fs/efivarfs/vars.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Originally from efivars.c
   4  *
   5  * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
   6  * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
   7  */
   8
   9 #include <linux/capability.h>
  10 #include <linux/types.h>
  11 #include <linux/errno.h>
  12 #include <linux/init.h>
  13 #include <linux/mm.h>
  14 #include <linux/module.h>
  15 #include <linux/string.h>
  16 #include <linux/smp.h>
  17 #include <linux/efi.h>
  18 #include <linux/device.h>
  19 #include <linux/slab.h>
  20 #include <linux/ctype.h>
  21 #include <linux/ucs2_string.h>
  22
  23 #include "internal.h"
  24
  25 MODULE_IMPORT_NS("EFIVAR");
  26
  27 static bool
  28 validate_device_path(efi_char16_t *var_name, int match, u8 *buffer,
  29                      unsigned long len)
  30 {
  31         struct efi_generic_dev_path *node;
  32         int offset = 0;
  33
  34         node = (struct efi_generic_dev_path *)buffer;
  35
  36         if (len < sizeof(*node))
  37                 return false;
  38
  39         while (offset <= len - sizeof(*node) &&
  40                node->length >= sizeof(*node) &&
  41                 node->length <= len - offset) {
  42                 offset += node->length;
  43
  44                 if ((node->type == EFI_DEV_END_PATH ||
  45                      node->type == EFI_DEV_END_PATH2) &&
  46                     node->sub_type == EFI_DEV_END_ENTIRE)
  47                         return true;
  48
  49                 node = (struct efi_generic_dev_path *)(buffer + offset);
  50         }
  51
  52         /*
  53          * If we're here then either node->length pointed past the end
  54          * of the buffer or we reached the end of the buffer without
  55          * finding a device path end node.
  56          */
  57         return false;
  58 }
  59
  60 static bool
  61 validate_boot_order(efi_char16_t *var_name, int match, u8 *buffer,
  62                     unsigned long len)
  63 {
  64         /* An array of 16-bit integers */
  65         if ((len % 2) != 0)
  66                 return false;
  67
  68         return true;
  69 }
  70
  71 static bool
  72 validate_load_option(efi_char16_t *var_name, int match, u8 *buffer,
  73                      unsigned long len)
  74 {
  75         u16 filepathlength;
  76         int i, desclength = 0, namelen;
  77
  78         namelen = ucs2_strnlen(var_name, EFI_VAR_NAME_LEN);
  79
  80         /* Either "Boot" or "Driver" followed by four digits of hex */
  81         for (i = match; i < match+4; i++) {
  82                 if (var_name[i] > 127 ||
  83                     hex_to_bin(var_name[i] & 0xff) < 0)
  84                         return true;
  85         }
  86
  87         /* Reject it if there's 4 digits of hex and then further content */
  88         if (namelen > match + 4)
  89                 return false;
  90
  91         /* A valid entry must be at least 8 bytes */
  92         if (len < 8)
  93                 return false;
  94
  95         filepathlength = buffer[4] | buffer[5] << 8;
  96
  97         /*
  98          * There's no stored length for the description, so it has to be
  99          * found by hand
 100          */
 101         desclength = ucs2_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;
 102
 103         /* Each boot entry must have a descriptor */
 104         if (!desclength)
 105                 return false;
 106
 107         /*
 108          * If the sum of the length of the description, the claimed filepath
 109          * length and the original header are greater than the length of the
 110          * variable, it's malformed
 111          */
 112         if ((desclength + filepathlength + 6) > len)
 113                 return false;
 114
 115         /*
 116          * And, finally, check the filepath
 117          */
 118         return validate_device_path(var_name, match, buffer + desclength + 6,
 119                                     filepathlength);
 120 }
 121
 122 static bool
 123 validate_uint16(efi_char16_t *var_name, int match, u8 *buffer,
 124                 unsigned long len)
 125 {
 126         /* A single 16-bit integer */
 127         if (len != 2)
 128                 return false;
 129
 130         return true;
 131 }
 132
 133 static bool
 134 validate_ascii_string(efi_char16_t *var_name, int match, u8 *buffer,
 135                       unsigned long len)
 136 {
 137         int i;
 138
 139         for (i = 0; i < len; i++) {
 140                 if (buffer[i] > 127)
 141                         return false;
 142
 143                 if (buffer[i] == 0)
 144                         return true;
 145         }
 146
 147         return false;
 148 }
 149
 150 struct variable_validate {
 151         efi_guid_t vendor;
 152         char *name;
 153         bool (*validate)(efi_char16_t *var_name, int match, u8 *data,
 154                          unsigned long len);
 155 };
 156
 157 /*
 158  * This is the list of variables we need to validate, as well as the
 159  * whitelist for what we think is safe not to default to immutable.
