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 #include <linux/ubsan.h>
  18 #include <kunit/test-bug.h>
  19
  20 #include "ubsan.h"
  21
  22 #ifdef CONFIG_UBSAN_TRAP
  23 /*
  24  * Only include matches for UBSAN checks that are actually compiled in.
  25  * The mappings of struct SanitizerKind (the -fsanitize=xxx args) to
  26  * enum SanitizerHandler (the traps) in Clang is in clang/lib/CodeGen/.
  27  */
  28 const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type)
  29 {
  30         switch (check_type) {
  31 #ifdef CONFIG_UBSAN_BOUNDS
  32         /*
  33          * SanitizerKind::ArrayBounds and SanitizerKind::LocalBounds
  34          * emit SanitizerHandler::OutOfBounds.
  35          */
  36         case ubsan_out_of_bounds:
  37                 return "UBSAN: array index out of bounds";
  38 #endif
  39 #ifdef CONFIG_UBSAN_SHIFT
  40         /*
  41          * SanitizerKind::ShiftBase and SanitizerKind::ShiftExponent
  42          * emit SanitizerHandler::ShiftOutOfBounds.
  43          */
  44         case ubsan_shift_out_of_bounds:
  45                 return "UBSAN: shift out of bounds";
  46 #endif
  47 #ifdef CONFIG_UBSAN_DIV_ZERO
  48         /*
  49          * SanitizerKind::IntegerDivideByZero emits
  50          * SanitizerHandler::DivremOverflow.
  51          */
  52         case ubsan_divrem_overflow:
  53                 return "UBSAN: divide/remainder overflow";
  54 #endif
  55 #ifdef CONFIG_UBSAN_UNREACHABLE
  56         /*
  57          * SanitizerKind::Unreachable emits
  58          * SanitizerHandler::BuiltinUnreachable.
  59          */
  60         case ubsan_builtin_unreachable:
  61                 return "UBSAN: unreachable code";
  62 #endif
  63 #if defined(CONFIG_UBSAN_BOOL) || defined(CONFIG_UBSAN_ENUM)
  64         /*
  65          * SanitizerKind::Bool and SanitizerKind::Enum emit
  66          * SanitizerHandler::LoadInvalidValue.
  67          */
  68         case ubsan_load_invalid_value:
  69                 return "UBSAN: loading invalid value";
  70 #endif
  71 #ifdef CONFIG_UBSAN_ALIGNMENT
  72         /*
  73          * SanitizerKind::Alignment emits SanitizerHandler::TypeMismatch
  74          * or SanitizerHandler::AlignmentAssumption.
  75          */
  76         case ubsan_alignment_assumption:
  77                 return "UBSAN: alignment assumption";
  78         case ubsan_type_mismatch:
  79                 return "UBSAN: type mismatch";
  80 #endif
  81         default:
  82                 return "UBSAN: unrecognized failure code";
  83         }
  84 }
  85
  86 #else
  87 static const char * const type_check_kinds[] = {
  88         "load of",
  89         "store to",
  90         "reference binding to",
  91         "member access within",
  92         "member call on",
  93         "constructor call on",
  94         "downcast of",
  95         "downcast of"
  96 };
  97
  98 #define REPORTED_BIT 31
  99
 100 #if (BITS_PER_LONG == 64) && defined(__BIG_ENDIAN)
 101 #define COLUMN_MASK (~(1U << REPORTED_BIT))
 102 #define LINE_MASK   (~0U)
 103 #else
 104 #define COLUMN_MASK   (~0U)
 105 #define LINE_MASK (~(1U << REPORTED_BIT))
 106 #endif
 107
 108 #define VALUE_LENGTH 40
 109
 110 static bool was_reported(struct source_location *location)
 111 {
 112         return test_and_set_bit(REPORTED_BIT, &location->reported);
 113 }
 114
 115 static bool suppress_report(struct source_location *loc)
 116 {
 117         return current->in_ubsan || was_reported(loc);
 118 }
 119
 120 static bool type_is_int(struct type_descriptor *type)
 121 {
 122         return type->type_kind == type_kind_int;
 123 }
 124
 125 static bool type_is_signed(struct type_descriptor *type)
 126 {
 127         WARN_ON(!type_is_int(type));
 128         return  type->type_info & 1;
 129 }
 130
 131 static unsigned type_bit_width(struct type_descriptor *type)
 132 {
 133         return 1 << (type->type_info >> 1);
 134 }
 135
 136 static bool is_inline_int(struct type_descriptor *type)
 137 {
 138         unsigned inline_bits = sizeof(unsigned long)*8;
 139         unsigned bits = type_bit_width(type);
 140
 141         WARN_ON(!type_is_int(type));
 142
 143         return bits <= inline_bits;
 144 }
 145
 146 static s_max get_signed_val(struct type_descriptor *type, void *val)
 147 {
 148         if (is_inline_int(type)) {
 149                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
 150                 unsigned long ulong_val = (unsigned long)val;
 151
 152                 return ((s_max)ulong_val) << extra_bits >> extra_bits;
 153         }
 154
 155         if (type_bit_width(type) == 64)
 156                 return *(s64 *)val;
 157
 158         return *(s_max *)val;
 159 }
 160
 161 static bool val_is_negative(struct type_descriptor *type, void *val)
 162 {
 163         return type_is_signed(type) && get_signed_val(type, val) < 0;
 164 }
 165
 166 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
 167 {
 168         if (is_inline_int(type))
 169                 return (unsigned long)val;
 170
 171         if (type_bit_width(type) == 64)
 172                 return *(u64 *)val;
 173
 174         return *(u_max *)val;
 175 }
 176
 177 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
