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 const char *kasan_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_metadata_fetch_row(char *buffer, void *row)
 131 {
 132         memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
 133 }
 134
 135 #ifdef CONFIG_KASAN_STACK
 136 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 137                                               char *token, size_t max_tok_len,
 138                                               unsigned long *value)
 139 {
 140         const char *sep = strchr(*frame_descr, ' ');
 141
 142         if (sep == NULL)
 143                 sep = *frame_descr + strlen(*frame_descr);
 144
 145         if (token != NULL) {
 146                 const size_t tok_len = sep - *frame_descr;
 147
 148                 if (tok_len + 1 > max_tok_len) {
 149                         pr_err("KASAN internal error: frame description too long: %s\n",
 150                                *frame_descr);
 151                         return false;
 152                 }
 153
 154                 /* Copy token (+ 1 byte for '\0'). */
 155                 strscpy(token, *frame_descr, tok_len + 1);
 156         }
 157
 158         /* Advance frame_descr past separator. */
 159         *frame_descr = sep + 1;
 160
 161         if (value != NULL && kstrtoul(token, 10, value)) {
 162                 pr_err("KASAN internal error: not a valid number: %s\n", token);
 163                 return false;
 164         }
 165
 166         return true;
 167 }
 168
 169 static void print_decoded_frame_descr(const char *frame_descr)
 170 {
 171         /*
 172          * We need to parse the following string:
 173          *    "n alloc_1 alloc_2 ... alloc_n"
 174          * where alloc_i looks like
 175          *    "offset size len name"
 176          * or "offset size len name:line".
 177          */
 178
 179         char token[64];
 180         unsigned long num_objects;
 181
 182         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 183                                   &num_objects))
 184                 return;
 185
 186         pr_err("\n");
 187         pr_err("This frame has %lu %s:\n", num_objects,
 188                num_objects == 1 ? "object" : "objects");
 189
 190         while (num_objects--) {
 191                 unsigned long offset;
 192                 unsigned long size;
 193
 194                 /* access offset */
 195                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 196                                           &offset))
 197                         return;
 198                 /* access size */
 199                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 200                                           &size))
 201                         return;
 202                 /* name length (unused) */
 203                 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
 204                         return;
 205                 /* object name */
 206                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 207                                           NULL))
 208                         return;
 209
 210                 /* Strip line number; without filename it's not very helpful. */
 211                 strreplace(token, ':', '\0');
 212
 213                 /* Finally, print object information. */
 214                 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
 215         }
 216 }
 217
 218 /* Returns true only if the address is on the current task's stack. */
 219 static bool __must_check get_address_stack_frame_info(const void *addr,
 220                                                       unsigned long *offset,
 221                                                       const char **frame_descr,
 222                                                       const void **frame_pc)
 223 {
 224         unsigned long aligned_addr;
 225         unsigned long mem_ptr;
 226         const u8 *shadow_bottom;
 227         const u8 *shadow_ptr;
 228         const unsigned long *frame;
 229
 230         BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 231
 232         aligned_addr = round_down((unsigned long)addr, sizeof(long));
 233         mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
 234         shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
 235         shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
 236
 237         while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
 238                 shadow_ptr--;
 239                 mem_ptr -= KASAN_GRANULE_SIZE;
 240         }
 241
 242         while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
 243                 shadow_ptr--;
 244                 mem_ptr -= KASAN_GRANULE_SIZE;
 245         }
 246
 247         if (shadow_ptr < shadow_bottom)
 248                 return false;
 249
 250         frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
 251         if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
 252                 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
 253                        frame[0]);
 254                 return false;
 255         }
 256
 257         *offset = (unsigned long)addr - (unsigned long)frame;
 258         *frame_descr = (const char *)frame[1];
 259         *frame_pc = (void *)frame[2];
 260
 261         return true;
 262 }
 263
 264 void kasan_print_address_stack_frame(const void *addr)
 265 {
 266         unsigned long offset;
 267         const char *frame_descr;
 268         const void *frame_pc;
 269
 270         if (WARN_ON(!object_is_on_stack(addr)))
 271                 return;
 272
 273         pr_err("The buggy address belongs to stack of task %s/%d\n",
 274                current->comm, task_pid_nr(current));
 275
 276         if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 277                                           &frame_pc))
 278                 return;
 279
 280         pr_err(" and is located at offset %lu in frame:\n", offset);
 281         pr_err(" %pS\n", frame_pc);
 282
 283         if (!frame_descr)
 284                 return;
 285
 286         print_decoded_frame_descr(frame_descr);
 287 }
 288 #endif /* CONFIG_KASAN_STACK */
 289
 290 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 291 void __asan_report_load##size##_noabort(unsigned long addr) \
 292 {                                                         \
 293         kasan_report(addr, size, false, _RET_IP_);        \
 294 }                                                         \
 295 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 296
 297 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 298 void __asan_report_store##size##_noabort(unsigned long addr) \
 299 {                                                          \
 300         kasan_report(addr, size, true, _RET_IP_);          \
 301 }                                                          \
 302 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 303
 304 DEFINE_ASAN_REPORT_LOAD(1);
 305 DEFINE_ASAN_REPORT_LOAD(2);
 306 DEFINE_ASAN_REPORT_LOAD(4);
 307 DEFINE_ASAN_REPORT_LOAD(8);
 308 DEFINE_ASAN_REPORT_LOAD(16);
 309 DEFINE_ASAN_REPORT_STORE(1);
 310 DEFINE_ASAN_REPORT_STORE(2);
 311 DEFINE_ASAN_REPORT_STORE(4);
 312 DEFINE_ASAN_REPORT_STORE(8);
 313 DEFINE_ASAN_REPORT_STORE(16);
 314
 315 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 316 {
 317         kasan_report(addr, size, false, _RET_IP_);
 318 }
 319 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 320
 321 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 322 {
 323         kasan_report(addr, size, true, _RET_IP_);
 324 }
 325 EXPORT_SYMBOL(__asan_report_store_n_noabort);