kernel/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 <asm/sections.h>
  27
  28 #include "kasan.h"
  29 #include "../slab.h"
  30
  31 /* Shadow layout customization. */
  32 #define SHADOW_BYTES_PER_BLOCK 1
  33 #define SHADOW_BLOCKS_PER_ROW 16
  34 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  35 #define SHADOW_ROWS_AROUND_ADDR 2
  36
  37 static const void *find_first_bad_addr(const void *addr, size_t size)
  38 {
  39         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  40         const void *first_bad_addr = addr;
  41
  42         while (!shadow_val && first_bad_addr < addr + size) {
  43                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  44                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  45         }
  46         return first_bad_addr;
  47 }
  48
  49 static void print_error_description(struct kasan_access_info *info)
  50 {
  51         const char *bug_type = "unknown crash";
  52         u8 shadow_val;
  53
  54         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  55                                                 info->access_size);
  56
  57         shadow_val = *(u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  58
  59         switch (shadow_val) {
  60         case KASAN_FREE_PAGE:
  61         case KASAN_KMALLOC_FREE:
  62                 bug_type = "use after free";
  63                 break;
  64         case KASAN_PAGE_REDZONE:
  65         case KASAN_KMALLOC_REDZONE:
  66         case KASAN_GLOBAL_REDZONE:
  67         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  68                 bug_type = "out of bounds access";
  69                 break;
  70         case KASAN_STACK_LEFT:
  71         case KASAN_STACK_MID:
  72         case KASAN_STACK_RIGHT:
  73         case KASAN_STACK_PARTIAL:
  74                 bug_type = "out of bounds on stack";
  75                 break;
  76         }
  77
  78         pr_err("BUG: KASan: %s in %pS at addr %p\n",
  79                 bug_type, (void *)info->ip,
  80                 info->access_addr);
  81         pr_err("%s of size %zu by task %s/%d\n",
  82                 info->is_write ? "Write" : "Read",
  83                 info->access_size, current->comm, task_pid_nr(current));
  84 }
  85
  86 static inline bool kernel_or_module_addr(const void *addr)
  87 {
  88         return (addr >= (void *)_stext && addr < (void *)_end)
  89                 || (addr >= (void *)MODULES_VADDR
  90                         && addr < (void *)MODULES_END);
  91 }
  92
  93 static inline bool init_task_stack_addr(const void *addr)
  94 {
  95         return addr >= (void *)&init_thread_union.stack &&
  96                 (addr <= (void *)&init_thread_union.stack +
  97                         sizeof(init_thread_union.stack));
  98 }
  99
 100 static void print_address_description(struct kasan_access_info *info)
 101 {
 102         const void *addr = info->access_addr;
 103
 104         if ((addr >= (void *)PAGE_OFFSET) &&
 105                 (addr < high_memory)) {
 106                 struct page *page = virt_to_head_page(addr);
 107
 108                 if (PageSlab(page)) {
 109                         void *object;
 110                         struct kmem_cache *cache = page->slab_cache;
 111                         void *last_object;
 112
 113                         object = virt_to_obj(cache, page_address(page), addr);
 114                         last_object = page_address(page) +
 115                                 page->objects * cache->size;
 116
 117                         if (unlikely(object > last_object))
 118                                 object = last_object; /* we hit into padding */
 119
 120                         object_err(cache, page, object,
 121                                 "kasan: bad access detected");
 122                         return;
 123                 }
 124                 dump_page(page, "kasan: bad access detected");
 125         }
 126
 127         if (kernel_or_module_addr(addr)) {
 128                 if (!init_task_stack_addr(addr))
 129                         pr_err("Address belongs to variable %pS\n", addr);
 130         }
 131
 132         dump_stack();
 133 }
 134
 135 static bool row_is_guilty(const void *row, const void *guilty)
 136 {
 137         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 138 }
 139
 140 static int shadow_pointer_offset(const void *row, const void *shadow)
 141 {
 142         /* The length of ">ff00ff00ff00ff00: " is
 143          *    3 + (BITS_PER_LONG/8)*2 chars.
