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