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
  21 #include "ubsan.h"
  22
  23 const char *type_check_kinds[] = {
  24         "load of",
  25         "store to",
  26         "reference binding to",
  27         "member access within",
  28         "member call on",
  29         "constructor call on",
  30         "downcast of",
  31         "downcast of"
  32 };
  33
  34 #define REPORTED_BIT 31
  35
  36 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
  37 #define COLUMN_MASK (~(1U << REPORTED_BIT))
  38 #define LINE_MASK   (~0U)
  39 #else
  40 #define COLUMN_MASK   (~0U)
  41 #define LINE_MASK (~(1U << REPORTED_BIT))
  42 #endif
  43
  44 #define VALUE_LENGTH 40
  45
  46 static bool was_reported(struct source_location *location)
  47 {
  48         return test_and_set_bit(REPORTED_BIT, &location->reported);
  49 }
  50
  51 static void print_source_location(const char *prefix,
  52                                 struct source_location *loc)
  53 {
  54         pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
  55                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
  56 }
  57
  58 static bool suppress_report(struct source_location *loc)
  59 {
  60         return current->in_ubsan || was_reported(loc);
  61 }
  62
  63 static bool type_is_int(struct type_descriptor *type)
  64 {
  65         return type->type_kind == type_kind_int;
  66 }
  67
  68 static bool type_is_signed(struct type_descriptor *type)
  69 {
  70         WARN_ON(!type_is_int(type));
  71         return  type->type_info & 1;
  72 }
  73
  74 static unsigned type_bit_width(struct type_descriptor *type)
  75 {
  76         return 1 << (type->type_info >> 1);
  77 }
  78
  79 static bool is_inline_int(struct type_descriptor *type)
  80 {
  81         unsigned inline_bits = sizeof(unsigned long)*8;
  82         unsigned bits = type_bit_width(type);
  83
  84         WARN_ON(!type_is_int(type));
  85
  86         return bits <= inline_bits;
  87 }
  88
  89 static s_max get_signed_val(struct type_descriptor *type, unsigned long val)
  90 {
  91         if (is_inline_int(type)) {
  92                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
  93                 return ((s_max)val) << extra_bits >> extra_bits;
  94         }
  95
  96         if (type_bit_width(type) == 64)
  97                 return *(s64 *)val;
  98
  99         return *(s_max *)val;
 100 }
 101
 102 static bool val_is_negative(struct type_descriptor *type, unsigned long val)
 103 {
 104         return type_is_signed(type) && get_signed_val(type, val) < 0;
 105 }
 106
 107 static u_max get_unsigned_val(struct type_descriptor *type, unsigned long val)
 108 {
 109         if (is_inline_int(type))
 110                 return val;
 111
 112         if (type_bit_width(type) == 64)
 113                 return *(u64 *)val;
 114
 115         return *(u_max *)val;
 116 }
 117
 118 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
 119         unsigned long value)
 120 {
 121         if (type_is_int(type)) {
 122                 if (type_bit_width(type) == 128) {
 123 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 124                         u_max val = get_unsigned_val(type, value);
 125
 126                         scnprintf(str, size, "0x%08x%08x%08x%08x",
 127                                 (u32)(val >> 96),
 128                                 (u32)(val >> 64),
 129                                 (u32)(val >> 32),
 130                                 (u32)(val));
 131 #else
 132                         WARN_ON(1);
 133 #endif
 134                 } else if (type_is_signed(type)) {
 135                         scnprintf(str, size, "%lld",
 136                                 (s64)get_signed_val(type, value));
 137                 } else {
 138                         scnprintf(str, size, "%llu",
 139                                 (u64)get_unsigned_val(type, value));
 140                 }
 141         }
 142 }
 143
 144 static DEFINE_SPINLOCK(report_lock);
 145
 146 static void ubsan_prologue(struct source_location *location,
 147                         unsigned long *flags)
 148 {
 149         current->in_ubsan++;
 150         spin_lock_irqsave(&report_lock, *flags);
 151
 152         pr_err("========================================"
 153                 "========================================\n");
 154         print_source_location("UBSAN: Undefined behaviour in", location);
 155 }
 156
 157 static void ubsan_epilogue(unsigned long *flags)
 158 {
 159         dump_stack();
 160         pr_err("========================================"
 161                 "========================================\n");
 162         spin_unlock_irqrestore(&report_lock, *flags);
 163         current->in_ubsan--;
 164 }
 165
