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
25MODULE_IMPORT_NS("EFIVAR");
26
27static bool
28validate_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
60static bool
61validate_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 bool
72validate_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(s: 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(ch: 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(data: (efi_char16_t *)(buffer + 6), maxlength: 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: buffer + desclength + 6,
119 len: filepathlength);
120}
121
122static bool
123validate_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 bool
134validate_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 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 */
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 "*". 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 */
199static bool
200variable_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
228char *
229efivar_get_utf8name(const efi_char16_t *name16, efi_guid_t *vendor)
230{
231 int len = ucs2_utf8size(src: name16);
232 char *name;
233
234 /* name, plus '-', plus GUID, plus NUL*/
235 name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
236 if (!name)
237 return NULL;
238
239 ucs2_as_utf8(dest: name, src: name16, maxlength: len);
240
241 name[len] = '-';
242
243 efi_guid_to_str(guid: vendor, out: name + len + 1);
244
245 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
246
247 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
248 strreplace(str: name, old: '/', new: '!');
249
250 return name;
251}
252
253bool
254efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
255 unsigned long data_size)
256{
257 int i;
258 unsigned long utf8_size;
259 u8 *utf8_name;
260
261 utf8_size = ucs2_utf8size(src: var_name);
262 utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
263 if (!utf8_name)
264 return false;
265
266 ucs2_as_utf8(dest: utf8_name, src: var_name, maxlength: utf8_size);
267 utf8_name[utf8_size] = '\0';
268
269 for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
270 const char *name = variable_validate[i].name;
271 int match = 0;
272
273 if (efi_guidcmp(left: vendor, right: variable_validate[i].vendor))
274 continue;
275
276 if (variable_matches(var_name: utf8_name, len: utf8_size+1, match_name: name, match: &match)) {
277 if (variable_validate[i].validate == NULL)
278 break;
279 kfree(objp: utf8_name);
280 return variable_validate[i].validate(var_name, match,
281 data, data_size);
282 }
283 }
284 kfree(objp: utf8_name);
285 return true;
286}
287
288bool
289efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
290 size_t len)
291{
292 int i;
293 bool found = false;
294 int match = 0;
295
296 /*
297 * Check if our variable is in the validated variables list
298 */
299 for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
300 if (efi_guidcmp(left: variable_validate[i].vendor, right: vendor))
301 continue;
302
303 if (variable_matches(var_name, len,
304 match_name: variable_validate[i].name, match: &match)) {
305 found = true;
306 break;
307 }
308 }
309
310 /*
311 * If it's in our list, it is removable.
312 */
313 return found;
314}
315
316/*
317 * Returns the size of variable_name, in bytes, including the
318 * terminating NULL character, or variable_name_size if no NULL
319 * character is found among the first variable_name_size bytes.
320 */
321static unsigned long var_name_strnsize(efi_char16_t *variable_name,
322 unsigned long variable_name_size)
323{
324 unsigned long len;
325 efi_char16_t c;
326
327 /*
328 * The variable name is, by definition, a NULL-terminated
329 * string, so make absolutely sure that variable_name_size is
330 * the value we expect it to be. If not, return the real size.
331 */
332 for (len = 2; len <= variable_name_size; len += sizeof(c)) {
333 c = variable_name[(len / sizeof(c)) - 1];
334 if (!c)
335 break;
336 }
337
338 return min(len, variable_name_size);
339}
340
341/*
342 * Print a warning when duplicate EFI variables are encountered and
343 * disable the sysfs workqueue since the firmware is buggy.
344 */
345static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
346 unsigned long len16)
347{
348 size_t i, len8 = len16 / sizeof(efi_char16_t);
349 char *str8;
350
351 str8 = kzalloc(len8, GFP_KERNEL);
352 if (!str8)
353 return;
354
355 for (i = 0; i < len8; i++)
356 str8[i] = str16[i];
357
358 printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
359 str8, vendor_guid);
360 kfree(objp: str8);
361}
362
363/**
364 * efivar_init - build the initial list of EFI variables
365 * @func: callback function to invoke for every variable
366 * @data: function-specific data to pass to @func
367 * @duplicate_check: fail if a duplicate variable is found
368 *
369 * Get every EFI variable from the firmware and invoke @func. @func
370 * should populate the initial dentry and inode tree.
