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
  29 #include <asm/sections.h>
  30
  31 #include <kunit/test.h>
  32
  33 #include "kasan.h"
  34 #include "../slab.h"
  35
  36 static unsigned long kasan_flags;
  37
  38 #define KASAN_BIT_REPORTED      0
  39 #define KASAN_BIT_MULTI_SHOT    1
  40
  41 bool kasan_save_enable_multi_shot(void)
  42 {
  43         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  44 }
  45 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  46
  47 void kasan_restore_multi_shot(bool enabled)
  48 {
  49         if (!enabled)
  50                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  51 }
  52 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  53
  54 static int __init kasan_set_multi_shot(char *str)
  55 {
  56         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  57         return 1;
  58 }
  59 __setup("kasan_multi_shot", kasan_set_multi_shot);
  60
  61 static void print_error_description(struct kasan_access_info *info)
  62 {
  63         pr_err("BUG: KASAN: %s in %pS\n",
  64                 get_bug_type(info), (void *)info->ip);
  65         if (info->access_size)
  66                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
  67                         info->is_write ? "Write" : "Read", info->access_size,
  68                         info->access_addr, current->comm, task_pid_nr(current));
  69         else
  70                 pr_err("%s at addr %px by task %s/%d\n",
  71                         info->is_write ? "Write" : "Read",
  72                         info->access_addr, current->comm, task_pid_nr(current));
  73 }
  74
  75 static DEFINE_SPINLOCK(report_lock);
  76
  77 static void start_report(unsigned long *flags)
  78 {
  79         /*
  80          * Make sure we don't end up in loop.
  81          */
  82         kasan_disable_current();
  83         spin_lock_irqsave(&report_lock, *flags);
  84         pr_err("==================================================================\n");
  85 }
  86
  87 static void end_report(unsigned long *flags)
  88 {
  89         pr_err("==================================================================\n");
  90         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  91         spin_unlock_irqrestore(&report_lock, *flags);
  92         if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
  93                 /*
  94                  * This thread may hit another WARN() in the panic path.
  95                  * Resetting this prevents additional WARN() from panicking the
  96                  * system on this thread.  Other threads are blocked by the
  97                  * panic_mutex in panic().
  98                  */
  99                 panic_on_warn = 0;
 100                 panic("panic_on_warn set ...\n");
 101         }
 102 #ifdef CONFIG_KASAN_HW_TAGS
 103         if (kasan_flag_panic)
 104                 panic("kasan.fault=panic set ...\n");
 105 #endif
 106         kasan_enable_current();
 107 }
 108
 109 static void print_stack(depot_stack_handle_t stack)
 110 {
 111         unsigned long *entries;
 112         unsigned int nr_entries;
 113
 114         nr_entries = stack_depot_fetch(stack, &entries);
 115         stack_trace_print(entries, nr_entries, 0);
 116 }
 117
 118 static void print_track(struct kasan_track *track, const char *prefix)
 119 {
 120         pr_err("%s by task %u:\n", prefix, track->pid);
 121         if (track->stack) {
 122                 print_stack(track->stack);
 123         } else {
 124                 pr_err("(stack is not available)\n");
 125         }
 126 }
 127
 128 struct page *kasan_addr_to_page(const void *addr)
 129 {
 130         if ((addr >= (void *)PAGE_OFFSET) &&
 131                         (addr < high_memory))
 132                 return virt_to_head_page(addr);
 133         return NULL;
 134 }
 135
 136 static void describe_object_addr(struct kmem_cache *cache, void *object,
 137                                 const void *addr)
 138 {
 139         unsigned long access_addr = (unsigned long)addr;
 140         unsigned long object_addr = (unsigned long)object;
 141         const char *rel_type;
 142         int rel_bytes;
 143
 144         pr_err("The buggy address belongs to the object at %px\n"
 145                " which belongs to the cache %s of size %d\n",
 146                 object, cache->name, cache->object_size);
 147
 148         if (!addr)
 149                 return;
 150
 151         if (access_addr < object_addr) {
 152                 rel_type = "to the left";
 153                 rel_bytes = object_addr - access_addr;
 154         } else if (access_addr >= object_addr + cache->object_size) {
 155                 rel_type = "to the right";
 156                 rel_bytes = access_addr - (object_addr + cache->object_size);
 157         } else {
 158                 rel_type = "inside";
 159                 rel_bytes = access_addr - object_addr;
 160         }
 161
