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 /* Metadata layout customization. */
  37 #define META_BYTES_PER_BLOCK 1
  38 #define META_BLOCKS_PER_ROW 16
  39 #define META_BYTES_PER_ROW (META_BLOCKS_PER_ROW * META_BYTES_PER_BLOCK)
  40 #define META_ROWS_AROUND_ADDR 2
  41
  42 static unsigned long kasan_flags;
  43
  44 #define KASAN_BIT_REPORTED      0
  45 #define KASAN_BIT_MULTI_SHOT    1
  46
  47 bool kasan_save_enable_multi_shot(void)
  48 {
  49         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  50 }
  51 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  52
  53 void kasan_restore_multi_shot(bool enabled)
  54 {
  55         if (!enabled)
  56                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  57 }
  58 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  59
  60 static int __init kasan_set_multi_shot(char *str)
  61 {
  62         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  63         return 1;
  64 }
  65 __setup("kasan_multi_shot", kasan_set_multi_shot);
  66
  67 static void print_error_description(struct kasan_access_info *info)
  68 {
  69         pr_err("BUG: KASAN: %s in %pS\n",
  70                 get_bug_type(info), (void *)info->ip);
  71         pr_err("%s of size %zu at addr %px by task %s/%d\n",
  72                 info->is_write ? "Write" : "Read", info->access_size,
  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)
  89 {
  90         pr_err("==================================================================\n");
  91         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  92         spin_unlock_irqrestore(&report_lock, *flags);
  93         if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
  94                 /*
  95                  * This thread may hit another WARN() in the panic path.
  96                  * Resetting this prevents additional WARN() from panicking the
  97                  * system on this thread.  Other threads are blocked by the
  98                  * panic_mutex in panic().
  99                  */
 100                 panic_on_warn = 0;
 101                 panic("panic_on_warn set ...\n");
 102         }
 103         kasan_enable_current();
 104 }
 105
 106 static void print_stack(depot_stack_handle_t stack)
 107 {
 108         unsigned long *entries;
 109         unsigned int nr_entries;
 110
 111         nr_entries = stack_depot_fetch(stack, &entries);
 112         stack_trace_print(entries, nr_entries, 0);
 113 }
 114
 115 static void print_track(struct kasan_track *track, const char *prefix)
 116 {
 117         pr_err("%s by task %u:\n", prefix, track->pid);
 118         if (track->stack) {
 119                 print_stack(track->stack);
 120         } else {
 121                 pr_err("(stack is not available)\n");
 122         }
 123 }
 124
 125 struct page *kasan_addr_to_page(const void *addr)
 126 {
 127         if ((addr >= (void *)PAGE_OFFSET) &&
 128                         (addr < high_memory))
 129                 return virt_to_head_page(addr);
 130         return NULL;
 131 }
 132
 133 static void describe_object_addr(struct kmem_cache *cache, void *object,
 134                                 const void *addr)
 135 {
 136         unsigned long access_addr = (unsigned long)addr;
 137         unsigned long object_addr = (unsigned long)object;
 138         const char *rel_type;
 139         int rel_bytes;
 140
 141         pr_err("The buggy address belongs to the object at %px\n"
 142                " which belongs to the cache %s of size %d\n",
 143                 object, cache->name, cache->object_size);
 144
 145         if (!addr)
 146                 return;
 147
 148         if (access_addr < object_addr) {
 149                 rel_type = "to the left";
 150                 rel_bytes = object_addr - access_addr;
 151         } else if (access_addr >= object_addr + cache->object_size) {
 152                 rel_type = "to the right";
 153                 rel_bytes = access_addr - (object_addr + cache->object_size);
 154         } else {
 155                 rel_type = "inside";
 156                 rel_bytes = access_addr - object_addr;
 157         }
 158
 159         pr_err("The buggy address is located %d bytes %s of\n"
 160                " %d-byte region [%px, %px)\n",
 161                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 162                 (void *)(object_addr + cache->object_size));
 163 }
