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/ftrace.h>
  17 #include <linux/kernel.h>
  18 #include <linux/mm.h>
  19 #include <linux/printk.h>
  20 #include <linux/sched.h>
  21 #include <linux/slab.h>
  22 #include <linux/stackdepot.h>
  23 #include <linux/stacktrace.h>
  24 #include <linux/string.h>
  25 #include <linux/types.h>
  26 #include <linux/kasan.h>
  27 #include <linux/module.h>
  28
  29 #include <asm/sections.h>
  30
  31 #include "kasan.h"
  32 #include "../slab.h"
  33
  34 /* Shadow layout customization. */
  35 #define SHADOW_BYTES_PER_BLOCK 1
  36 #define SHADOW_BLOCKS_PER_ROW 16
  37 #define SHADOW_BYTES_PER_ROW (SHADOW_BLOCKS_PER_ROW * SHADOW_BYTES_PER_BLOCK)
  38 #define SHADOW_ROWS_AROUND_ADDR 2
  39
  40 static const void *find_first_bad_addr(const void *addr, size_t size)
  41 {
  42         u8 shadow_val = *(u8 *)kasan_mem_to_shadow(addr);
  43         const void *first_bad_addr = addr;
  44
  45         while (!shadow_val && first_bad_addr < addr + size) {
  46                 first_bad_addr += KASAN_SHADOW_SCALE_SIZE;
  47                 shadow_val = *(u8 *)kasan_mem_to_shadow(first_bad_addr);
  48         }
  49         return first_bad_addr;
  50 }
  51
  52 static void print_error_description(struct kasan_access_info *info)
  53 {
  54         const char *bug_type = "unknown-crash";
  55         u8 *shadow_addr;
  56
  57         info->first_bad_addr = find_first_bad_addr(info->access_addr,
  58                                                 info->access_size);
  59
  60         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  61
  62         /*
  63          * If shadow byte value is in [0, KASAN_SHADOW_SCALE_SIZE) we can look
  64          * at the next shadow byte to determine the type of the bad access.
  65          */
  66         if (*shadow_addr > 0 && *shadow_addr <= KASAN_SHADOW_SCALE_SIZE - 1)
  67                 shadow_addr++;
  68
  69         switch (*shadow_addr) {
  70         case 0 ... KASAN_SHADOW_SCALE_SIZE - 1:
  71                 /*
  72                  * In theory it's still possible to see these shadow values
  73                  * due to a data race in the kernel code.
  74                  */
  75                 bug_type = "out-of-bounds";
  76                 break;
  77         case KASAN_PAGE_REDZONE:
  78         case KASAN_KMALLOC_REDZONE:
  79                 bug_type = "slab-out-of-bounds";
  80                 break;
  81         case KASAN_GLOBAL_REDZONE:
  82                 bug_type = "global-out-of-bounds";
  83                 break;
  84         case KASAN_STACK_LEFT:
  85         case KASAN_STACK_MID:
  86         case KASAN_STACK_RIGHT:
  87         case KASAN_STACK_PARTIAL:
  88                 bug_type = "stack-out-of-bounds";
  89                 break;
  90         case KASAN_FREE_PAGE:
  91         case KASAN_KMALLOC_FREE:
  92                 bug_type = "use-after-free";
  93                 break;
  94         case KASAN_USE_AFTER_SCOPE:
  95                 bug_type = "use-after-scope";
  96                 break;
  97         }
  98
  99         pr_err("BUG: KASAN: %s in %pS at addr %p\n",
 100                 bug_type, (void *)info->ip,
 101                 info->access_addr);
 102         pr_err("%s of size %zu by task %s/%d\n",
 103                 info->is_write ? "Write" : "Read",
 104                 info->access_size, current->comm, task_pid_nr(current));
 105 }
 106
 107 static inline bool kernel_or_module_addr(const void *addr)
 108 {
 109         if (addr >= (void *)_stext && addr < (void *)_end)
 110                 return true;
 111         if (is_module_address((unsigned long)addr))
 112                 return true;
 113         return false;
 114 }
 115
 116 static inline bool init_task_stack_addr(const void *addr)
 117 {
 118         return addr >= (void *)&init_thread_union.stack &&
 119                 (addr <= (void *)&init_thread_union.stack +
 120                         sizeof(init_thread_union.stack));
 121 }
 122
 123 static DEFINE_SPINLOCK(report_lock);
 124
 125 static void kasan_start_report(unsigned long *flags)
 126 {
 127         /*
 128          * Make sure we don't end up in loop.
