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
  12 #include <linux/export.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/init.h>
  15 #include <linux/kasan.h>
  16 #include <linux/kernel.h>
  17 #include <linux/kfence.h>
  18 #include <linux/kmemleak.h>
  19 #include <linux/linkage.h>
  20 #include <linux/memblock.h>
  21 #include <linux/memory.h>
  22 #include <linux/mm.h>
  23 #include <linux/module.h>
  24 #include <linux/printk.h>
  25 #include <linux/sched.h>
  26 #include <linux/sched/task_stack.h>
  27 #include <linux/slab.h>
  28 #include <linux/stacktrace.h>
  29 #include <linux/string.h>
  30 #include <linux/types.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/bug.h>
  33
  34 #include "kasan.h"
  35 #include "../slab.h"
  36
  37 /*
  38  * All functions below always inlined so compiler could
  39  * perform better optimizations in each of __asan_loadX/__assn_storeX
  40  * depending on memory access size X.
  41  */
  42
  43 static __always_inline bool memory_is_poisoned_1(unsigned long addr)
  44 {
  45         s8 shadow_value = *(s8 *)kasan_mem_to_shadow((void *)addr);
  46
  47         if (unlikely(shadow_value)) {
  48                 s8 last_accessible_byte = addr & KASAN_GRANULE_MASK;
  49                 return unlikely(last_accessible_byte >= shadow_value);
  50         }
  51
  52         return false;
  53 }
  54
  55 static __always_inline bool memory_is_poisoned_2_4_8(unsigned long addr,
  56                                                 unsigned long size)
  57 {
  58         u8 *shadow_addr = (u8 *)kasan_mem_to_shadow((void *)addr);
  59
  60         /*
  61          * Access crosses 8(shadow size)-byte boundary. Such access maps
  62          * into 2 shadow bytes, so we need to check them both.
  63          */
  64         if (unlikely(((addr + size - 1) & KASAN_GRANULE_MASK) < size - 1))
  65                 return *shadow_addr || memory_is_poisoned_1(addr + size - 1);
  66
  67         return memory_is_poisoned_1(addr + size - 1);
  68 }
  69
  70 static __always_inline bool memory_is_poisoned_16(unsigned long addr)
  71 {
  72         u16 *shadow_addr = (u16 *)kasan_mem_to_shadow((void *)addr);
  73
  74         /* Unaligned 16-bytes access maps into 3 shadow bytes. */
  75         if (unlikely(!IS_ALIGNED(addr, KASAN_GRANULE_SIZE)))
  76                 return *shadow_addr || memory_is_poisoned_1(addr + 15);
  77
  78         return *shadow_addr;
  79 }
  80
  81 static __always_inline unsigned long bytes_is_nonzero(const u8 *start,
  82                                         size_t size)
  83 {
  84         while (size) {
  85                 if (unlikely(*start))
  86                         return (unsigned long)start;
  87                 start++;
  88                 size--;
  89         }
  90
  91         return 0;
  92 }
  93
  94 static __always_inline unsigned long memory_is_nonzero(const void *start,
  95                                                 const void *end)
  96 {
  97         unsigned int words;
  98         unsigned long ret;
  99         unsigned int prefix = (unsigned long)start % 8;
 100
 101         if (end - start <= 16)
 102                 return bytes_is_nonzero(start, end - start);
 103
 104         if (prefix) {
 105                 prefix = 8 - prefix;
 106                 ret = bytes_is_nonzero(start, prefix);
 107                 if (unlikely(ret))
 108                         return ret;
 109                 start += prefix;
 110         }
 111
 112         words = (end - start) / 8;
 113         while (words) {
 114                 if (unlikely(*(u64 *)start))
 115                         return bytes_is_nonzero(start, 8);
 116                 start += 8;
 117                 words--;
 118         }
 119
 120         return bytes_is_nonzero(start, (end - start) % 8);
 121 }
 122
 123 static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 124                                                 size_t size)
 125 {
 126         unsigned long ret;
 127
 128         ret = memory_is_nonzero(kasan_mem_to_shadow((void *)addr),
 129                         kasan_mem_to_shadow((void *)addr + size - 1) + 1);
 130
 131         if (unlikely(ret)) {
 132                 unsigned long last_byte = addr + size - 1;
 133                 s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 134
