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