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 void __ubsan_handle_divrem_overflow(void *_data, void *lhs, void *rhs)
 167 {
 168         struct overflow_data *data = _data;
 169         char rhs_val_str[VALUE_LENGTH];
 170
 171         if (suppress_report(&data->location))
 172                 return;
 173
 174         ubsan_prologue(&data->location, "division-overflow");
 175
 176         val_to_string(rhs_val_str, sizeof(rhs_val_str), data->type, rhs);
 177
 178         if (type_is_signed(data->type) && get_signed_val(data->type, rhs) == -1)
 179                 pr_err("division of %s by -1 cannot be represented in type %s\n",
 180                         rhs_val_str, data->type->type_name);
 181         else
 182                 pr_err("division by zero\n");
 183
 184         ubsan_epilogue();
 185 }
 186 EXPORT_SYMBOL(__ubsan_handle_divrem_overflow);
 187
 188 static void handle_null_ptr_deref(struct type_mismatch_data_common *data)
 189 {
 190         if (suppress_report(data->location))
 191                 return;
 192
 193         ubsan_prologue(data->location, "null-ptr-deref");
 194
 195         pr_err("%s null pointer of type %s\n",
 196                 type_check_kinds[data->type_check_kind],
 197                 data->type->type_name);
 198
 199         ubsan_epilogue();
 200 }
 201
 202 static void handle_misaligned_access(struct type_mismatch_data_common *data,
 203                                 unsigned long ptr)
 204 {
 205         if (suppress_report(data->location))
 206                 return;
 207
 208         ubsan_prologue(data->location, "misaligned-access");
 209
 210         pr_err("%s misaligned address %p for type %s\n",
 211                 type_check_kinds[data->type_check_kind],
 212                 (void *)ptr, data->type->type_name);
 213         pr_err("which requires %ld byte alignment\n", data->alignment);
 214
 215         ubsan_epilogue();
 216 }
 217
 218 static void handle_object_size_mismatch(struct type_mismatch_data_common *data,
 219                                         unsigned long ptr)
 220 {
 221         if (suppress_report(data->location))
 222                 return;
 223
 224         ubsan_prologue(data->location, "object-size-mismatch");
 225         pr_err("%s address %p with insufficient space\n",
 226                 type_check_kinds[data->type_check_kind],
 227                 (void *) ptr);
 228         pr_err("for an object of type %s\n", data->type->type_name);
 229         ubsan_epilogue();
 230 }
 231
 232 static void ubsan_type_mismatch_common(struct type_mismatch_data_common *data,
 233                                 unsigned long ptr)
 234 {
 235         unsigned long flags = user_access_save();
 236
 237         if (!ptr)
 238                 handle_null_ptr_deref(data);
 239         else if (data->alignment && !IS_ALIGNED(ptr, data->alignment))
 240                 handle_misaligned_access(data, ptr);
 241         else
 242                 handle_object_size_mismatch(data, ptr);
 243
 244         user_access_restore(flags);
 245 }
 246
 247 void __ubsan_handle_type_mismatch(struct type_mismatch_data *data,
 248                                 void *ptr)
 249 {
 250         struct type_mismatch_data_common common_data = {
 251                 .location = &data->location,
 252                 .type = data->type,
 253                 .alignment = data->alignment,
 254                 .type_check_kind = data->type_check_kind
 255         };
 256
 257         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 258 }
 259 EXPORT_SYMBOL(__ubsan_handle_type_mismatch);
 260
 261 void __ubsan_handle_type_mismatch_v1(void *_data, void *ptr)
 262 {
 263         struct type_mismatch_data_v1 *data = _data;
 264         struct type_mismatch_data_common common_data = {
 265                 .location = &data->location,
 266                 .type = data->type,
 267                 .alignment = 1UL << data->log_alignment,
 268                 .type_check_kind = data->type_check_kind
 269         };
 270
 271         ubsan_type_mismatch_common(&common_data, (unsigned long)ptr);
 272 }
 273 EXPORT_SYMBOL(__ubsan_handle_type_mismatch_v1);
 274
 275 void __ubsan_handle_out_of_bounds(void *_data, void *index)
 276 {
 277         struct out_of_bounds_data *data = _data;
 278         char index_str[VALUE_LENGTH];
 279
 280         if (suppress_report(&data->location))
 281                 return;
 282
 283         ubsan_prologue(&data->location, "array-index-out-of-bounds");
