mm/kasan/report.c

   1 /*
   2  * This file contains error reporting code.
   3  *
   4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   6  *
   7  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   8  *        Andrey Konovalov <adech.fo@gmail.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License version 2 as
  12  * published by the Free Software Foundation.
  13  *
  14  */
  15
  16 #include <linux/bitops.h>
  17 #include <linux/ftrace.h>
  18 #include <linux/init.h>
  19 #include <linux/kernel.h>
  20 #include <linux/mm.h>
  21 #include <linux/printk.h>
  22 #include <linux/sched.h>
  23 #include <linux/slab.h>
  24 #include <linux/stackdepot.h>
  25 #include <linux/stacktrace.h>
  26 #include <linux/string.h>
  27 #include <linux/types.h>
  28 #include <linux/kasan.h>
  29 #include <linux/module.h>
  30
  31 #include <asm/sections.h>
  32
  33 #include "kasan.h"
  34 #include "../slab.h"
  35
  36 /* Shadow layout customization. */
  37 #define SHADOW_BYTES_PER_BLOCK 1
  38 #define SHADOW_BLOCKS_PER_ROW 16
  39 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  40 #define SHADOW_ROWS_AROUND_ADDR 2
  41
  42 static const void *find_first_bad_addr(const void *addr, size_t size)
  43 {
  44         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  45         const void *first_bad_addr = addr;
  46
  47         while (!shadow_val && first_bad_addr < addr + size) {
  48                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  49                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  50         }
  51         return first_bad_addr;
  52 }
  53
  54 static void print_error_description(struct kasan_access_info *info)
  55 {
  56         const char *bug_type = "unknown-crash";
  57         u8 *shadow_addr;
  58
  59         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  60                                                 info->access_size);
  61
  62         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  63
  64         /*
  65          * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
  66          * at the next shadow byte to determine the type of the bad access.
  67          */
  68         if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
  69                 shadow_addr++;
  70
  71         switch (*shadow_addr) {
  72         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  73                 /*
  74                  * In theory it's still possible to see these shadow values
  75                  * due to a data race in the kernel code.
  76                  */
  77                 bug_type = "out-of-bounds";
  78                 break;
  79         case KASAN_PAGE_REDZONE:
  80         case KASAN_KMALLOC_REDZONE:
  81                 bug_type = "slab-out-of-bounds";
  82                 break;
  83         case KASAN_GLOBAL_REDZONE:
  84                 bug_type = "global-out-of-bounds";
  85                 break;
  86         case KASAN_STACK_LEFT:
  87         case KASAN_STACK_MID:
  88         case KASAN_STACK_RIGHT:
  89         case KASAN_STACK_PARTIAL:
  90                 bug_type = "stack-out-of-bounds";
  91                 break;
  92         case KASAN_FREE_PAGE:
  93         case KASAN_KMALLOC_FREE:
  94                 bug_type = "use-after-free";
  95                 break;
  96         case KASAN_USE_AFTER_SCOPE:
  97                 bug_type = "use-after-scope";
  98                 break;
  99         }
 100
 101         pr_err("BUG: KASAN: %s in %pS at addr %p\n",
 102                 bug_type, (void *)info->ip,
 103                 info->access_addr);
 104         pr_err("%s of size %zu by task %s/%d\n",
 105                 info->is_write ? "Write" : "Read",
 106                 info->access_size, current->comm, task_pid_nr(current));
 107 }
 108
 109 static inline bool kernel_or_module_addr(const void *addr)
 110 {
 111         if (addr >= (void *)_stext && addr < (void *)_end)
 112                 return true;
 113         if (is_module_address((unsigned long)addr))
 114                 return true;
 115         return false;
 116 }
 117
 118 static inline bool init_task_stack_addr(const void *addr)
 119 {
 120         return addr >= (void *)&init_thread_union.stack &&
 121                 (addr <= (void *)&init_thread_union.stack +
 122                         sizeof(init_thread_union.stack));
 123 }
 124
 125 static DEFINE_SPINLOCK(report_lock);
 126
 127 static void kasan_start_report(unsigned long *flags)
 128 {
 129         /*
 130          * Make sure we don't end up in loop.
