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         if (info->type == KASAN_REPORT_INVALID_FREE) {
  90                 pr_err("BUG: KASAN: double-free or invalid-free in %pS\n",
  91                        (void *)info->ip);
  92                 return;
  93         }
  94
  95         pr_err("BUG: KASAN: %s in %pS\n",
  96                 kasan_get_bug_type(info), (void *)info->ip);
  97         if (info->access_size)
  98                 pr_err("%s of size %zu at addr %px by task %s/%d\n",
  99                         info->is_write ? "Write" : "Read", info->access_size,
 100                         info->access_addr, current->comm, task_pid_nr(current));
 101         else
 102                 pr_err("%s at addr %px by task %s/%d\n",
 103                         info->is_write ? "Write" : "Read",
 104                         info->access_addr, current->comm, task_pid_nr(current));
 105 }
 106
 107 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 108 static void update_kunit_status(bool sync)
 109 {
 110         struct kunit *test;
 111         struct kunit_resource *resource;
 112         struct kunit_kasan_status *status;
 113
 114         test = current->kunit_test;
 115         if (!test)
 116                 return;
 117
 118         resource = kunit_find_named_resource(test, "kasan_status");
 119         if (!resource) {
 120                 kunit_set_failure(test);
 121                 return;
 122         }
 123
 124         status = (struct kunit_kasan_status *)resource->data;
 125         WRITE_ONCE(status->report_found, true);
 126         WRITE_ONCE(status->sync_fault, sync);
 127
 128         kunit_put_resource(resource);
 129 }
 130 #else
 131 static void update_kunit_status(bool sync) { }
 132 #endif
 133
 134 static DEFINE_SPINLOCK(report_lock);
 135
 136 static void start_report(unsigned long *flags, bool sync)
 137 {
 138         /* Respect the /proc/sys/kernel/traceoff_on_warning interface. */
 139         disable_trace_on_warning();
 140         /* Update status of the currently running KASAN test. */
 141         update_kunit_status(sync);
 142         /* Make sure we don't end up in loop. */
 143         kasan_disable_current();
 144         spin_lock_irqsave(&report_lock, *flags);
 145         pr_err("==================================================================\n");
 146 }
 147
 148 static void end_report(unsigned long *flags, void *addr)
 149 {
 150         if (addr)
 151                 trace_error_report_end(ERROR_DETECTOR_KASAN,
 152                                        (unsigned long)addr);
 153         pr_err("==================================================================\n");
 154         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 155         spin_unlock_irqrestore(&report_lock, *flags);
 156         if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 157                 panic("panic_on_warn set ...\n");
 158         if (kasan_arg_fault == KASAN_ARG_FAULT_PANIC)
 159                 panic("kasan.fault=panic set ...\n");
 160         kasan_enable_current();
 161 }
 162
 163 static void print_track(struct kasan_track *track, const char *prefix)
 164 {
 165         pr_err("%s by task %u:\n", prefix, track->pid);
 166         if (track->stack) {
 167                 stack_depot_print(track->stack);
 168         } else {
 169                 pr_err("(stack is not available)\n");
 170         }
 171 }
 172
 173 struct page *kasan_addr_to_page(const void *addr)
 174 {
 175         if ((addr >= (void *)PAGE_OFFSET) &&
 176                         (addr < high_memory))
 177                 return virt_to_head_page(addr);
 178         return NULL;
 179 }
 180
 181 struct slab *kasan_addr_to_slab(const void *addr)
 182 {
 183         if ((addr >= (void *)PAGE_OFFSET) &&
 184                         (addr < high_memory))
 185                 return virt_to_slab(addr);
 186         return NULL;
 187 }
 188
 189 static void describe_object_addr(struct kmem_cache *cache, void *object,
 190                                 const void *addr)
 191 {
 192         unsigned long access_addr = (unsigned long)addr;
 193         unsigned long object_addr = (unsigned long)object;
 194         const char *rel_type;
 195         int rel_bytes;
 196
 197         pr_err("The buggy address belongs to the object at %px\n"
 198                " which belongs to the cache %s of size %d\n",
 199                 object, cache->name, cache->object_size);
 200
 201         if (access_addr < object_addr) {
 202                 rel_type = "to the left";
 203                 rel_bytes = object_addr - access_addr;
 204         } else if (access_addr >= object_addr + cache->object_size) {
 205                 rel_type = "to the right";
 206                 rel_bytes = access_addr - (object_addr + cache->object_size);
 207         } else {
 208                 rel_type = "inside";
 209                 rel_bytes = access_addr - object_addr;
 210         }
 211
 212         pr_err("The buggy address is located %d bytes %s of\n"
 213                " %d-byte region [%px, %px)\n",
 214                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 215                 (void *)(object_addr + cache->object_size));
 216 }
 217
 218 static void describe_object_stacks(struct kmem_cache *cache, void *object,
 219                                         const void *addr, u8 tag)
 220 {
 221         struct kasan_alloc_meta *alloc_meta;
 222         struct kasan_track *free_track;
 223
 224         alloc_meta = kasan_get_alloc_meta(cache, object);
