lib/ubsan.c

   1 /*
   2  * UBSAN error reporting functions
   3  *
   4  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   5  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  */
  12
  13 #include <linux/bitops.h>
  14 #include <linux/bug.h>
  15 #include <linux/ctype.h>
  16 #include <linux/init.h>
  17 #include <linux/kernel.h>
  18 #include <linux/types.h>
  19 #include <linux/sched.h>
  20 #include <linux/uaccess.h>
  21
  22 #include "ubsan.h"
  23
  24 const char *type_check_kinds[] = {
  25         "load of",
  26         "store to",
  27         "reference binding to",
  28         "member access within",
  29         "member call on",
  30         "constructor call on",
  31         "downcast of",
  32         "downcast of"
  33 };
  34
  35 #define REPORTED_BIT 31
  36
  37 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
  38 #define COLUMN_MASK (~(1U << REPORTED_BIT))
  39 #define LINE_MASK   (~0U)
  40 #else
  41 #define COLUMN_MASK   (~0U)
  42 #define LINE_MASK (~(1U << REPORTED_BIT))
  43 #endif
  44
  45 #define VALUE_LENGTH 40
  46
  47 static bool was_reported(struct source_location *location)
  48 {
  49         return test_and_set_bit(REPORTED_BIT, &location->reported);
  50 }
  51
  52 static void print_source_location(const char *prefix,
  53                                 struct source_location *loc)
  54 {
  55         pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
  56                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
  57 }
  58
  59 static bool suppress_report(struct source_location *loc)
  60 {
  61         return current->in_ubsan || was_reported(loc);
  62 }
  63
  64 static bool type_is_int(struct type_descriptor *type)
  65 {
  66         return type->type_kind == type_kind_int;
  67 }
  68
  69 static bool type_is_signed(struct type_descriptor *type)
  70 {
  71         WARN_ON(!type_is_int(type));
  72         return  type->type_info & 1;
  73 }
  74
  75 static unsigned type_bit_width(struct type_descriptor *type)
  76 {
  77         return 1 << (type->type_info >> 1);
  78 }
  79
  80 static bool is_inline_int(struct type_descriptor *type)
  81 {
  82         unsigned inline_bits = sizeof(unsigned long)*8;
  83         unsigned bits = type_bit_width(type);
  84
  85         WARN_ON(!type_is_int(type));
  86
  87         return bits <= inline_bits;
  88 }
  89
  90 static s_max get_signed_val(struct type_descriptor *type, void *val)
  91 {
  92         if (is_inline_int(type)) {
  93                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
  94                 unsigned long ulong_val = (unsigned long)val;
  95
  96                 return ((s_max)ulong_val) << extra_bits >> extra_bits;
  97         }
  98
  99         if (type_bit_width(type) == 64)
 100                 return *(s64 *)val;
 101
 102         return *(s_max *)val;
 103 }
 104
 105 static bool val_is_negative(struct type_descriptor *type, void *val)
 106 {
 107         return type_is_signed(type) && get_signed_val(type, val) < 0;
 108 }
 109
 110 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
 111 {
 112         if (is_inline_int(type))
 113                 return (unsigned long)val;
 114
 115         if (type_bit_width(type) == 64)
 116                 return *(u64 *)val;
 117
 118         return *(u_max *)val;
 119 }
 120
 121 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
 122                         void *value)
 123 {
 124         if (type_is_int(type)) {
 125                 if (type_bit_width(type) == 128) {
 126 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 127                         u_max val = get_unsigned_val(type, value);
 128
 129                         scnprintf(str, size, "0x%08x%08x%08x%08x",
 130                                 (u32)(val >> 96),
 131                                 (u32)(val >> 64),
 132                                 (u32)(val >> 32),
 133                                 (u32)(val));
 134 #else
 135                         WARN_ON(1);
 136 #endif
 137                 } else if (type_is_signed(type)) {
 138                         scnprintf(str, size, "%lld",
 139                                 (s64)get_signed_val(type, value));
 140                 } else {
 141                         scnprintf(str, size, "%llu",
 142                                 (u64)get_unsigned_val(type, value));
 143                 }
 144         }
 145 }
 146
 147 static DEFINE_SPINLOCK(report_lock);
 148
 149 static void ubsan_prologue(struct source_location *location,
 150                         unsigned long *flags)
 151 {
 152         current->in_ubsan++;
 153         spin_lock_irqsave(&report_lock, *flags);
 154
 155         pr_err("========================================"
 156                 "========================================\n");
 157         print_source_location("UBSAN: Undefined behaviour in", location);
 158 }
 159
 160 static void ubsan_epilogue(unsigned long *flags)
 161 {
 162         dump_stack();