 178                         void *value)
 179 {
 180         if (type_is_int(type)) {
 181                 if (type_bit_width(type) == 128) {
 182 #if defined(CONFIG_ARCH_SUPPORTS_INT128)
 183                         u_max val = get_unsigned_val(type, value);
 184
 185                         scnprintf(str, size, "0x%08x%08x%08x%08x",
 186                                 (u32)(val >> 96),
 187                                 (u32)(val >> 64),
 188                                 (u32)(val >> 32),
 189                                 (u32)(val));
 190 #else
 191                         WARN_ON(1);
 192 #endif
 193                 } else if (type_is_signed(type)) {
 194                         scnprintf(str, size, "%lld",
 195                                 (s64)get_signed_val(type, value));
 196                 } else {
 197                         scnprintf(str, size, "%llu",
 198                                 (u64)get_unsigned_val(type, value));
 199                 }
 200         }
 201 }
 202
 203 static void ubsan_prologue(struct source_location *loc, const char *reason)
 204 {
 205         current->in_ubsan++;
 206
 207         pr_err("========================================"
 208                 "========================================\n");
 209         pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
 210                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
 211
 212         kunit_fail_current_test("%s in %s", reason, loc->file_name);
 213 }
 214
 215 static void ubsan_epilogue(void)
 216 {
 217         dump_stack();
 218         pr_err("========================================"
 219                 "========================================\n");
 220
 221         current->in_ubsan--;
 222
 223         check_panic_on_warn("UBSAN");
 224 }
 225
 226 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
 227 {
 228         struct overflow_data *data = _data;
 229         char rhs_val_str[VALUE_LENGTH];
 230
 231         if (suppress_report(&data->location))
 232                 return;
 233
 234         ubsan_prologue(&data->location, "division-overflow");
 235
 236         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 237
 238         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 239                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 240                         rhs_val_str, data->type->type_name);
 241         else
 242                 pr_err("division by zero\n");
 243
 244         ubsan_epilogue();
 245 }
 246 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 247
 248 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 249 {
 250         if (suppress_report(data->location))
 251                 return;
 252
 253         ubsan_prologue(data->location, "null-ptr-deref");
 254
 255         pr_err("%s null pointer of type %s\n",
 256                 type_check_kinds[data->type_check_kind],
 257                 data->type->type_name);
 258
 259         ubsan_epilogue();
 260 }
 261
 262 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 263                                 unsigned long ptr)
 264 {
 265         if (suppress_report(data->location))
 266                 return;
 267
 268         ubsan_prologue(data->location, "misaligned-access");
 269
 270         pr_err("%s misaligned address %p for type %s\n",
 271                 type_check_kinds[data->type_check_kind],
 272                 (void *)ptr, data->type->type_name);
 273         pr_err("which requires %ld byte alignment\n", data->alignment);
 274
 275         ubsan_epilogue();
 276 }
 277
 278 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 279                                         unsigned long ptr)
 280 {
 281         if (suppress_report(data->location))
 282                 return;
 283
 284         ubsan_prologue(data->location, "object-size-mismatch");
 285         pr_err("%s address %p with insufficient space\n",
 286                 type_check_kinds[data->type_check_kind],
 287                 (void *) ptr);
 288         pr_err("for an object of type %s\n", data->type->type_name);
 289         ubsan_epilogue();
 290 }
 291
 292 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 293                                 unsigned long ptr)
 294 {
 295         unsigned long flags = user_access_save();
 296
 297         if (!ptr)
 298                 handle_null_ptr_deref(data);
 299         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 300                 handle_misaligned_access(data, ptr);
 301         else
 302                 handle_object_size_mismatch(data, ptr);
 303
 304         user_access_restore(flags);
 305 }
 306
 307 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 308                                 void *ptr)
 309 {
 310         struct type_mismatch_data_common common_data = {
 311                 .location = &data->location,
 312                 .type = data->type,
 313                 .alignment = data->alignment,
 314                 .type_check_kind = data->type_check_kind
 315         };
 316
 317         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 318 }
 319 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 320
 321 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