 225         if (alloc_meta) {
 226                 print_track(&alloc_meta->alloc_track, "Allocated");
 227                 pr_err("\n");
 228         }
 229
 230         free_track = kasan_get_free_track(cache, object, tag);
 231         if (free_track) {
 232                 print_track(free_track, "Freed");
 233                 pr_err("\n");
 234         }
 235
 236 #ifdef CONFIG_KASAN_GENERIC
 237         if (!alloc_meta)
 238                 return;
 239         if (alloc_meta->aux_stack[0]) {
 240                 pr_err("Last potentially related work creation:\n");
 241                 stack_depot_print(alloc_meta->aux_stack[0]);
 242                 pr_err("\n");
 243         }
 244         if (alloc_meta->aux_stack[1]) {
 245                 pr_err("Second to last potentially related work creation:\n");
 246                 stack_depot_print(alloc_meta->aux_stack[1]);
 247                 pr_err("\n");
 248         }
 249 #endif
 250 }
 251
 252 static void describe_object(struct kmem_cache *cache, void *object,
 253                                 const void *addr, u8 tag)
 254 {
 255         if (kasan_stack_collection_enabled())
 256                 describe_object_stacks(cache, object, addr, tag);
 257         describe_object_addr(cache, object, addr);
 258 }
 259
 260 static inline bool kernel_or_module_addr(const void *addr)
 261 {
 262         if (is_kernel((unsigned long)addr))
 263                 return true;
 264         if (is_module_address((unsigned long)addr))
 265                 return true;
 266         return false;
 267 }
 268
 269 static inline bool init_task_stack_addr(const void *addr)
 270 {
 271         return addr >= (void *)&init_thread_union.stack &&
 272                 (addr <= (void *)&init_thread_union.stack +
 273                         sizeof(init_thread_union.stack));
 274 }
 275
 276 static void print_address_description(void *addr, u8 tag)
 277 {
 278         struct page *page = kasan_addr_to_page(addr);
 279
 280         dump_stack_lvl(KERN_ERR);
 281         pr_err("\n");
 282
 283         if (page && PageSlab(page)) {
 284                 struct slab *slab = page_slab(page);
 285                 struct kmem_cache *cache = slab->slab_cache;
 286                 void *object = nearest_obj(cache, slab, addr);
 287
 288                 describe_object(cache, object, addr, tag);
 289                 pr_err("\n");
 290         }
 291
 292         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 293                 pr_err("The buggy address belongs to the variable:\n");
 294                 pr_err(" %pS\n", addr);
 295                 pr_err("\n");
 296         }
 297
 298         if (object_is_on_stack(addr)) {
 299                 /*
 300                  * Currently, KASAN supports printing frame information only
 301                  * for accesses to the task's own stack.
 302                  */
 303                 kasan_print_address_stack_frame(addr);
 304                 pr_err("\n");
 305         }
 306
 307         if (is_vmalloc_addr(addr)) {
 308                 struct vm_struct *va = find_vm_area(addr);
 309
 310                 if (va) {
 311                         pr_err("The buggy address belongs to the virtual mapping at\n"
 312                                " [%px, %px) created by:\n"
 313                                " %pS\n",
 314                                va->addr, va->addr + va->size, va->caller);
 315                         pr_err("\n");
 316
 317                         page = vmalloc_to_page(page);
 318                 }
 319         }
 320
 321         if (page) {
 322                 pr_err("The buggy address belongs to the physical page:\n");
 323                 dump_page(page, "kasan: bad access detected");
 324                 pr_err("\n");
 325         }
 326 }
 327
 328 static bool meta_row_is_guilty(const void *row, const void *addr)
 329 {
 330         return (row <= addr) && (addr < row + META_MEM_BYTES_PER_ROW);
 331 }
 332
 333 static int meta_pointer_offset(const void *row, const void *addr)
 334 {
 335         /*
 336          * Memory state around the buggy address:
 337          *  ff00ff00ff00ff00: 00 00 00 05 fe fe fe fe fe fe fe fe fe fe fe fe
 338          *  ...
 339          *
 340          * The length of ">ff00ff00ff00ff00: " is
 341          *    3 + (BITS_PER_LONG / 8) * 2 chars.
 342          * The length of each granule metadata is 2 bytes
 343          *    plus 1 byte for space.
 344          */
 345         return 3 + (BITS_PER_LONG / 8) * 2 +
 346                 (addr - row) / KASAN_GRANULE_SIZE * 3 + 1;
 347 }
 348
 349 static void print_memory_metadata(const void *addr)
 350 {
 351         int i;
 352         void *row;
 353
 354         row = (void *)round_down((unsigned long)addr, META_MEM_BYTES_PER_ROW)
 355                         - META_ROWS_AROUND_ADDR * META_MEM_BYTES_PER_ROW;
 356
 357         pr_err("Memory state around the buggy address:\n");
 358
 359         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 360                 char buffer[4 + (BITS_PER_LONG / 8) * 2];
 361                 char metadata[META_BYTES_PER_ROW];
 362
 363                 snprintf(buffer, sizeof(buffer),
 364                                 (i == 0) ? ">%px: " : " %px: ", row);
 365
 366                 /*
 367                  * We should not pass a shadow pointer to generic
 368                  * function, because generic functions may try to
 369                  * access kasan mapping for the passed address.
