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 of code borrowed from https://github.com/xairy/linux 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_val;
  54
  55         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  56                                                 info->access_size);
  57
  58         shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  59
  60         switch (shadow_val) {
  61         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  62                 bug_type = "out-of-bounds";
  63                 break;
  64         case KASAN_PAGE_REDZONE:
  65         case KASAN_KMALLOC_REDZONE:
  66                 bug_type = "slab-out-of-bounds";
  67                 break;
  68         case KASAN_GLOBAL_REDZONE:
  69                 bug_type = "global-out-of-bounds";
  70                 break;
  71         case KASAN_STACK_LEFT:
  72         case KASAN_STACK_MID:
  73         case KASAN_STACK_RIGHT:
  74         case KASAN_STACK_PARTIAL:
  75                 bug_type = "stack-out-of-bounds";
  76                 break;
  77         case KASAN_FREE_PAGE:
  78         case KASAN_KMALLOC_FREE:
  79                 bug_type = "use-after-free";
  80                 break;
  81         }
  82
  83         pr_err("BUG: KASan: %s in %pS at addr %p\n",
  84                 bug_type, (void *)info->ip,
  85                 info->access_addr);
  86         pr_err("%s of size %zu by task %s/%d\n",
  87                 info->is_write ? "Write" : "Read",
  88                 info->access_size, current->comm, task_pid_nr(current));
  89 }
  90
  91 static inline bool kernel_or_module_addr(const void *addr)
  92 {
  93         if (addr >= (void *)_stext && addr < (void *)_end)
  94                 return true;
  95         if (is_module_address((unsigned long)addr))
  96                 return true;
  97         return false;
  98 }
  99
 100 static inline bool init_task_stack_addr(const void *addr)
 101 {
 102         return addr >= (void *)&init_thread_union.stack &&
 103                 (addr <= (void *)&init_thread_union.stack +
 104                         sizeof(init_thread_union.stack));
 105 }
 106
 107 static void print_address_description(struct kasan_access_info *info)
 108 {
 109         const void *addr = info->access_addr;
 110
 111         if ((addr >= (void *)PAGE_OFFSET) &&
 112                 (addr < high_memory)) {
 113                 struct page *page = virt_to_head_page(addr);
 114
 115                 if (PageSlab(page)) {
 116                         void *object;
 117                         struct kmem_cache *cache = page->slab_cache;
 118                         void *last_object;
 119
 120                         object = virt_to_obj(cache, page_address(page), addr);
 121                         last_object = page_address(page) +
 122                                 page->objects * cache->size;
 123
 124                         if (unlikely(object > last_object))
 125                                 object = last_object; /* we hit into padding */
 126
 127                         object_err(cache, page, object,
 128                                 "kasan: bad access detected");
 129                         return;
 130                 }
 131                 dump_page(page, "kasan: bad access detected");
 132         }
 133
 134         if (kernel_or_module_addr(addr)) {
 135                 if (!init_task_stack_addr(addr))
 136                         pr_err("Address belongs to variable %pS\n", addr);
 137         }
 138
 139         dump_stack();
 140 }
 141
 142 static bool row_is_guilty(const void *row, const void *guilty)
 143 {
 144         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 145 }
 146
 147 static int shadow_pointer_offset(const void *row, const void *shadow)
 148 {
 149         /* The length of ">ff00ff00ff00ff00: " is
 150          *    3 + (BITS_PER_LONG/8)*2 chars.
 151          */
 152         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 153                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 154 }
 155
 156 static void print_shadow_for_address(const void *addr)
 157 {
 158         int i;
 159         const void *shadow = kasan_mem_to_shadow(addr);
 160         const void *shadow_row;
 161
 162         shadow_row = (void *)round_down((unsigned long)shadow,
 163                                         SHADOW_BYTES_PER_ROW)
 164                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 165
 166         pr_err("Memory state around the buggy address:\n");
 167
 168         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 169                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 170                 char buffer[4 + (BITS_PER_LONG/8)*2];
 171                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 172
 173                 snprintf(buffer, sizeof(buffer),
 174                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 175                 /*
 176                  * We should not pass a shadow pointer to generic
 177                  * function, because generic functions may try to
 178                  * access kasan mapping for the passed address.
