lib/ubsan.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * UBSAN error reporting functions
   4  *
   5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
   7  */
   8
   9 #include <linux/bitops.h>
  10 #include <linux/bug.h>
  11 #include <linux/ctype.h>
  12 #include <linux/init.h>
  13 #include <linux/kernel.h>
  14 #include <linux/types.h>
  15 #include <linux/sched.h>
  16 #include <linux/uaccess.h>
  17
  18 #include "ubsan.h"
  19
  20 const char *type_check_kinds[] = {
  21         "load of",
  22         "store to",
  23         "reference binding to",
  24         "member access within",
  25         "member call on",
  26         "constructor call on",
  27         "downcast of",
  28         "downcast of"
  29 };
  30
  31 #define REPORTED_BIT 31
  32
  33 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
  34 #define COLUMN_MASK (~(1U << REPORTED_BIT))
  35 #define LINE_MASK   (~0U)
  36 #else
  37 #define COLUMN_MASK   (~0U)
  38 #define LINE_MASK (~(1U << REPORTED_BIT))
  39 #endif
  40
  41 #define VALUE_LENGTH 40
  42
  43 static bool was_reported(struct source_location *location)
  44 {
  45         return test_and_set_bit(REPORTED_BIT, &location->reported);
  46 }
  47
  48 static void print_source_location(const char *prefix,
  49                                 struct source_location *loc)
  50 {
  51         pr_err("%s %s:%d:%d\n", prefix, loc->file_name,
  52                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
  53 }
  54
  55 static bool suppress_report(struct source_location *loc)
  56 {
  57         return current->in_ubsan || was_reported(loc);
  58 }
  59
  60 static bool type_is_int(struct type_descriptor *type)
  61 {
  62         return type->type_kind == type_kind_int;
  63 }
  64
  65 static bool type_is_signed(struct type_descriptor *type)
  66 {
  67         WARN_ON(!type_is_int(type));
  68         return  type->type_info & 1;
  69 }
  70
  71 static unsigned type_bit_width(struct type_descriptor *type)
  72 {
  73         return 1 << (type->type_info >> 1);
  74 }
  75
  76 static bool is_inline_int(struct type_descriptor *type)
  77 {
  78         unsigned inline_bits = sizeof(unsigned long)*8;
  79         unsigned bits = type_bit_width(type);
  80
  81         WARN_ON(!type_is_int(type));
  82
  83         return bits <= inline_bits;
  84 }
  85
  86 static s_max get_signed_val(struct type_descriptor *type, void *val)
  87 {
  88         if (is_inline_int(type)) {
  89                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
  90                 unsigned long ulong_val = (unsigned long)val;
  91
  92                 return ((s_max)ulong_val) << extra_bits >> extra_bits;
  93         }
  94
  95         if (type_bit_width(type) == 64)
  96                 return *(s64 *)val;
  97
  98         return *(s_max *)val;
  99 }
 100
 101 static bool val_is_negative(struct type_descriptor *type, void *val)
 102 {
 103         return type_is_signed(type) && get_signed_val(type, val) < 0;
 104 }
 105
 106 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
 107 {
 108         if (is_inline_int(type))
 109                 return (unsigned long)val;
 110
 111         if (type_bit_width(type) == 64)
 112                 return *(u64 *)val;
 113
 114         return *(u_max *)val;
 115 }
 116
 117 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
 118                         void *value)
 119 {
 120         if (type_is_int(type)) {
 121                 if (type_bit_width(type) == 128) {
 122 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 123                         u_max val = get_unsigned_val(type, value);
 124
 125                         scnprintf(str, size, "0x%08x%08x%08x%08x",
 126                                 (u32)(val >> 96),
 127                                 (u32)(val >> 64),
 128                                 (u32)(val >> 32),
 129                                 (u32)(val));
 130 #else
 131                         WARN_ON(1);
 132 #endif
 133                 } else if (type_is_signed(type)) {
 134                         scnprintf(str, size, "%lld",
 135                                 (s64)get_signed_val(type, value));
 136                 } else {
 137                         scnprintf(str, size, "%llu",
 138                                 (u64)get_unsigned_val(type, value));
 139                 }
 140         }
 141 }
 142
 143 static DEFINE_SPINLOCK(report_lock);
 144
 145 static void ubsan_prologue(struct source_location *location,
 146                         unsigned long *flags)
 147 {
 148         current->in_ubsan++;
 149         spin_lock_irqsave(&report_lock, *flags);
 150
 151         pr_err("========================================"
 152                 "========================================\n");
 153         print_source_location("UBSAN: Undefined behaviour in", location);
 154 }
 155
 156 static void ubsan_epilogue(unsigned long *flags)
 157 {
 158         dump_stack();
 159         pr_err("========================================"
