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/stackdepot.h>
  22 #include <linux/stacktrace.h>
  23 #include <linux/string.h>
  24 #include <linux/types.h>
  25 #include <linux/kasan.h>
  26 #include <linux/module.h>
  27
  28 #include <asm/sections.h>
  29
  30 #include "kasan.h"
  31 #include "../slab.h"
  32
  33 /* Shadow layout customization. */
  34 #define SHADOW_BYTES_PER_BLOCK 1
  35 #define SHADOW_BLOCKS_PER_ROW 16
  36 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  37 #define SHADOW_ROWS_AROUND_ADDR 2
  38
  39 static const void *find_first_bad_addr(const void *addr, size_t size)
  40 {
  41         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  42         const void *first_bad_addr = addr;
  43
  44         while (!shadow_val && first_bad_addr < addr + size) {
  45                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  46                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  47         }
  48         return first_bad_addr;
  49 }
  50
  51 static void print_error_description(struct kasan_access_info *info)
  52 {
  53         const char *bug_type = "unknown-crash";
  54         u8 *shadow_addr;
  55
  56         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  57                                                 info->access_size);
  58
  59         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  60
  61         /*
  62          * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
  63          * at the next shadow byte to determine the type of the bad access.
  64          */
  65         if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
  66                 shadow_addr++;
  67
  68         switch (*shadow_addr) {
  69         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  70                 /*
  71                  * In theory it's still possible to see these shadow values
  72                  * due to a data race in the kernel code.
  73                  */
  74                 bug_type = "out-of-bounds";
  75                 break;
  76         case KASAN_PAGE_REDZONE:
  77         case KASAN_KMALLOC_REDZONE:
  78                 bug_type = "slab-out-of-bounds";
  79                 break;
  80         case KASAN_GLOBAL_REDZONE:
  81                 bug_type = "global-out-of-bounds";
  82                 break;
  83         case KASAN_STACK_LEFT:
  84         case KASAN_STACK_MID:
  85         case KASAN_STACK_RIGHT:
  86         case KASAN_STACK_PARTIAL:
  87                 bug_type = "stack-out-of-bounds";
  88                 break;
  89         case KASAN_FREE_PAGE:
  90         case KASAN_KMALLOC_FREE:
  91                 bug_type = "use-after-free";
  92                 break;
  93         case KASAN_USE_AFTER_SCOPE:
  94                 bug_type = "use-after-scope";
  95                 break;
  96         }
  97
  98         pr_err("BUG: KASAN: %s in %pS at addr %p\n",
  99                 bug_type, (void *)info->ip,
 100                 info->access_addr);
 101         pr_err("%s of size %zu by task %s/%d\n",
 102                 info->is_write ? "Write" : "Read",
 103                 info->access_size, current->comm, task_pid_nr(current));
 104 }
 105
 106 static inline bool kernel_or_module_addr(const void *addr)
 107 {
 108         if (addr >= (void *)_stext && addr < (void *)_end)
 109                 return true;
 110         if (is_module_address((unsigned long)addr))
 111                 return true;
 112         return false;
 113 }
 114
 115 static inline bool init_task_stack_addr(const void *addr)
 116 {
 117         return addr >= (void *)&init_thread_union.stack &&
 118                 (addr <= (void *)&init_thread_union.stack +
 119                         sizeof(init_thread_union.stack));
 120 }
 121
 122 static DEFINE_SPINLOCK(report_lock);
 123
 124 static void kasan_start_report(unsigned long *flags)
 125 {
 126         /*
 127          * Make sure we don't end up in loop.
 128          */
 129         kasan_disable_current();
 130         spin_lock_irqsave(&report_lock, *flags);
 131         pr_err("==================================================================\n");
 132 }
 133
 134 static void kasan_end_report(unsigned long *flags)
 135 {
 136         pr_err("==================================================================\n");
 137         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 138         spin_unlock_irqrestore(&report_lock, *flags);
 139         kasan_enable_current();
 140 }
 141
 142 static void print_track(struct kasan_track *track)
 143 {
 144         pr_err("PID = %u\n", track->pid);
 145         if (track->stack) {
 146                 struct stack_trace trace;
 147
 148                 depot_fetch_stack(track->stack, &trace);
 149                 print_stack_trace(&trace, 0);
 150         } else {
 151                 pr_err("(stack is not available)\n");
 152         }
 153 }
 154
 155 static void kasan_object_err(struct kmem_cache *cache, void *object)
 156 {
 157         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 158
 159         dump_stack();
 160         pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
 161                 cache->object_size);
 162
 163         if (!(cache->flags & SLAB_KASAN))
 164                 return;
 165
 166         pr_err("Allocated:\n");
 167         print_track(&alloc_info->alloc_track);
 168         pr_err("Freed:\n");
 169         print_track(&alloc_info->free_track);
 170 }
 171
 172 void kasan_report_double_free(struct kmem_cache *cache, void *object,
 173                         s8 shadow)
 174 {
 175         unsigned long flags;
 176
 177         kasan_start_report(&flags);
 178         pr_err("BUG: Double free or freeing an invalid pointer\n");
 179         pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
 180         kasan_object_err(cache, object);
 181         kasan_end_report(&flags);
 182 }
 183
 184 static void print_address_description(struct kasan_access_info *info)
 185 {
 186         const void *addr = info->access_addr;
 187
 188         if ((addr >= (void *)PAGE_OFFSET) &&
 189                 (addr < high_memory)) {
 190                 struct page *page = virt_to_head_page(addr);
 191
 192                 if (PageSlab(page)) {
 193                         void *object;
 194                         struct kmem_cache *cache = page->slab_cache;
 195                         object = nearest_obj(cache, page,
 196                                                 (void *)info->access_addr);
 197                         kasan_object_err(cache, object);
 198                         return;
 199                 }
 200                 dump_page(page, "kasan: bad access detected");
 201         }
 202
 203         if (kernel_or_module_addr(addr)) {
 204                 if (!init_task_stack_addr(addr))
 205                         pr_err("Address belongs to variable %pS\n", addr);
 206         }
 207         dump_stack();
 208 }
 209
 210 static bool row_is_guilty(const void *row, const void *guilty)
 211 {
 212         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 213 }
 214
 215 static int shadow_pointer_offset(const void *row, const void *shadow)
 216 {
 217         /* The length of ">ff00ff00ff00ff00: " is
 218          *    3 + (BITS_PER_LONG/8)*2 chars.