 163         pr_err("========================================"
 164                 "========================================\n");
 165         spin_unlock_irqrestore(&report_lock, *flags);
 166         current->in_ubsan--;
 167 }
 168
 169 static void handle_overflow(struct overflow_data *data, void *lhs,
 170                         void *rhs, char op)
 171 {
 172
 173         struct type_descriptor *type = data->type;
 174         unsigned long flags;
 175         char lhs_val_str[VALUE_LENGTH];
 176         char rhs_val_str[VALUE_LENGTH];
 177
 178         if (suppress_report(&data->location))
 179                 return;
 180
 181         ubsan_prologue(&data->location, &flags);
 182
 183         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
 184         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
 185         pr_err("%s integer overflow:\n",
 186                 type_is_signed(type) ? "signed" : "unsigned");
 187         pr_err("%s %c %s cannot be represented in type %s\n",
 188                 lhs_val_str,
 189                 op,
 190                 rhs_val_str,
 191                 type->type_name);
 192
 193         ubsan_epilogue(&flags);
 194 }
 195
 196 void __ubsan_handle_add_overflow(struct overflow_data *data,
 197                                 void *lhs, void *rhs)
 198 {
 199
 200         handle_overflow(data, lhs, rhs, '+');
 201 }
 202 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
 203
 204 void __ubsan_handle_sub_overflow(struct overflow_data *data,
 205                                 void *lhs, void *rhs)
 206 {
 207         handle_overflow(data, lhs, rhs, '-');
 208 }
 209 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
 210
 211 void __ubsan_handle_mul_overflow(struct overflow_data *data,
 212                                 void *lhs, void *rhs)
 213 {
 214         handle_overflow(data, lhs, rhs, '*');
 215 }
 216 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
 217
 218 void __ubsan_handle_negate_overflow(struct overflow_data *data,
 219                                 void *old_val)
 220 {
 221         unsigned long flags;
 222         char old_val_str[VALUE_LENGTH];
 223
 224         if (suppress_report(&data->location))
 225                 return;
 226
 227         ubsan_prologue(&data->location, &flags);
 228
 229         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
 230
 231         pr_err("negation of %s cannot be represented in type %s:\n",
 232                 old_val_str, data->type->type_name);
 233
 234         ubsan_epilogue(&flags);
 235 }
 236 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
 237
 238
 239 void __ubsan_handle_divrem_overflow(struct overflow_data *data,
 240                                 void *lhs, void *rhs)
 241 {
 242         unsigned long flags;
 243         char rhs_val_str[VALUE_LENGTH];
 244
 245         if (suppress_report(&data->location))
 246                 return;
 247
 248         ubsan_prologue(&data->location, &flags);
 249
 250         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 251
 252         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 253                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 254                         rhs_val_str, data->type->type_name);
 255         else
 256                 pr_err("division by zero\n");
 257
 258         ubsan_epilogue(&flags);
 259 }
 260 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 261
 262 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 263 {
 264         unsigned long flags;
 265
 266         if (suppress_report(data->location))
 267                 return;
 268
 269         ubsan_prologue(data->location, &flags);
 270
 271         pr_err("%s null pointer of type %s\n",
 272                 type_check_kinds[data->type_check_kind],
 273                 data->type->type_name);
 274
 275         ubsan_epilogue(&flags);
 276 }
 277
 278 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 279                                 unsigned long ptr)
 280 {
 281         unsigned long flags;
 282
 283         if (suppress_report(data->location))
 284                 return;
 285
 286         ubsan_prologue(data->location, &flags);
 287
 288         pr_err("%s misaligned address %p for type %s\n",
 289                 type_check_kinds[data->type_check_kind],
 290                 (void *)ptr, data->type->type_name);
 291         pr_err("which requires %ld byte alignment\n", data->alignment);
 292
 293         ubsan_epilogue(&flags);
 294 }
 295
 296 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 297                                         unsigned long ptr)
 298 {
 299         unsigned long flags;
 300
 301         if (suppress_report(data->location))
 302                 return;
 303
 304         ubsan_prologue(data->location, &flags);
 305         pr_err("%s address %p with insufficient space\n",
 306                 type_check_kinds[data->type_check_kind],
 307                 (void *) ptr);
