mm/kasan/report_generic.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * This file contains generic KASAN specific error reporting 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/bitops.h>
  13 #include <linux/ftrace.h>
  14 #include <linux/init.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mm.h>
  17 #include <linux/printk.h>
  18 #include <linux/sched.h>
  19 #include <linux/sched/task_stack.h>
  20 #include <linux/slab.h>
  21 #include <linux/stackdepot.h>
  22 #include <linux/stacktrace.h>
  23 #include <linux/string.h>
  24 #include <linux/types.h>
  25 #include <linux/kasan.h>
  26 #include <linux/module.h>
  27
  28 #include <asm/sections.h>
  29
  30 #include "kasan.h"
  31 #include "../slab.h"
  32
  33 void *kasan_find_first_bad_addr(void *addr, size_t size)
  34 {
  35         void *p = addr;
  36
  37         if (!addr_has_metadata(p))
  38                 return p;
  39
  40         while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
  41                 p += KASAN_GRANULE_SIZE;
  42
  43         return p;
  44 }
  45
  46 size_t kasan_get_alloc_size(void *object, struct kmem_cache *cache)
  47 {
  48         size_t size = 0;
  49         u8 *shadow;
  50
  51         /*
  52          * Skip the addr_has_metadata check, as this function only operates on
  53          * slab memory, which must have metadata.
  54          */
  55
  56         /*
  57          * The loop below returns 0 for freed objects, for which KASAN cannot
  58          * calculate the allocation size based on the metadata.
  59          */
  60         shadow = (u8 *)kasan_mem_to_shadow(object);
  61         while (size < cache->object_size) {
  62                 if (*shadow == 0)
  63                         size += KASAN_GRANULE_SIZE;
  64                 else if (*shadow >= 1 && *shadow <= KASAN_GRANULE_SIZE - 1)
  65                         return size + *shadow;
  66                 else
  67                         return size;
  68                 shadow++;
  69         }
  70
  71         return cache->object_size;
  72 }
  73
  74 static const char *get_shadow_bug_type(struct kasan_report_info *info)
  75 {
  76         const char *bug_type = "unknown-crash";
  77         u8 *shadow_addr;
  78
  79         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  80
  81         /*
  82          * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
  83          * at the next shadow byte to determine the type of the bad access.
  84          */
  85         if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
  86                 shadow_addr++;
  87
  88         switch (*shadow_addr) {
  89         case 0 ... KASAN_GRANULE_SIZE - 1:
  90                 /*
  91                  * In theory it's still possible to see these shadow values
  92                  * due to a data race in the kernel code.
  93                  */
  94                 bug_type = "out-of-bounds";
  95                 break;
  96         case KASAN_PAGE_REDZONE:
  97         case KASAN_SLAB_REDZONE:
  98                 bug_type = "slab-out-of-bounds";
  99                 break;
 100         case KASAN_GLOBAL_REDZONE:
 101                 bug_type = "global-out-of-bounds";
 102                 break;
 103         case KASAN_STACK_LEFT:
 104         case KASAN_STACK_MID:
 105         case KASAN_STACK_RIGHT:
 106         case KASAN_STACK_PARTIAL:
 107                 bug_type = "stack-out-of-bounds";
 108                 break;
 109         case KASAN_PAGE_FREE:
 110                 bug_type = "use-after-free";
 111                 break;
 112         case KASAN_SLAB_FREE:
 113         case KASAN_SLAB_FREETRACK:
 114                 bug_type = "slab-use-after-free";
 115                 break;
 116         case KASAN_ALLOCA_LEFT:
 117         case KASAN_ALLOCA_RIGHT:
 118                 bug_type = "alloca-out-of-bounds";
 119                 break;
 120         case KASAN_VMALLOC_INVALID:
 121                 bug_type = "vmalloc-out-of-bounds";
 122                 break;
 123         }
 124
 125         return bug_type;
 126 }
 127
 128 static const char *get_wild_bug_type(struct kasan_report_info *info)
 129 {
 130         const char *bug_type = "unknown-crash";
 131
 132         if ((unsigned long)info->access_addr < PAGE_SIZE)
 133                 bug_type = "null-ptr-deref";
 134         else if ((unsigned long)info->access_addr < TASK_SIZE)
 135                 bug_type = "user-memory-access";
 136         else
 137                 bug_type = "wild-memory-access";
 138
 139         return bug_type;
 140 }
 141
 142 static const char *get_bug_type(struct kasan_report_info *info)
 143 {
 144         /*
 145          * If access_size is a negative number, then it has reason to be
 146          * defined as out-of-bounds bug type.
