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 *find_first_bad_addr(void *addr, size_t size)
  34 {
  35         void *p = addr;
  36
  37         while (p < addr + size && !(*(u8 *)kasan_mem_to_shadow(p)))
  38                 p += KASAN_GRANULE_SIZE;
  39         return p;
  40 }
  41
  42 static const char *get_shadow_bug_type(struct kasan_access_info *info)
  43 {
  44         const char *bug_type = "unknown-crash";
  45         u8 *shadow_addr;
  46
  47         shadow_addr = (u8 *)kasan_mem_to_shadow(info->first_bad_addr);
  48
  49         /*
  50          * If shadow byte value is in [0, KASAN_GRANULE_SIZE) we can look
  51          * at the next shadow byte to determine the type of the bad access.
  52          */
  53         if (*shadow_addr > 0 && *shadow_addr <= KASAN_GRANULE_SIZE - 1)
  54                 shadow_addr++;
  55
  56         switch (*shadow_addr) {
  57         case 0 ... KASAN_GRANULE_SIZE - 1:
  58                 /*
  59                  * In theory it's still possible to see these shadow values
  60                  * due to a data race in the kernel code.
  61                  */
  62                 bug_type = "out-of-bounds";
  63                 break;
  64         case KASAN_PAGE_REDZONE:
  65         case KASAN_KMALLOC_REDZONE:
  66                 bug_type = "slab-out-of-bounds";
  67                 break;
  68         case KASAN_GLOBAL_REDZONE:
  69                 bug_type = "global-out-of-bounds";
  70                 break;
  71         case KASAN_STACK_LEFT:
  72         case KASAN_STACK_MID:
  73         case KASAN_STACK_RIGHT:
  74         case KASAN_STACK_PARTIAL:
  75                 bug_type = "stack-out-of-bounds";
  76                 break;
  77         case KASAN_FREE_PAGE:
  78         case KASAN_KMALLOC_FREE:
  79         case KASAN_KMALLOC_FREETRACK:
  80                 bug_type = "use-after-free";
  81                 break;
  82         case KASAN_ALLOCA_LEFT:
  83         case KASAN_ALLOCA_RIGHT:
  84                 bug_type = "alloca-out-of-bounds";
  85                 break;
  86         case KASAN_VMALLOC_INVALID:
  87                 bug_type = "vmalloc-out-of-bounds";
  88                 break;
  89         }
  90
  91         return bug_type;
  92 }
  93
  94 static const char *get_wild_bug_type(struct kasan_access_info *info)
  95 {
  96         const char *bug_type = "unknown-crash";
  97
  98         if ((unsigned long)info->access_addr < PAGE_SIZE)
  99                 bug_type = "null-ptr-deref";
 100         else if ((unsigned long)info->access_addr < TASK_SIZE)
 101                 bug_type = "user-memory-access";
 102         else
 103                 bug_type = "wild-memory-access";
 104
 105         return bug_type;
 106 }
 107
 108 const char *get_bug_type(struct kasan_access_info *info)
 109 {
 110         /*
 111          * If access_size is a negative number, then it has reason to be
 112          * defined as out-of-bounds bug type.
 113          *
 114          * Casting negative numbers to size_t would indeed turn up as
 115          * a large size_t and its value will be larger than ULONG_MAX/2,
 116          * so that this can qualify as out-of-bounds.
 117          */
 118         if (info->access_addr + info->access_size < info->access_addr)
 119                 return "out-of-bounds";
 120
 121         if (addr_has_metadata(info->access_addr))
 122                 return get_shadow_bug_type(info);
 123         return get_wild_bug_type(info);
 124 }
 125
 126 void metadata_fetch_row(char *buffer, void *row)
 127 {
 128         memcpy(buffer, kasan_mem_to_shadow(row), META_BYTES_PER_ROW);
 129 }
 130
 131 #if CONFIG_KASAN_STACK
 132 static bool __must_check tokenize_frame_descr(const char **frame_descr,
 133                                               char *token, size_t max_tok_len,
 134                                               unsigned long *value)
 135 {
 136         const char *sep = strchr(*frame_descr, ' ');
 137
 138         if (sep == NULL)
 139                 sep = *frame_descr + strlen(*frame_descr);
 140
 141         if (token != NULL) {
 142                 const size_t tok_len = sep - *frame_descr;
 143
 144                 if (tok_len + 1 > max_tok_len) {
 145                         pr_err("KASAN internal error: frame description too long: %s\n",
 146                                *frame_descr);
 147                         return false;
 148                 }
 149
 150                 /* Copy token (+ 1 byte for '\0'). */
 151                 strlcpy(token, *frame_descr, tok_len + 1);
 152         }
 153
 154         /* Advance frame_descr past separator. */
 155         *frame_descr = sep + 1;
 156
 157         if (value != NULL && kstrtoul(token, 10, value)) {
 158                 pr_err("KASAN internal error: not a valid number: %s\n", token);
 159                 return false;
 160         }
 161
 162         return true;
 163 }
 164
 165 static void print_decoded_frame_descr(const char *frame_descr)
 166 {
 167         /*
 168          * We need to parse the following string:
 169          *    "n alloc_1 alloc_2 ... alloc_n"
 170          * where alloc_i looks like
 171          *    "offset size len name"
 172          * or "offset size len name:line".
