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1// SPDX-License-Identifier: GPL-2.0+2/*3 * Originally from efivars.c4 *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 25MODULE_IMPORT_NS(EFIVAR);26 27static bool28validate_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 end54 * of the buffer or we reached the end of the buffer without55 * finding a device path end node.56 */57 return false;58}59 60static bool61validate_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 71static bool72validate_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 be99 * found by hand100 */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 filepath109 * length and the original header are greater than the length of the110 * variable, it's malformed111 */112 if ((desclength + filepathlength + 6) > len)113 return false;114 115 /*116 * And, finally, check the filepath117 */118 return validate_device_path(var_name, match, buffer + desclength + 6,119 filepathlength);120}121 122static bool123validate_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 133static bool134validate_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 150struct 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 the159 * 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 the162 * validation routine. If not, it is assumed valid, but still used for163 * whitelisting.164 *165 * Note that it's sorted by {vendor,name}, but globbed names must come after166 * any other name with the same prefix.167 */168static 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 "*". A193 * 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_name196 * that @var_name matches, regardless of the return value.197 * @return: whether @var_name fully matches @match_name.198 */199static bool200variable_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 in219 * @var_name.220 */221 if (*match < len && c == var_name[*match])222 continue;223 return false;224 }225 }226}227 228bool229efivar_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 263bool264efivar_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 list273 */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 291static 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 the315 * terminating NULL character, or variable_name_size if no NULL316 * character is found among the first variable_name_size bytes.317 */318static 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-terminated326 * string, so make absolutely sure that variable_name_size is327 * 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 and340 * disable the sysfs workqueue since the firmware is buggy.341 */342static 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 variables362 * @func: callback function to invoke for every variable363 * @data: function-specific data to pass to @func364 * @head: initialised head of variable list365 *366 * Get every EFI variable from the firmware and invoke @func. @func367 * 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 */371int 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 sizes393 * above a certain threshold, the lowest seen in the wild394 * 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 the411 * same variable name on multiple calls to412 * get_next_variable(). Terminate the loop413 * immediately as there is no guarantee that414 * 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();449free:450 kfree(variable_name);451 452 return err;453}454 455/**456 * efivar_entry_add - add entry to variable list457 * @entry: entry to add to list458 * @head: list head459 *460 * Returns 0 on success, or a kernel error code on failure.461 */462int 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 list477 * @entry: entry to add to list478 * @head: list head479 */480void __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 list487 * @entry: entry to remove from list488 *489 * Returns 0 on success, or a kernel error code on failure.490 */491void 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 list498 * @entry: entry to remove499 *500 * Remove @entry from the variable list and release the list lock.501 *502 * NOTE: slightly weird locking semantics here - we expect to be503 * called with the efivars lock already held, and we release it before504 * returning. This is because this function is usually called after505 * set_variable() while the lock is still held.506 */507static 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 list515 * @entry: entry containing variable to delete516 *517 * Delete the variable from the firmware and remove @entry from the518 * variable list. It is the caller's responsibility to free @entry519 * 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 */524int 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 variable547 * @entry: entry for this variable548 * @size: location to store the variable's size549 */550int 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 variable574 * @attributes: variable attributes575 * @size: size of @data buffer576 * @data: buffer to store variable data577 *578 * The caller MUST call efivar_entry_iter_begin() and579 * efivar_entry_iter_end() before and after the invocation of this580 * function, respectively.581 */582int __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 variable597 * @attributes: variable attributes598 * @size: size of @data buffer599 * @data: buffer to store variable data600 */601int 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 get618 * @attributes: attributes of variable to be written619 * @size: size of data buffer620 * @data: buffer containing data to write621 * @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 is626 * 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 a631 * converted EFI status code if either of set_variable() or632 * 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 */637int 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 conditional652 * set_variable call, and removal of the variable from the efivars653 * 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 (which670 * could either be an append or an overwrite), or the variable to be671 * deleted. Perform a GetVariable() so we can tell what actually672 * 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 else682 efivar_unlock();683 684 if (status && status != EFI_BUFFER_TOO_SMALL)685 return efi_status_to_err(status);686 687 return 0;688 689out:690 efivar_unlock();691 return err;692 693}694 695/**696 * efivar_entry_iter - iterate over variable list697 * @func: callback function698 * @head: head of variable list699 * @data: function-specific data to pass to callback700 *701 * Iterate over the list of EFI variables and call @func with every702 * entry on the list. It is safe for @func to remove entries in the703 * 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 loop707 * - @func is called from atomic context708 */709int 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}728