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 static const char * const 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 bool suppress_report(struct source_location *loc)
  49 {
  50         return current->in_ubsan || was_reported(loc);
  51 }
  52
  53 static bool type_is_int(struct type_descriptor *type)
  54 {
  55         return type->type_kind == type_kind_int;
  56 }
  57
  58 static bool type_is_signed(struct type_descriptor *type)
  59 {
  60         WARN_ON(!type_is_int(type));
  61         return  type->type_info & 1;
  62 }
  63
  64 static unsigned type_bit_width(struct type_descriptor *type)
  65 {
  66         return 1 << (type->type_info >> 1);
  67 }
  68
  69 static bool is_inline_int(struct type_descriptor *type)
  70 {
  71         unsigned inline_bits = sizeof(unsigned long)*8;
  72         unsigned bits = type_bit_width(type);
  73
  74         WARN_ON(!type_is_int(type));
  75
  76         return bits <= inline_bits;
  77 }
  78
  79 static s_max get_signed_val(struct type_descriptor *type, void *val)
  80 {
  81         if (is_inline_int(type)) {
  82                 unsigned extra_bits = sizeof(s_max)*8 - type_bit_width(type);
  83                 unsigned long ulong_val = (unsigned long)val;
  84
  85                 return ((s_max)ulong_val) << extra_bits >> extra_bits;
  86         }
  87
  88         if (type_bit_width(type) == 64)
  89                 return *(s64 *)val;
  90
  91         return *(s_max *)val;
  92 }
  93
  94 static bool val_is_negative(struct type_descriptor *type, void *val)
  95 {
  96         return type_is_signed(type) && get_signed_val(type, val) < 0;
  97 }
  98
  99 static u_max get_unsigned_val(struct type_descriptor *type, void *val)
 100 {
 101         if (is_inline_int(type))
 102                 return (unsigned long)val;
 103
 104         if (type_bit_width(type) == 64)
 105                 return *(u64 *)val;
 106
 107         return *(u_max *)val;
 108 }
 109
 110 static void val_to_string(char *str, size_t size, struct type_descriptor *type,
 111                         void *value)
 112 {
 113         if (type_is_int(type)) {
 114                 if (type_bit_width(type) == 128) {
 115 #if defined(CONFIG_ARCH_SUPPORTS_INT128)
 116                         u_max val = get_unsigned_val(type, value);
 117
 118                         scnprintf(str, size, "0x%08x%08x%08x%08x",
 119                                 (u32)(val >> 96),
 120                                 (u32)(val >> 64),
 121                                 (u32)(val >> 32),
 122                                 (u32)(val));
 123 #else
 124                         WARN_ON(1);
 125 #endif
 126                 } else if (type_is_signed(type)) {
 127                         scnprintf(str, size, "%lld",
 128                                 (s64)get_signed_val(type, value));
 129                 } else {
 130                         scnprintf(str, size, "%llu",
 131                                 (u64)get_unsigned_val(type, value));
 132                 }
 133         }
 134 }
 135
 136 static void ubsan_prologue(struct source_location *loc, const char *reason)
 137 {
 138         current->in_ubsan++;
 139
 140         pr_err("========================================"
 141                 "========================================\n");
 142         pr_err("UBSAN: %s in %s:%d:%d\n", reason, loc->file_name,
 143                 loc->line & LINE_MASK, loc->column & COLUMN_MASK);
 144 }
 145
 146 static void ubsan_epilogue(void)
 147 {
 148         dump_stack();
 149         pr_err("========================================"
 150                 "========================================\n");
 151
 152         current->in_ubsan--;
 153
 154         if (panic_on_warn) {
 155                 /*
 156                  * This thread may hit another WARN() in the panic path.
 157                  * Resetting this prevents additional WARN() from panicking the
 158                  * system on this thread.  Other threads are blocked by the
 159                  * panic_mutex in panic().
 160                  */
 161                 panic_on_warn = 0;
 162                 panic("panic_on_warn set ...\n");
 163         }
 164 }
 165
 166 static void handle_overflow(struct overflow_data *data, void *lhs,
 167                         void *rhs, char op)
 168 {
 169
 170         struct type_descriptor *type = data->type;
 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, type_is_signed(type) ?
