mm/kasan/kasan.c

   1 /*
   2  * This file contains core KASAN 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 <andreyknvl@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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17 #define DISABLE_BRANCH_PROFILING
  18
  19 #include <linux/export.h>
  20 #include <linux/interrupt.h>
  21 #include <linux/init.h>
  22 #include <linux/kasan.h>
  23 #include <linux/kernel.h>
  24 #include <linux/kmemleak.h>
  25 #include <linux/linkage.h>
  26 #include <linux/memblock.h>
  27 #include <linux/memory.h>
  28 #include <linux/mm.h>
  29 #include <linux/module.h>
  30 #include <linux/printk.h>
  31 #include <linux/sched.h>
  32 #include <linux/sched/task_stack.h>
  33 #include <linux/slab.h>
  34 #include <linux/stacktrace.h>
  35 #include <linux/string.h>
  36 #include <linux/types.h>
  37 #include <linux/vmalloc.h>
  38 #include <linux/bug.h>
  39
  40 #include "kasan.h"
  41 #include "../slab.h"
  42
  43 /*
  44  * All functions below always inlined so compiler could
  45  * perform better optimizations in each of __asan_loadX/__assn_storeX
  46  * depending on memory access size X.
  47  */
  48
  49 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
  50 {
  51         s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
  52
  53         if (unlikely(shadow_value)) {
  54                 s8 last_accessible_byte = addr & KASAN_SHADOW_MASK;
  55                 return unlikely(last_accessible_byte >= shadow_value);
  56         }
  57
  58         return false;
  59 }
  60
  61 static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
  62                                                 unsigned long size)
  63 {
  64         u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);
  65
  66         /*
  67          * Access crosses 8(shadow size)-byte boundary. Such access maps
  68          * into 2 shadow bytes, so we need to check them both.
  69          */
  70         if (unlikely(((addr + size - 1) & KASAN_SHADOW_MASK) < size - 1))
  71                 return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
  72
  73         return memory_is_poisoned_1(addr + size - 1);
  74 }
  75
  76 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
  77 {
  78         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
  79
  80         /* Unaligned 16-bytes access maps into 3 shadow bytes. */
  81         if (unlikely(!IS_ALIGNED(addr, KASAN_SHADOW_SCALE_SIZE)))
  82                 return *shadow_addr || memory_is_poisoned_1(addr + 15);
  83
  84         return *shadow_addr;
  85 }
  86
  87 static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
  88                                         size_t size)
  89 {
  90         while (size) {
  91                 if (unlikely(*start))
  92                         return (unsigned long)start;
  93                 start++;
  94                 size--;
  95         }
  96
  97         return 0;
  98 }
  99
 100 static __always_inline unsigned long memory_is_nonzero(const void *start,
 101                                                 const void *end)
 102 {
 103         unsigned int words;
 104         unsigned long ret;
 105         unsigned int prefix = (unsigned long)start % 8;
 106
 107         if (end - start <= 16)
 108                 return bytes_is_nonzero(start, end - start);
 109
 110         if (prefix) {
 111                 prefix = 8 - prefix;
 112                 ret = bytes_is_nonzero(start, prefix);
 113                 if (unlikely(ret))
 114                         return ret;
 115                 start += prefix;
 116         }
 117
 118         words = (end - start) / 8;
 119         while (words) {
 120                 if (unlikely(*(u64 *)start))
 121                         return bytes_is_nonzero(start, 8);
 122                 start += 8;
 123                 words--;
 124         }
 125
 126         return bytes_is_nonzero(start, (end - start) % 8);
 127 }
 128
 129 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 130                                                 size_t size)
 131 {
 132         unsigned long ret;
 133
 134         ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
