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