 135                 if (unlikely(ret != (unsigned long)last_shadow ||
 136                         ((long)(last_byte & KASAN_GRANULE_MASK) >= *last_shadow)))
 137                         return true;
 138         }
 139         return false;
 140 }
 141
 142 static __always_inline bool memory_is_poisoned(unsigned long addr, size_t size)
 143 {
 144         if (__builtin_constant_p(size)) {
 145                 switch (size) {
 146                 case 1:
 147                         return memory_is_poisoned_1(addr);
 148                 case 2:
 149                 case 4:
 150                 case 8:
 151                         return memory_is_poisoned_2_4_8(addr, size);
 152                 case 16:
 153                         return memory_is_poisoned_16(addr);
 154                 default:
 155                         BUILD_BUG();
 156                 }
 157         }
 158
 159         return memory_is_poisoned_n(addr, size);
 160 }
 161
 162 static __always_inline bool check_region_inline(unsigned long addr,
 163                                                 size_t size, bool write,
 164                                                 unsigned long ret_ip)
 165 {
 166         if (unlikely(size == 0))
 167                 return true;
 168
 169         if (unlikely(addr + size < addr))
 170                 return !kasan_report(addr, size, write, ret_ip);
 171
 172         if (unlikely((void *)addr <
 173                 kasan_shadow_to_mem((void *)KASAN_SHADOW_START))) {
 174                 return !kasan_report(addr, size, write, ret_ip);
 175         }
 176
 177         if (likely(!memory_is_poisoned(addr, size)))
 178                 return true;
 179
 180         return !kasan_report(addr, size, write, ret_ip);
 181 }
 182
 183 bool kasan_check_range(unsigned long addr, size_t size, bool write,
 184                                         unsigned long ret_ip)
 185 {
 186         return check_region_inline(addr, size, write, ret_ip);
 187 }
 188
 189 bool kasan_byte_accessible(const void *addr)
 190 {
 191         s8 shadow_byte = READ_ONCE(*(s8 *)kasan_mem_to_shadow(addr));
 192
 193         return shadow_byte >= 0 && shadow_byte < KASAN_GRANULE_SIZE;
 194 }
 195
 196 void kasan_cache_shrink(struct kmem_cache *cache)
 197 {
 198         kasan_quarantine_remove_cache(cache);
 199 }
 200
 201 void kasan_cache_shutdown(struct kmem_cache *cache)
 202 {
 203         if (!__kmem_cache_empty(cache))
 204                 kasan_quarantine_remove_cache(cache);
 205 }
 206
 207 static void register_global(struct kasan_global *global)
 208 {
 209         size_t aligned_size = round_up(global->size, KASAN_GRANULE_SIZE);
 210
 211         kasan_unpoison(global->beg, global->size, false);
 212
 213         kasan_poison(global->beg + aligned_size,
 214                      global->size_with_redzone - aligned_size,
 215                      KASAN_GLOBAL_REDZONE, false);
 216 }
 217
 218 void __asan_register_globals(struct kasan_global *globals, size_t size)
 219 {
 220         int i;
 221
 222         for (i = 0; i < size; i++)
 223                 register_global(&globals[i]);
 224 }
 225 EXPORT_SYMBOL(__asan_register_globals);
 226
 227 void __asan_unregister_globals(struct kasan_global *globals, size_t size)
 228 {
 229 }
 230 EXPORT_SYMBOL(__asan_unregister_globals);
 231
 232 #define DEFINE_ASAN_LOAD_STORE(size)                                    \
 233         void __asan_load##size(unsigned long addr)                      \
 234         {                                                               \
 235                 check_region_inline(addr, size, false, _RET_IP_);       \
 236         }                                                               \
 237         EXPORT_SYMBOL(__asan_load##size);                               \
 238         __alias(__asan_load##size)                                      \
 239         void __asan_load##size##_noabort(unsigned long);                \
 240         EXPORT_SYMBOL(__asan_load##size##_noabort);                     \
 241         void __asan_store##size(unsigned long addr)                     \
 242         {                                                               \
 243                 check_region_inline(addr, size, true, _RET_IP_);        \
 244         }                                                               \
 245         EXPORT_SYMBOL(__asan_store##size);                              \