 322 {
 323         struct type_mismatch_data_v1 *data = _data;
 324         struct type_mismatch_data_common common_data = {
 325                 .location = &data->location,
 326                 .type = data->type,
 327                 .alignment = 1UL << data->log_alignment,
 328                 .type_check_kind = data->type_check_kind
 329         };
 330
 331         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 332 }
 333 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 334
 335 void __ubsan_handle_out_of_bounds(void *_data, void *index)
 336 {
 337         struct out_of_bounds_data *data = _data;
 338         char index_str[VALUE_LENGTH];
 339
 340         if (suppress_report(&data->location))
 341                 return;
 342
 343         ubsan_prologue(&data->location, "array-index-out-of-bounds");
 344
 345         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 346         pr_err("index %s is out of range for type %s\n", index_str,
 347                 data->array_type->type_name);
 348         ubsan_epilogue();
 349 }
 350 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 351
 352 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
 353 {
 354         struct shift_out_of_bounds_data *data = _data;
 355         struct type_descriptor *rhs_type = data->rhs_type;
 356         struct type_descriptor *lhs_type = data->lhs_type;
 357         char rhs_str[VALUE_LENGTH];
 358         char lhs_str[VALUE_LENGTH];
 359         unsigned long ua_flags = user_access_save();
 360
 361         if (suppress_report(&data->location))
 362                 goto out;
 363
 364         ubsan_prologue(&data->location, "shift-out-of-bounds");
 365
 366         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 367         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 368
 369         if (val_is_negative(rhs_type, rhs))
 370                 pr_err("shift exponent %s is negative\n", rhs_str);
 371
 372         else if (get_unsigned_val(rhs_type, rhs) >=
 373                 type_bit_width(lhs_type))
 374                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 375                         rhs_str,
 376                         type_bit_width(lhs_type),
 377                         lhs_type->type_name);
 378         else if (val_is_negative(lhs_type, lhs))
 379                 pr_err("left shift of negative value %s\n",
 380                         lhs_str);
 381         else
 382                 pr_err("left shift of %s by %s places cannot be"
 383                         " represented in type %s\n",
 384                         lhs_str, rhs_str,
 385                         lhs_type->type_name);
 386
 387         ubsan_epilogue();
 388 out:
 389         user_access_restore(ua_flags);
 390 }
 391 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 392
 393
 394 void __ubsan_handle_builtin_unreachable(void *_data)
 395 {
 396         struct unreachable_data *data = _data;
 397         ubsan_prologue(&data->location, "unreachable");
 398         pr_err("calling __builtin_unreachable()\n");
 399         ubsan_epilogue();
 400         panic("can't return from __builtin_unreachable()");
 401 }
 402 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 403
 404 void __ubsan_handle_load_invalid_value(void *_data, void *val)
 405 {
 406         struct invalid_value_data *data = _data;
 407         char val_str[VALUE_LENGTH];
 408         unsigned long ua_flags = user_access_save();
 409
 410         if (suppress_report(&data->location))
 411                 goto out;
 412
 413         ubsan_prologue(&data->location, "invalid-load");
 414
 415         val_to_string(val_str, sizeof(val_str), data->type, val);
 416
 417         pr_err("load of value %s is not a valid value for type %s\n",
 418                 val_str, data->type->type_name);
 419
 420         ubsan_epilogue();
 421 out:
 422         user_access_restore(ua_flags);
 423 }
 424 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
 425
 426 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
 427                                          unsigned long align,
 428                                          unsigned long offset)
 429 {
 430         struct alignment_assumption_data *data = _data;
 431         unsigned long real_ptr;
 432
 433         if (suppress_report(&data->location))
 434                 return;
 435
 436         ubsan_prologue(&data->location, "alignment-assumption");
 437
 438         if (offset)
 439                 pr_err("assumption of %lu byte alignment (with offset of %lu byte) for pointer of type %s failed",
 440                        align, offset, data->type->type_name);
 441         else
 442                 pr_err("assumption of %lu byte alignment for pointer of type %s failed",
 443                        align, data->type->type_name);
 444
 445         real_ptr = ptr - offset;
 446         pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes",
 447                offset ? "offset " : "", BIT(real_ptr ? __ffs(real_ptr) : 0),
 448                real_ptr & (align - 1));
 449
 450         ubsan_epilogue();
 451 }
 452 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);
 453
 454 #endif /* !CONFIG_UBSAN_TRAP */