mm/kasan/generic.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains core generic KASAN code.
   4  *
   5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  *
   8  * Some code borrowed from https://github.com/xairy/kasan-prototype by
   9  *        Andrey Konovalov <andreyknvl@gmail.com>
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License version 2 as
  13  * published by the Free Software Foundation.
  14  *
  15  */
  16
  17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  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 bool 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 true;
 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 false;
 179         }
 180
 181         if (likely(!memory_is_poisoned(addr, size)))
 182                 return true;
 183
 184         kasan_report(addr, size, write, ret_ip);
 185         return false;
 186 }
 187
 188 bool check_memory_region(unsigned long addr, size_t size, bool write,
 189                                 unsigned long ret_ip)
 190 {
 191         return check_memory_region_inline(addr, size, write, ret_ip);
 192 }
 193
 194 void kasan_cache_shrink(struct kmem_cache *cache)
 195 {
 196         quarantine_remove_cache(cache);
 197 }
 198
 199 void kasan_cache_shutdown(struct kmem_cache *cache)
 200 {
 201         if (!__kmem_cache_empty(cache))
 202                 quarantine_remove_cache(cache);
 203 }
 204
 205 static void register_global(struct kasan_global *global)
 206 {
 207         size_t aligned_size = round_up(global->size, KASAN_SHADOW_SCALE_SIZE);
 208
 209         kasan_unpoison_shadow(global->beg, global->size);
 210
 211         kasan_poison_shadow(global->beg + aligned_size,
 212                 global->size_with_redzone - aligned_size,
 213                 KASAN_GLOBAL_REDZONE);
 214 }
 215
 216 void __asan_register_globals(struct kasan_global *globals, size_t size)
 217 {
 218         int i;
 219
 220         for (i = 0; i < size; i++)
 221                 register_global(&globals[i]);
 222 }
 223 EXPORT_SYMBOL(__asan_register_globals);
 224
 225 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 226 {
 227 }
 228 EXPORT_SYMBOL(__asan_unregister_globals);
 229
 230 #define DEFINE_ASAN_LOAD_STORE(size)                                    \
 231         void __asan_load##size(unsigned long addr)                      \
 232         {                                                               \
 233                 check_memory_region_inline(addr, size, false, _RET_IP_);\
 234         }                                                               \
 235         EXPORT_SYMBOL(__asan_load##size);                               \
 236         __alias(__asan_load##size)                                      \
 237         void __asan_load##size##_noabort(unsigned long);                \
 238         EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
 239         void __asan_store##size(unsigned long addr)                     \
 240         {                                                               \
 241                 check_memory_region_inline(addr, size, true, _RET_IP_); \
 242         }                                                               \
 243         EXPORT_SYMBOL(__asan_store##size);                              \
 244         __alias(__asan_store##size)                                     \
 245         void __asan_store##size##_noabort(unsigned long);               \
 246         EXPORT_SYMBOL(__asan_store##size##_noabort)
 247
 248 DEFINE_ASAN_LOAD_STORE(1);
 249 DEFINE_ASAN_LOAD_STORE(2);
 250 DEFINE_ASAN_LOAD_STORE(4);
 251 DEFINE_ASAN_LOAD_STORE(8);
 252 DEFINE_ASAN_LOAD_STORE(16);
 253
 254 void __asan_loadN(unsigned long addr, size_t size)
 255 {
 256         check_memory_region(addr, size, false, _RET_IP_);
 257 }
 258 EXPORT_SYMBOL(__asan_loadN);
 259
 260 __alias(__asan_loadN)
 261 void __asan_loadN_noabort(unsigned long, size_t);
 262 EXPORT_SYMBOL(__asan_loadN_noabort);
 263
 264 void __asan_storeN(unsigned long addr, size_t size)
 265 {
 266         check_memory_region(addr, size, true, _RET_IP_);
 267 }
 268 EXPORT_SYMBOL(__asan_storeN);
 269
 270 __alias(__asan_storeN)
 271 void __asan_storeN_noabort(unsigned long, size_t);
 272 EXPORT_SYMBOL(__asan_storeN_noabort);
 273
 274 /* to shut up compiler complaints */
 275 void __asan_handle_no_return(void) {}
 276 EXPORT_SYMBOL(__asan_handle_no_return);
 277
 278 /* Emitted by compiler to poison alloca()ed objects. */
 279 void __asan_alloca_poison(unsigned long addr, size_t size)
 280 {
 281         size_t rounded_up_size = round_up(size, KASAN_SHADOW_SCALE_SIZE);
 282         size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
 283                         rounded_up_size;
 284         size_t rounded_down_size = round_down(size, KASAN_SHADOW_SCALE_SIZE);
 285
 286         const void *left_redzone = (const void *)(addr -
 287                         KASAN_ALLOCA_REDZONE_SIZE);
 288         const void *right_redzone = (const void *)(addr + rounded_up_size);
 289
 290         WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));
 291
 292         kasan_unpoison_shadow((const void *)(addr + rounded_down_size),
 293                               size - rounded_down_size);
 294         kasan_poison_shadow(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
 295                         KASAN_ALLOCA_LEFT);
 296         kasan_poison_shadow(right_redzone,
 297                         padding_size + KASAN_ALLOCA_REDZONE_SIZE,
 298                         KASAN_ALLOCA_RIGHT);
 299 }
 300 EXPORT_SYMBOL(__asan_alloca_poison);
 301
 302 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
 303 void __asan_allocas_unpoison(const void *stack_top, const void *stack_bottom)
 304 {
 305         if (unlikely(!stack_top || stack_top > stack_bottom))
 306                 return;
 307
 308         kasan_unpoison_shadow(stack_top, stack_bottom - stack_top);
 309 }
 310 EXPORT_SYMBOL(__asan_allocas_unpoison);
 311
 312 /* Emitted by the compiler to [un]poison local variables. */
 313 #define DEFINE_ASAN_SET_SHADOW(byte) \
 314         void __asan_set_shadow_##byte(const void *addr, size_t size)    \
 315         {                                                               \
 316                 __memset((void *)addr, 0x##byte, size);                 \
 317         }                                                               \
 318         EXPORT_SYMBOL(__asan_set_shadow_##byte)
 319
 320 DEFINE_ASAN_SET_SHADOW(00);
 321 DEFINE_ASAN_SET_SHADOW(f1);
 322 DEFINE_ASAN_SET_SHADOW(f2);
 323 DEFINE_ASAN_SET_SHADOW(f3);
 324 DEFINE_ASAN_SET_SHADOW(f5);
 325 DEFINE_ASAN_SET_SHADOW(f8);