 308         pr_err("for an object of type %s\n", data->type->type_name);
 309         ubsan_epilogue(&flags);
 310 }
 311
 312 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 313                                 unsigned long ptr)
 314 {
 315         unsigned long flags = user_access_save();
 316
 317         if (!ptr)
 318                 handle_null_ptr_deref(data);
 319         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 320                 handle_misaligned_access(data, ptr);
 321         else
 322                 handle_object_size_mismatch(data, ptr);
 323
 324         user_access_restore(flags);
 325 }
 326
 327 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 328                                 void *ptr)
 329 {
 330         struct type_mismatch_data_common common_data = {
 331                 .location = &data->location,
 332                 .type = data->type,
 333                 .alignment = data->alignment,
 334                 .type_check_kind = data->type_check_kind
 335         };
 336
 337         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 338 }
 339 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 340
 341 void __ubsan_handle_type_mismatch_v1(struct type_mismatch_data_v1 *data,
 342                                 void *ptr)
 343 {
 344
 345         struct type_mismatch_data_common common_data = {
 346                 .location = &data->location,
 347                 .type = data->type,
 348                 .alignment = 1UL << data->log_alignment,
 349                 .type_check_kind = data->type_check_kind
 350         };
 351
 352         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 353 }
 354 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 355
 356 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index)
 357 {
 358         unsigned long flags;
 359         char index_str[VALUE_LENGTH];
 360
 361         if (suppress_report(&data->location))
 362                 return;
 363
 364         ubsan_prologue(&data->location, &flags);
 365
 366         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 367         pr_err("index %s is out of range for type %s\n", index_str,
 368                 data->array_type->type_name);
 369         ubsan_epilogue(&flags);
 370 }
 371 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 372
 373 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
 374                                         void *lhs, void *rhs)
 375 {
 376         unsigned long flags;
 377         struct type_descriptor *rhs_type = data->rhs_type;
 378         struct type_descriptor *lhs_type = data->lhs_type;
 379         char rhs_str[VALUE_LENGTH];
 380         char lhs_str[VALUE_LENGTH];
 381
 382         if (suppress_report(&data->location))
 383                 return;
 384
 385         ubsan_prologue(&data->location, &flags);
 386
 387         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 388         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 389
 390         if (val_is_negative(rhs_type, rhs))
 391                 pr_err("shift exponent %s is negative\n", rhs_str);
 392
 393         else if (get_unsigned_val(rhs_type, rhs) >=
 394                 type_bit_width(lhs_type))
 395                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 396                         rhs_str,
 397                         type_bit_width(lhs_type),
 398                         lhs_type->type_name);
 399         else if (val_is_negative(lhs_type, lhs))
 400                 pr_err("left shift of negative value %s\n",
 401                         lhs_str);
 402         else
 403                 pr_err("left shift of %s by %s places cannot be"
 404                         " represented in type %s\n",
 405                         lhs_str, rhs_str,
 406                         lhs_type->type_name);
 407
 408         ubsan_epilogue(&flags);
 409 }
 410 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 411
 412
 413 void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
 414 {
 415         unsigned long flags;
 416
 417         ubsan_prologue(&data->location, &flags);
 418         pr_err("calling __builtin_unreachable()\n");
 419         ubsan_epilogue(&flags);
 420         panic("can't return from __builtin_unreachable()");
 421 }
 422 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 423
 424 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
 425                                 void *val)
 426 {
 427         unsigned long flags;
 428         char val_str[VALUE_LENGTH];
 429
 430         if (suppress_report(&data->location))
 431                 return;
 432
 433         ubsan_prologue(&data->location, &flags);
 434
 435         val_to_string(val_str, sizeof(val_str), data->type, val);
 436
 437         pr_err("load of value %s is not a valid value for type %s\n",
 438                 val_str, data->type->type_name);
 439
 440         ubsan_epilogue(&flags);
 441 }
 442 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);