 131          */
 132         kasan_disable_current();
 133         spin_lock_irqsave(&report_lock, *flags);
 134         pr_err("==================================================================\n");
 135 }
 136
 137 static void kasan_end_report(unsigned long *flags)
 138 {
 139         pr_err("==================================================================\n");
 140         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 141         spin_unlock_irqrestore(&report_lock, *flags);
 142         if (panic_on_warn)
 143                 panic("panic_on_warn set ...\n");
 144         kasan_enable_current();
 145 }
 146
 147 static void print_track(struct kasan_track *track)
 148 {
 149         pr_err("PID = %u\n", track->pid);
 150         if (track->stack) {
 151                 struct stack_trace trace;
 152
 153                 depot_fetch_stack(track->stack, &trace);
 154                 print_stack_trace(&trace, 0);
 155         } else {
 156                 pr_err("(stack is not available)\n");
 157         }
 158 }
 159
 160 static void kasan_object_err(struct kmem_cache *cache, void *object)
 161 {
 162         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 163
 164         dump_stack();
 165         pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
 166                 cache->object_size);
 167
 168         if (!(cache->flags & SLAB_KASAN))
 169                 return;
 170
 171         pr_err("Allocated:\n");
 172         print_track(&alloc_info->alloc_track);
 173         pr_err("Freed:\n");
 174         print_track(&alloc_info->free_track);
 175 }
 176
 177 void kasan_report_double_free(struct kmem_cache *cache, void *object,
 178                         s8 shadow)
 179 {
 180         unsigned long flags;
 181
 182         kasan_start_report(&flags);
 183         pr_err("BUG: Double free or freeing an invalid pointer\n");
 184         pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
 185         kasan_object_err(cache, object);
 186         kasan_end_report(&flags);
 187 }
 188
 189 static void print_address_description(struct kasan_access_info *info)
 190 {
 191         const void *addr = info->access_addr;
 192
 193         if ((addr >= (void *)PAGE_OFFSET) &&
 194                 (addr < high_memory)) {
 195                 struct page *page = virt_to_head_page(addr);
 196
 197                 if (PageSlab(page)) {
 198                         void *object;
 199                         struct kmem_cache *cache = page->slab_cache;
 200                         object = nearest_obj(cache, page,
 201                                                 (void *)info->access_addr);
 202                         kasan_object_err(cache, object);
 203                         return;
 204                 }
 205                 dump_page(page, "kasan: bad access detected");
 206         }
 207
 208         if (kernel_or_module_addr(addr)) {
 209                 if (!init_task_stack_addr(addr))
 210                         pr_err("Address belongs to variable %pS\n", addr);
 211         }
 212         dump_stack();
 213 }
 214
 215 static bool row_is_guilty(const void *row, const void *guilty)
 216 {
 217         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 218 }
 219
 220 static int shadow_pointer_offset(const void *row, const void *shadow)
 221 {
 222         /* The length of ">ff00ff00ff00ff00: " is
 223          *    3 + (BITS_PER_LONG/8)*2 chars.
 224          */
 225         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 226                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 227 }
 228
 229 static void print_shadow_for_address(const void *addr)
 230 {
 231         int i;
 232         const void *shadow = kasan_mem_to_shadow(addr);
 233         const void *shadow_row;
 234
 235         shadow_row = (void *)round_down((unsigned long)shadow,
 236                                         SHADOW_BYTES_PER_ROW)
 237                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 238
 239         pr_err("Memory state around the buggy address:\n");
 240
 241         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 242                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 243                 char buffer[4 + (BITS_PER_LONG/8)*2];
 244                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 245
 246                 snprintf(buffer, sizeof(buffer),
 247                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 248                 /*
 249                  * We should not pass a shadow pointer to generic
 250                  * function, because generic functions may try to
 251                  * access kasan mapping for the passed address.
