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 static void print_address_description(struct kasan_access_info *info)
 119 {
 120         const void *addr = info->access_addr;
 121
 122         if ((addr >= (void *)PAGE_OFFSET) &&
 123                 (addr < high_memory)) {
 124                 struct page *page = virt_to_head_page(addr);
 125
 126                 if (PageSlab(page)) {
 127                         void *object;
 128                         struct kmem_cache *cache = page->slab_cache;
 129                         void *last_object;
 130
 131                         object = virt_to_obj(cache, page_address(page), addr);
 132                         last_object = page_address(page) +
 133                                 page->objects * cache->size;
 134
 135                         if (unlikely(object > last_object))
 136                                 object = last_object; /* we hit into padding */
 137
 138                         object_err(cache, page, object,
 139                                 "kasan: bad access detected");
 140                         return;
 141                 }
 142                 dump_page(page, "kasan: bad access detected");
 143         }
 144
 145         if (kernel_or_module_addr(addr)) {
 146                 if (!init_task_stack_addr(addr))
 147                         pr_err("Address belongs to variable %pS\n", addr);
 148         }
 149
 150         dump_stack();
 151 }
 152
 153 static bool row_is_guilty(const void *row, const void *guilty)
 154 {
 155         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 156 }
 157
 158 static int shadow_pointer_offset(const void *row, const void *shadow)
 159 {
 160         /* The length of ">ff00ff00ff00ff00: " is
 161          *    3 + (BITS_PER_LONG/8)*2 chars.
 162          */
 163         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 164                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 165 }
 166
 167 static void print_shadow_for_address(const void *addr)
 168 {
 169         int i;
 170         const void *shadow = kasan_mem_to_shadow(addr);
 171         const void *shadow_row;
 172
 173         shadow_row = (void *)round_down((unsigned long)shadow,
 174                                         SHADOW_BYTES_PER_ROW)
 175                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 176
 177         pr_err("Memory state around the buggy address:\n");
 178
 179         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 180                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 181                 char buffer[4 + (BITS_PER_LONG/8)*2];
 182                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 183
 184                 snprintf(buffer, sizeof(buffer),
 185                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 186                 /*
 187                  * We should not pass a shadow pointer to generic
 188                  * function, because generic functions may try to
 189                  * access kasan mapping for the passed address.
 190                  */
 191                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 192                 print_hex_dump(KERN_ERR, buffer,
 193                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 194                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 195
 196                 if (row_is_guilty(shadow_row, shadow))
 197                         pr_err("%*c\n",
 198                                 shadow_pointer_offset(shadow_row, shadow),
 199                                 '^');
 200
 201                 shadow_row += SHADOW_BYTES_PER_ROW;
 202         }
 203 }
 204
 205 static DEFINE_SPINLOCK(report_lock);
 206
 207 static void kasan_report_error(struct kasan_access_info *info)
 208 {
 209         unsigned long flags;
 210         const char *bug_type;
 211
 212         /*
 213          * Make sure we don't end up in loop.
 214          */
 215         kasan_disable_current();
 216         spin_lock_irqsave(&report_lock, flags);
 217         pr_err("==================================================================\n");
 218         if (info->access_addr <
 219                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 220                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 221                         bug_type = "null-ptr-deref";
 222                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 223                         bug_type = "user-memory-access";
 224                 else
 225                         bug_type = "wild-memory-access";
 226                 pr_err("BUG: KASAN: %s on address %p\n",
 227                         bug_type, info->access_addr);
 228                 pr_err("%s of size %zu by task %s/%d\n",
 229                         info->is_write ? "Write" : "Read",
 230                         info->access_size, current->comm,
 231                         task_pid_nr(current));
 232                 dump_stack();
 233         } else {
 234                 print_error_description(info);
 235                 print_address_description(info);
 236                 print_shadow_for_address(info->first_bad_addr);
 237         }
 238         pr_err("==================================================================\n");
 239         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 240         spin_unlock_irqrestore(&report_lock, flags);
 241         kasan_enable_current();
 242 }
 243
 244 void kasan_report(unsigned long addr, size_t size,
 245                 bool is_write, unsigned long ip)
 246 {
 247         struct kasan_access_info info;
 248
 249         if (likely(!kasan_report_enabled()))
 250                 return;
 251
 252         info.access_addr = (void *)addr;
 253         info.access_size = size;
 254         info.is_write = is_write;
 255         info.ip = ip;
 256
 257         kasan_report_error(&info);
 258 }
 259
 260
 261 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 262 void __asan_report_load##size##_noabort(unsigned long addr) \
 263 {                                                         \
 264         kasan_report(addr, size, false, _RET_IP_);        \
 265 }                                                         \
 266 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 267
 268 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 269 void __asan_report_store##size##_noabort(unsigned long addr) \
 270 {                                                          \
 271         kasan_report(addr, size, true, _RET_IP_);          \
 272 }                                                          \
 273 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 274
 275 DEFINE_ASAN_REPORT_LOAD(1);
 276 DEFINE_ASAN_REPORT_LOAD(2);
 277 DEFINE_ASAN_REPORT_LOAD(4);
 278 DEFINE_ASAN_REPORT_LOAD(8);
 279 DEFINE_ASAN_REPORT_LOAD(16);
 280 DEFINE_ASAN_REPORT_STORE(1);
 281 DEFINE_ASAN_REPORT_STORE(2);
 282 DEFINE_ASAN_REPORT_STORE(4);
 283 DEFINE_ASAN_REPORT_STORE(8);
 284 DEFINE_ASAN_REPORT_STORE(16);
 285
 286 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 287 {
 288         kasan_report(addr, size, false, _RET_IP_);
 289 }
 290 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 291
 292 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 293 {
 294         kasan_report(addr, size, true, _RET_IP_);
 295 }
 296 EXPORT_SYMBOL(__asan_report_store_n_noabort);