summaryrefslogtreecommitdiff
path: root/fs/efivarfs/vars.c
blob: f7d43c847ee9518cf3aa128688fdc15817e74941 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
// SPDX-License-Identifier: GPL-2.0+
/*
 * Originally from efivars.c
 *
 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
 */

#include <linux/capability.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/smp.h>
#include <linux/efi.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/ucs2_string.h>

#include "internal.h"

MODULE_IMPORT_NS("EFIVAR");

static bool
validate_device_path(efi_char16_t *var_name, int match, u8 *buffer,
		     unsigned long len)
{
	struct efi_generic_dev_path *node;
	int offset = 0;

	node = (struct efi_generic_dev_path *)buffer;

	if (len < sizeof(*node))
		return false;

	while (offset <= len - sizeof(*node) &&
	       node->length >= sizeof(*node) &&
		node->length <= len - offset) {
		offset += node->length;

		if ((node->type == EFI_DEV_END_PATH ||
		     node->type == EFI_DEV_END_PATH2) &&
		    node->sub_type == EFI_DEV_END_ENTIRE)
			return true;

		node = (struct efi_generic_dev_path *)(buffer + offset);
	}

	/*
	 * If we're here then either node->length pointed past the end
	 * of the buffer or we reached the end of the buffer without
	 * finding a device path end node.
	 */
	return false;
}

static bool
validate_boot_order(efi_char16_t *var_name, int match, u8 *buffer,
		    unsigned long len)
{
	/* An array of 16-bit integers */
	if ((len % 2) != 0)
		return false;

	return true;
}

static bool
validate_load_option(efi_char16_t *var_name, int match, u8 *buffer,
		     unsigned long len)
{
	u16 filepathlength;
	int i, desclength = 0, namelen;

	namelen = ucs2_strnlen(var_name, EFI_VAR_NAME_LEN);

	/* Either "Boot" or "Driver" followed by four digits of hex */
	for (i = match; i < match+4; i++) {
		if (var_name[i] > 127 ||
		    hex_to_bin(var_name[i] & 0xff) < 0)
			return true;
	}

	/* Reject it if there's 4 digits of hex and then further content */
	if (namelen > match + 4)
		return false;

	/* A valid entry must be at least 8 bytes */
	if (len < 8)
		return false;

	filepathlength = buffer[4] | buffer[5] << 8;

	/*
	 * There's no stored length for the description, so it has to be
	 * found by hand
	 */
	desclength = ucs2_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;

	/* Each boot entry must have a descriptor */
	if (!desclength)
		return false;

	/*
	 * If the sum of the length of the description, the claimed filepath
	 * length and the original header are greater than the length of the
	 * variable, it's malformed
	 */
	if ((desclength + filepathlength + 6) > len)
		return false;

	/*
	 * And, finally, check the filepath
	 */
	return validate_device_path(var_name, match, buffer + desclength + 6,
				    filepathlength);
}

static bool
validate_uint16(efi_char16_t *var_name, int match, u8 *buffer,
		unsigned long len)
{
	/* A single 16-bit integer */
	if (len != 2)
		return false;

	return true;
}

static bool
validate_ascii_string(efi_char16_t *var_name, int match, u8 *buffer,
		      unsigned long len)
{
	int i;

	for (i = 0; i < len; i++) {
		if (buffer[i] > 127)
			return false;

		if (buffer[i] == 0)
			return true;
	}

	return false;
}

struct variable_validate {
	efi_guid_t vendor;
	char *name;
	bool (*validate)(efi_char16_t *var_name, int match, u8 *data,
			 unsigned long len);
};

/*
 * This is the list of variables we need to validate, as well as the
 * whitelist for what we think is safe not to default to immutable.
 *
 * If it has a validate() method that's not NULL, it'll go into the
 * validation routine.  If not, it is assumed valid, but still used for
 * whitelisting.
 *
 * Note that it's sorted by {vendor,name}, but globbed names must come after
 * any other name with the same prefix.
 */
static const struct variable_validate variable_validate[] = {
	{ EFI_GLOBAL_VARIABLE_GUID, "BootNext", validate_uint16 },
	{ EFI_GLOBAL_VARIABLE_GUID, "BootOrder", validate_boot_order },
	{ EFI_GLOBAL_VARIABLE_GUID, "Boot*", validate_load_option },
	{ EFI_GLOBAL_VARIABLE_GUID, "DriverOrder", validate_boot_order },
	{ EFI_GLOBAL_VARIABLE_GUID, "Driver*", validate_load_option },
	{ EFI_GLOBAL_VARIABLE_GUID, "ConIn", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "ConInDev", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "ConOut", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "ConOutDev", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "ErrOut", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "ErrOutDev", validate_device_path },
	{ EFI_GLOBAL_VARIABLE_GUID, "Lang", validate_ascii_string },
	{ EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
	{ EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
	{ EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
	{ LINUX_EFI_CRASH_GUID, "*", NULL },
	{ NULL_GUID, "", NULL },
};

