_multi_shot", kasan_set_multi_shot);
  61
  62 static void print_error_description(struct kasan_access_info *info)
  63 {
  64         pr_err("BUG: KASAN: %s in %pS\n",
  65                 kasan_get_bug_type(info), (void *)info->ip);
  66         if (info->access_size)
  67                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
  68                         info->is_write ? "Write" : "Read", info->access_size,
  69                         info->access_addr, current->comm, task_pid_nr(current));
  70         else
  71                 pr_err("%s at addr %px by task %s/%d\n",
  72                         info->is_write ? "Write" : "Read",
  73                         info->access_addr, current->comm, task_pid_nr(current));
  74 }
  75
  76 static DEFINE_SPINLOCK(report_lock);
  77
  78 static void start_report(unsigned long *flags)
  79 {
  80         /*
  81          * Make sure we don't end up in loop.
  82          */
  83         kasan_disable_current();
  84         spin_lock_irqsave(&report_lock, *flags);
  85         pr_err("==================================================================\n");
  86 }
  87
  88 static void end_report(unsigned long *flags, unsigned long addr)
  89 {
  90         trace_error_report_end(ERROR_DETECTOR_KASAN, addr);
  91         pr_err("==================================================================\n");
  92         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  93         spin_unlock_irqrestore(&report_lock, *flags);
  94         if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
  95                 /*
  96                  * This thread may hit another WARN() in the panic path.
  97                  * Resetting this prevents additional WARN() from panicking the
  98                  * system on this thread.  Other threads are blocked by the
  99                  * panic_mutex in panic().
 100                  */
 101                 panic_on_warn = 0;
 102                 panic("panic_on_warn set ...\n");
 103         }
 104 #ifdef CONFIG_KASAN_HW_TAGS
 105         if (kasan_flag_panic)
 106                 panic("kasan.fault=panic set ...\n");
 107 #endif
 108         kasan_enable_current();
 109 }
 110
 111 static void print_stack(depot_stack_handle_t stack)
 112 {
 113         unsigned long *entries;
 114         unsigned int nr_entries;
 115
 116         nr_entries = stack_depot_fetch(stack, &entries);
 117         stack_trace_print(entries, nr_entries, 0);
 118 }
 119
 120 static void print_track(struct kasan_track *track, const char *prefix)
 121 {
 122         pr_err("%s by task %u:\n", prefix, track->pid);
 123         if (track->stack) {
 124                 print_stack(track->stack);
 125         } else {
 126                 pr_err("(stack is not available)\n");
 127         }
 128 }
 129
 130 struct page *kasan_addr_to_page(const void *addr)
 131 {
 132         if ((addr >= (void *)PAGE_OFFSET) &&
 133                         (addr < high_memory))
 134                 return virt_to_head_page(addr);
 135         return NULL;
 136 }
 137
 138 static void describe_object_addr(struct kmem_cache *cache, void *object,
 139                                 const void *addr)
 140 {
 141         unsigned long access_addr = (unsigned long)addr;
 142         unsigned long object_addr = (unsigned long)object;
 143         const char *rel_type;
 144         int rel_bytes;
 145
 146         pr_err("The buggy address belongs to the object at %px\n"
 147                " which belongs to the cache %s of size %d\n",
 148                 object, cache->name, cache->object_size);
 149
 150         if (!addr)
 151                 return;
 152
 153         if (access_addr < object_addr) {
 154                 rel_type = "to the left";
 155                 rel_bytes = object_addr - access_addr;
 156         } else if (access_addr >= object_addr + cache->object_size) {
 157                 rel_type = "to the right";
 158                 rel_bytes = access_addr - (object_addr + cache->object_size);
 159         } else {
 160                 rel_type = "inside";
 161                 rel_bytes = access_addr - object_addr;
 162         }
 163
 164         pr_err("The buggy address is located %d bytes %s of\n"
 165                " %d-byte region [%px, %px)\n",
 166                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 167                 (void *)(object_addr + cache->object_size));
 168 }
 169
 170 static void describe_object_stacks(struct kmem_cache *cache, void *object,
 171                                         const void *addr, u8 tag)
 172 {