 160  *
 161  * If it has a validate() method that's not NULL, it'll go into the
 162  * validation routine.  If not, it is assumed valid, but still used for
 163  * whitelisting.
 164  *
 165  * Note that it's sorted by {vendor,name}, but globbed names must come after
 166  * any other name with the same prefix.
 167  */
 168 static const struct variable_validate variable_validate[] = {
 169         { EFI_GLOBAL_VARIABLE_GUID, "BootNext", validate_uint16 },
 170         { EFI_GLOBAL_VARIABLE_GUID, "BootOrder", validate_boot_order },
 171         { EFI_GLOBAL_VARIABLE_GUID, "Boot*", validate_load_option },
 172         { EFI_GLOBAL_VARIABLE_GUID, "DriverOrder", validate_boot_order },
 173         { EFI_GLOBAL_VARIABLE_GUID, "Driver*", validate_load_option },
 174         { EFI_GLOBAL_VARIABLE_GUID, "ConIn", validate_device_path },
 175         { EFI_GLOBAL_VARIABLE_GUID, "ConInDev", validate_device_path },
 176         { EFI_GLOBAL_VARIABLE_GUID, "ConOut", validate_device_path },
 177         { EFI_GLOBAL_VARIABLE_GUID, "ConOutDev", validate_device_path },
 178         { EFI_GLOBAL_VARIABLE_GUID, "ErrOut", validate_device_path },
 179         { EFI_GLOBAL_VARIABLE_GUID, "ErrOutDev", validate_device_path },
 180         { EFI_GLOBAL_VARIABLE_GUID, "Lang", validate_ascii_string },
 181         { EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
 182         { EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
 183         { EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
 184         { LINUX_EFI_CRASH_GUID, "*", NULL },
 185         { NULL_GUID, "", NULL },
 186 };
 187
 188 /*
 189  * Check if @var_name matches the pattern given in @match_name.
 190  *
 191  * @var_name: an array of @len non-NUL characters.
 192  * @match_name: a NUL-terminated pattern string, optionally ending in "*". A
 193  *              final "*" character matches any trailing characters @var_name,
 194  *              including the case when there are none left in @var_name.
 195  * @match: on output, the number of non-wildcard characters in @match_name
 196  *         that @var_name matches, regardless of the return value.
 197  * @return: whether @var_name fully matches @match_name.
 198  */
 199 static bool
 200 variable_matches(const char *var_name, size_t len, const char *match_name,
 201                  int *match)
 202 {
 203         for (*match = 0; ; (*match)++) {
 204                 char c = match_name[*match];
 205
 206                 switch (c) {
 207                 case '*':
 208                         /* Wildcard in @match_name means we've matched. */
 209                         return true;
 210
 211                 case '\0':
 212                         /* @match_name has ended. Has @var_name too? */
 213                         return (*match == len);
 214
 215                 default:
 216                         /*
 217                          * We've reached a non-wildcard char in @match_name.
 218                          * Continue only if there's an identical character in
 219                          * @var_name.
