mm/kasan/report.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains common generic and tag-based 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  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  */
  16
  17 #include <linux/bitops.h>
  18 #include <linux/ftrace.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/printk.h>
  23 #include <linux/sched.h>
  24 #include <linux/slab.h>
  25 #include <linux/stackdepot.h>
  26 #include <linux/stacktrace.h>
  27 #include <linux/string.h>
  28 #include <linux/types.h>
  29 #include <linux/kasan.h>
  30 #include <linux/module.h>
  31 #include <linux/sched/task_stack.h>
  32
  33 #include <asm/sections.h>
  34
  35 #include "kasan.h"
  36 #include "../slab.h"
  37
  38 /* Shadow layout customization. */
  39 #define SHADOW_BYTES_PER_BLOCK 1
  40 #define SHADOW_BLOCKS_PER_ROW 16
  41 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  42 #define SHADOW_ROWS_AROUND_ADDR 2
  43
  44 static unsigned long kasan_flags;
  45
  46 #define KASAN_BIT_REPORTED      0
  47 #define KASAN_BIT_MULTI_SHOT    1
  48
  49 bool kasan_save_enable_multi_shot(void)
  50 {
  51         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  52 }
  53 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
  54
  55 void kasan_restore_multi_shot(bool enabled)
  56 {
  57         if (!enabled)
  58                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  59 }
  60 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
  61
  62 static int __init kasan_set_multi_shot(char *str)
  63 {
  64         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
  65         return 1;
  66 }
  67 __setup("kasan_multi_shot", kasan_set_multi_shot);
  68
  69 static void print_error_description(struct kasan_access_info *info)
  70 {
  71         pr_err("BUG: KASAN: %s in %pS\n",
  72                 get_bug_type(info), (void *)info->ip);
  73         pr_err("%s of size %zu at addr %px by task %s/%d\n",
  74                 info->is_write ? "Write" : "Read", info->access_size,
  75                 info->access_addr, current->comm, task_pid_nr(current));
  76 }
  77
  78 static DEFINE_SPINLOCK(report_lock);
  79
  80 static void start_report(unsigned long *flags)
  81 {
  82         /*
  83          * Make sure we don't end up in loop.
  84          */
  85         kasan_disable_current();
  86         spin_lock_irqsave(&report_lock, *flags);
  87         pr_err("==================================================================\n");
  88 }
  89
  90 static void end_report(unsigned long *flags)
  91 {
  92         pr_err("==================================================================\n");
  93         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
  94         spin_unlock_irqrestore(&report_lock, *flags);
  95         if (panic_on_warn)
  96                 panic("panic_on_warn set ...\n");
  97         kasan_enable_current();
  98 }
  99
 100 static void print_track(struct kasan_track *track, const char *prefix)
 101 {
 102         pr_err("%s by task %u:\n", prefix, track->pid);
 103         if (track->stack) {
 104                 unsigned long *entries;
 105                 unsigned int nr_entries;
 106
 107                 nr_entries = stack_depot_fetch(track->stack, &entries);
 108                 stack_trace_print(entries, nr_entries, 0);
 109         } else {
 110                 pr_err("(stack is not available)\n");
 111         }
 112 }
 113
 114 static struct page *addr_to_page(const void *addr)
 115 {
 116         if ((addr >= (void *)PAGE_OFFSET) &&
 117                         (addr < high_memory))
 118                 return virt_to_head_page(addr);
 119         return NULL;
 120 }
 121
 122 static void describe_object_addr(struct kmem_cache *cache, void *object,
 123                                 const void *addr)
 124 {
 125         unsigned long access_addr = (unsigned long)addr;
 126         unsigned long object_addr = (unsigned long)object;
 127         const char *rel_type;
 128         int rel_bytes;
 129
 130         pr_err("The buggy address belongs to the object at %px\n"
 131                " which belongs to the cache %s of size %d\n",
 132                 object, cache->name, cache->object_size);
 133
 134         if (!addr)
 135                 return;
 136
 137         if (access_addr < object_addr) {
 138                 rel_type = "to the left";
 139                 rel_bytes = object_addr - access_addr;
 140         } else if (access_addr >= object_addr + cache->object_size) {
 141                 rel_type = "to the right";
 142                 rel_bytes = access_addr - (object_addr + cache->object_size);
 143         } else {
 144                 rel_type = "inside";
 145                 rel_bytes = access_addr - object_addr;
 146         }
 147
 148         pr_err("The buggy address is located %d bytes %s of\n"
 149                " %d-byte region [%px, %px)\n",
 150                 rel_bytes, rel_type, cache->object_size, (void *)object_addr,
 151                 (void *)(object_addr + cache->object_size));
 152 }
 153
 154 static void describe_object(struct kmem_cache *cache, void *object,
 155                                 const void *addr)
 156 {
 157         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 158
 159         if (cache->flags & SLAB_KASAN) {
 160                 print_track(&alloc_info->alloc_track, "Allocated");
 161                 pr_err("\n");
 162                 print_track(&alloc_info->free_track, "Freed");
 163                 pr_err("\n");
 164         }
 165
 166         describe_object_addr(cache, object, addr);
 167 }
 168
 169 static inline bool kernel_or_module_addr(const void *addr)
 170 {
 171         if (addr >= (void *)_stext && addr < (void *)_end)
 172                 return true;
 173         if (is_module_address((unsigned long)addr))
 174                 return true;
 175         return false;
 176 }
 177
 178 static inline bool init_task_stack_addr(const void *addr)
 179 {
 180         return addr >= (void *)&init_thread_union.stack &&