 147          *
 148          * Casting negative numbers to size_t would indeed turn up as
 149          * a large size_t and its value will be larger than ULONG_MAX/2,
 150          * so that this can qualify as out-of-bounds.
 151          */
 152         if (info->access_addr + info->access_size < info->access_addr)
 153                 return "out-of-bounds";
 154
 155         if (addr_has_metadata(info->access_addr))
 156                 return get_shadow_bug_type(info);
 157         return get_wild_bug_type(info);
 158 }
 159
 160 void kasan_complete_mode_report_info(struct kasan_report_info *info)
 161 {
 162         struct kasan_alloc_meta *alloc_meta;
 163         struct kasan_free_meta *free_meta;
 164
 165         if (!info->bug_type)
 166                 info->bug_type = get_bug_type(info);
 167
 168         if (!info->cache || !info->object)
 169                 return;
 170
 171         alloc_meta = kasan_get_alloc_meta(info->cache, info->object);
 172         if (alloc_meta)
 173                 memcpy(&info->alloc_track, &alloc_meta->alloc_track,
 174                        sizeof(info->alloc_track));
 175
 176         if (*(u8 *)kasan_mem_to_shadow(info->object) == KASAN_SLAB_FREETRACK) {
 177                 /* Free meta must be present with KASAN_SLAB_FREETRACK. */
 178                 free_meta = kasan_get_free_meta(info->cache, info->object);
 179                 memcpy(&info->free_track, &free_meta->free_track,
 180                        sizeof(info->free_track));
 181         }
 182 }
 183
 184 void kasan_metadata_fetch_row(char *buffer, void *row)
 185 {
 186         memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
 187 }
 188
 189 void kasan_print_aux_stacks(struct kmem_cache *cache, const void *object)
 190 {
 191         struct kasan_alloc_meta *alloc_meta;
 192
 193         alloc_meta = kasan_get_alloc_meta(cache, object);
 194         if (!alloc_meta)
 195                 return;
 196
 197         if (alloc_meta->aux_stack[0]) {
 198                 pr_err("Last potentially related work creation:\n");
 199                 stack_depot_print(alloc_meta->aux_stack[0]);
 200                 pr_err("\n");
 201         }
 202         if (alloc_meta->aux_stack[1]) {
 203                 pr_err("Second to last potentially related work creation:\n");
 204                 stack_depot_print(alloc_meta->aux_stack[1]);
 205                 pr_err("\n");
 206         }
 207 }
 208
 209 #ifdef CONFIG_KASAN_STACK
 210 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 211                                               char *token, size_t max_tok_len,
 212                                               unsigned long *value)
 213 {
 214         const char *sep = strchr(*frame_descr, ' ');
 215
 216         if (sep == NULL)
 217                 sep = *frame_descr + strlen(*frame_descr);
 218
 219         if (token != NULL) {
 220                 const size_t tok_len = sep - *frame_descr;
 221
 222                 if (tok_len + 1 > max_tok_len) {
 223                         pr_err("KASAN internal error: frame description too long: %s\n",
 224                                *frame_descr);
 225                         return false;
 226                 }
 227
 228                 /* Copy token (+ 1 byte for '\0'). */
 229                 strscpy(token, *frame_descr, tok_len + 1);
 230         }
 231
 232         /* Advance frame_descr past separator. */
 233         *frame_descr = sep + 1;
 234
 235         if (value != NULL && kstrtoul(token, 10, value)) {
 236                 pr_err("KASAN internal error: not a valid number: %s\n", token);
 237                 return false;
 238         }
 239
 240         return true;
 241 }
 242
 243 static void print_decoded_frame_descr(const char *frame_descr)
 244 {
 245         /*
 246          * We need to parse the following string:
 247          *    "n alloc_1 alloc_2 ... alloc_n"
 248          * where alloc_i looks like
 249          *    "offset size len name"
 250          * or "offset size len name:line".