 173         struct kasan_alloc_meta *alloc_meta;
 174         struct kasan_track *free_track;
 175
 176         alloc_meta = kasan_get_alloc_meta(cache, object);
 177         if (alloc_meta) {
 178                 print_track(&alloc_meta->alloc_track, "Allocated");
 179                 pr_err("\n");
 180         }
 181
 182         free_track = kasan_get_free_track(cache, object, tag);
 183         if (free_track) {
 184                 print_track(free_track, "Freed");
 185                 pr_err("\n");
 186         }
 187
 188 #ifdef CONFIG_KASAN_GENERIC
 189         if (!alloc_meta)
 190                 return;
 191         if (alloc_meta->aux_stack[0]) {
 192                 pr_err("Last potentially related work creation:\n");
 193                 print_stack(alloc_meta->aux_stack[0]);
 194                 pr_err("\n");
 195         }
 196         if (alloc_meta->aux_stack[1]) {
 197                 pr_err("Second to last potentially related work creation:\n");
 198                 print_stack(alloc_meta->aux_stack[1]);
 199                 pr_err("\n");
 200         }
 201 #endif
 202 }
 203
 204 static void describe_object(struct kmem_cache *cache, void *object,
 205                                 const void *addr, u8 tag)
 206 {
 207         if (kasan_stack_collection_enabled())
 208                 describe_object_stacks(cache, object, addr, tag);
 209         describe_object_addr(cache, object, addr);
 210 }
 211
 212 static inline bool kernel_or_module_addr(const void *addr)
 213 {
 214         if (addr >= (void *)_stext && addr < (void *)_end)
 215                 return true;
 216         if (is_module_address((unsigned long)addr))
 217                 return true;
 218         return false;
 219 }
 220
 221 static inline bool init_task_stack_addr(const void *addr)
 222 {
 223         return addr >= (void *)&init_thread_union.stack &&
 224                 (addr <= (void *)&init_thread_union.stack +
 225                         sizeof(init_thread_union.stack));
 226 }
 227
 228 static void print_address_description(void *addr, u8 tag)
 229 {
 230         struct page *page = kasan_addr_to_page(addr);
 231
 232         dump_stack();
 233         pr_err("\n");
 234
 235         if (page && PageSlab(page)) {
 236                 struct kmem_cache *cache = page->slab_cache;
 237                 void *object = nearest_obj(cache, page, addr);
 238
 239                 describe_object(cache, object, addr, tag);
 240         }
 241
 242         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 243                 pr_err("The buggy address belongs to the variable:\n");
 244                 pr_err(" %pS\n", addr);
 245         }
 246
 247         if (page) {
 248                 pr_err("The buggy address belongs to the page:\n");
 249                 dump_page(page, "kasan: bad access detected");
 250         }
 251
 252         kasan_print_address_stack_frame(addr);
 253 }
 254
 255 static bool meta_row_is_guilty(const void *row, const void *addr)
 256 {
 257         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 258 }
 259
 260 static int meta_pointer_offset(const void *row, const void *addr)
 261 {
 262         /*
 263          * Memory state around the buggy address:
 264          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 265          *  ...
 266          *
 267          * The length of ">ff00ff00ff00ff00: " is
 268          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 269          * The length of each granule metadata is 2 bytes
 270          *    plus 1 byte for space.
 271          */
 272         return 3 + (BITS_PER_LONG / 8) * 2 +
 273                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 274 }
 275
 276 static void print_memory_metadata(const void *addr)
 277 {
 278         int i;
 279         void *row;
 280
 281         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 282                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 283
 284         pr_err("Memory state around the buggy address:\n");
 285
 286         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 287                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 288                 char metadata[META_BYTES_PER_ROW];
 289
 290                 snprintf(buffer, sizeof(buffer),
 291                                 (i == 0) ? ">%px: " : " %px: ", row);
 292
 293                 /*
 294                  * We should not pass a shadow pointer to generic
 295                  * function, because generic functions may try to
 296                  * access kasan mapping for the passed address.
