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