 144          */
 145         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 146                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 147 }
 148
 149 static void print_shadow_for_address(const void *addr)
 150 {
 151         int i;
 152         const void *shadow = kasan_mem_to_shadow(addr);
 153         const void *shadow_row;
 154
 155         shadow_row = (void *)round_down((unsigned long)shadow,
 156                                         SHADOW_BYTES_PER_ROW)
 157                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 158
 159         pr_err("Memory state around the buggy address:\n");
 160
 161         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 162                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 163                 char buffer[4 + (BITS_PER_LONG/8)*2];
 164
 165                 snprintf(buffer, sizeof(buffer),
 166                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 167
 168                 kasan_disable_current();
 169                 print_hex_dump(KERN_ERR, buffer,
 170                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 171                         shadow_row, SHADOW_BYTES_PER_ROW, 0);
 172                 kasan_enable_current();
 173
 174                 if (row_is_guilty(shadow_row, shadow))
 175                         pr_err("%*c\n",
 176                                 shadow_pointer_offset(shadow_row, shadow),
 177                                 '^');
 178
 179                 shadow_row += SHADOW_BYTES_PER_ROW;
 180         }
 181 }
 182
 183 static DEFINE_SPINLOCK(report_lock);
 184
 185 void kasan_report_error(struct kasan_access_info *info)
 186 {
 187         unsigned long flags;
 188
 189         spin_lock_irqsave(&report_lock, flags);
 190         pr_err("================================="
 191                 "=================================\n");
 192         print_error_description(info);
 193         print_address_description(info);
 194         print_shadow_for_address(info->first_bad_addr);
 195         pr_err("================================="
 196                 "=================================\n");
 197         spin_unlock_irqrestore(&report_lock, flags);
 198 }
 199
 200 void kasan_report_user_access(struct kasan_access_info *info)
 201 {
 202         unsigned long flags;
 203
 204         spin_lock_irqsave(&report_lock, flags);
 205         pr_err("================================="
 206                 "=================================\n");
 207         pr_err("BUG: KASan: user-memory-access on address %p\n",
 208                 info->access_addr);
 209         pr_err("%s of size %zu by task %s/%d\n",
 210                 info->is_write ? "Write" : "Read",
 211                 info->access_size, current->comm, task_pid_nr(current));
 212         dump_stack();
 213         pr_err("================================="
 214                 "=================================\n");
 215         spin_unlock_irqrestore(&report_lock, flags);
 216 }
 217
 218 void kasan_report(unsigned long addr, size_t size,
 219                 bool is_write, unsigned long ip)
 220 {
 221         struct kasan_access_info info;
 222
 223         if (likely(!kasan_enabled()))
 224                 return;
 225
 226         info.access_addr = (void *)addr;
 227         info.access_size = size;
 228         info.is_write = is_write;
 229         info.ip = ip;
 230         kasan_report_error(&info);
 231 }
 232
 233
 234 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 235 void __asan_report_load##size##_noabort(unsigned long addr) \
 236 {                                                         \
 237         kasan_report(addr, size, false, _RET_IP_);        \
 238 }                                                         \
 239 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 240
 241 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 242 void __asan_report_store##size##_noabort(unsigned long addr) \
 243 {                                                          \
 244         kasan_report(addr, size, true, _RET_IP_);          \
 245 }                                                          \
 246 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 247
 248 DEFINE_ASAN_REPORT_LOAD(1);
 249 DEFINE_ASAN_REPORT_LOAD(2);
 250 DEFINE_ASAN_REPORT_LOAD(4);
 251 DEFINE_ASAN_REPORT_LOAD(8);
 252 DEFINE_ASAN_REPORT_LOAD(16);
 253 DEFINE_ASAN_REPORT_STORE(1);
 254 DEFINE_ASAN_REPORT_STORE(2);
 255 DEFINE_ASAN_REPORT_STORE(4);
 256 DEFINE_ASAN_REPORT_STORE(8);
 257 DEFINE_ASAN_REPORT_STORE(16);
 258
 259 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 260 {
 261         kasan_report(addr, size, false, _RET_IP_);
 262 }
 263 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 264
 265 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 266 {
 267         kasan_report(addr, size, true, _RET_IP_);
 268 }
 269 EXPORT_SYMBOL(__asan_report_store_n_noabort);