 160                 "========================================\n");
 161         spin_unlock_irqrestore(&report_lock, *flags);
 162         current->in_ubsan--;
 163 }
 164
 165 static void handle_overflow(struct overflow_data *data, void *lhs,
 166                         void *rhs, char op)
 167 {
 168
 169         struct type_descriptor *type = data->type;
 170         unsigned long flags;
 171         char lhs_val_str[VALUE_LENGTH];
 172         char rhs_val_str[VALUE_LENGTH];
 173
 174         if (suppress_report(&data->location))
 175                 return;
 176
 177         ubsan_prologue(&data->location, &flags);
 178
 179         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
 180         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
 181         pr_err("%s integer overflow:\n",
 182                 type_is_signed(type) ? "signed" : "unsigned");
 183         pr_err("%s %c %s cannot be represented in type %s\n",
 184                 lhs_val_str,
 185                 op,
 186                 rhs_val_str,
 187                 type->type_name);
 188
 189         ubsan_epilogue(&flags);
 190 }
 191
 192 void __ubsan_handle_add_overflow(struct overflow_data *data,
 193                                 void *lhs, void *rhs)
 194 {
 195
 196         handle_overflow(data, lhs, rhs, '+');
 197 }
 198 EXPORT_SYMBOL(__ubsan_handle_add_overflow);
 199
 200 void __ubsan_handle_sub_overflow(struct overflow_data *data,
 201                                 void *lhs, void *rhs)
 202 {
 203         handle_overflow(data, lhs, rhs, '-');
 204 }
 205 EXPORT_SYMBOL(__ubsan_handle_sub_overflow);
 206
 207 void __ubsan_handle_mul_overflow(struct overflow_data *data,
 208                                 void *lhs, void *rhs)
 209 {
 210         handle_overflow(data, lhs, rhs, '*');
 211 }
 212 EXPORT_SYMBOL(__ubsan_handle_mul_overflow);
 213
 214 void __ubsan_handle_negate_overflow(struct overflow_data *data,
 215                                 void *old_val)
 216 {
 217         unsigned long flags;
 218         char old_val_str[VALUE_LENGTH];
 219
 220         if (suppress_report(&data->location))
 221                 return;
 222
 223         ubsan_prologue(&data->location, &flags);
 224
 225         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
 226
 227         pr_err("negation of %s cannot be represented in type %s:\n",
 228                 old_val_str, data->type->type_name);
 229
 230         ubsan_epilogue(&flags);
 231 }
 232 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
 233
 234
 235 void __ubsan_handle_divrem_overflow(struct overflow_data *data,
 236                                 void *lhs, void *rhs)
 237 {
 238         unsigned long flags;
 239         char rhs_val_str[VALUE_LENGTH];
 240
 241         if (suppress_report(&data->location))
 242                 return;
 243
 244         ubsan_prologue(&data->location, &flags);
 245
 246         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 247
 248         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 249                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 250                         rhs_val_str, data->type->type_name);
 251         else
 252                 pr_err("division by zero\n");
 253
 254         ubsan_epilogue(&flags);
 255 }
 256 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 257
 258 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 259 {
 260         unsigned long flags;
 261
 262         if (suppress_report(data->location))
 263                 return;
 264
 265         ubsan_prologue(data->location, &flags);
 266
 267         pr_err("%s null pointer of type %s\n",
 268                 type_check_kinds[data->type_check_kind],
 269                 data->type->type_name);
 270
 271         ubsan_epilogue(&flags);
 272 }
 273
 274 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 275                                 unsigned long ptr)
 276 {
 277         unsigned long flags;
 278
 279         if (suppress_report(data->location))
 280                 return;
 281
 282         ubsan_prologue(data->location, &flags);
 283
 284         pr_err("%s misaligned address %p for type %s\n",
 285                 type_check_kinds[data->type_check_kind],
 286                 (void *)ptr, data->type->type_name);
 287         pr_err("which requires %ld byte alignment\n", data->alignment);
 288
 289         ubsan_epilogue(&flags);
 290 }
 291
 292 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 293                                         unsigned long ptr)
 294 {
 295         unsigned long flags;
 296
 297         if (suppress_report(data->location))
 298                 return;
 299
 300         ubsan_prologue(data->location, &flags);
 301         pr_err("%s address %p with insufficient space\n",
 302                 type_check_kinds[data->type_check_kind],
 303                 (void *) ptr);
 304         pr_err("for an object of type %s\n", data->type->type_name);
 305         ubsan_epilogue(&flags);
 306 }
 307