371 *
372 * Returns 0 on success, or a kernel error code on failure.
373 */
374int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
375 void *data, bool duplicate_check)
376{
377 unsigned long variable_name_size = 512;
378 efi_char16_t *variable_name;
379 efi_status_t status;
380 efi_guid_t vendor_guid;
381 int err = 0;
382
383 variable_name = kzalloc(variable_name_size, GFP_KERNEL);
384 if (!variable_name) {
385 printk(KERN_ERR "efivars: Memory allocation failed.\n");
386 return -ENOMEM;
387 }
388
389 err = efivar_lock();
390 if (err)
391 goto free;
392
393 /*
394 * A small set of old UEFI implementations reject sizes
395 * above a certain threshold, the lowest seen in the wild
396 * is 512.
397 */
398
399 do {
400 variable_name_size = 512;
401 BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);
402
403 status = efivar_get_next_variable(name_size: &variable_name_size,
404 name: variable_name,
405 vendor: &vendor_guid);
406 switch (status) {
407 case EFI_SUCCESS:
408 variable_name_size = var_name_strnsize(variable_name,
409 variable_name_size);
410
411 /*
412 * Some firmware implementations return the
413 * same variable name on multiple calls to
414 * get_next_variable(). Terminate the loop
415 * immediately as there is no guarantee that
416 * we'll ever see a different variable name,
417 * and may end up looping here forever.
418 */
419 if (duplicate_check &&
420 efivarfs_variable_is_present(variable_name,
421 vendor: &vendor_guid, data)) {
422 dup_variable_bug(str16: variable_name, vendor_guid: &vendor_guid,
423 len16: variable_name_size);
424 status = EFI_NOT_FOUND;
425 } else {
426 err = func(variable_name, vendor_guid,
427 variable_name_size, data);
428 if (err)
429 status = EFI_NOT_FOUND;
430 }
431 break;
432 case EFI_UNSUPPORTED:
433 err = -EOPNOTSUPP;
434 status = EFI_NOT_FOUND;
435 break;
436 case EFI_NOT_FOUND:
437 break;
438 case EFI_BUFFER_TOO_SMALL:
439 pr_warn("efivars: Variable name size exceeds maximum (%lu > 512)\n",
440 variable_name_size);
441 status = EFI_NOT_FOUND;
442 break;
443 default:
444 pr_warn("efivars: get_next_variable: status=%lx\n", status);
445 status = EFI_NOT_FOUND;
446 break;
447 }
448
449 } while (status != EFI_NOT_FOUND);
450
451 efivar_unlock();
452free:
453 kfree(objp: variable_name);
454
455 return err;
456}
457
458/**
459 * efivar_entry_delete - delete variable
460 * @entry: entry containing variable to delete
461 *
462 * Delete the variable from the firmware. It is the caller's
463 * responsibility to free @entry (by deleting the dentry/inode) once
464 * we return.
465 *
466 * Returns 0 on success, -EINTR if we can't grab the semaphore,
467 * converted EFI status code if set_variable() fails.