 129          */
 130         kasan_disable_current();
 131         spin_lock_irqsave(&report_lock, *flags);
 132         pr_err("==================================================================\n");
 133 }
 134
 135 static void kasan_end_report(unsigned long *flags)
 136 {
 137         pr_err("==================================================================\n");
 138         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 139         spin_unlock_irqrestore(&report_lock, *flags);
 140         kasan_enable_current();
 141 }
 142
 143 static void print_track(struct kasan_track *track)
 144 {
 145         pr_err("PID = %u\n", track->pid);
 146         if (track->stack) {
 147                 struct stack_trace trace;
 148
 149                 depot_fetch_stack(track->stack, &trace);
 150                 print_stack_trace(&trace, 0);
 151         } else {
 152                 pr_err("(stack is not available)\n");
 153         }
 154 }
 155
 156 static void kasan_object_err(struct kmem_cache *cache, void *object)
 157 {
 158         struct kasan_alloc_meta *alloc_info = get_alloc_info(cache, object);
 159
 160         dump_stack();
 161         pr_err("Object at %p, in cache %s size: %d\n", object, cache->name,
 162                 cache->object_size);
 163
 164         if (!(cache->flags & SLAB_KASAN))
 165                 return;
 166
 167         pr_err("Allocated:\n");
 168         print_track(&alloc_info->alloc_track);
 169         pr_err("Freed:\n");
 170         print_track(&alloc_info->free_track);
 171 }
 172
 173 void kasan_report_double_free(struct kmem_cache *cache, void *object,
 174                         s8 shadow)
 175 {
 176         unsigned long flags;
 177
 178         kasan_start_report(&flags);
 179         pr_err("BUG: Double free or freeing an invalid pointer\n");
 180         pr_err("Unexpected shadow byte: 0x%hhX\n", shadow);
 181         kasan_object_err(cache, object);
 182         kasan_end_report(&flags);
 183 }
 184
 185 static void print_address_description(struct kasan_access_info *info)
 186 {
 187         const void *addr = info->access_addr;
 188
 189         if ((addr >= (void *)PAGE_OFFSET) &&
 190                 (addr < high_memory)) {
 191                 struct page *page = virt_to_head_page(addr);
 192
 193                 if (PageSlab(page)) {
 194                         void *object;
 195                         struct kmem_cache *cache = page->slab_cache;
 196                         object = nearest_obj(cache, page,
 197                                                 (void *)info->access_addr);
 198                         kasan_object_err(cache, object);
 199                         return;
 200                 }
 201                 dump_page(page, "kasan: bad access detected");
 202         }
 203
 204         if (kernel_or_module_addr(addr)) {
 205                 if (!init_task_stack_addr(addr))
 206                         pr_err("Address belongs to variable %pS\n", addr);
 207         }
 208         dump_stack();
 209 }
 210
 211 static bool row_is_guilty(const void *row, const void *guilty)
 212 {
 213         return (row <= guilty) && (guilty < row + SHADOW_BYTES_PER_ROW);
 214 }
 215
 216 static int shadow_pointer_offset(const void *row, const void *shadow)
 217 {
 218         /* The length of ">ff00ff00ff00ff00: " is
 219          *    3 + (BITS_PER_LONG/8)*2 chars.