 179                  */
 180                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 181                 print_hex_dump(KERN_ERR, buffer,
 182                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 183                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 184
 185                 if (row_is_guilty(shadow_row, shadow))
 186                         pr_err("%*c\n",
 187                                 shadow_pointer_offset(shadow_row, shadow),
 188                                 '^');
 189
 190                 shadow_row += SHADOW_BYTES_PER_ROW;
 191         }
 192 }
 193
 194 static DEFINE_SPINLOCK(report_lock);
 195
 196 static void kasan_report_error(struct kasan_access_info *info)
 197 {
 198         unsigned long flags;
 199         const char *bug_type;
 200
 201         /*
 202          * Make sure we don't end up in loop.
 203          */
 204         kasan_disable_current();
 205         spin_lock_irqsave(&report_lock, flags);
 206         pr_err("================================="
 207                 "=================================\n");
 208         if (info->access_addr <
 209                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 210                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 211                         bug_type = "null-ptr-deref";
 212                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 213                         bug_type = "user-memory-access";
 214                 else
 215                         bug_type = "wild-memory-access";
 216                 pr_err("BUG: KASan: %s on address %p\n",
 217                         bug_type, info->access_addr);
 218                 pr_err("%s of size %zu by task %s/%d\n",
 219                         info->is_write ? "Write" : "Read",
 220                         info->access_size, current->comm,
 221                         task_pid_nr(current));
 222                 dump_stack();
 223         } else {
 224                 print_error_description(info);
 225                 print_address_description(info);
 226                 print_shadow_for_address(info->first_bad_addr);
 227         }
 228         pr_err("================================="
 229                 "=================================\n");
 230         spin_unlock_irqrestore(&report_lock, flags);
 231         kasan_enable_current();
 232 }
 233
 234 void kasan_report(unsigned long addr, size_t size,
 235                 bool is_write, unsigned long ip)
 236 {
 237         struct kasan_access_info info;
 238
 239         if (likely(!kasan_report_enabled()))
 240                 return;
 241
 242         info.access_addr = (void *)addr;
 243         info.access_size = size;
 244         info.is_write = is_write;
 245         info.ip = ip;
 246
 247         kasan_report_error(&info);
 248 }
 249
 250
 251 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 252 void __asan_report_load##size##_noabort(unsigned long addr) \
 253 {                                                         \
 254         kasan_report(addr, size, false, _RET_IP_);        \
 255 }                                                         \
 256 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 257
 258 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 259 void __asan_report_store##size##_noabort(unsigned long addr) \
 260 {                                                          \
 261         kasan_report(addr, size, true, _RET_IP_);          \
 262 }                                                          \
 263 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 264
 265 DEFINE_ASAN_REPORT_LOAD(1);
 266 DEFINE_ASAN_REPORT_LOAD(2);
 267 DEFINE_ASAN_REPORT_LOAD(4);
 268 DEFINE_ASAN_REPORT_LOAD(8);
 269 DEFINE_ASAN_REPORT_LOAD(16);
 270 DEFINE_ASAN_REPORT_STORE(1);
 271 DEFINE_ASAN_REPORT_STORE(2);
 272 DEFINE_ASAN_REPORT_STORE(4);
 273 DEFINE_ASAN_REPORT_STORE(8);
 274 DEFINE_ASAN_REPORT_STORE(16);
 275
 276 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 277 {
 278         kasan_report(addr, size, false, _RET_IP_);
 279 }
 280 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 281
 282 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 283 {
 284         kasan_report(addr, size, true, _RET_IP_);
 285 }
 286 EXPORT_SYMBOL(__asan_report_store_n_noabort);