468 */
469int efivar_entry_delete(struct efivar_entry *entry)
470{
471 efi_status_t status;
472 int err;
473
474 err = efivar_lock();
475 if (err)
476 return err;
477
478 status = efivar_set_variable_locked(name: entry->var.VariableName,
479 vendor: &entry->var.VendorGuid,
480 attr: 0, data_size: 0, NULL, nonblocking: false);
481 efivar_unlock();
482 if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND))
483 return efi_status_to_err(status);
484
485 return 0;
486}
487
488/**
489 * efivar_entry_size - obtain the size of a variable
490 * @entry: entry for this variable
491 * @size: location to store the variable's size
492 */
493int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
494{
495 efi_status_t status;
496 int err;
497
498 *size = 0;
499
500 err = efivar_lock();
501 if (err)
502 return err;
503
504 status = efivar_get_variable(name: entry->var.VariableName,
505 vendor: &entry->var.VendorGuid, NULL, size, NULL);
506 efivar_unlock();
507
508 if (status != EFI_BUFFER_TOO_SMALL)
509 return efi_status_to_err(status);
510
511 return 0;
512}
513
514/**
515 * __efivar_entry_get - call get_variable()
516 * @entry: read data for this variable
517 * @attributes: variable attributes
518 * @size: size of @data buffer
519 * @data: buffer to store variable data
520 *
521 * The caller MUST call efivar_entry_iter_begin() and
522 * efivar_entry_iter_end() before and after the invocation of this
523 * function, respectively.
524 */
525int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
526 unsigned long *size, void *data)
527{
528 efi_status_t status;
529
530 status = efivar_get_variable(name: entry->var.VariableName,
531 vendor: &entry->var.VendorGuid,
532 attr: attributes, size, data);
533
534 return efi_status_to_err(status);
535}
536
537/**
538 * efivar_entry_get - call get_variable()
539 * @entry: read data for this variable
540 * @attributes: variable attributes
541 * @size: size of @data buffer
542 * @data: buffer to store variable data
543 */
544int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
545 unsigned long *size, void *data)
546{
547 int err;
548
549 err = efivar_lock();
550 if (err)
551 return err;
552 err = __efivar_entry_get(entry, attributes, size, data);
553 efivar_unlock();
554
555 return err;
556}
557
558/**
559 * efivar_entry_set_get_size - call set_variable() and get new size (atomic)
560 * @entry: entry containing variable to set and get
561 * @attributes: attributes of variable to be written
562 * @size: size of data buffer
563 * @data: buffer containing data to write
564 * @set: did the set_variable() call succeed?
565 *
566 * This is a pretty special (complex) function. See efivarfs_file_write().
567 *
568 * Atomically call set_variable() for @entry and if the call is
569 * successful, return the new size of the variable from get_variable()
570 * in @size. The success of set_variable() is indicated by @set.
571 *
572 * Returns 0 on success, -EINVAL if the variable data is invalid,
573 * -ENOSPC if the firmware does not have enough available space, or a
574 * converted EFI status code if either of set_variable() or
575 * get_variable() fail.
576 *
577 * If the EFI variable does not exist when calling set_variable()
578 * (EFI_NOT_FOUND).
579 */
580int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
581 unsigned long *size, void *data, bool *set)
582{
583 efi_char16_t *name = entry->var.VariableName;
584 efi_guid_t *vendor = &entry->var.VendorGuid;
585 efi_status_t status;
586 int err;
587
588 *set = false;
589
590 if (efivar_validate(vendor: *vendor, var_name: name, data, data_size: *size) == false)
591 return -EINVAL;
592
593 /*
594 * The lock here protects the get_variable call and the
595 * conditional set_variable call
596 */
597 err = efivar_lock();
598 if (err)
599 return err;
600
601 status = efivar_set_variable_locked(name, vendor, attr: attributes, data_size: *size,
602 data, nonblocking: false);
603 if (status != EFI_SUCCESS) {
604 err = efi_status_to_err(status);
605 goto out;
606 }
607
608 *set = true;
609
610 /*
611 * Writing to the variable may have caused a change in size (which
612 * could either be an append or an overwrite), or the variable to be
613 * deleted. Perform a GetVariable() so we can tell what actually
614 * happened.
615 */
616 *size = 0;
617 status = efivar_get_variable(name: entry->var.VariableName,
618 vendor: &entry->var.VendorGuid,
619 NULL, size, NULL);
620
621 efivar_unlock();
622
623 if (status && status != EFI_BUFFER_TOO_SMALL)
624 return efi_status_to_err(status);
625
626 return 0;
627
628out:
629 efivar_unlock();
630 return err;
631
632}
633

source code of linux/fs/efivarfs/vars.c