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/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/printk.h>
  19 #include <linux/sched.h>
  20 #include <linux/slab.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
  27 #include <asm/sections.h>
  28
  29 #include "kasan.h"
  30 #include "../slab.h"
  31
  32 /* Shadow layout customization. */
  33 #define SHADOW_BYTES_PER_BLOCK 1
  34 #define SHADOW_BLOCKS_PER_ROW 16
  35 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  36 #define SHADOW_ROWS_AROUND_ADDR 2
  37
  38 static const void *find_first_bad_addr(const void *addr, size_t size)
  39 {
  40         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  41         const void *first_bad_addr = addr;
  42
  43         while (!shadow_val && first_bad_addr < addr + size) {
  44                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  45                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  46         }
  47         return first_bad_addr;
  48 }
  49
  50 static void print_error_description(struct kasan_access_info *info)
  51 {
  52         const char *bug_type = "unknown-crash";
  53         u8 *shadow_addr;
  54
  55         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  56                                                 info->access_size);
  57
  58         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  59
  60         /*
  61          * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
  62          * at the next shadow byte to determine the type of the bad access.
  63          */
  64         if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
  65                 shadow_addr++;
  66
  67         switch (*shadow_addr) {
  68         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  69                 /*
  70                  * In theory it's still possible to see these shadow values
  71                  * due to a data race in the kernel code.
  72                  */
  73                 bug_type = "out-of-bounds";
  74                 break;
  75         case KASAN_PAGE_REDZONE:
  76         case KASAN_KMALLOC_REDZONE:
  77                 bug_type = "slab-out-of-bounds";
  78                 break;
  79         case KASAN_GLOBAL_REDZONE:
  80                 bug_type = "global-out-of-bounds";
  81                 break;
  82         case KASAN_STACK_LEFT:
  83         case KASAN_STACK_MID:
  84         case KASAN_STACK_RIGHT:
  85         case KASAN_STACK_PARTIAL:
  86                 bug_type = "stack-out-of-bounds";
  87                 break;
  88         case KASAN_FREE_PAGE:
  89         case KASAN_KMALLOC_FREE:
  90                 bug_type = "use-after-free";
  91                 break;
  92         }
  93
  94         pr_err("BUG: KASAN: %s in %pS at addr %p\n",
  95                 bug_type, (void *)info->ip,
  96                 info->access_addr);
  97         pr_err("%s of size %zu by task %s/%d\n",
  98                 info->is_write ? "Write" : "Read",
  99                 info->access_size, current->comm, task_pid_nr(current));
 100 }
 101
 102 static inline bool kernel_or_module_addr(const void *addr)
 103 {
 104         if (addr >= (void *)_stext && addr < (void *)_end)
 105                 return true;
 106         if (is_module_address((unsigned long)addr))
 107                 return true;
 108         return false;
 109 }
 110
 111 static inline bool init_task_stack_addr(const void *addr)
 112 {
 113         return addr >= (void *)&init_thread_union.stack &&
 114                 (addr <= (void *)&init_thread_union.stack +
 115                         sizeof(init_thread_union.stack));
 116 }
 117
 118 #ifdef CONFIG_SLAB
 119 static void print_track(struct kasan_track *track)
 120 {
 121         pr_err("PID = %u, CPU = %u, timestamp = %lu\n", track->pid,
 122                track->cpu, (unsigned long)track->when);
 123 }
 124
 125 static void object_err(struct kmem_cache *cache, struct page *page,
 126                         void *object, char *unused_reason)
 127 {
 128         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 129         struct kasan_free_meta *free_info;
 130
 131         dump_stack();
 132         pr_err("Object at %p, in cache %s\n", object, cache->name);
 133         if (!(cache->flags & SLAB_KASAN))
 134                 return;
 135         switch (alloc_info->state) {
 136         case KASAN_STATE_INIT:
 137                 pr_err("Object not allocated yet\n");
 138                 break;
 139         case KASAN_STATE_ALLOC:
 140                 pr_err("Object allocated with size %u bytes.\n",
 141                        alloc_info->alloc_size);
 142                 pr_err("Allocation:\n");
 143                 print_track(&alloc_info->track);
 144                 break;
 145         case KASAN_STATE_FREE:
 146                 pr_err("Object freed, allocated with size %u bytes\n",
 147                        alloc_info->alloc_size);
 148                 free_info = get_free_info(cache, object);
 149                 pr_err("Allocation:\n");
 150                 print_track(&alloc_info->track);
 151                 pr_err("Deallocation:\n");
 152                 print_track(&free_info->track);
 153                 break;
 154         }
 155 }
 156 #endif
 157
 158 static void print_address_description(struct kasan_access_info *info)
 159 {
 160         const void *addr = info->access_addr;
 161
 162         if ((addr >= (void *)PAGE_OFFSET) &&
 163                 (addr < high_memory)) {
 164                 struct page *page = virt_to_head_page(addr);
 165
 166                 if (PageSlab(page)) {
 167                         void *object;
 168                         struct kmem_cache *cache = page->slab_cache;
 169                         object = nearest_obj(cache, page,
 170                                                 (void *)info->access_addr);
 171                         object_err(cache, page, object,
 172                                         "kasan: bad access detected");
 173                         return;
 174                 }
 175                 dump_page(page, "kasan: bad access detected");
 176         }
 177
 178         if (kernel_or_module_addr(addr)) {
 179                 if (!init_task_stack_addr(addr))
 180                         pr_err("Address belongs to variable %pS\n", addr);
 181         }
 182         dump_stack();
 183 }
 184
 185 static bool row_is_guilty(const void *row, const void *guilty)
 186 {
 187         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 188 }
 189
 190 static int shadow_pointer_offset(const void *row, const void *shadow)
 191 {
 192         /* The length of ">ff00ff00ff00ff00: " is
 193          *    3 + (BITS_PER_LONG/8)*2 chars.
