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 <a.ryabinin@samsung.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
  26 #include "kasan.h"
  27
  28 /* Shadow layout customization. */
  29 #define SHADOW_BYTES_PER_BLOCK 1
  30 #define SHADOW_BLOCKS_PER_ROW 16
  31 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  32 #define SHADOW_ROWS_AROUND_ADDR 2
  33
  34 static const void *find_first_bad_addr(const void *addr, size_t size)
  35 {
  36         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  37         const void *first_bad_addr = addr;
  38
  39         while (!shadow_val && first_bad_addr < addr + size) {
  40                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  41                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  42         }
  43         return first_bad_addr;
  44 }
  45
  46 static void print_error_description(struct kasan_access_info *info)
  47 {
  48         const char *bug_type = "unknown crash";
  49         u8 shadow_val;
  50
  51         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  52                                                 info->access_size);
  53
  54         shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  55
  56         switch (shadow_val) {
  57         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  58                 bug_type = "out of bounds access";
  59                 break;
  60         }
  61
  62         pr_err("BUG: KASan: %s in %pS at addr %p\n",
  63                 bug_type, (void *)info->ip,
  64                 info->access_addr);
  65         pr_err("%s of size %zu by task %s/%d\n",
  66                 info->is_write ? "Write" : "Read",
  67                 info->access_size, current->comm, task_pid_nr(current));
  68 }
  69
  70 static void print_address_description(struct kasan_access_info *info)
  71 {
  72         dump_stack();
  73 }
  74
  75 static bool row_is_guilty(const void *row, const void *guilty)
  76 {
  77         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
  78 }
  79
  80 static int shadow_pointer_offset(const void *row, const void *shadow)
  81 {
  82         /* The length of ">ff00ff00ff00ff00: " is
  83          *    3 + (BITS_PER_LONG/8)*2 chars.
  84          */
  85         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
  86                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
  87 }
  88
  89 static void print_shadow_for_address(const void *addr)
  90 {
  91         int i;
  92         const void *shadow = kasan_mem_to_shadow(addr);
  93         const void *shadow_row;
  94
  95         shadow_row = (void *)round_down((unsigned long)shadow,
  96                                         SHADOW_BYTES_PER_ROW)
  97                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
  98
  99         pr_err("Memory state around the buggy address:\n");
 100
 101         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 102                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 103                 char buffer[4 + (BITS_PER_LONG/8)*2];
 104
 105                 snprintf(buffer, sizeof(buffer),
 106                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 107
 108                 kasan_disable_current();
 109                 print_hex_dump(KERN_ERR, buffer,
 110                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 111                         shadow_row, SHADOW_BYTES_PER_ROW, 0);
 112                 kasan_enable_current();
 113
 114                 if (row_is_guilty(shadow_row, shadow))
 115                         pr_err("%*c\n",
 116                                 shadow_pointer_offset(shadow_row, shadow),
 117                                 '^');
 118
 119                 shadow_row += SHADOW_BYTES_PER_ROW;
 120         }
 121 }
 122
 123 static DEFINE_SPINLOCK(report_lock);
 124
 125 void kasan_report_error(struct kasan_access_info *info)
 126 {
 127         unsigned long flags;
 128
 129         spin_lock_irqsave(&report_lock, flags);
 130         pr_err("================================="
 131                 "=================================\n");
 132         print_error_description(info);
 133         print_address_description(info);
 134         print_shadow_for_address(info->first_bad_addr);
 135         pr_err("================================="
 136                 "=================================\n");
 137         spin_unlock_irqrestore(&report_lock, flags);
 138 }
 139
 140 void kasan_report_user_access(struct kasan_access_info *info)
 141 {
 142         unsigned long flags;
 143
 144         spin_lock_irqsave(&report_lock, flags);
 145         pr_err("================================="
 146                 "=================================\n");
 147         pr_err("BUG: KASan: user-memory-access on address %p\n",
 148                 info->access_addr);
 149         pr_err("%s of size %zu by task %s/%d\n",
 150                 info->is_write ? "Write" : "Read",
 151                 info->access_size, current->comm, task_pid_nr(current));
 152         dump_stack();
 153         pr_err("================================="
 154                 "=================================\n");
 155         spin_unlock_irqrestore(&report_lock, flags);
 156 }
 157
 158 void kasan_report(unsigned long addr, size_t size,
 159                 bool is_write, unsigned long ip)
 160 {
 161         struct kasan_access_info info;
 162
 163         if (likely(!kasan_enabled()))
 164                 return;
 165
 166         info.access_addr = (void *)addr;
 167         info.access_size = size;
 168         info.is_write = is_write;
 169         info.ip = ip;
 170         kasan_report_error(&info);
 171 }
 172
 173
 174 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 175 void __asan_report_load##size##_noabort(unsigned long addr) \
 176 {                                                         \
 177         kasan_report(addr, size, false, _RET_IP_);        \
 178 }                                                         \
 179 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 180
 181 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 182 void __asan_report_store##size##_noabort(unsigned long addr) \
 183 {                                                          \
 184         kasan_report(addr, size, true, _RET_IP_);          \
 185 }                                                          \
 186 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 187
 188 DEFINE_ASAN_REPORT_LOAD(1);
 189 DEFINE_ASAN_REPORT_LOAD(2);
 190 DEFINE_ASAN_REPORT_LOAD(4);
 191 DEFINE_ASAN_REPORT_LOAD(8);
 192 DEFINE_ASAN_REPORT_LOAD(16);
 193 DEFINE_ASAN_REPORT_STORE(1);
 194 DEFINE_ASAN_REPORT_STORE(2);
 195 DEFINE_ASAN_REPORT_STORE(4);
 196 DEFINE_ASAN_REPORT_STORE(8);
 197 DEFINE_ASAN_REPORT_STORE(16);
 198
 199 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 200 {
 201         kasan_report(addr, size, false, _RET_IP_);
 202 }
 203 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 204
 205 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 206 {
 207         kasan_report(addr, size, true, _RET_IP_);
 208 }
 209 EXPORT_SYMBOL(__asan_report_store_n_noabort);