 164
 165 static void describe_object(struct kmem_cache *cache, void *object,
 166                                 const void *addr, u8 tag)
 167 {
 168         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 169
 170         if (cache->flags & SLAB_KASAN) {
 171                 struct kasan_track *free_track;
 172
 173                 print_track(&alloc_info->alloc_track, "Allocated");
 174                 pr_err("\n");
 175                 free_track = kasan_get_free_track(cache, object, tag);
 176                 if (free_track) {
 177                         print_track(free_track, "Freed");
 178                         pr_err("\n");
 179                 }
 180
 181 #ifdef CONFIG_KASAN_GENERIC
 182                 if (alloc_info->aux_stack[0]) {
 183                         pr_err("Last potentially related work creation:\n");
 184                         print_stack(alloc_info->aux_stack[0]);
 185                         pr_err("\n");
 186                 }
 187                 if (alloc_info->aux_stack[1]) {
 188                         pr_err("Second to last potentially related work creation:\n");
 189                         print_stack(alloc_info->aux_stack[1]);
 190                         pr_err("\n");
 191                 }
 192 #endif
 193         }
 194
 195         describe_object_addr(cache, object, addr);
 196 }
 197
 198 static inline bool kernel_or_module_addr(const void *addr)
 199 {
 200         if (addr >= (void *)_stext && addr < (void *)_end)
 201                 return true;
 202         if (is_module_address((unsigned long)addr))
 203                 return true;
 204         return false;
 205 }
 206
 207 static inline bool init_task_stack_addr(const void *addr)
 208 {
 209         return addr >= (void *)&init_thread_union.stack &&
 210                 (addr <= (void *)&init_thread_union.stack +
 211                         sizeof(init_thread_union.stack));
 212 }
 213
 214 static void print_address_description(void *addr, u8 tag)
 215 {
 216         struct page *page = kasan_addr_to_page(addr);
 217
 218         dump_stack();
 219         pr_err("\n");
 220
 221         if (page && PageSlab(page)) {
 222                 struct kmem_cache *cache = page->slab_cache;
 223                 void *object = nearest_obj(cache, page, addr);
 224
 225                 describe_object(cache, object, addr, tag);
 226         }
 227
 228         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 229                 pr_err("The buggy address belongs to the variable:\n");
 230                 pr_err(" %pS\n", addr);
 231         }
 232
 233         if (page) {
 234                 pr_err("The buggy address belongs to the page:\n");
 235                 dump_page(page, "kasan: bad access detected");
 236         }
 237
 238         print_address_stack_frame(addr);
 239 }
 240
 241 static bool row_is_guilty(const void *row, const void *guilty)
 242 {
 243         return (row <= guilty) && (guilty < row + META_BYTES_PER_ROW);
 244 }
 245
 246 static int shadow_pointer_offset(const void *row, const void *shadow)
 247 {
 248         /* The length of ">ff00ff00ff00ff00: " is
 249          *    3 + (BITS_PER_LONG/8)*2 chars.
 250          */
 251         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 252                 (shadow - row) / META_BYTES_PER_BLOCK + 1;
 253 }
 254
 255 static void print_memory_metadata(const void *addr)
 256 {
 257         int i;
 258         const void *shadow = kasan_mem_to_shadow(addr);
 259         const void *shadow_row;
 260
 261         shadow_row = (void *)round_down((unsigned long)shadow,
 262                                         META_BYTES_PER_ROW)
 263                 - META_ROWS_AROUND_ADDR * META_BYTES_PER_ROW;
 264
 265         pr_err("Memory state around the buggy address:\n");
 266
 267         for (i = -META_ROWS_AROUND_ADDR; i <= META_ROWS_AROUND_ADDR; i++) {
 268                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 269                 char buffer[4 + (BITS_PER_LONG/8)*2];
 270                 char shadow_buf[META_BYTES_PER_ROW];
 271
 272                 snprintf(buffer, sizeof(buffer),
 273                         (i == 0) ? ">%px: " : " %px: ", kaddr);
 274                 /*
 275                  * We should not pass a shadow pointer to generic
 276                  * function, because generic functions may try to
 277                  * access kasan mapping for the passed address.