 297                  */
 298                 kasan_metadata_fetch_row(&metadata[0], row);
 299
 300                 print_hex_dump(KERN_ERR, buffer,
 301                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 302                         metadata, META_BYTES_PER_ROW, 0);
 303
 304                 if (meta_row_is_guilty(row, addr))
 305                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 306
 307                 row += META_MEM_BYTES_PER_ROW;
 308         }
 309 }
 310
 311 static bool report_enabled(void)
 312 {
 313 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 314         if (current->kasan_depth)
 315                 return false;
 316 #endif
 317         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 318                 return true;
 319         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 320 }
 321
 322 #if IS_ENABLED(CONFIG_KUNIT)
 323 static void kasan_update_kunit_status(struct kunit *cur_test)
 324 {
 325         struct kunit_resource *resource;
 326         struct kunit_kasan_expectation *kasan_data;
 327
 328         resource = kunit_find_named_resource(cur_test, "kasan_data");
 329
 330         if (!resource) {
 331                 kunit_set_failure(cur_test);
 332                 return;
 333         }
 334
 335         kasan_data = (struct kunit_kasan_expectation *)resource->data;
 336         WRITE_ONCE(kasan_data->report_found, true);
 337         kunit_put_resource(resource);
 338 }
 339 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 340
 341 void kasan_report_invalid_free(void *object, unsigned long ip)
 342 {
 343         unsigned long flags;
 344         u8 tag = get_tag(object);
 345
 346         object = kasan_reset_tag(object);
 347
 348 #if IS_ENABLED(CONFIG_KUNIT)
 349         if (current->kunit_test)
 350                 kasan_update_kunit_status(current->kunit_test);
 351 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 352
 353         start_report(&flags);
 354         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 355         kasan_print_tags(tag, object);
 356         pr_err("\n");
 357         print_address_description(object, tag);
 358         pr_err("\n");
 359         print_memory_metadata(object);
 360         end_report(&flags, (unsigned long)object);
 361 }
 362
 363 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 364                                 unsigned long ip)
 365 {
 366         struct kasan_access_info info;
 367         void *tagged_addr;
 368         void *untagged_addr;
 369         unsigned long flags;
 370
 371 #if IS_ENABLED(CONFIG_KUNIT)
 372         if (current->kunit_test)
 373                 kasan_update_kunit_status(current->kunit_test);
 374 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 375
 376         disable_trace_on_warning();
 377
 378         tagged_addr = (void *)addr;
 379         untagged_addr = kasan_reset_tag(tagged_addr);
 380
 381         info.access_addr = tagged_addr;
 382         if (addr_has_metadata(untagged_addr))
 383                 info.first_bad_addr =
 384                         kasan_find_first_bad_addr(tagged_addr, size);
 385         else
 386                 info.first_bad_addr = untagged_addr;
 387         info.access_size = size;
 388         info.is_write = is_write;
 389         info.ip = ip;
 390
 391         start_report(&flags);
 392
 393         print_error_description(&info);
 394         if (addr_has_metadata(untagged_addr))
 395                 kasan_print_tags(get_tag(tagged_addr), info.first_bad_addr);
 396         pr_err("\n");
 397
 398         if (addr_has_metadata(untagged_addr)) {
 399                 print_address_description(untagged_addr, get_tag(tagged_addr));
 400                 pr_err("\n");
 401                 print_memory_metadata(info.first_bad_addr);
 402         } else {
 403                 dump_stack();
 404         }
 405
 406         end_report(&flags, addr);
 407 }
 408
 409 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 410                         unsigned long ip)
 411 {
 412         unsigned long flags = user_access_save();
 413         bool ret = false;
 414
 415         if (likely(report_enabled())) {
 416                 __kasan_report(addr, size, is_write, ip);
 417                 ret = true;
 418         }
 419
 420         user_access_restore(flags);
 421
 422         return ret;
 423 }
 424
 425 #ifdef CONFIG_KASAN_INLINE
 426 /*
 427  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 428  * canonical half of the address space) cause out-of-bounds shadow memory reads
 429  * before the actual access. For addresses in the low canonical half of the
 430  * address space, as well as most non-canonical addresses, that out-of-bounds
 431  * shadow memory access lands in the non-canonical part of the address space.
 432  * Help the user figure out what the original bogus pointer was.
 433  */
 434 void kasan_non_canonical_hook(unsigned long addr)
 435 {
 436         unsigned long orig_addr;
 437         const char *bug_type;
 438
 439         if (addr < KASAN_SHADOW_OFFSET)
 440                 return;
 441
 442         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 443         /*
 444          * For faults near the shadow address for NULL, we can be fairly certain
 445          * that this is a KASAN shadow memory access.
 446          * For faults that correspond to shadow for low canonical addresses, we
 447          * can still be pretty sure - that shadow region is a fairly narrow
 448          * chunk of the non-canonical address space.
 449          * But faults that look like shadow for non-canonical addresses are a
 450          * really large chunk of the address space. In that case, we still
 451          * print the decoded address, but make it clear that this is not
 452          * necessarily what's actually going on.
 453          */
 454         if (orig_addr < PAGE_SIZE)
 455                 bug_type = "null-ptr-deref";
 456         else if (orig_addr < TASK_SIZE)
 457                 bug_type = "probably user-memory-access";
 458         else
 459                 bug_type = "maybe wild-memory-access";
 460         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 461                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 462 }
 463 #endif