 181                 (addr <= (void *)&init_thread_union.stack +
 182                         sizeof(init_thread_union.stack));
 183 }
 184
 185 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 186                                               char *token, size_t max_tok_len,
 187                                               unsigned long *value)
 188 {
 189         const char *sep = strchr(*frame_descr, ' ');
 190
 191         if (sep == NULL)
 192                 sep = *frame_descr + strlen(*frame_descr);
 193
 194         if (token != NULL) {
 195                 const size_t tok_len = sep - *frame_descr;
 196
 197                 if (tok_len + 1 > max_tok_len) {
 198                         pr_err("KASAN internal error: frame description too long: %s\n",
 199                                *frame_descr);
 200                         return false;
 201                 }
 202
 203                 /* Copy token (+ 1 byte for '\0'). */
 204                 strlcpy(token, *frame_descr, tok_len + 1);
 205         }
 206
 207         /* Advance frame_descr past separator. */
 208         *frame_descr = sep + 1;
 209
 210         if (value != NULL && kstrtoul(token, 10, value)) {
 211                 pr_err("KASAN internal error: not a valid number: %s\n", token);
 212                 return false;
 213         }
 214
 215         return true;
 216 }
 217
 218 static void print_decoded_frame_descr(const char *frame_descr)
 219 {
 220         /*
 221          * We need to parse the following string:
 222          *    "n alloc_1 alloc_2 ... alloc_n"
 223          * where alloc_i looks like
 224          *    "offset size len name"
 225          * or "offset size len name:line".
 226          */
 227
 228         char token[64];
 229         unsigned long num_objects;
 230
 231         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 232                                   &num_objects))
 233                 return;
 234
 235         pr_err("\n");
 236         pr_err("this frame has %lu %s:\n", num_objects,
 237                num_objects == 1 ? "object" : "objects");
 238
 239         while (num_objects--) {
 240                 unsigned long offset;
 241                 unsigned long size;
 242
 243                 /* access offset */
 244                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 245                                           &offset))
 246                         return;
 247                 /* access size */
 248                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 249                                           &size))
 250                         return;
 251                 /* name length (unused) */
 252                 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
 253                         return;
 254                 /* object name */
 255                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 256                                           NULL))
 257                         return;
 258
 259                 /* Strip line number; without filename it's not very helpful. */
 260                 strreplace(token, ':', '\0');
 261
 262                 /* Finally, print object information. */
 263                 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
 264         }
 265 }
 266
 267 static bool __must_check get_address_stack_frame_info(const void *addr,
 268                                                       unsigned long *offset,
 269                                                       const char **frame_descr,
 270                                                       const void **frame_pc)
 271 {
 272         unsigned long aligned_addr;
 273         unsigned long mem_ptr;
 274         const u8 *shadow_bottom;
 275         const u8 *shadow_ptr;
 276         const unsigned long *frame;
 277
 278         BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 279
 280         /*
 281          * NOTE: We currently only support printing frame information for
 282          * accesses to the task's own stack.
 283          */
 284         if (!object_is_on_stack(addr))
 285                 return false;
 286
 287         aligned_addr = round_down((unsigned long)addr, sizeof(long));
 288         mem_ptr = round_down(aligned_addr, KASAN_SHADOW_SCALE_SIZE);
 289         shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
 290         shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
 291
 292         while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
 293                 shadow_ptr--;
 294                 mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
 295         }
 296
 297         while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
 298                 shadow_ptr--;
 299                 mem_ptr -= KASAN_SHADOW_SCALE_SIZE;
 300         }
 301
 302         if (shadow_ptr < shadow_bottom)
 303                 return false;
 304
 305         frame = (const unsigned long *)(mem_ptr + KASAN_SHADOW_SCALE_SIZE);
 306         if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
 307                 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
 308                        frame[0]);
 309                 return false;
 310         }
 311
 312         *offset = (unsigned long)addr - (unsigned long)frame;
 313         *frame_descr = (const char *)frame[1];
 314         *frame_pc = (void *)frame[2];
 315
 316         return true;
 317 }
 318
 319 static void print_address_stack_frame(const void *addr)
 320 {
 321         unsigned long offset;
 322         const char *frame_descr;
 323         const void *frame_pc;
 324
 325         if (IS_ENABLED(CONFIG_KASAN_SW_TAGS))
 326                 return;
 327
 328         if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 329                                           &frame_pc))
 330                 return;
 331
 332         /*
 333          * get_address_stack_frame_info only returns true if the given addr is
 334          * on the current task's stack.