 162         pr_err("The buggy address is located %d bytes %s of\n"
 163                " %d-byte region [%px, %px)\n",
 164                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 165                 (void *)(object_addr + cache->object_size));
 166 }
 167
 168 static void describe_object_stacks(struct kmem_cache *cache, void *object,
 169                                         const void *addr, u8 tag)
 170 {
 171         struct kasan_alloc_meta *alloc_meta;
 172         struct kasan_track *free_track;
 173
 174         alloc_meta = kasan_get_alloc_meta(cache, object);
 175         if (alloc_meta) {
 176                 print_track(&alloc_meta->alloc_track, "Allocated");
 177                 pr_err("\n");
 178         }
 179
 180         free_track = kasan_get_free_track(cache, object, tag);
 181         if (free_track) {
 182                 print_track(free_track, "Freed");
 183                 pr_err("\n");
 184         }
 185
 186 #ifdef CONFIG_KASAN_GENERIC
 187         if (!alloc_meta)
 188                 return;
 189         if (alloc_meta->aux_stack[0]) {
 190                 pr_err("Last potentially related work creation:\n");
 191                 print_stack(alloc_meta->aux_stack[0]);
 192                 pr_err("\n");
 193         }
 194         if (alloc_meta->aux_stack[1]) {
 195                 pr_err("Second to last potentially related work creation:\n");
 196                 print_stack(alloc_meta->aux_stack[1]);
 197                 pr_err("\n");
 198         }
 199 #endif
 200 }
 201
 202 static void describe_object(struct kmem_cache *cache, void *object,
 203                                 const void *addr, u8 tag)
 204 {
 205         if (kasan_stack_collection_enabled())
 206                 describe_object_stacks(cache, object, addr, tag);
 207         describe_object_addr(cache, object, addr);
 208 }
 209
 210 static inline bool kernel_or_module_addr(const void *addr)
 211 {
 212         if (addr >= (void *)_stext && addr < (void *)_end)
 213                 return true;
 214         if (is_module_address((unsigned long)addr))
 215                 return true;
 216         return false;
 217 }
 218
 219 static inline bool init_task_stack_addr(const void *addr)
 220 {
 221         return addr >= (void *)&init_thread_union.stack &&
 222                 (addr <= (void *)&init_thread_union.stack +
 223                         sizeof(init_thread_union.stack));
 224 }
 225
 226 static void print_address_description(void *addr, u8 tag)
 227 {
 228         struct page *page = kasan_addr_to_page(addr);
 229
 230         dump_stack();
 231         pr_err("\n");
 232
 233         if (page && PageSlab(page)) {
 234                 struct kmem_cache *cache = page->slab_cache;
 235                 void *object = nearest_obj(cache, page, addr);
 236
 237                 describe_object(cache, object, addr, tag);
 238         }
 239
 240         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 241                 pr_err("The buggy address belongs to the variable:\n");
 242                 pr_err(" %pS\n", addr);
 243         }
 244
 245         if (page) {
 246                 pr_err("The buggy address belongs to the page:\n");
 247                 dump_page(page, "kasan: bad access detected");
 248         }
 249
 250         print_address_stack_frame(addr);
 251 }
 252
 253 static bool meta_row_is_guilty(const void *row, const void *addr)
 254 {
 255         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 256 }
 257
 258 static int meta_pointer_offset(const void *row, const void *addr)
 259 {
 260         /*
 261          * Memory state around the buggy address:
 262          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 263          *  ...
 264          *
 265          * The length of ">ff00ff00ff00ff00: " is
 266          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 267          * The length of each granule metadata is 2 bytes
 268          *    plus 1 byte for space.
 269          */
 270         return 3 + (BITS_PER_LONG / 8) * 2 +
 271                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 272 }
 273
 274 static void print_memory_metadata(const void *addr)
 275 {
 276         int i;
 277         void *row;
 278
 279         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 280                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 281
 282         pr_err("Memory state around the buggy address:\n");
 283
 284         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 285                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 286                 char metadata[META_BYTES_PER_ROW];
 287
 288                 snprintf(buffer, sizeof(buffer),
 289                                 (i == 0) ? ">%px: " : " %px: ", row);
 290
 291                 /*
 292                  * We should not pass a shadow pointer to generic
 293                  * function, because generic functions may try to
 294                  * access kasan mapping for the passed address.