 135                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 136
 137         if (unlikely(ret)) {
 138                 unsigned long last_byte = addr + size - 1;
 139                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 140
 141                 if (unlikely(ret != (unsigned long)last_shadow ||
 142                         ((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 143                         return true;
 144         }
 145         return false;
 146 }
 147
 148 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 149 {
 150         if (__builtin_constant_p(size)) {
 151                 switch (size) {
 152                 case 1:
 153                         return memory_is_poisoned_1(addr);
 154                 case 2:
 155                 case 4:
 156                 case 8:
 157                         return memory_is_poisoned_2_4_8(addr, size);
 158                 case 16:
 159                         return memory_is_poisoned_16(addr);
 160                 default:
 161                         BUILD_BUG();
 162                 }
 163         }
 164
 165         return memory_is_poisoned_n(addr, size);
 166 }
 167
 168 static __always_inline void check_memory_region_inline(unsigned long addr,
 169                                                 size_t size, bool write,
 170                                                 unsigned long ret_ip)
 171 {
 172         if (unlikely(size == 0))
 173                 return;
 174
 175         if (unlikely((void *)addr <
 176                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 177                 kasan_report(addr, size, write, ret_ip);
 178                 return;
 179         }
 180
 181         if (likely(!memory_is_poisoned(addr, size)))
 182                 return;
 183
 184         kasan_report(addr, size, write, ret_ip);
 185 }
 186
 187 void check_memory_region(unsigned long addr, size_t size, bool write,
 188                                 unsigned long ret_ip)
 189 {
 190         check_memory_region_inline(addr, size, write, ret_ip);
 191 }
 192
 193 void kasan_cache_shrink(struct kmem_cache *cache)
 194 {
 195         quarantine_remove_cache(cache);
 196 }
 197
 198 void kasan_cache_shutdown(struct kmem_cache *cache)
 199 {
 200         if (!__kmem_cache_empty(cache))
 201                 quarantine_remove_cache(cache);
 202 }
 203
 204 static void register_global(struct kasan_global *global)
 205 {
 206         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 207
 208         kasan_unpoison_shadow(global->beg, global->size);
 209
 210         kasan_poison_shadow(global->beg + aligned_size,
 211                 global->size_with_redzone - aligned_size,
 212                 KASAN_GLOBAL_REDZONE);
 213 }
 214
 215 void __asan_register_globals(struct kasan_global *globals, size_t size)
 216 {
 217         int i;
 218
 219         for (i = 0; i < size; i++)
 220                 register_global(&globals[i]);
 221 }
 222 EXPORT_SYMBOL(__asan_register_globals);
 223
 224 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 225 {
 226 }
 227 EXPORT_SYMBOL(__asan_unregister_globals);
 228
 229 #define DEFINE_ASAN_LOAD_STORE(size)                                    \
 230         void __asan_load##size(unsigned long addr)                      \
 231         {                                                               \
 232                 check_memory_region_inline(addr, size, false, _RET_IP_);\
 233         }                                                               \
 234         EXPORT_SYMBOL(__asan_load##size);                               \
 235         __alias(__asan_load##size)                                      \
 236         void __asan_load##size##_noabort(unsigned long);                \
 237         EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
 238         void __asan_store##size(unsigned long addr)                     \
 239         {                                                               \
 240                 check_memory_region_inline(addr, size, true, _RET_IP_); \
 241         }                                                               \