 173          */
 174
 175         char token[64];
 176         unsigned long num_objects;
 177
 178         if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 179                                   &num_objects))
 180                 return;
 181
 182         pr_err("\n");
 183         pr_err("this frame has %lu %s:\n", num_objects,
 184                num_objects == 1 ? "object" : "objects");
 185
 186         while (num_objects--) {
 187                 unsigned long offset;
 188                 unsigned long size;
 189
 190                 /* access offset */
 191                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 192                                           &offset))
 193                         return;
 194                 /* access size */
 195                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 196                                           &size))
 197                         return;
 198                 /* name length (unused) */
 199                 if (!tokenize_frame_descr(&frame_descr, NULL, 0, NULL))
 200                         return;
 201                 /* object name */
 202                 if (!tokenize_frame_descr(&frame_descr, token, sizeof(token),
 203                                           NULL))
 204                         return;
 205
 206                 /* Strip line number; without filename it's not very helpful. */
 207                 strreplace(token, ':', '\0');
 208
 209                 /* Finally, print object information. */
 210                 pr_err(" [%lu, %lu) '%s'", offset, offset + size, token);
 211         }
 212 }
 213
 214 static bool __must_check get_address_stack_frame_info(const void *addr,
 215                                                       unsigned long *offset,
 216                                                       const char **frame_descr,
 217                                                       const void **frame_pc)
 218 {
 219         unsigned long aligned_addr;
 220         unsigned long mem_ptr;
 221         const u8 *shadow_bottom;
 222         const u8 *shadow_ptr;
 223         const unsigned long *frame;
 224
 225         BUILD_BUG_ON(IS_ENABLED(CONFIG_STACK_GROWSUP));
 226
 227         /*
 228          * NOTE: We currently only support printing frame information for
 229          * accesses to the task's own stack.
 230          */
 231         if (!object_is_on_stack(addr))
 232                 return false;
 233
 234         aligned_addr = round_down((unsigned long)addr, sizeof(long));
 235         mem_ptr = round_down(aligned_addr, KASAN_GRANULE_SIZE);
 236         shadow_ptr = kasan_mem_to_shadow((void *)aligned_addr);
 237         shadow_bottom = kasan_mem_to_shadow(end_of_stack(current));
 238
 239         while (shadow_ptr >= shadow_bottom && *shadow_ptr != KASAN_STACK_LEFT) {
 240                 shadow_ptr--;
 241                 mem_ptr -= KASAN_GRANULE_SIZE;
 242         }
 243
 244         while (shadow_ptr >= shadow_bottom && *shadow_ptr == KASAN_STACK_LEFT) {
 245                 shadow_ptr--;
 246                 mem_ptr -= KASAN_GRANULE_SIZE;
 247         }
 248
 249         if (shadow_ptr < shadow_bottom)
 250                 return false;
 251
 252         frame = (const unsigned long *)(mem_ptr + KASAN_GRANULE_SIZE);
 253         if (frame[0] != KASAN_CURRENT_STACK_FRAME_MAGIC) {
 254                 pr_err("KASAN internal error: frame info validation failed; invalid marker: %lu\n",
 255                        frame[0]);
 256                 return false;
 257         }
 258
 259         *offset = (unsigned long)addr - (unsigned long)frame;
 260         *frame_descr = (const char *)frame[1];
 261         *frame_pc = (void *)frame[2];
 262
 263         return true;
 264 }
 265
 266 void print_address_stack_frame(const void *addr)
 267 {
 268         unsigned long offset;
 269         const char *frame_descr;
 270         const void *frame_pc;
 271
 272         if (!get_address_stack_frame_info(addr, &offset, &frame_descr,
 273                                           &frame_pc))
 274                 return;
 275
 276         /*
 277          * get_address_stack_frame_info only returns true if the given addr is
 278          * on the current task's stack.
 279          */
 280         pr_err("\n");
 281         pr_err("addr %px is located in stack of task %s/%d at offset %lu in frame:\n",
 282                addr, current->comm, task_pid_nr(current), offset);
 283         pr_err(" %pS\n", frame_pc);
 284
 285         if (!frame_descr)
 286                 return;
 287
 288         print_decoded_frame_descr(frame_descr);
 289 }
 290 #endif /* CONFIG_KASAN_STACK */
 291
 292 #define DEFINE_ASAN_REPORT_LOAD(size)                     \
 293 void __asan_report_load##size##_noabort(unsigned long addr) \
 294 {                                                         \
 295         kasan_report(addr, size, false, _RET_IP_);        \
 296 }                                                         \
 297 EXPORT_SYMBOL(__asan_report_load##size##_noabort)
 298
 299 #define DEFINE_ASAN_REPORT_STORE(size)                     \
 300 void __asan_report_store##size##_noabort(unsigned long addr) \
 301 {                                                          \
 302         kasan_report(addr, size, true, _RET_IP_);          \
 303 }                                                          \
 304 EXPORT_SYMBOL(__asan_report_store##size##_noabort)
 305
 306 DEFINE_ASAN_REPORT_LOAD(1);
 307 DEFINE_ASAN_REPORT_LOAD(2);
 308 DEFINE_ASAN_REPORT_LOAD(4);
 309 DEFINE_ASAN_REPORT_LOAD(8);
 310 DEFINE_ASAN_REPORT_LOAD(16);
 311 DEFINE_ASAN_REPORT_STORE(1);
 312 DEFINE_ASAN_REPORT_STORE(2);
 313 DEFINE_ASAN_REPORT_STORE(4);
 314 DEFINE_ASAN_REPORT_STORE(8);
 315 DEFINE_ASAN_REPORT_STORE(16);
 316
 317 void __asan_report_load_n_noabort(unsigned long addr, size_t size)
 318 {
 319         kasan_report(addr, size, false, _RET_IP_);
 320 }
 321 EXPORT_SYMBOL(__asan_report_load_n_noabort);
 322
 323 void __asan_report_store_n_noabort(unsigned long addr, size_t size)
 324 {
 325         kasan_report(addr, size, true, _RET_IP_);
 326 }
 327 EXPORT_SYMBOL(__asan_report_store_n_noabort);