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 bool location_is_valid(struct source_location *loc)
 145 {
 146         return loc->file_name != NULL;
 147 }
 148
 149 static DEFINE_SPINLOCK(report_lock);
 150
 151 static void ubsan_prologue(struct source_location *location,
 152                         unsigned long *flags)
 153 {
 154         current->in_ubsan++;
 155         spin_lock_irqsave(&report_lock, *flags);
 156
 157         pr_err("========================================"
 158                 "========================================\n");
 159         print_source_location("UBSAN: Undefined behaviour in", location);
 160 }
 161
 162 static void ubsan_epilogue(unsigned long *flags)
 163 {
 164         dump_stack();
 165         pr_err("========================================"
 166                 "========================================\n");
 167         spin_unlock_irqrestore(&report_lock, *flags);
 168         current->in_ubsan--;
 169 }
 170
 171 static void handle_overflow(struct overflow_data *data, unsigned long lhs,
 172                         unsigned long rhs, char op)
 173 {
 174
 175         struct type_descriptor *type = data->type;
 176         unsigned long flags;
 177         char lhs_val_str[VALUE_LENGTH];
 178         char rhs_val_str[VALUE_LENGTH];
 179
 180         if (suppress_report(&data->location))
 181                 return;
 182
 183         ubsan_prologue(&data->location, &flags);
 184
 185         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
 186         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
 187         pr_err("%s integer overflow:\n",
 188                 type_is_signed(type) ? "signed" : "unsigned");
 189         pr_err("%s %c %s cannot be represented in type %s\n",
 190                 lhs_val_str,
 191                 op,
 192                 rhs_val_str,
 193                 type->type_name);
 194
 195         ubsan_epilogue(&flags);
 196 }
 197
 198 void __ubsan_handle_add_overflow(struct overflow_data *data,
 199                                 unsigned long lhs,
 200                                 unsigned long rhs)
 201 {
 202
 203         handle_overflow(data, lhs, rhs, '+');
 204 }
 205 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
 206
 207 void __ubsan_handle_sub_overflow(struct overflow_data *data,
 208                                 unsigned long lhs,
 209                                 unsigned long rhs)
 210 {
 211         handle_overflow(data, lhs, rhs, '-');
 212 }
 213 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
 214
 215 void __ubsan_handle_mul_overflow(struct overflow_data *data,
 216                                 unsigned long lhs,
 217                                 unsigned long rhs)
 218 {
 219         handle_overflow(data, lhs, rhs, '*');
 220 }
 221 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
 222
 223 void __ubsan_handle_negate_overflow(struct overflow_data *data,
 224                                 unsigned long old_val)
 225 {
 226         unsigned long flags;
 227         char old_val_str[VALUE_LENGTH];
 228
 229         if (suppress_report(&data->location))
 230                 return;
 231
 232         ubsan_prologue(&data->location, &flags);
 233
 234         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
 235
 236         pr_err("negation of %s cannot be represented in type %s:\n",
 237                 old_val_str, data->type->type_name);
 238
 239         ubsan_epilogue(&flags);
 240 }
 241 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
 242
 243
 244 void __ubsan_handle_divrem_overflow(struct overflow_data *data,
 245                                 unsigned long lhs,
 246                                 unsigned long rhs)
 247 {
 248         unsigned long flags;
 249         char rhs_val_str[VALUE_LENGTH];
 250
 251         if (suppress_report(&data->location))
 252                 return;
 253
 254         ubsan_prologue(&data->location, &flags);
 255
 256         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 257
 258         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 259                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 260                         rhs_val_str, data->type->type_name);
 261         else
 262                 pr_err("division by zero\n");
 263
 264         ubsan_epilogue(&flags);
 265 }
 266 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 267
 268 static void handle_null_ptr_deref(struct type_mismatch_data *data)
 269 {
 270         unsigned long flags;
 271
 272         if (suppress_report(&data->location))
 273                 return;
 274
 275         ubsan_prologue(&data->location, &flags);
 276
 277         pr_err("%s null pointer of type %s\n",
 278                 type_check_kinds[data->type_check_kind],
 279                 data->type->type_name);
 280
 281         ubsan_epilogue(&flags);
 282 }
 283
 284 static void handle_missaligned_access(struct type_mismatch_data *data,
 285                                 unsigned long ptr)
 286 {
 287         unsigned long flags;
 288
 289         if (suppress_report(&data->location))
 290                 return;
 291
 292         ubsan_prologue(&data->location, &flags);
 293
 294         pr_err("%s misaligned address %p for type %s\n",
 295                 type_check_kinds[data->type_check_kind],
 296                 (void *)ptr, data->type->type_name);
 297         pr_err("which requires %ld byte alignment\n", data->alignment);
 298
 299         ubsan_epilogue(&flags);
 300 }
 301
 302 static void handle_object_size_mismatch(struct type_mismatch_data *data,