 278                  */
 279                 memcpy(shadow_buf, shadow_row, META_BYTES_PER_ROW);
 280                 print_hex_dump(KERN_ERR, buffer,
 281                         DUMP_PREFIX_NONE, META_BYTES_PER_ROW, 1,
 282                         shadow_buf, META_BYTES_PER_ROW, 0);
 283
 284                 if (row_is_guilty(shadow_row, shadow))
 285                         pr_err("%*c\n",
 286                                 shadow_pointer_offset(shadow_row, shadow),
 287                                 '^');
 288
 289                 shadow_row += META_BYTES_PER_ROW;
 290         }
 291 }
 292
 293 static bool report_enabled(void)
 294 {
 295 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 296         if (current->kasan_depth)
 297                 return false;
 298 #endif
 299         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 300                 return true;
 301         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 302 }
 303
 304 #if IS_ENABLED(CONFIG_KUNIT)
 305 static void kasan_update_kunit_status(struct kunit *cur_test)
 306 {
 307         struct kunit_resource *resource;
 308         struct kunit_kasan_expectation *kasan_data;
 309
 310         resource = kunit_find_named_resource(cur_test, "kasan_data");
 311
 312         if (!resource) {
 313                 kunit_set_failure(cur_test);
 314                 return;
 315         }
 316
 317         kasan_data = (struct kunit_kasan_expectation *)resource->data;
 318         kasan_data->report_found = true;
 319         kunit_put_resource(resource);
 320 }
 321 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 322
 323 void kasan_report_invalid_free(void *object, unsigned long ip)
 324 {
 325         unsigned long flags;
 326         u8 tag = get_tag(object);
 327
 328         object = reset_tag(object);
 329
 330 #if IS_ENABLED(CONFIG_KUNIT)
 331         if (current->kunit_test)
 332                 kasan_update_kunit_status(current->kunit_test);
 333 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 334
 335         start_report(&flags);
 336         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 337         print_tags(tag, object);
 338         pr_err("\n");
 339         print_address_description(object, tag);
 340         pr_err("\n");
 341         print_memory_metadata(object);
 342         end_report(&flags);
 343 }
 344
 345 static void __kasan_report(unsigned long addr, size_t size, bool is_write,
 346                                 unsigned long ip)
 347 {
 348         struct kasan_access_info info;
 349         void *tagged_addr;
 350         void *untagged_addr;
 351         unsigned long flags;
 352
 353 #if IS_ENABLED(CONFIG_KUNIT)
 354         if (current->kunit_test)
 355                 kasan_update_kunit_status(current->kunit_test);
 356 #endif /* IS_ENABLED(CONFIG_KUNIT) */
 357
 358         disable_trace_on_warning();
 359
 360         tagged_addr = (void *)addr;
 361         untagged_addr = reset_tag(tagged_addr);
 362
 363         info.access_addr = tagged_addr;
 364         if (addr_has_metadata(untagged_addr))
 365                 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
 366         else
 367                 info.first_bad_addr = untagged_addr;
 368         info.access_size = size;
 369         info.is_write = is_write;
 370         info.ip = ip;
 371
 372         start_report(&flags);
 373
 374         print_error_description(&info);
 375         if (addr_has_metadata(untagged_addr))
 376                 print_tags(get_tag(tagged_addr), info.first_bad_addr);
 377         pr_err("\n");
 378
 379         if (addr_has_metadata(untagged_addr)) {
 380                 print_address_description(untagged_addr, get_tag(tagged_addr));
 381                 pr_err("\n");
 382                 print_memory_metadata(info.first_bad_addr);
 383         } else {
 384                 dump_stack();
 385         }
 386
 387         end_report(&flags);
 388 }
 389
 390 bool kasan_report(unsigned long addr, size_t size, bool is_write,
 391                         unsigned long ip)
 392 {
 393         unsigned long flags = user_access_save();
 394         bool ret = false;
 395
 396         if (likely(report_enabled())) {
 397                 __kasan_report(addr, size, is_write, ip);
 398                 ret = true;
 399         }
 400
 401         user_access_restore(flags);
 402
 403         return ret;
 404 }
 405
 406 #ifdef CONFIG_KASAN_INLINE
 407 /*
 408  * With CONFIG_KASAN_INLINE, accesses to bogus pointers (outside the high
 409  * canonical half of the address space) cause out-of-bounds shadow memory reads
 410  * before the actual access. For addresses in the low canonical half of the
 411  * address space, as well as most non-canonical addresses, that out-of-bounds
 412  * shadow memory access lands in the non-canonical part of the address space.
 413  * Help the user figure out what the original bogus pointer was.
 414  */
 415 void kasan_non_canonical_hook(unsigned long addr)
 416 {
 417         unsigned long orig_addr;
 418         const char *bug_type;
 419
 420         if (addr < KASAN_SHADOW_OFFSET)
 421                 return;
 422
 423         orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 424         /*
 425          * For faults near the shadow address for NULL, we can be fairly certain
 426          * that this is a KASAN shadow memory access.
 427          * For faults that correspond to shadow for low canonical addresses, we
 428          * can still be pretty sure - that shadow region is a fairly narrow
 429          * chunk of the non-canonical address space.
 430          * But faults that look like shadow for non-canonical addresses are a
 431          * really large chunk of the address space. In that case, we still
 432          * print the decoded address, but make it clear that this is not
 433          * necessarily what's actually going on.
 434          */
 435         if (orig_addr < PAGE_SIZE)
 436                 bug_type = "null-ptr-deref";
 437         else if (orig_addr < TASK_SIZE)
 438                 bug_type = "probably user-memory-access";
 439         else
 440                 bug_type = "maybe wild-memory-access";
 441         pr_alert("KASAN: %s in range [0x%016lx-0x%016lx]\n", bug_type,
 442                  orig_addr, orig_addr + KASAN_GRANULE_SIZE - 1);
 443 }
 444 #endif