 220                          */
 221                         if (*match < len && c == var_name[*match])
 222                                 continue;
 223                         return false;
 224                 }
 225         }
 226 }
 227
 228 bool
 229 efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
 230                 unsigned long data_size)
 231 {
 232         int i;
 233         unsigned long utf8_size;
 234         u8 *utf8_name;
 235
 236         utf8_size = ucs2_utf8size(var_name);
 237         utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
 238         if (!utf8_name)
 239                 return false;
 240
 241         ucs2_as_utf8(utf8_name, var_name, utf8_size);
 242         utf8_name[utf8_size] = '\0';
 243
 244         for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
 245                 const char *name = variable_validate[i].name;
 246                 int match = 0;
 247
 248                 if (efi_guidcmp(vendor, variable_validate[i].vendor))
 249                         continue;
 250
 251                 if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
 252                         if (variable_validate[i].validate == NULL)
 253                                 break;
 254                         kfree(utf8_name);
 255                         return variable_validate[i].validate(var_name, match,
 256                                                              data, data_size);
 257                 }
 258         }
 259         kfree(utf8_name);
 260         return true;
 261 }
 262
 263 bool
 264 efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
 265                              size_t len)
 266 {
 267         int i;
 268         bool found = false;
 269         int match = 0;
 270
 271         /*
 272          * Check if our variable is in the validated variables list
 273          */
 274         for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
 275                 if (efi_guidcmp(variable_validate[i].vendor, vendor))
 276                         continue;
 277
 278                 if (variable_matches(var_name, len,
 279                                      variable_validate[i].name, &match)) {
 280                         found = true;
 281                         break;
 282                 }
 283         }
 284
 285         /*
 286          * If it's in our list, it is removable.
 287          */
 288         return found;
 289 }
 290
 291 static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor,
 292                                 struct list_head *head)
 293 {
 294         struct efivar_entry *entry, *n;
 295         unsigned long strsize1, strsize2;
 296         bool found = false;
 297
 298         strsize1 = ucs2_strsize(variable_name, EFI_VAR_NAME_LEN);
 299         list_for_each_entry_safe(entry, n, head, list) {
 300                 strsize2 = ucs2_strsize(entry->var.VariableName, EFI_VAR_NAME_LEN);
 301                 if (strsize1 == strsize2 &&
 302                         !memcmp(variable_name, &(entry->var.VariableName),
 303                                 strsize2) &&
 304                         !efi_guidcmp(entry->var.VendorGuid,
 305                                 *vendor)) {
 306                         found = true;
 307                         break;
 308                 }
 309         }
 310         return found;
 311 }
 312
 313 /*
 314  * Returns the size of variable_name, in bytes, including the
 315  * terminating NULL character, or variable_name_size if no NULL
 316  * character is found among the first variable_name_size bytes.
 317  */
 318 static unsigned long var_name_strnsize(efi_char16_t *variable_name,
 319                                        unsigned long variable_name_size)
 320 {
 321         unsigned long len;
 322         efi_char16_t c;
 323
 324         /*
 325          * The variable name is, by definition, a NULL-terminated
 326          * string, so make absolutely sure that variable_name_size is
 327          * the value we expect it to be. If not, return the real size.
 328          */
 329         for (len = 2; len <= variable_name_size; len += sizeof(c)) {
 330                 c = variable_name[(len / sizeof(c)) - 1];
 331                 if (!c)
 332                         break;
 333         }
 334
 335         return min(len, variable_name_size);
 336 }
 337
 338 /*
 339  * Print a warning when duplicate EFI variables are encountered and
 340  * disable the sysfs workqueue since the firmware is buggy.