 220          */
 221         return 3 + (BITS_PER_LONG/8)*2 + (shadow - row)*2 +
 222                 (shadow - row) / SHADOW_BYTES_PER_BLOCK + 1;
 223 }
 224
 225 static void print_shadow_for_address(const void *addr)
 226 {
 227         int i;
 228         const void *shadow = kasan_mem_to_shadow(addr);
 229         const void *shadow_row;
 230
 231         shadow_row = (void *)round_down((unsigned long)shadow,
 232                                         SHADOW_BYTES_PER_ROW)
 233                 - SHADOW_ROWS_AROUND_ADDR * SHADOW_BYTES_PER_ROW;
 234
 235         pr_err("Memory state around the buggy address:\n");
 236
 237         for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 238                 const void *kaddr = kasan_shadow_to_mem(shadow_row);
 239                 char buffer[4 + (BITS_PER_LONG/8)*2];
 240                 char shadow_buf[SHADOW_BYTES_PER_ROW];
 241
 242                 snprintf(buffer, sizeof(buffer),
 243                         (i == 0) ? ">%p: " : " %p: ", kaddr);
 244                 /*
 245                  * We should not pass a shadow pointer to generic
 246                  * function, because generic functions may try to
 247                  * access kasan mapping for the passed address.
 248                  */
 249                 memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
 250                 print_hex_dump(KERN_ERR, buffer,
 251                         DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
 252                         shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 253
 254                 if (row_is_guilty(shadow_row, shadow))
 255                         pr_err("%*c\n",
 256                                 shadow_pointer_offset(shadow_row, shadow),
 257                                 '^');
 258
 259                 shadow_row += SHADOW_BYTES_PER_ROW;
 260         }
 261 }
 262
 263 static void kasan_report_error(struct kasan_access_info *info)
 264 {
 265         unsigned long flags;
 266         const char *bug_type;
 267
 268         kasan_start_report(&flags);
 269
 270         if (info->access_addr <
 271                         kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) {
 272                 if ((unsigned long)info->access_addr < PAGE_SIZE)
 273                         bug_type = "null-ptr-deref";
 274                 else if ((unsigned long)info->access_addr < TASK_SIZE)
 275                         bug_type = "user-memory-access";
 276                 else
 277                         bug_type = "wild-memory-access";
 278                 pr_err("BUG: KASAN: %s on address %p\n",
 279                         bug_type, info->access_addr);
 280                 pr_err("%s of size %zu by task %s/%d\n",
 281                         info->is_write ? "Write" : "Read",
 282                         info->access_size, current->comm,
 283                         task_pid_nr(current));
 284                 dump_stack();
 285         } else {
 286                 print_error_description(info);
 287                 print_address_description(info);
 288                 print_shadow_for_address(info->first_bad_addr);
 289         }
 290
 291         kasan_end_report(&flags);
 292 }
 293
 294 void kasan_report(unsigned long addr, size_t size,
 295                 bool is_write, unsigned long ip)
 296 {
 297         struct kasan_access_info info;
 298
 299         if (likely(!kasan_report_enabled()))
 300                 return;
 301
 302         disable_trace_on_warning();
 303
 304         info.access_addr = (void *)addr;
 305         info.access_size = size;
 306         info.is_write = is_write;
 307         info.ip = ip;
 308
 309         kasan_report_error(&info);
 310 }
 311
 312
 313 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 314 void __asan_report_load##size##_noabort(unsigned long addr) \
 315 {                                                         \
 316         kasan_report(addr, size, false, _RET_IP_);        \
 317 }                                                         \
 318 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 319
 320 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 321 void __asan_report_store##size##_noabort(unsigned long addr) \
 322 {                                                          \
 323         kasan_report(addr, size, true, _RET_IP_);          \
 324 }                                                          \
 325 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 326
 327 DEFINE_ASAN_REPORT_LOAD(1);
 328 DEFINE_ASAN_REPORT_LOAD(2);
 329 DEFINE_ASAN_REPORT_LOAD(4);
 330 DEFINE_ASAN_REPORT_LOAD(8);
 331 DEFINE_ASAN_REPORT_LOAD(16);
 332 DEFINE_ASAN_REPORT_STORE(1);
 333 DEFINE_ASAN_REPORT_STORE(2);
 334 DEFINE_ASAN_REPORT_STORE(4);
 335 DEFINE_ASAN_REPORT_STORE(8);
 336 DEFINE_ASAN_REPORT_STORE(16);
 337
 338 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 339 {
 340         kasan_report(addr, size, false, _RET_IP_);
 341 }
 342 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 343
 344 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 345 {
 346         kasan_report(addr, size, true, _RET_IP_);
 347 }
 348 EXPORT_SYMBOL(__asan_report_store_n_noabort);