 303                                         unsigned long ptr)
 304 {
 305         unsigned long flags;
 306
 307         if (suppress_report(&data->location))
 308                 return;
 309
 310         ubsan_prologue(&data->location, &flags);
 311         pr_err("%s address %p with insufficient space\n",
 312                 type_check_kinds[data->type_check_kind],
 313                 (void *) ptr);
 314         pr_err("for an object of type %s\n", data->type->type_name);
 315         ubsan_epilogue(&flags);
 316 }
 317
 318 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 319                                 unsigned long ptr)
 320 {
 321
 322         if (!ptr)
 323                 handle_null_ptr_deref(data);
 324         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 325                 handle_missaligned_access(data, ptr);
 326         else
 327                 handle_object_size_mismatch(data, ptr);
 328 }
 329 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 330
 331 void __ubsan_handle_nonnull_return(struct nonnull_return_data *data)
 332 {
 333         unsigned long flags;
 334
 335         if (suppress_report(&data->location))
 336                 return;
 337
 338         ubsan_prologue(&data->location, &flags);
 339
 340         pr_err("null pointer returned from function declared to never return null\n");
 341
 342         if (location_is_valid(&data->attr_location))
 343                 print_source_location("returns_nonnull attribute specified in",
 344                                 &data->attr_location);
 345
 346         ubsan_epilogue(&flags);
 347 }
 348 EXPORT_SYMBOL(__ubsan_handle_nonnull_return);
 349
 350 void __ubsan_handle_vla_bound_not_positive(struct vla_bound_data *data,
 351                                         unsigned long bound)
 352 {
 353         unsigned long flags;
 354         char bound_str[VALUE_LENGTH];
 355
 356         if (suppress_report(&data->location))
 357                 return;
 358
 359         ubsan_prologue(&data->location, &flags);
 360
 361         val_to_string(bound_str, sizeof(bound_str), data->type, bound);
 362         pr_err("variable length array bound value %s <= 0\n", bound_str);
 363
 364         ubsan_epilogue(&flags);
 365 }
 366 EXPORT_SYMBOL(__ubsan_handle_vla_bound_not_positive);
 367
 368 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data,
 369                                 unsigned long index)
 370 {
 371         unsigned long flags;
 372         char index_str[VALUE_LENGTH];
 373
 374         if (suppress_report(&data->location))
 375                 return;
 376
 377         ubsan_prologue(&data->location, &flags);
 378
 379         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 380         pr_err("index %s is out of range for type %s\n", index_str,
 381                 data->array_type->type_name);
 382         ubsan_epilogue(&flags);
 383 }
 384 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 385
 386 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
 387                                         unsigned long lhs, unsigned long rhs)
 388 {
 389         unsigned long flags;
 390         struct type_descriptor *rhs_type = data->rhs_type;
 391         struct type_descriptor *lhs_type = data->lhs_type;
 392         char rhs_str[VALUE_LENGTH];
 393         char lhs_str[VALUE_LENGTH];
 394
 395         if (suppress_report(&data->location))
 396                 return;
 397
 398         ubsan_prologue(&data->location, &flags);
 399
 400         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 401         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 402
 403         if (val_is_negative(rhs_type, rhs))
 404                 pr_err("shift exponent %s is negative\n", rhs_str);
 405
 406         else if (get_unsigned_val(rhs_type, rhs) >=
 407                 type_bit_width(lhs_type))
 408                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 409                         rhs_str,
 410                         type_bit_width(lhs_type),
 411                         lhs_type->type_name);
 412         else if (val_is_negative(lhs_type, lhs))
 413                 pr_err("left shift of negative value %s\n",
 414                         lhs_str);
 415         else
 416                 pr_err("left shift of %s by %s places cannot be"
 417                         " represented in type %s\n",
 418                         lhs_str, rhs_str,
 419                         lhs_type->type_name);
 420
 421         ubsan_epilogue(&flags);
 422 }
 423 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 424
 425
 426 void __noreturn
 427 __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
 428 {
 429         unsigned long flags;
 430
 431         ubsan_prologue(&data->location, &flags);
 432         pr_err("calling __builtin_unreachable()\n");
 433         ubsan_epilogue(&flags);
 434         panic("can't return from __builtin_unreachable()");
 435 }
 436 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 437
 438 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
 439                                 unsigned long val)
 440 {
 441         unsigned long flags;
 442         char val_str[VALUE_LENGTH];
 443
 444         if (suppress_report(&data->location))
 445                 return;
 446
 447         ubsan_prologue(&data->location, &flags);
 448
 449         val_to_string(val_str, sizeof(val_str), data->type, val);
 450
 451         pr_err("load of value %s is not a valid value for type %s\n",
 452                 val_str, data->type->type_name);
 453
 454         ubsan_epilogue(&flags);
 455 }
 456 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);