 219          */
 220         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 221                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 222 }
 223
 224 static void print_shadow_for_address(const void *addr)
 225 {
 226         int i;
 227         const void *shadow = kasan_mem_to_shadow(addr);
 228         const void *shadow_row;
 229
 230         shadow_row = (void *)round_down((unsigned long)shadow,
 231                                         SHADOW_BYTES_PER_ROW)
 232                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 233
 234         pr_err("Memory state around the buggy address:\n");
 235
 236         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 237                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 238                 char buffer[4 + (BITS_PER_LONG/8)*2];
 239                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 240
 241                 snprintf(buffer, sizeof(buffer),
 242                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 243                 /*
 244                  * We should not pass a shadow pointer to generic
 245                  * function, because generic functions may try to
 246                  * access kasan mapping for the passed address.
 247                  */
 248                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 249                 print_hex_dump(KERN_ERR, buffer,
 250                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 251                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 252
 253                 if (row_is_guilty(shadow_row, shadow))
 254                         pr_err("%*c\n",
 255                                 shadow_pointer_offset(shadow_row, shadow),
 256                                 '^');
 257
 258                 shadow_row += SHADOW_BYTES_PER_ROW;
 259         }
 260 }
 261
 262 static void kasan_report_error(struct kasan_access_info *info)
 263 {
 264         unsigned long flags;
 265         const char *bug_type;
 266
 267         kasan_start_report(&flags);
 268
 269         if (info->access_addr <
 270                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 271                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 272                         bug_type = "null-ptr-deref";
 273                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 274                         bug_type = "user-memory-access";
 275                 else
 276                         bug_type = "wild-memory-access";
 277                 pr_err("BUG: KASAN: %s on address %p\n",
 278                         bug_type, info->access_addr);
 279                 pr_err("%s of size %zu by task %s/%d\n",
 280                         info->is_write ? "Write" : "Read",
 281                         info->access_size, current->comm,
 282                         task_pid_nr(current));
 283                 dump_stack();
 284         } else {
 285                 print_error_description(info);
 286                 print_address_description(info);
 287                 print_shadow_for_address(info->first_bad_addr);
 288         }
 289
 290         kasan_end_report(&flags);
 291 }
 292
 293 void kasan_report(unsigned long addr, size_t size,
 294                 bool is_write, unsigned long ip)
 295 {
 296         struct kasan_access_info info;
 297
 298         if (likely(!kasan_report_enabled()))
 299                 return;
 300
 301         info.access_addr = (void *)addr;
 302         info.access_size = size;
 303         info.is_write = is_write;
 304         info.ip = ip;
 305
 306         kasan_report_error(&info);
 307 }
 308
 309
 310 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 311 void __asan_report_load##size##_noabort(unsigned long addr) \
 312 {                                                         \
 313         kasan_report(addr, size, false, _RET_IP_);        \
 314 }                                                         \
 315 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 316
 317 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 318 void __asan_report_store##size##_noabort(unsigned long addr) \
 319 {                                                          \
 320         kasan_report(addr, size, true, _RET_IP_);          \
 321 }                                                          \
 322 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 323
 324 DEFINE_ASAN_REPORT_LOAD(1);
 325 DEFINE_ASAN_REPORT_LOAD(2);
 326 DEFINE_ASAN_REPORT_LOAD(4);
 327 DEFINE_ASAN_REPORT_LOAD(8);
 328 DEFINE_ASAN_REPORT_LOAD(16);
 329 DEFINE_ASAN_REPORT_STORE(1);
 330 DEFINE_ASAN_REPORT_STORE(2);
 331 DEFINE_ASAN_REPORT_STORE(4);
 332 DEFINE_ASAN_REPORT_STORE(8);
 333 DEFINE_ASAN_REPORT_STORE(16);
 334
 335 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 336 {
 337         kasan_report(addr, size, false, _RET_IP_);
 338 }
 339 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 340
 341 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 342 {
 343         kasan_report(addr, size, true, _RET_IP_);
 344 }
 345 EXPORT_SYMBOL(__asan_report_store_n_noabort);