 178                         "signed-integer-overflow" :
 179                         "unsigned-integer-overflow");
 180
 181         val_to_string(lhs_val_str, sizeof(lhs_val_str), type, lhs);
 182         val_to_string(rhs_val_str, sizeof(rhs_val_str), type, rhs);
 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();
 190 }
 191
 192 void __ubsan_handle_add_overflow(void *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(void *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(void *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(void *_data, void *old_val)
 215 {
 216         struct overflow_data *data = _data;
 217         char old_val_str[VALUE_LENGTH];
 218
 219         if (suppress_report(&data->location))
 220                 return;
 221
 222         ubsan_prologue(&data->location, "negation-overflow");
 223
 224         val_to_string(old_val_str, sizeof(old_val_str), data->type, old_val);
 225
 226         pr_err("negation of %s cannot be represented in type %s:\n",
 227                 old_val_str, data->type->type_name);
 228
 229         ubsan_epilogue();
 230 }
 231 EXPORT_SYMBOL(__ubsan_handle_negate_overflow);
 232
 233
 234 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
 235 {
 236         struct overflow_data *data = _data;
 237         char rhs_val_str[VALUE_LENGTH];
 238
 239         if (suppress_report(&data->location))
 240                 return;
 241
 242         ubsan_prologue(&data->location, "division-overflow");
 243
 244         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 245
 246         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 247                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 248                         rhs_val_str, data->type->type_name);
 249         else
 250                 pr_err("division by zero\n");
 251
 252         ubsan_epilogue();
 253 }
 254 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 255
 256 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 257 {
 258         if (suppress_report(data->location))
 259                 return;
 260
 261         ubsan_prologue(data->location, "null-ptr-deref");
 262
 263         pr_err("%s null pointer of type %s\n",
 264                 type_check_kinds[data->type_check_kind],
 265                 data->type->type_name);
 266
 267         ubsan_epilogue();
 268 }
 269
 270 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 271                                 unsigned long ptr)
 272 {
 273         if (suppress_report(data->location))
 274                 return;
 275
 276         ubsan_prologue(data->location, "misaligned-access");
 277
 278         pr_err("%s misaligned address %p for type %s\n",
 279                 type_check_kinds[data->type_check_kind],
 280                 (void *)ptr, data->type->type_name);
 281         pr_err("which requires %ld byte alignment\n", data->alignment);
 282
 283         ubsan_epilogue();
 284 }
 285
 286 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 287                                         unsigned long ptr)
 288 {
 289         if (suppress_report(data->location))
 290                 return;
 291
 292         ubsan_prologue(data->location, "object-size-mismatch");
 293         pr_err("%s address %p with insufficient space\n",
 294                 type_check_kinds[data->type_check_kind],
 295                 (void *) ptr);
 296         pr_err("for an object of type %s\n", data->type->type_name);
 297         ubsan_epilogue();
 298 }
 299
 300 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 301                                 unsigned long ptr)
 302 {
 303         unsigned long flags = user_access_save();
 304
 305         if (!ptr)
 306                 handle_null_ptr_deref(data);
 307         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 308                 handle_misaligned_access(data, ptr);
 309         else
 310                 handle_object_size_mismatch(data, ptr);
 311
 312         user_access_restore(flags);
 313 }
 314
 315 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 316                                 void *ptr)
 317 {
 318         struct type_mismatch_data_common common_data = {
 319                 .location = &data->location,
 320                 .type = data->type,
 321                 .alignment = data->alignment,
 322                 .type_check_kind = data->type_check_kind
 323         };
 324
 325         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 326 }
 327 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 328
 329 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
 330 {
 331         struct type_mismatch_data_v1 *data = _data;
 332         struct type_mismatch_data_common common_data = {
 333                 .location = &data->location,
 334                 .type = data->type,
 335                 .alignment = 1UL << data->log_alignment,
 336                 .type_check_kind = data->type_check_kind
 337         };
 338
 339         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 340 }
 341 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 342
 343 void __ubsan_handle_out_of_bounds(void *_data, void *index)
 344 {
 345         struct out_of_bounds_data *data = _data;
 346         char index_str[VALUE_LENGTH];
 347
 348         if (suppress_report(&data->location))
 349                 return;
 350
 351         ubsan_prologue(&data->location, "array-index-out-of-bounds");
 352
 353         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 354         pr_err("index %s is out of range for type %s\n", index_str,
 355                 data->array_type->type_name);
 356         ubsan_epilogue();
 357 }
 358 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 359
 360 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
 361 {
 362         struct shift_out_of_bounds_data *data = _data;
 363         struct type_descriptor *rhs_type = data->rhs_type;
 364         struct type_descriptor *lhs_type = data->lhs_type;
 365         char rhs_str[VALUE_LENGTH];
 366         char lhs_str[VALUE_LENGTH];
 367         unsigned long ua_flags = user_access_save();
 368
 369         if (suppress_report(&data->location))
 370                 goto out;
 371
 372         ubsan_prologue(&data->location, "shift-out-of-bounds");
 373
 374         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 375         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 376
 377         if (val_is_negative(rhs_type, rhs))
 378                 pr_err("shift exponent %s is negative\n", rhs_str);
 379
 380         else if (get_unsigned_val(rhs_type, rhs) >=
 381                 type_bit_width(lhs_type))
 382                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 383                         rhs_str,
 384                         type_bit_width(lhs_type),
 385                         lhs_type->type_name);
 386         else if (val_is_negative(lhs_type, lhs))
 387                 pr_err("left shift of negative value %s\n",
 388                         lhs_str);
 389         else
 390                 pr_err("left shift of %s by %s places cannot be"
 391                         " represented in type %s\n",
 392                         lhs_str, rhs_str,
 393                         lhs_type->type_name);
 394
 395         ubsan_epilogue();
 396 out:
 397         user_access_restore(ua_flags);
 398 }
 399 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 400
 401
 402 void __ubsan_handle_builtin_unreachable(void *_data)
 403 {
 404         struct unreachable_data *data = _data;
 405         ubsan_prologue(&data->location, "unreachable");
 406         pr_err("calling __builtin_unreachable()\n");
 407         ubsan_epilogue();
 408         panic("can't return from __builtin_unreachable()");
 409 }
 410 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 411
 412 void __ubsan_handle_load_invalid_value(void *_data, void *val)
 413 {
 414         struct invalid_value_data *data = _data;
 415         char val_str[VALUE_LENGTH];
 416
 417         if (suppress_report(&data->location))
 418                 return;
 419
 420         ubsan_prologue(&data->location, "invalid-load");
 421
 422         val_to_string(val_str, sizeof(val_str), data->type, val);
 423
 424         pr_err("load of value %s is not a valid value for type %s\n",
 425                 val_str, data->type->type_name);
 426
 427         ubsan_epilogue();
 428 }
 429 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);