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