 295                  */
 296                 metadata_fetch_row(&metadata[0], row);
 297
 298                 print_hex_dump(KERN_ERR, buffer,
 299                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 300                         metadata, META_BYTES_PER_ROW, 0);
 301
 302                 if (meta_row_is_guilty(row, addr))
 303                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 304
 305                 row += META_MEM_BYTES_PER_ROW;
 306         }
 307 }
 308
 309 static bool report_enabled(void)
 310 {
 311 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 312         if (current->kasan_depth)
 313                 return false;
 314 #endif
 315         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 316                 return true;
 317         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 318 }
 319
 320 #if IS_ENABLED(CONFIG_KUNIT)
 321 static void kasan_update_kunit_status(struct kunit *cur_test)
 322 {
 323         struct kunit_resource *resource;
 324         struct kunit_kasan_expectation *kasan_data;
 325
 326         resource = kunit_find_named_resource(cur_test, "kasan_data");
 327
 328         if (!resource) {
 329                 kunit_set_failure(cur_test);
 330                 return;
 331         }
 332
 333         kasan_data = (struct kunit_kasan_expectation *)resource->data;
 334         kasan_data->report_found = true;
 335         kunit_put_resource(resource);
 336 }
 337 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 338
 339 void kasan_report_invalid_free(void *object, unsigned long ip)
 340 {
 341         unsigned long flags;
 342         u8 tag = get_tag(object);
 343
 344         object = kasan_reset_tag(object);
 345
 346 #if IS_ENABLED(CONFIG_KUNIT)
 347         if (current->kunit_test)
 348                 kasan_update_kunit_status(current->kunit_test);
 349 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 350
 351         start_report(&flags);
 352         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 353         print_tags(tag, object);
 354         pr_err("\n");
 355         print_address_description(object, tag);
 356         pr_err("\n");
 357         print_memory_metadata(object);
 358         end_report(&flags);
 359 }
 360
 361 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 362                                 unsigned long ip)
 363 {
 364         struct kasan_access_info info;
 365         void *tagged_addr;
 366         void *untagged_addr;
 367         unsigned long flags;
 368
 369 #if IS_ENABLED(CONFIG_KUNIT)
 370         if (current->kunit_test)
 371                 kasan_update_kunit_status(current->kunit_test);
 372 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 373
 374         disable_trace_on_warning();
 375
 376         tagged_addr = (void *)addr;
 377         untagged_addr = kasan_reset_tag(tagged_addr);
 378
 379         info.access_addr = tagged_addr;
 380         if (addr_has_metadata(untagged_addr))
 381                 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
 382         else
 383                 info.first_bad_addr = untagged_addr;
 384         info.access_size = size;
 385         info.is_write = is_write;
 386         info.ip = ip;
 387
 388         start_report(&flags);
 389
 390         print_error_description(&info);
 391         if (addr_has_metadata(untagged_addr))
 392                 print_tags(get_tag(tagged_addr), info.first_bad_addr);
 393         pr_err("\n");
 394
 395         if (addr_has_metadata(untagged_addr)) {
 396                 print_address_description(untagged_addr, get_tag(tagged_addr));
 397                 pr_err("\n");
 398                 print_memory_metadata(info.first_bad_addr);
 399         } else {
 400                 dump_stack();
 401         }
 402
 403         end_report(&flags);
 404 }
 405
 406 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 407                         unsigned long ip)
 408 {
 409         unsigned long flags = user_access_save();
 410         bool ret = false;
 411
 412         if (likely(report_enabled())) {
 413                 __kasan_report(addr, size, is_write, ip);
 414                 ret = true;
 415         }
 416
 417         user_access_restore(flags);
 418
 419         return ret;
 420 }
 421
 422 #ifdef CONFIG_KASAN_INLINE
 423 /*
 424  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 425  * canonical half of the address space) cause out-of-bounds shadow memory reads
 426  * before the actual access. For addresses in the low canonical half of the
 427  * address space, as well as most non-canonical addresses, that out-of-bounds
 428  * shadow memory access lands in the non-canonical part of the address space.
 429  * Help the user figure out what the original bogus pointer was.
 430  */
 431 void kasan_non_canonical_hook(unsigned long addr)
 432 {
 433         unsigned long orig_addr;
 434         const char *bug_type;
 435
 436         if (addr < KASAN_SHADOW_OFFSET)
 437                 return;
 438
 439         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 440         /*
 441          * For faults near the shadow address for NULL, we can be fairly certain
 442          * that this is a KASAN shadow memory access.
 443          * For faults that correspond to shadow for low canonical addresses, we
 444          * can still be pretty sure - that shadow region is a fairly narrow
 445          * chunk of the non-canonical address space.
 446          * But faults that look like shadow for non-canonical addresses are a
 447          * really large chunk of the address space. In that case, we still
 448          * print the decoded address, but make it clear that this is not
 449          * necessarily what's actually going on.
 450          */
 451         if (orig_addr < PAGE_SIZE)
 452                 bug_type = "null-ptr-deref";
 453         else if (orig_addr < TASK_SIZE)
 454                 bug_type = "probably user-memory-access";
 455         else
 456                 bug_type = "maybe wild-memory-access";
 457         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 458                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 459 }
 460 #endif