 308 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 309                                 unsigned long ptr)
 310 {
 311         unsigned long flags = user_access_save();
 312
 313         if (!ptr)
 314                 handle_null_ptr_deref(data);
 315         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 316                 handle_misaligned_access(data, ptr);
 317         else
 318                 handle_object_size_mismatch(data, ptr);
 319
 320         user_access_restore(flags);
 321 }
 322
 323 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 324                                 void *ptr)
 325 {
 326         struct type_mismatch_data_common common_data = {
 327                 .location = &data->location,
 328                 .type = data->type,
 329                 .alignment = data->alignment,
 330                 .type_check_kind = data->type_check_kind
 331         };
 332
 333         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 334 }
 335 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 336
 337 void __ubsan_handle_type_mismatch_v1(struct type_mismatch_data_v1 *data,
 338                                 void *ptr)
 339 {
 340
 341         struct type_mismatch_data_common common_data = {
 342                 .location = &data->location,
 343                 .type = data->type,
 344                 .alignment = 1UL << data->log_alignment,
 345                 .type_check_kind = data->type_check_kind
 346         };
 347
 348         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 349 }
 350 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 351
 352 void __ubsan_handle_out_of_bounds(struct out_of_bounds_data *data, void *index)
 353 {
 354         unsigned long flags;
 355         char index_str[VALUE_LENGTH];
 356
 357         if (suppress_report(&data->location))
 358                 return;
 359
 360         ubsan_prologue(&data->location, &flags);
 361
 362         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 363         pr_err("index %s is out of range for type %s\n", index_str,
 364                 data->array_type->type_name);
 365         ubsan_epilogue(&flags);
 366 }
 367 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 368
 369 void __ubsan_handle_shift_out_of_bounds(struct shift_out_of_bounds_data *data,
 370                                         void *lhs, void *rhs)
 371 {
 372         unsigned long flags;
 373         struct type_descriptor *rhs_type = data->rhs_type;
 374         struct type_descriptor *lhs_type = data->lhs_type;
 375         char rhs_str[VALUE_LENGTH];
 376         char lhs_str[VALUE_LENGTH];
 377         unsigned long ua_flags = user_access_save();
 378
 379         if (suppress_report(&data->location))
 380                 goto out;
 381
 382         ubsan_prologue(&data->location, &flags);
 383
 384         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 385         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 386
 387         if (val_is_negative(rhs_type, rhs))
 388                 pr_err("shift exponent %s is negative\n", rhs_str);
 389
 390         else if (get_unsigned_val(rhs_type, rhs) >=
 391                 type_bit_width(lhs_type))
 392                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 393                         rhs_str,
 394                         type_bit_width(lhs_type),
 395                         lhs_type->type_name);
 396         else if (val_is_negative(lhs_type, lhs))
 397                 pr_err("left shift of negative value %s\n",
 398                         lhs_str);
 399         else
 400                 pr_err("left shift of %s by %s places cannot be"
 401                         " represented in type %s\n",
 402                         lhs_str, rhs_str,
 403                         lhs_type->type_name);
 404
 405         ubsan_epilogue(&flags);
 406 out:
 407         user_access_restore(ua_flags);
 408 }
 409 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 410
 411
 412 void __ubsan_handle_builtin_unreachable(struct unreachable_data *data)
 413 {
 414         unsigned long flags;
 415
 416         ubsan_prologue(&data->location, &flags);
 417         pr_err("calling __builtin_unreachable()\n");
 418         ubsan_epilogue(&flags);
 419         panic("can't return from __builtin_unreachable()");
 420 }
 421 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 422
 423 void __ubsan_handle_load_invalid_value(struct invalid_value_data *data,
 424                                 void *val)
 425 {
 426         unsigned long flags;
 427         char val_str[VALUE_LENGTH];
 428
 429         if (suppress_report(&data->location))
 430                 return;
 431
 432         ubsan_prologue(&data->location, &flags);
 433
 434         val_to_string(val_str, sizeof(val_str), data->type, val);
 435
 436         pr_err("load of value %s is not a valid value for type %s\n",
 437                 val_str, data->type->type_name);
 438
 439         ubsan_epilogue(&flags);
 440 }
 441 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);