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 #include "../slab.h"
  28
  29 /* Shadow layout customization. */
  30 #define SHADOW_BYTES_PER_BLOCK 1
  31 #define SHADOW_BLOCKS_PER_ROW 16
  32 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  33 #define SHADOW_ROWS_AROUND_ADDR 2
  34
  35 static const void *find_first_bad_addr(const void *addr, size_t size)
  36 {
  37         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  38         const void *first_bad_addr = addr;
  39
  40         while (!shadow_val && first_bad_addr < addr + size) {
  41                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  42                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  43         }
  44         return first_bad_addr;
  45 }
  46
  47 static void print_error_description(struct kasan_access_info *info)
  48 {
  49         const char *bug_type = "unknown crash";
  50         u8 shadow_val;
  51
  52         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  53                                                 info->access_size);
  54
  55         shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  56
  57         switch (shadow_val) {
  58         case KASAN_FREE_PAGE:
  59         case KASAN_KMALLOC_FREE:
  60                 bug_type = "use after free";
  61                 break;
  62         case KASAN_PAGE_REDZONE:
  63         case KASAN_KMALLOC_REDZONE:
  64         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  65                 bug_type = "out of bounds access";
  66                 break;
  67         case KASAN_STACK_LEFT:
  68         case KASAN_STACK_MID:
  69         case KASAN_STACK_RIGHT:
  70         case KASAN_STACK_PARTIAL:
  71                 bug_type = "out of bounds on stack";
  72                 break;
  73         }
  74
  75         pr_err("BUG: KASan: %s in %pS at addr %p\n",
  76                 bug_type, (void *)info->ip,
  77                 info->access_addr);
  78         pr_err("%s of size %zu by task %s/%d\n",
  79                 info->is_write ? "Write" : "Read",
  80                 info->access_size, current->comm, task_pid_nr(current));
  81 }
  82
  83 static void print_address_description(struct kasan_access_info *info)
  84 {
  85         const void *addr = info->access_addr;
  86
  87         if ((addr >= (void *)PAGE_OFFSET) &&
  88                 (addr < high_memory)) {
  89                 struct page *page = virt_to_head_page(addr);
  90
  91                 if (PageSlab(page)) {
  92                         void *object;
  93                         struct kmem_cache *cache = page->slab_cache;
  94                         void *last_object;
  95
  96                         object = virt_to_obj(cache, page_address(page), addr);
  97                         last_object = page_address(page) +
  98                                 page->objects * cache->size;
  99
 100                         if (unlikely(object > last_object))
 101                                 object = last_object; /* we hit into padding */
 102
 103                         object_err(cache, page, object,
 104                                 "kasan: bad access detected");
 105                         return;
 106                 }
 107                 dump_page(page, "kasan: bad access detected");
 108         }
 109
 110         dump_stack();
 111 }
 112
 113 static bool row_is_guilty(const void *row, const void *guilty)
 114 {
 115         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 116 }
 117
 118 static int shadow_pointer_offset(const void *row, const void *shadow)
 119 {
 120         /* The length of ">ff00ff00ff00ff00: " is
 121          *    3 + (BITS_PER_LONG/8)*2 chars.
 122          */
 123         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 124                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 125 }
 126
 127 static void print_shadow_for_address(const void *addr)
 128 {
 129         int i;
 130         const void *shadow = kasan_mem_to_shadow(addr);
 131         const void *shadow_row;
 132
 133         shadow_row = (void *)round_down((unsigned long)shadow,
 134                                         SHADOW_BYTES_PER_ROW)
 135                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 136
 137         pr_err("Memory state around the buggy address:\n");
 138
 139         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 140                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 141                 char buffer[4 + (BITS_PER_LONG/8)*2];
 142
 143                 snprintf(buffer, sizeof(buffer),
 144                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 145
 146                 kasan_disable_current();
 147                 print_hex_dump(KERN_ERR, buffer,
 148                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 149                         shadow_row, SHADOW_BYTES_PER_ROW, 0);
 150                 kasan_enable_current();
 151
 152                 if (row_is_guilty(shadow_row, shadow))
 153                         pr_err("%*c\n",
 154                                 shadow_pointer_offset(shadow_row, shadow),
 155                                 '^');
 156
 157                 shadow_row += SHADOW_BYTES_PER_ROW;
 158         }
 159 }
 160
 161 static DEFINE_SPINLOCK(report_lock);
 162
 163 void kasan_report_error(struct kasan_access_info *info)
 164 {
 165         unsigned long flags;
 166
 167         spin_lock_irqsave(&report_lock, flags);
 168         pr_err("================================="
 169                 "=================================\n");
 170         print_error_description(info);
 171         print_address_description(info);
 172         print_shadow_for_address(info->first_bad_addr);
 173         pr_err("================================="
 174                 "=================================\n");
 175         spin_unlock_irqrestore(&report_lock, flags);
 176 }
 177
 178 void kasan_report_user_access(struct kasan_access_info *info)
 179 {
 180         unsigned long flags;
 181
 182         spin_lock_irqsave(&report_lock, flags);
 183         pr_err("================================="
 184                 "=================================\n");
 185         pr_err("BUG: KASan: user-memory-access on address %p\n",
 186                 info->access_addr);
 187         pr_err("%s of size %zu by task %s/%d\n",
 188                 info->is_write ? "Write" : "Read",
 189                 info->access_size, current->comm, task_pid_nr(current));
 190         dump_stack();
 191         pr_err("================================="
 192                 "=================================\n");
 193         spin_unlock_irqrestore(&report_lock, flags);
 194 }
 195
 196 void kasan_report(unsigned long addr, size_t size,
 197                 bool is_write, unsigned long ip)
 198 {
 199         struct kasan_access_info info;
 200
 201         if (likely(!kasan_enabled()))
 202                 return;
 203
 204         info.access_addr = (void *)addr;
 205         info.access_size = size;
 206         info.is_write = is_write;
 207         info.ip = ip;
 208         kasan_report_error(&info);
 209 }
 210
 211
 212 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 213 void __asan_report_load##size##_noabort(unsigned long addr) \
 214 {                                                         \
 215         kasan_report(addr, size, false, _RET_IP_);        \
 216 }                                                         \
 217 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 218
 219 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 220 void __asan_report_store##size##_noabort(unsigned long addr) \
 221 {                                                          \
 222         kasan_report(addr, size, true, _RET_IP_);          \
 223 }                                                          \
 224 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 225
 226 DEFINE_ASAN_REPORT_LOAD(1);
 227 DEFINE_ASAN_REPORT_LOAD(2);
 228 DEFINE_ASAN_REPORT_LOAD(4);
 229 DEFINE_ASAN_REPORT_LOAD(8);
 230 DEFINE_ASAN_REPORT_LOAD(16);
 231 DEFINE_ASAN_REPORT_STORE(1);
 232 DEFINE_ASAN_REPORT_STORE(2);
 233 DEFINE_ASAN_REPORT_STORE(4);
 234 DEFINE_ASAN_REPORT_STORE(8);
 235 DEFINE_ASAN_REPORT_STORE(16);
 236
 237 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 238 {
 239         kasan_report(addr, size, false, _RET_IP_);
 240 }
 241 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 242
 243 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 244 {
 245         kasan_report(addr, size, true, _RET_IP_);
 246 }
 247 EXPORT_SYMBOL(__asan_report_store_n_noabort);