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