 166 static void handle_overflow(struct overflow_data *data, unsigned long lhs,
 167                         unsigned long rhs, char op)
 168 {
 169
 170         struct type_descriptor *type = data->type;
 171         unsigned long flags;
 172         char lhs_val_str[VALUE_LENGTH];
 173         char rhs_val_str[VALUE_LENGTH];
 174
 175         if (suppress_report(&data->location))
 176                 return;
 177
 178         ubsan_prologue(&data->location, &flags);
 179
 180         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
 181         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
 182         pr_err("%s integer overflow:\n",
 183                 type_is_signed(type) ? "signed" : "unsigned");
 184         pr_err("%s %c %s cannot be represented in type %s\n",
 185                 lhs_val_str,
 186                 op,
 187                 rhs_val_str,
 188                 type->type_name);
 189
 190         ubsan_epilogue(&flags);
 191 }
 192
 193 void __ubsan_handle_add_overflow(struct overflow_data *data,
 194                                 unsigned long lhs,
 195                                 unsigned long rhs)
 196 {
 197
 198         handle_overflow(data, lhs, rhs, '+');
 199 }
 200 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
 201
 202 void __ubsan_handle_sub_overflow(struct overflow_data *data,
 203                                 unsigned long lhs,
 204                                 unsigned long rhs)
 205 {
 206         handle_overflow(data, lhs, rhs, '-');
 207 }
 208 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
 209
 210 void __ubsan_handle_mul_overflow(struct overflow_data *data,
 211                                 unsigned long lhs,
 212                                 unsigned long 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                                 unsigned long 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                                 unsigned long lhs,
 241                                 unsigned long rhs)
 242 {
 243         unsigned long flags;
 244         char rhs_val_str[VALUE_LENGTH];
 245
 246         if (suppress_report(&data->location))
 247                 return;
 248
 249         ubsan_prologue(&data->location, &flags);
 250
 251         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 252
 253         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 254                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 255                         rhs_val_str, data->type->type_name);
 256         else
 257                 pr_err("division by zero\n");
 258
 259         ubsan_epilogue(&flags);
 260 }
 261 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 262
 263 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 264 {
 265         unsigned long flags;
 266
 267         if (suppress_report(data->location))
 268                 return;
 269
 270         ubsan_prologue(data->location, &flags);
 271
 272         pr_err("%s null pointer of type %s\n",
 273                 type_check_kinds[data->type_check_kind],
 274                 data->type->type_name);
 275
 276         ubsan_epilogue(&flags);
 277 }
 278
 279 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 280                                 unsigned long ptr)
 281 {
 282         unsigned long flags;
 283
 284         if (suppress_report(data->location))
 285                 return;
 286
 287         ubsan_prologue(data->location, &flags);
 288
 289         pr_err("%s misaligned address %p for type %s\n",
 290                 type_check_kinds[data->type_check_kind],
 291                 (void *)ptr, data->type->type_name);
 292         pr_err("which requires %ld byte alignment\n", data->alignment);
 293
 294         ubsan_epilogue(&flags);
 295 }
 296
 297 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 298                                         unsigned long ptr)
 299 {
 300         unsigned long flags;
 301
 302         if (suppress_report(data->location))
 303                 return;
 304
 305         ubsan_prologue(data->location, &flags);
 306         pr_err("%s address %p with insufficient space\n",
 307                 type_check_kinds[data->type_check_kind],
 308                 (void *) ptr);
 309         pr_err("for an object of type %s\n", data->type->type_name);
 310         ubsan_epilogue(&flags);
 311 }
 312
 313 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 314                                 unsigned long ptr)
 315 {
 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
 325 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 326                                 unsigned long ptr)
 327 {
 328         struct type_mismatch_data_common common_data = {
 329                 .location = &data->location,
 330                 .type = data->type,