 246         __alias(__asan_store##size)                                     \
 247         void __asan_store##size##_noabort(unsigned long);               \
 248         EXPORT_SYMBOL(__asan_store##size##_noabort)
 249
 250 DEFINE_ASAN_LOAD_STORE(1);
 251 DEFINE_ASAN_LOAD_STORE(2);
 252 DEFINE_ASAN_LOAD_STORE(4);
 253 DEFINE_ASAN_LOAD_STORE(8);
 254 DEFINE_ASAN_LOAD_STORE(16);
 255
 256 void __asan_loadN(unsigned long addr, size_t size)
 257 {
 258         kasan_check_range(addr, size, false, _RET_IP_);
 259 }
 260 EXPORT_SYMBOL(__asan_loadN);
 261
 262 __alias(__asan_loadN)
 263 void __asan_loadN_noabort(unsigned long, size_t);
 264 EXPORT_SYMBOL(__asan_loadN_noabort);
 265
 266 void __asan_storeN(unsigned long addr, size_t size)
 267 {
 268         kasan_check_range(addr, size, true, _RET_IP_);
 269 }
 270 EXPORT_SYMBOL(__asan_storeN);
 271
 272 __alias(__asan_storeN)
 273 void __asan_storeN_noabort(unsigned long, size_t);
 274 EXPORT_SYMBOL(__asan_storeN_noabort);
 275
 276 /* to shut up compiler complaints */
 277 void __asan_handle_no_return(void) {}
 278 EXPORT_SYMBOL(__asan_handle_no_return);
 279
 280 /* Emitted by compiler to poison alloca()ed objects. */
 281 void __asan_alloca_poison(unsigned long addr, size_t size)
 282 {
 283         size_t rounded_up_size = round_up(size, KASAN_GRANULE_SIZE);
 284         size_t padding_size = round_up(size, KASAN_ALLOCA_REDZONE_SIZE) -
 285                         rounded_up_size;
 286         size_t rounded_down_size = round_down(size, KASAN_GRANULE_SIZE);
 287
 288         const void *left_redzone = (const void *)(addr -
 289                         KASAN_ALLOCA_REDZONE_SIZE);
 290         const void *right_redzone = (const void *)(addr + rounded_up_size);
 291
 292         WARN_ON(!IS_ALIGNED(addr, KASAN_ALLOCA_REDZONE_SIZE));
 293
 294         kasan_unpoison((const void *)(addr + rounded_down_size),
 295                         size - rounded_down_size, false);
 296         kasan_poison(left_redzone, KASAN_ALLOCA_REDZONE_SIZE,
 297                      KASAN_ALLOCA_LEFT, false);
 298         kasan_poison(right_redzone, padding_size + KASAN_ALLOCA_REDZONE_SIZE,
 299                      KASAN_ALLOCA_RIGHT, false);
 300 }
 301 EXPORT_SYMBOL(__asan_alloca_poison);
 302
 303 /* Emitted by compiler to unpoison alloca()ed areas when the stack unwinds. */
 304 void __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(stack_top, stack_bottom - stack_top, false);
 310 }
 311 EXPORT_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
 321 DEFINE_ASAN_SET_SHADOW(00);
 322 DEFINE_ASAN_SET_SHADOW(f1);
 323 DEFINE_ASAN_SET_SHADOW(f2);
 324 DEFINE_ASAN_SET_SHADOW(f3);
 325 DEFINE_ASAN_SET_SHADOW(f5);
 326 DEFINE_ASAN_SET_SHADOW(f8);
 327
 328 void kasan_record_aux_stack(void *addr)
 329 {
 330         struct page *page = kasan_addr_to_page(addr);
 331         struct kmem_cache *cache;
 332         struct kasan_alloc_meta *alloc_meta;
 333         void *object;
 334
 335         if (is_kfence_address(addr) || !(page && PageSlab(page)))
 336                 return;
 337
 338         cache = page->slab_cache;
 339         object = nearest_obj(cache, page, addr);
 340         alloc_meta = kasan_get_alloc_meta(cache, object);
 341         if (!alloc_meta)
 342                 return;
 343
 344         alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
 345         alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
 346 }
 347
 348 void kasan_set_free_info(struct kmem_cache *cache,
 349                                 void *object, u8 tag)
 350 {
 351         struct kasan_free_meta *free_meta;
 352
 353         free_meta = kasan_get_free_meta(cache, object);
 354         if (!free_meta)
 355                 return;
 356
 357         kasan_set_track(&free_meta->free_track, GFP_NOWAIT);
 358         /* The object was freed and has free track set. */
 359         *(u8 *)kasan_mem_to_shadow(object) = KASAN_KMALLOC_FREETRACK;
 360 }
 361
 362 struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
 363                                 void *object, u8 tag)
 364 {
 365         if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_KMALLOC_FREETRACK)
 366                 return NULL;
 367         /* Free meta must be present with KASAN_KMALLOC_FREETRACK. */
 368         return &kasan_get_free_meta(cache, object)->free_track;
 369 }