 251          */
 252
 253         char token[64];
 254         unsigned long num_objects;
 255
 256         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 257                                   &num_objects))
 258                 return;
 259
 260         pr_err("\n");
 261         pr_err("This frame has %lu %s:\n", num_objects,
 262                num_objects == 1 ? "object" : "objects");
 263
 264         while (num_objects--) {
 265                 unsigned long offset;
 266                 unsigned long size;
 267
 268                 /* access offset */
 269                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 270                                           &offset))
 271                         return;
 272                 /* access size */
 273                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 274                                           &size))
 275                         return;
 276                 /* name length (unused) */
 277                 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
 278                         return;
 279                 /* object name */
 280                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 281                                           NULL))
 282                         return;
 283
 284                 /* Strip line number; without filename it's not very helpful. */
 285                 strreplace(token, ':', '\0');
 286
 287                 /* Finally, print object information. */
 288                 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
 289         }
 290 }
 291
 292 /* Returns true only if the address is on the current task's stack. */
 293 static bool __must_check get_address_stack_frame_info(const void *addr,
 294                                                       unsigned long *offset,
 295                                                       const char **frame_descr,
 296                                                       const void **frame_pc)
 297 {
 298         unsigned long aligned_addr;
 299         unsigned long mem_ptr;
 300         const u8 *shadow_bottom;
 301         const u8 *shadow_ptr;
 302         const unsigned long *frame;
 303
 304         BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 305
 306         aligned_addr = round_down((unsigned long)addr, sizeof(long));
 307         mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
 308         shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
 309         shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
 310
 311         while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
 312                 shadow_ptr--;
 313                 mem_ptr -= KASAN_GRANULE_SIZE;
 314         }
 315
 316         while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
 317                 shadow_ptr--;
 318                 mem_ptr -= KASAN_GRANULE_SIZE;
 319         }
 320
 321         if (shadow_ptr < shadow_bottom)
 322                 return false;
 323
 324         frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
 325         if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
 326                 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
 327                        frame[0]);
 328                 return false;
 329         }
 330
 331         *offset = (unsigned long)addr - (unsigned long)frame;
 332         *frame_descr = (const char *)frame[1];
 333         *frame_pc = (void *)frame[2];
 334
 335         return true;
 336 }
 337
 338 void kasan_print_address_stack_frame(const void *addr)
 339 {
 340         unsigned long offset;
 341         const char *frame_descr;
 342         const void *frame_pc;
 343
 344         if (WARN_ON(!object_is_on_stack(addr)))
 345                 return;
 346
 347         pr_err("The buggy address belongs to stack of task %s/%d\n",
 348                current->comm, task_pid_nr(current));
 349
 350         if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 351                                           &frame_pc))
 352                 return;
 353
 354         pr_err(" and is located at offset %lu in frame:\n", offset);
 355         pr_err(" %pS\n", frame_pc);
 356
 357         if (!frame_descr)
 358                 return;
 359
 360         print_decoded_frame_descr(frame_descr);
 361 }
 362 #endif /* CONFIG_KASAN_STACK */
 363
 364 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 365 void __asan_report_load##size##_noabort(unsigned long addr) \
 366 {                                                         \
 367         kasan_report(addr, size, false, _RET_IP_);        \
 368 }                                                         \
 369 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 370
 371 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 372 void __asan_report_store##size##_noabort(unsigned long addr) \
 373 {                                                          \
 374         kasan_report(addr, size, true, _RET_IP_);          \
 375 }                                                          \
 376 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 377
 378 DEFINE_ASAN_REPORT_LOAD(1);
 379 DEFINE_ASAN_REPORT_LOAD(2);
 380 DEFINE_ASAN_REPORT_LOAD(4);
 381 DEFINE_ASAN_REPORT_LOAD(8);
 382 DEFINE_ASAN_REPORT_LOAD(16);
 383 DEFINE_ASAN_REPORT_STORE(1);
 384 DEFINE_ASAN_REPORT_STORE(2);
 385 DEFINE_ASAN_REPORT_STORE(4);
 386 DEFINE_ASAN_REPORT_STORE(8);
 387 DEFINE_ASAN_REPORT_STORE(16);
 388
 389 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 390 {
 391         kasan_report(addr, size, false, _RET_IP_);
 392 }
 393 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 394
 395 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 396 {
 397         kasan_report(addr, size, true, _RET_IP_);
 398 }
 399 EXPORT_SYMBOL(__asan_report_store_n_noabort);