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