 335          */
 336         pr_err("\n");
 337         pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
 338                addr, current->comm, task_pid_nr(current), offset);
 339         pr_err(" %pS\n", frame_pc);
 340
 341         if (!frame_descr)
 342                 return;
 343
 344         print_decoded_frame_descr(frame_descr);
 345 }
 346
 347 static void print_address_description(void *addr)
 348 {
 349         struct page *page = addr_to_page(addr);
 350
 351         dump_stack();
 352         pr_err("\n");
 353
 354         if (page && PageSlab(page)) {
 355                 struct kmem_cache *cache = page->slab_cache;
 356                 void *object = nearest_obj(cache, page, addr);
 357
 358                 describe_object(cache, object, addr);
 359         }
 360
 361         if (kernel_or_module_addr(addr) && !init_task_stack_addr(addr)) {
 362                 pr_err("The buggy address belongs to the variable:\n");
 363                 pr_err(" %pS\n", addr);
 364         }
 365
 366         if (page) {
 367                 pr_err("The buggy address belongs to the page:\n");
 368                 dump_page(page, "kasan: bad access detected");
 369         }
 370
 371         print_address_stack_frame(addr);
 372 }
 373
 374 static bool row_is_guilty(const void *row, const void *guilty)
 375 {
 376         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 377 }
 378
 379 static int shadow_pointer_offset(const void *row, const void *shadow)
 380 {
 381         /* The length of ">ff00ff00ff00ff00: " is
 382          *    3 + (BITS_PER_LONG/8)*2 chars.
 383          */
 384         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 385                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 386 }
 387
 388 static void print_shadow_for_address(const void *addr)
 389 {
 390         int i;
 391         const void *shadow = kasan_mem_to_shadow(addr);
 392         const void *shadow_row;
 393
 394         shadow_row = (void *)round_down((unsigned long)shadow,
 395                                         SHADOW_BYTES_PER_ROW)
 396                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 397
 398         pr_err("Memory state around the buggy address:\n");
 399
 400         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 401                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 402                 char buffer[4 + (BITS_PER_LONG/8)*2];
 403                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 404
 405                 snprintf(buffer, sizeof(buffer),
 406                         (i == 0) ? ">%px: " : " %px: ", kaddr);
 407                 /*
 408                  * We should not pass a shadow pointer to generic
 409                  * function, because generic functions may try to
 410                  * access kasan mapping for the passed address.
 411                  */
 412                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 413                 print_hex_dump(KERN_ERR, buffer,
 414                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 415                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 416
 417                 if (row_is_guilty(shadow_row, shadow))
 418                         pr_err("%*c\n",
 419                                 shadow_pointer_offset(shadow_row, shadow),
 420                                 '^');
 421
 422                 shadow_row += SHADOW_BYTES_PER_ROW;
 423         }
 424 }
 425
 426 static bool report_enabled(void)
 427 {
 428         if (current->kasan_depth)
 429                 return false;
 430         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 431                 return true;
 432         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 433 }
 434
 435 void kasan_report_invalid_free(void *object, unsigned long ip)
 436 {
 437         unsigned long flags;
 438
 439         start_report(&flags);
 440         pr_err("BUG: KASAN: double-free or invalid-free in %pS\n", (void *)ip);
 441         print_tags(get_tag(object), reset_tag(object));
 442         object = reset_tag(object);
 443         pr_err("\n");
 444         print_address_description(object);
 445         pr_err("\n");
 446         print_shadow_for_address(object);
 447         end_report(&flags);
 448 }
 449
 450 void __kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip)
 451 {
 452         struct kasan_access_info info;
 453         void *tagged_addr;
 454         void *untagged_addr;
 455         unsigned long flags;
 456
 457         if (likely(!report_enabled()))
 458                 return;
 459
 460         disable_trace_on_warning();
 461
 462         tagged_addr = (void *)addr;
 463         untagged_addr = reset_tag(tagged_addr);
 464
 465         info.access_addr = tagged_addr;
 466         if (addr_has_shadow(untagged_addr))
 467                 info.first_bad_addr = find_first_bad_addr(tagged_addr, size);
 468         else
 469                 info.first_bad_addr = untagged_addr;
 470         info.access_size = size;
 471         info.is_write = is_write;
 472         info.ip = ip;
 473
 474         start_report(&flags);
 475
 476         print_error_description(&info);
 477         if (addr_has_shadow(untagged_addr))
 478                 print_tags(get_tag(tagged_addr), info.first_bad_addr);
 479         pr_err("\n");
 480
 481         if (addr_has_shadow(untagged_addr)) {
 482                 print_address_description(untagged_addr);
 483                 pr_err("\n");
 484                 print_shadow_for_address(info.first_bad_addr);
 485         } else {
 486                 dump_stack();
 487         }
 488
 489         end_report(&flags);
 490 }