 341  */
 342 static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
 343                              unsigned long len16)
 344 {
 345         size_t i, len8 = len16 / sizeof(efi_char16_t);
 346         char *str8;
 347
 348         str8 = kzalloc(len8, GFP_KERNEL);
 349         if (!str8)
 350                 return;
 351
 352         for (i = 0; i < len8; i++)
 353                 str8[i] = str16[i];
 354
 355         printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
 356                str8, vendor_guid);
 357         kfree(str8);
 358 }
 359
 360 /**
 361  * efivar_init - build the initial list of EFI variables
 362  * @func: callback function to invoke for every variable
 363  * @data: function-specific data to pass to @func
 364  * @head: initialised head of variable list
 365  *
 366  * Get every EFI variable from the firmware and invoke @func. @func
 367  * should call efivar_entry_add() to build the list of variables.
 368  *
 369  * Returns 0 on success, or a kernel error code on failure.
 370  */
 371 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *,
 372                             struct list_head *),
 373                 void *data, struct list_head *head)
 374 {
 375         unsigned long variable_name_size = 512;
 376         efi_char16_t *variable_name;
 377         efi_status_t status;
 378         efi_guid_t vendor_guid;
 379         int err = 0;
 380
 381         variable_name = kzalloc(variable_name_size, GFP_KERNEL);
 382         if (!variable_name) {
 383                 printk(KERN_ERR "efivars: Memory allocation failed.\n");
 384                 return -ENOMEM;
 385         }
 386
 387         err = efivar_lock();
 388         if (err)
 389                 goto free;
 390
 391         /*
 392          * A small set of old UEFI implementations reject sizes
 393          * above a certain threshold, the lowest seen in the wild
 394          * is 512.
 395          */
 396
 397         do {
 398                 variable_name_size = 512;
 399                 BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);
 400
 401                 status = efivar_get_next_variable(&variable_name_size,
 402                                                   variable_name,
 403                                                   &vendor_guid);
 404                 switch (status) {
 405                 case EFI_SUCCESS:
 406                         variable_name_size = var_name_strnsize(variable_name,
 407                                                                variable_name_size);
 408
 409                         /*
 410                          * Some firmware implementations return the
 411                          * same variable name on multiple calls to
 412                          * get_next_variable(). Terminate the loop
 413                          * immediately as there is no guarantee that
 414                          * we'll ever see a different variable name,
 415                          * and may end up looping here forever.
 416                          */
 417                         if (variable_is_present(variable_name, &vendor_guid,
 418                                                 head)) {
 419                                 dup_variable_bug(variable_name, &vendor_guid,
 420                                                  variable_name_size);
 421                                 status = EFI_NOT_FOUND;
 422                         } else {
 423                                 err = func(variable_name, vendor_guid,
 424                                            variable_name_size, data, head);
 425                                 if (err)
 426                                         status = EFI_NOT_FOUND;
 427                         }
 428                         break;
 429                 case EFI_UNSUPPORTED:
 430                         err = -EOPNOTSUPP;
 431                         status = EFI_NOT_FOUND;
 432                         break;
 433                 case EFI_NOT_FOUND:
 434                         break;
 435                 case EFI_BUFFER_TOO_SMALL:
 436                         pr_warn("efivars: Variable name size exceeds maximum (%lu > 512)\n",
 437                                 variable_name_size);
 438                         status = EFI_NOT_FOUND;
 439                         break;
 440                 default:
 441                         pr_warn("efivars: get_next_variable: status=%lx\n", status);
 442                         status = EFI_NOT_FOUND;
 443                         break;
 444                 }
 445
 446         } while (status != EFI_NOT_FOUND);
 447
 448         efivar_unlock();
 449 free:
 450         kfree(variable_name);
 451
 452         return err;
 453 }
 454
 455 /**
 456  * efivar_entry_add - add entry to variable list
 457  * @entry: entry to add to list
 458  * @head: list head
 459  *
 460  * Returns 0 on success, or a kernel error code on failure.