 242         EXPORT_SYMBOL(__asan_store##size);                              \
 243         __alias(__asan_store##size)                                     \
 244         void __asan_store##size##_noabort(unsigned long);               \
 245         EXPORT_SYMBOL(__asan_store##size##_noabort)
 246
 247 DEFINE_ASAN_LOAD_STORE(1);
 248 DEFINE_ASAN_LOAD_STORE(2);
 249 DEFINE_ASAN_LOAD_STORE(4);
 250 DEFINE_ASAN_LOAD_STORE(8);
 251 DEFINE_ASAN_LOAD_STORE(16);
 252
 253 void __asan_loadN(unsigned long addr, size_t size)
 254 {
 255         check_memory_region(addr, size, false, _RET_IP_);
 256 }
 257 EXPORT_SYMBOL(__asan_loadN);
 258
 259 __alias(__asan_loadN)
 260 void __asan_loadN_noabort(unsigned long, size_t);
 261 EXPORT_SYMBOL(__asan_loadN_noabort);
 262
 263 void __asan_storeN(unsigned long addr, size_t size)
 264 {
 265         check_memory_region(addr, size, true, _RET_IP_);
 266 }
 267 EXPORT_SYMBOL(__asan_storeN);
 268
 269 __alias(__asan_storeN)
 270 void __asan_storeN_noabort(unsigned long, size_t);
 271 EXPORT_SYMBOL(__asan_storeN_noabort);
 272
 273 /* to shut up compiler complaints */
 274 void __asan_handle_no_return(void) {}
 275 EXPORT_SYMBOL(__asan_handle_no_return);
 276
 277 /* Emitted by compiler to poison large objects when they go out of scope. */
 278 void __asan_poison_stack_memory(const void *addr, size_t size)
 279 {
 280         /*
 281          * Addr is KASAN_SHADOW_SCALE_SIZE-aligned and the object is surrounded
 282          * by redzones, so we simply round up size to simplify logic.
 283          */
 284         kasan_poison_shadow(addr, round_up(size, KASAN_SHADOW_SCALE_SIZE),
 285                             KASAN_USE_AFTER_SCOPE);
 286 }
 287 EXPORT_SYMBOL(__asan_poison_stack_memory);
 288
 289 /* Emitted by compiler to unpoison large objects when they go into scope. */
 290 void __asan_unpoison_stack_memory(const void *addr, size_t size)
 291 {
 292         kasan_unpoison_shadow(addr, size);
 293 }
 294 EXPORT_SYMBOL(__asan_unpoison_stack_memory);
 295
 296 /* Emitted by compiler to poison alloca()ed objects. */
 297 void __asan_alloca_poison(unsigned long addr, size_t size)
 298 {
 299         size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 300         size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
 301                         rounded_up_size;
 302         size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE);
 303
 304         const void *left_redzone = (const void *)(addr -
 305                         KASAN_ALLOCA_REDZONE_SIZE);
 306         const void *right_redzone = (const void *)(addr + rounded_up_size);
 307
 308         WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));
 309
 310         kasan_unpoison_shadow((const void *)(addr + rounded_down_size),
 311                               size - rounded_down_size);
 312         kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
 313                         KASAN_ALLOCA_LEFT);
 314         kasan_poison_shadow(right_redzone,
 315                         padding_size + KASAN_ALLOCA_REDZONE_SIZE,
 316                         KASAN_ALLOCA_RIGHT);
 317 }
 318 EXPORT_SYMBOL(__asan_alloca_poison);
 319
 320 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
 321 void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
 322 {
 323         if (unlikely(!stack_top || stack_top > stack_bottom))
 324                 return;
 325
 326         kasan_unpoison_shadow(stack_top, stack_bottom - stack_top);
 327 }
 328 EXPORT_SYMBOL(__asan_allocas_unpoison);
 329
 330 /* Emitted by the compiler to [un]poison local variables. */
 331 #define DEFINE_ASAN_SET_SHADOW(byte) \
 332         void __asan_set_shadow_##byte(const void *addr, size_t size)    \
 333         {                                                               \
 334                 __memset((void *)addr, 0x##byte, size);                 \
 335         }                                                               \
 336         EXPORT_SYMBOL(__asan_set_shadow_##byte)
 337
 338 DEFINE_ASAN_SET_SHADOW(00);
 339 DEFINE_ASAN_SET_SHADOW(f1);
 340 DEFINE_ASAN_SET_SHADOW(f2);
 341 DEFINE_ASAN_SET_SHADOW(f3);
 342 DEFINE_ASAN_SET_SHADOW(f5);
 343 DEFINE_ASAN_SET_SHADOW(f8);