 252                  */
 253                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 254                 print_hex_dump(KERN_ERR, buffer,
 255                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 256                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 257
 258                 if (row_is_guilty(shadow_row, shadow))
 259                         pr_err("%*c\n",
 260                                 shadow_pointer_offset(shadow_row, shadow),
 261                                 '^');
 262
 263                 shadow_row += SHADOW_BYTES_PER_ROW;
 264         }
 265 }
 266
 267 static void kasan_report_error(struct kasan_access_info *info)
 268 {
 269         unsigned long flags;
 270         const char *bug_type;
 271
 272         kasan_start_report(&flags);
 273
 274         if (info->access_addr <
 275                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 276                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 277                         bug_type = "null-ptr-deref";
 278                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 279                         bug_type = "user-memory-access";
 280                 else
 281                         bug_type = "wild-memory-access";
 282                 pr_err("BUG: KASAN: %s on address %p\n",
 283                         bug_type, info->access_addr);
 284                 pr_err("%s of size %zu by task %s/%d\n",
 285                         info->is_write ? "Write" : "Read",
 286                         info->access_size, current->comm,
 287                         task_pid_nr(current));
 288                 dump_stack();
 289         } else {
 290                 print_error_description(info);
 291                 print_address_description(info);
 292                 print_shadow_for_address(info->first_bad_addr);
 293         }
 294
 295         kasan_end_report(&flags);
 296 }
 297
 298 static unsigned long kasan_flags;
 299
 300 #define KASAN_BIT_REPORTED      0
 301 #define KASAN_BIT_MULTI_SHOT    1
 302
 303 bool kasan_save_enable_multi_shot(void)
 304 {
 305         return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 306 }
 307 EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot);
 308
 309 void kasan_restore_multi_shot(bool enabled)
 310 {
 311         if (!enabled)
 312                 clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 313 }
 314 EXPORT_SYMBOL_GPL(kasan_restore_multi_shot);
 315
 316 static int __init kasan_set_multi_shot(char *str)
 317 {
 318         set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags);
 319         return 1;
 320 }
 321 __setup("kasan_multi_shot", kasan_set_multi_shot);
 322
 323 static inline bool kasan_report_enabled(void)
 324 {
 325         if (current->kasan_depth)
 326                 return false;
 327         if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags))
 328                 return true;
 329         return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags);
 330 }
 331
 332 void kasan_report(unsigned long addr, size_t size,
 333                 bool is_write, unsigned long ip)
 334 {
 335         struct kasan_access_info info;
 336
 337         if (likely(!kasan_report_enabled()))
 338                 return;
 339
 340         disable_trace_on_warning();
 341
 342         info.access_addr = (void *)addr;
 343         info.access_size = size;
 344         info.is_write = is_write;
 345         info.ip = ip;
 346
 347         kasan_report_error(&info);
 348 }
 349
 350
 351 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 352 void __asan_report_load##size##_noabort(unsigned long addr) \
 353 {                                                         \
 354         kasan_report(addr, size, false, _RET_IP_);        \
 355 }                                                         \
 356 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 357
 358 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 359 void __asan_report_store##size##_noabort(unsigned long addr) \
 360 {                                                          \
 361         kasan_report(addr, size, true, _RET_IP_);          \
 362 }                                                          \
 363 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 364
 365 DEFINE_ASAN_REPORT_LOAD(1);
 366 DEFINE_ASAN_REPORT_LOAD(2);
 367 DEFINE_ASAN_REPORT_LOAD(4);
 368 DEFINE_ASAN_REPORT_LOAD(8);
 369 DEFINE_ASAN_REPORT_LOAD(16);
 370 DEFINE_ASAN_REPORT_STORE(1);
 371 DEFINE_ASAN_REPORT_STORE(2);
 372 DEFINE_ASAN_REPORT_STORE(4);
 373 DEFINE_ASAN_REPORT_STORE(8);
 374 DEFINE_ASAN_REPORT_STORE(16);
 375
 376 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 377 {
 378         kasan_report(addr, size, false, _RET_IP_);
 379 }
 380 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 381
 382 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 383 {
 384         kasan_report(addr, size, true, _RET_IP_);
 385 }
 386 EXPORT_SYMBOL(__asan_report_store_n_noabort);