 284
 285         val_to_string(index_str, sizeof(index_str), data->index_type, index);
 286         pr_err("index %s is out of range for type %s\n", index_str,
 287                 data->array_type->type_name);
 288         ubsan_epilogue();
 289 }
 290 EXPORT_SYMBOL(__ubsan_handle_out_of_bounds);
 291
 292 void __ubsan_handle_shift_out_of_bounds(void *_data, void *lhs, void *rhs)
 293 {
 294         struct shift_out_of_bounds_data *data = _data;
 295         struct type_descriptor *rhs_type = data->rhs_type;
 296         struct type_descriptor *lhs_type = data->lhs_type;
 297         char rhs_str[VALUE_LENGTH];
 298         char lhs_str[VALUE_LENGTH];
 299         unsigned long ua_flags = user_access_save();
 300
 301         if (suppress_report(&data->location))
 302                 goto out;
 303
 304         ubsan_prologue(&data->location, "shift-out-of-bounds");
 305
 306         val_to_string(rhs_str, sizeof(rhs_str), rhs_type, rhs);
 307         val_to_string(lhs_str, sizeof(lhs_str), lhs_type, lhs);
 308
 309         if (val_is_negative(rhs_type, rhs))
 310                 pr_err("shift exponent %s is negative\n", rhs_str);
 311
 312         else if (get_unsigned_val(rhs_type, rhs) >=
 313                 type_bit_width(lhs_type))
 314                 pr_err("shift exponent %s is too large for %u-bit type %s\n",
 315                         rhs_str,
 316                         type_bit_width(lhs_type),
 317                         lhs_type->type_name);
 318         else if (val_is_negative(lhs_type, lhs))
 319                 pr_err("left shift of negative value %s\n",
 320                         lhs_str);
 321         else
 322                 pr_err("left shift of %s by %s places cannot be"
 323                         " represented in type %s\n",
 324                         lhs_str, rhs_str,
 325                         lhs_type->type_name);
 326
 327         ubsan_epilogue();
 328 out:
 329         user_access_restore(ua_flags);
 330 }
 331 EXPORT_SYMBOL(__ubsan_handle_shift_out_of_bounds);
 332
 333
 334 void __ubsan_handle_builtin_unreachable(void *_data)
 335 {
 336         struct unreachable_data *data = _data;
 337         ubsan_prologue(&data->location, "unreachable");
 338         pr_err("calling __builtin_unreachable()\n");
 339         ubsan_epilogue();
 340         panic("can't return from __builtin_unreachable()");
 341 }
 342 EXPORT_SYMBOL(__ubsan_handle_builtin_unreachable);
 343
 344 void __ubsan_handle_load_invalid_value(void *_data, void *val)
 345 {
 346         struct invalid_value_data *data = _data;
 347         char val_str[VALUE_LENGTH];
 348
 349         if (suppress_report(&data->location))
 350                 return;
 351
 352         ubsan_prologue(&data->location, "invalid-load");
 353
 354         val_to_string(val_str, sizeof(val_str), data->type, val);
 355
 356         pr_err("load of value %s is not a valid value for type %s\n",
 357                 val_str, data->type->type_name);
 358
 359         ubsan_epilogue();
 360 }
 361 EXPORT_SYMBOL(__ubsan_handle_load_invalid_value);
 362
 363 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
 364                                          unsigned long align,
 365                                          unsigned long offset);
 366 void __ubsan_handle_alignment_assumption(void *_data, unsigned long ptr,
 367                                          unsigned long align,
 368                                          unsigned long offset)
 369 {
 370         struct alignment_assumption_data *data = _data;
 371         unsigned long real_ptr;
 372
 373         if (suppress_report(&data->location))
 374                 return;
 375
 376         ubsan_prologue(&data->location, "alignment-assumption");
 377
 378         if (offset)
 379                 pr_err("assumption of %lu byte alignment (with offset of %lu byte) for pointer of type %s failed",
 380                        align, offset, data->type->type_name);
 381         else
 382                 pr_err("assumption of %lu byte alignment for pointer of type %s failed",
 383                        align, data->type->type_name);
 384
 385         real_ptr = ptr - offset;
 386         pr_err("%saddress is %lu aligned, misalignment offset is %lu bytes",
 387                offset ? "offset " : "", BIT(real_ptr ? __ffs(real_ptr) : 0),
 388                real_ptr & (align - 1));
 389
 390         ubsan_epilogue();
 391 }
 392 EXPORT_SYMBOL(__ubsan_handle_alignment_assumption);