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