 461  */
 462 int efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
 463 {
 464         int err;
 465
 466         err = efivar_lock();
 467         if (err)
 468                 return err;
 469         list_add(&entry->list, head);
 470         efivar_unlock();
 471
 472         return 0;
 473 }
 474
 475 /**
 476  * __efivar_entry_add - add entry to variable list
 477  * @entry: entry to add to list
 478  * @head: list head
 479  */
 480 void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
 481 {
 482         list_add(&entry->list, head);
 483 }
 484
 485 /**
 486  * efivar_entry_remove - remove entry from variable list
 487  * @entry: entry to remove from list
 488  *
 489  * Returns 0 on success, or a kernel error code on failure.
 490  */
 491 void efivar_entry_remove(struct efivar_entry *entry)
 492 {
 493         list_del(&entry->list);
 494 }
 495
 496 /*
 497  * efivar_entry_list_del_unlock - remove entry from variable list
 498  * @entry: entry to remove
 499  *
 500  * Remove @entry from the variable list and release the list lock.
 501  *
 502  * NOTE: slightly weird locking semantics here - we expect to be
 503  * called with the efivars lock already held, and we release it before
 504  * returning. This is because this function is usually called after
 505  * set_variable() while the lock is still held.
 506  */
 507 static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
 508 {
 509         list_del(&entry->list);
 510         efivar_unlock();
 511 }
 512
 513 /**
 514  * efivar_entry_delete - delete variable and remove entry from list
 515  * @entry: entry containing variable to delete
 516  *
 517  * Delete the variable from the firmware and remove @entry from the
 518  * variable list. It is the caller's responsibility to free @entry
 519  * once we return.
 520  *
 521  * Returns 0 on success, -EINTR if we can't grab the semaphore,
 522  * converted EFI status code if set_variable() fails.
 523  */
 524 int efivar_entry_delete(struct efivar_entry *entry)
 525 {
 526         efi_status_t status;
 527         int err;
 528
 529         err = efivar_lock();
 530         if (err)
 531                 return err;
 532
 533         status = efivar_set_variable_locked(entry->var.VariableName,
 534                                             &entry->var.VendorGuid,
 535                                             0, 0, NULL, false);
 536         if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
 537                 efivar_unlock();
 538                 return efi_status_to_err(status);
 539         }
 540
 541         efivar_entry_list_del_unlock(entry);
 542         return 0;
 543 }
 544
 545 /**
 546  * efivar_entry_size - obtain the size of a variable
 547  * @entry: entry for this variable
 548  * @size: location to store the variable's size
 549  */
 550 int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
 551 {
 552         efi_status_t status;
 553         int err;
 554
 555         *size = 0;
 556
 557         err = efivar_lock();
 558         if (err)
 559                 return err;
 560
 561         status = efivar_get_variable(entry->var.VariableName,
 562                                      &entry->var.VendorGuid, NULL, size, NULL);
 563         efivar_unlock();
 564
 565         if (status != EFI_BUFFER_TOO_SMALL)
 566                 return efi_status_to_err(status);
 567
 568         return 0;
 569 }
 570
 571 /**
 572  * __efivar_entry_get - call get_variable()
 573  * @entry: read data for this variable
 574  * @attributes: variable attributes
 575  * @size: size of @data buffer
 576  * @data: buffer to store variable data
 577  *
 578  * The caller MUST call efivar_entry_iter_begin() and
 579  * efivar_entry_iter_end() before and after the invocation of this
 580  * function, respectively.
 581  */
 582 int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 583                        unsigned long *size, void *data)
 584 {
 585         efi_status_t status;
 586
 587         status = efivar_get_variable(entry->var.VariableName,
 588                                      &entry->var.VendorGuid,
 589                                      attributes, size, data);
 590
 591         return efi_status_to_err(status);
 592 }
 593
 594 /**
 595  * efivar_entry_get - call get_variable()
 596  * @entry: read data for this variable
 597  * @attributes: variable attributes
 598  * @size: size of @data buffer
 599  * @data: buffer to store variable data
 600  */
 601 int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
 602                      unsigned long *size, void *data)
 603 {
 604         int err;
 605
 606         err = efivar_lock();
 607         if (err)
 608                 return err;
 609         err = __efivar_entry_get(entry, attributes, size, data);
 610         efivar_unlock();
 611
 612         return 0;
 613 }
 614
 615 /**
 616  * efivar_entry_set_get_size - call set_variable() and get new size (atomic)
 617  * @entry: entry containing variable to set and get
 618  * @attributes: attributes of variable to be written
 619  * @size: size of data buffer
 620  * @data: buffer containing data to write
 621  * @set: did the set_variable() call succeed?