 194          */
 195         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 196                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 197 }
 198
 199 static void print_shadow_for_address(const void *addr)
 200 {
 201         int i;
 202         const void *shadow = kasan_mem_to_shadow(addr);
 203         const void *shadow_row;
 204
 205         shadow_row = (void *)round_down((unsigned long)shadow,
 206                                         SHADOW_BYTES_PER_ROW)
 207                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 208
 209         pr_err("Memory state around the buggy address:\n");
 210
 211         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 212                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 213                 char buffer[4 + (BITS_PER_LONG/8)*2];
 214                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 215
 216                 snprintf(buffer, sizeof(buffer),
 217                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 218                 /*
 219                  * We should not pass a shadow pointer to generic
 220                  * function, because generic functions may try to
 221                  * access kasan mapping for the passed address.
 222                  */
 223                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 224                 print_hex_dump(KERN_ERR, buffer,
 225                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 226                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 227
 228                 if (row_is_guilty(shadow_row, shadow))
 229                         pr_err("%*c\n",
 230                                 shadow_pointer_offset(shadow_row, shadow),
 231                                 '^');
 232
 233                 shadow_row += SHADOW_BYTES_PER_ROW;
 234         }
 235 }
 236
 237 static DEFINE_SPINLOCK(report_lock);
 238
 239 static void kasan_report_error(struct kasan_access_info *info)
 240 {
 241         unsigned long flags;
 242         const char *bug_type;
 243
 244         /*
 245          * Make sure we don't end up in loop.
 246          */
 247         kasan_disable_current();
 248         spin_lock_irqsave(&report_lock, flags);
 249         pr_err("==================================================================\n");
 250         if (info->access_addr <
 251                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 252                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 253                         bug_type = "null-ptr-deref";
 254                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 255                         bug_type = "user-memory-access";
 256                 else
 257                         bug_type = "wild-memory-access";
 258                 pr_err("BUG: KASAN: %s on address %p\n",
 259                         bug_type, info->access_addr);
 260                 pr_err("%s of size %zu by task %s/%d\n",
 261                         info->is_write ? "Write" : "Read",
 262                         info->access_size, current->comm,
 263                         task_pid_nr(current));
 264                 dump_stack();
 265         } else {
 266                 print_error_description(info);
 267                 print_address_description(info);
 268                 print_shadow_for_address(info->first_bad_addr);
 269         }
 270         pr_err("==================================================================\n");
 271         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 272         spin_unlock_irqrestore(&report_lock, flags);
 273         kasan_enable_current();
 274 }
 275
 276 void kasan_report(unsigned long addr, size_t size,
 277                 bool is_write, unsigned long ip)
 278 {
 279         struct kasan_access_info info;
 280
 281         if (likely(!kasan_report_enabled()))
 282                 return;
 283
 284         info.access_addr = (void *)addr;
 285         info.access_size = size;
 286         info.is_write = is_write;
 287         info.ip = ip;
 288
 289         kasan_report_error(&info);
 290 }
 291
 292
 293 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 294 void __asan_report_load##size##_noabort(unsigned long addr) \
 295 {                                                         \
 296         kasan_report(addr, size, false, _RET_IP_);        \
 297 }                                                         \
 298 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 299
 300 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 301 void __asan_report_store##size##_noabort(unsigned long addr) \
 302 {                                                          \
 303         kasan_report(addr, size, true, _RET_IP_);          \
 304 }                                                          \
 305 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 306
 307 DEFINE_ASAN_REPORT_LOAD(1);
 308 DEFINE_ASAN_REPORT_LOAD(2);
 309 DEFINE_ASAN_REPORT_LOAD(4);
 310 DEFINE_ASAN_REPORT_LOAD(8);
 311 DEFINE_ASAN_REPORT_LOAD(16);
 312 DEFINE_ASAN_REPORT_STORE(1);
 313 DEFINE_ASAN_REPORT_STORE(2);
 314 DEFINE_ASAN_REPORT_STORE(4);
 315 DEFINE_ASAN_REPORT_STORE(8);
 316 DEFINE_ASAN_REPORT_STORE(16);
 317
 318 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 319 {
 320         kasan_report(addr, size, false, _RET_IP_);
 321 }
 322 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 323
 324 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 325 {
 326         kasan_report(addr, size, true, _RET_IP_);
 327 }
 328 EXPORT_SYMBOL(__asan_report_store_n_noabort);