 370                  */
 371                 kasan_metadata_fetch_row(&metadata[0], row);
 372
 373                 print_hex_dump(KERN_ERR, buffer,
 374                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 375                         metadata, META_BYTES_PER_ROW, 0);
 376
 377                 if (meta_row_is_guilty(row, addr))
 378                         pr_err("%*c\n", meta_pointer_offset(row, addr), '^');
 379
 380                 row += META_MEM_BYTES_PER_ROW;
 381         }
 382 }
 383
 384 static bool report_enabled(void)
 385 {
 386 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 387         if (current->kasan_depth)
 388                 return false;
 389 #endif
 390         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 391                 return true;
 392         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 393 }
 394
 395 #ifdef CONFIG_KASAN_HW_TAGS
 396 void kasan_report_async(void)
 397 {
 398         unsigned long flags;
 399
 400         start_report(&flags, false);
 401         pr_err("BUG: KASAN: invalid-access\n");
 402         pr_err("Asynchronous mode enabled: no access details available\n");
 403         pr_err("\n");
 404         dump_stack_lvl(KERN_ERR);
 405         end_report(&flags, NULL);
 406 }
 407 #endif /* CONFIG_KASAN_HW_TAGS */
 408
 409 static void print_report(struct kasan_access_info *info)
 410 {
 411         void *tagged_addr = info->access_addr;
 412         void *untagged_addr = kasan_reset_tag(tagged_addr);
 413         u8 tag = get_tag(tagged_addr);
 414
 415         print_error_description(info);
 416         if (addr_has_metadata(untagged_addr))
 417                 kasan_print_tags(tag, info->first_bad_addr);
 418         pr_err("\n");
 419
 420         if (addr_has_metadata(untagged_addr)) {
 421                 print_address_description(untagged_addr, tag);
 422                 print_memory_metadata(info->first_bad_addr);
 423         } else {
 424                 dump_stack_lvl(KERN_ERR);
 425         }
 426 }
 427
 428 void kasan_report_invalid_free(void *ptr, unsigned long ip)
 429 {
 430         unsigned long flags;
 431         struct kasan_access_info info;
 432
 433         start_report(&flags, true);
 434
 435         info.type = KASAN_REPORT_INVALID_FREE;
 436         info.access_addr = ptr;
 437         info.first_bad_addr = kasan_reset_tag(ptr);
 438         info.access_size = 0;
 439         info.is_write = false;
 440         info.ip = ip;
 441
 442         print_report(&info);
 443
 444         end_report(&flags, ptr);
 445 }
 446
 447 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 448                         unsigned long ip)
 449 {
 450         bool ret = true;
 451         void *ptr = (void *)addr;
 452         unsigned long ua_flags = user_access_save();
 453         unsigned long irq_flags;
 454         struct kasan_access_info info;
 455
 456         if (unlikely(!report_enabled())) {
 457                 ret = false;
 458                 goto out;
 459         }
 460
 461         start_report(&irq_flags, true);
 462
 463         info.type = KASAN_REPORT_ACCESS;
 464         info.access_addr = ptr;
 465         info.first_bad_addr = kasan_find_first_bad_addr(ptr, size);
 466         info.access_size = size;
 467         info.is_write = is_write;
 468         info.ip = ip;
 469
 470         print_report(&info);
 471
 472         end_report(&irq_flags, ptr);
 473
 474 out:
 475         user_access_restore(ua_flags);
 476
 477         return ret;
 478 }
 479
 480 #ifdef CONFIG_KASAN_INLINE
 481 /*
 482  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 483  * canonical half of the address space) cause out-of-bounds shadow memory reads
 484  * before the actual access. For addresses in the low canonical half of the
 485  * address space, as well as most non-canonical addresses, that out-of-bounds
 486  * shadow memory access lands in the non-canonical part of the address space.
 487  * Help the user figure out what the original bogus pointer was.
 488  */
 489 void kasan_non_canonical_hook(unsigned long addr)
 490 {
 491         unsigned long orig_addr;
 492         const char *bug_type;
 493
 494         if (addr < KASAN_SHADOW_OFFSET)
 495                 return;
 496
 497         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 498         /*
 499          * For faults near the shadow address for NULL, we can be fairly certain
 500          * that this is a KASAN shadow memory access.
 501          * For faults that correspond to shadow for low canonical addresses, we
 502          * can still be pretty sure - that shadow region is a fairly narrow
 503          * chunk of the non-canonical address space.
 504          * But faults that look like shadow for non-canonical addresses are a
 505          * really large chunk of the address space. In that case, we still
 506          * print the decoded address, but make it clear that this is not
 507          * necessarily what's actually going on.
 508          */
 509         if (orig_addr < PAGE_SIZE)
 510                 bug_type = "null-ptr-deref";
 511         else if (orig_addr < TASK_SIZE)
 512                 bug_type = "probably user-memory-access";
 513         else
 514                 bug_type = "maybe wild-memory-access";
 515         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 516                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 517 }
 518 #endif