 622  *
 623  * This is a pretty special (complex) function. See efivarfs_file_write().
 624  *
 625  * Atomically call set_variable() for @entry and if the call is
 626  * successful, return the new size of the variable from get_variable()
 627  * in @size. The success of set_variable() is indicated by @set.
 628  *
 629  * Returns 0 on success, -EINVAL if the variable data is invalid,
 630  * -ENOSPC if the firmware does not have enough available space, or a
 631  * converted EFI status code if either of set_variable() or
 632  * get_variable() fail.
 633  *
 634  * If the EFI variable does not exist when calling set_variable()
 635  * (EFI_NOT_FOUND), @entry is removed from the variable list.
 636  */
 637 int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
 638                               unsigned long *size, void *data, bool *set)
 639 {
 640         efi_char16_t *name = entry->var.VariableName;
 641         efi_guid_t *vendor = &entry->var.VendorGuid;
 642         efi_status_t status;
 643         int err;
 644
 645         *set = false;
 646
 647         if (efivar_validate(*vendor, name, data, *size) == false)
 648                 return -EINVAL;
 649
 650         /*
 651          * The lock here protects the get_variable call, the conditional
 652          * set_variable call, and removal of the variable from the efivars
 653          * list (in the case of an authenticated delete).
 654          */
 655         err = efivar_lock();
 656         if (err)
 657                 return err;
 658
 659         status = efivar_set_variable_locked(name, vendor, attributes, *size,
 660                                             data, false);
 661         if (status != EFI_SUCCESS) {
 662                 err = efi_status_to_err(status);
 663                 goto out;
 664         }
 665
 666         *set = true;
 667
 668         /*
 669          * Writing to the variable may have caused a change in size (which
 670          * could either be an append or an overwrite), or the variable to be
 671          * deleted. Perform a GetVariable() so we can tell what actually
 672          * happened.
 673          */
 674         *size = 0;
 675         status = efivar_get_variable(entry->var.VariableName,
 676                                     &entry->var.VendorGuid,
 677                                     NULL, size, NULL);
 678
 679         if (status == EFI_NOT_FOUND)
 680                 efivar_entry_list_del_unlock(entry);
 681         else
 682                 efivar_unlock();
 683
 684         if (status && status != EFI_BUFFER_TOO_SMALL)
 685                 return efi_status_to_err(status);
 686
 687         return 0;
 688
 689 out:
 690         efivar_unlock();
 691         return err;
 692
 693 }
 694
 695 /**
 696  * efivar_entry_iter - iterate over variable list
 697  * @func: callback function
 698  * @head: head of variable list
 699  * @data: function-specific data to pass to callback
 700  *
 701  * Iterate over the list of EFI variables and call @func with every
 702  * entry on the list. It is safe for @func to remove entries in the
 703  * list via efivar_entry_delete() while iterating.
 704  *
 705  * Some notes for the callback function:
 706  *  - a non-zero return value indicates an error and terminates the loop
 707  *  - @func is called from atomic context
 708  */
 709 int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
 710                       struct list_head *head, void *data)
 711 {
 712         struct efivar_entry *entry, *n;
 713         int err = 0;
 714
 715         err = efivar_lock();
 716         if (err)
 717                 return err;
 718
 719         list_for_each_entry_safe(entry, n, head, list) {
 720                 err = func(entry, data);
 721                 if (err)
 722                         break;
 723         }
 724         efivar_unlock();
 725
 726         return err;
 727 }