 331                 .alignment = data->alignment,
 332                 .type_check_kind = data->type_check_kind
 333         };
 334
 335         ubsan_type_mismatch_common(&common_data, ptr);
 336 }
 337 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 338
 339 void __ubsan_handle_type_mismatch_v1(struct type_mismatch_data_v1 *data,
 340                                 unsigned long ptr)
 341 {
 342
 343         struct type_mismatch_data_common common_data = {
 344                 .location = &data->location,
 345                 .type = data->type,
 346                 .alignment = 1UL << data->log_alignment,
 347                 .type_check_kind = data->type_check_kind
 348         };
 349
 350         ubsan_type_mismatch_common(&common_data, ptr);
 351 }
 352 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 353
 354 void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
 355                                         unsigned long bound)
 356 {
 357         unsigned long flags;
 358         char bound_str[VALUE_LENGTH];
 359
 360         if (suppress_report(&data->location))
 361                 return;
 362
 363         ubsan_prologue(&data->location, &flags);
 364
 365         val_to_string(bound_str, sizeof(bound_str), data->type, bound);
 366         pr_err("variable length array bound value %s <= 0\n", bound_str);
 367
 368         ubsan_epilogue(&flags);
 369 }
 370 EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
 371
 372 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
 373                                 unsigned long index)
 374 {
 375         unsigned long flags;
 376         char index_str[VALUE_LENGTH];
 377
 378         if (suppress_report(&data->location))
 379                 return;
 380
 381         ubsan_prologue(&data->location, &flags);
 382
 383         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 384         pr_err("index %s is out of range for type %s\n", index_str,
 385                 data->array_type->type_name);
 386         ubsan_epilogue(&flags);
 387 }
 388 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 389
 390 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
 391                                         unsigned long lhs, unsigned long rhs)
 392 {
 393         unsigned long flags;
 394         struct type_descriptor *rhs_type = data->rhs_type;
 395         struct type_descriptor *lhs_type = data->lhs_type;
 396         char rhs_str[VALUE_LENGTH];
 397         char lhs_str[VALUE_LENGTH];
 398
 399         if (suppress_report(&data->location))
 400                 return;
 401
 402         ubsan_prologue(&data->location, &flags);
 403
 404         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 405         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 406
 407         if (val_is_negative(rhs_type, rhs))
 408                 pr_err("shift exponent %s is negative\n", rhs_str);
 409
 410         else if (get_unsigned_val(rhs_type, rhs) >=
 411                 type_bit_width(lhs_type))
 412                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 413                         rhs_str,
 414                         type_bit_width(lhs_type),
 415                         lhs_type->type_name);
 416         else if (val_is_negative(lhs_type, lhs))
 417                 pr_err("left shift of negative value %s\n",
 418                         lhs_str);
 419         else
 420                 pr_err("left shift of %s by %s places cannot be"
 421                         " represented in type %s\n",
 422                         lhs_str, rhs_str,
 423                         lhs_type->type_name);
 424
 425         ubsan_epilogue(&flags);
 426 }
 427 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 428
 429
 430 void __noreturn
 431 __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
 432 {
 433         unsigned long flags;
 434
 435         ubsan_prologue(&data->location, &flags);
 436         pr_err("calling __builtin_unreachable()\n");
 437         ubsan_epilogue(&flags);
 438         panic("can't return from __builtin_unreachable()");
 439 }
 440 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 441
 442 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
 443                                 unsigned long val)
 444 {
 445         unsigned long flags;
 446         char val_str[VALUE_LENGTH];
 447
 448         if (suppress_report(&data->location))
 449                 return;
 450
 451         ubsan_prologue(&data->location, &flags);
 452
 453         val_to_string(val_str, sizeof(val_str), data->type, val);
 454
 455         pr_err("load of value %s is not a valid value for type %s\n",
 456                 val_str, data->type->type_name);
 457
 458         ubsan_epilogue(&flags);
 459 }
 460 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);