/*
 * Check if @var_name matches the pattern given in @match_name.
 *
 * @var_name: an array of @len non-NUL characters.
 * @match_name: a NUL-terminated pattern string, optionally ending in "*". A
 *              final "*" character matches any trailing characters @var_name,
 *              including the case when there are none left in @var_name.
 * @match: on output, the number of non-wildcard characters in @match_name
 *         that @var_name matches, regardless of the return value.
 * @return: whether @var_name fully matches @match_name.
 */
static bool
variable_matches(const char *var_name, size_t len, const char *match_name,
		 int *match)
{
	for (*match = 0; ; (*match)++) {
		char c = match_name[*match];

		switch (c) {
		case '*':
			/* Wildcard in @match_name means we've matched. */
			return true;

		case '\0':
			/* @match_name has ended. Has @var_name too? */
			return (*match == len);

		default:
			/*
			 * We've reached a non-wildcard char in @match_name.
			 * Continue only if there's an identical character in
			 * @var_name.
			 */
			if (*match < len && c == var_name[*match])
				continue;
			return false;
		}
	}
}

bool
efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
		unsigned long data_size)
{
	int i;
	unsigned long utf8_size;
	u8 *utf8_name;

	utf8_size = ucs2_utf8size(var_name);
	utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
	if (!utf8_name)
		return false;

	ucs2_as_utf8(utf8_name, var_name, utf8_size);
	utf8_name[utf8_size] = '\0';

	for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
		const char *name = variable_validate[i].name;
		int match = 0;

		if (efi_guidcmp(vendor, variable_validate[i].vendor))
			continue;

		if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
			if (variable_validate[i].validate == NULL)
				break;
			kfree(utf8_name);
			return variable_validate[i].validate(var_name, match,
							     data, data_size);
		}
	}
	kfree(utf8_name);
	return true;
}

bool
efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
			     size_t len)
{
	int i;
	bool found = false;
	int match = 0;

	/*
	 * Check if our variable is in the validated variables list
	 */
	for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
		if (efi_guidcmp(variable_validate[i].vendor, vendor))
			continue;

		if (variable_matches(var_name, len,
				     variable_validate[i].name, &match)) {
			found = true;
			break;
		}
	}

	/*
	 * If it's in our list, it is removable.
	 */
	return found;
}

static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor,
				struct list_head *head)
{
	struct efivar_entry *entry, *n;
	unsigned long strsize1, strsize2;
	bool found = false;

	strsize1 = ucs2_strsize(variable_name, EFI_VAR_NAME_LEN);
	list_for_each_entry_safe(entry, n, head, list) {
		strsize2 = ucs2_strsize(entry->var.VariableName, EFI_VAR_NAME_LEN);
		if (strsize1 == strsize2 &&
			!memcmp(variable_name, &(entry->var.VariableName),
				strsize2) &&
			!efi_guidcmp(entry->var.VendorGuid,
				*vendor)) {
			found = true;
			break;
		}
	}
	return found;
}

/*
 * Returns the size of variable_name, in bytes, including the
 * terminating NULL character, or variable_name_size if no NULL
 * character is found among the first variable_name_size bytes.
 */
static unsigned long var_name_strnsize(efi_char16_t *variable_name,
				       unsigned long variable_name_size)
{
	unsigned long len;
	efi_char16_t c;

	/*
	 * The variable name is, by definition, a NULL-terminated
	 * string, so make absolutely sure that variable_name_size is
	 * the value we expect it to be. If not, return the real size.
	 */
	for (len = 2; len <= variable_name_size; len += sizeof(c)) {
		c = variable_name[(len / sizeof(c)) - 1];
		if (!c)
			break;
	}

	return min(len, variable_name_size);
}

/*
 * Print a warning when duplicate EFI variables are encountered and
 * disable the sysfs workqueue since the firmware is buggy.
 */
static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
			     unsigned long len16)
{
	size_t i, len8 = len16 / sizeof(efi_char16_t);
	char *str8;

	str8 = kzalloc(len8, GFP_KERNEL);
	if (!str8)
		return;

	for (i = 0; i < len8; i++)
		str8[i] = str16[i];

	printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
	       str8, vendor_guid);
	kfree(str8);
}

/**
 * efivar_init - build the initial list of EFI variables
 * @func: callback function to invoke for every variable
 * @data: function-specific data to pass to @func
 * @head: initialised head of variable list
 *
 * Get every EFI variable from the firmware and invoke @func. @func
 * should call efivar_entry_add() to build the list of variables.
 *
 * Returns 0 on success, or a kernel error code on failure.
 */
int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *,
			    struct list_head *),
		void *data, struct list_head *head)
{
	unsigned long variable_name_size = 512;
	efi_char16_t *variable_name;
	efi_status_t status;
	efi_guid_t vendor_guid;
	int err = 0;

	variable_name = kzalloc(variable_name_size, GFP_KERNEL);
	if (!variable_name) {
		printk(KERN_ERR "efivars: Memory allocation failed.\n");
		return -ENOMEM;
	}

	err = efivar_lock();
	if (err)
		goto free;

	/*
	 * A small set of old UEFI implementations reject sizes
	 * above a certain threshold, the lowest seen in the wild
	 * is 512.
	 */

	do {
		variable_name_size = 512;
		BUILD_BUG_ON(EFI_VAR_NAME_LEN < 512);

		status = efivar_get_next_variable(&variable_name_size,
						  variable_name,
						  &vendor_guid);
		switch (status) {
		case EFI_SUCCESS:
			variable_name_size = var_name_strnsize(variable_name,
							       variable_name_size);

			/*
			 * Some firmware implementations return the
			 * same variable name on multiple calls to
			 * get_next_variable(). Terminate the loop
			 * immediately as there is no guarantee that
			 * we'll ever see a different variable name,
			 * and may end up looping here forever.
			 */
			if (variable_is_present(variable_name, &vendor_guid,
						head)) {
				dup_variable_bug(variable_name, &vendor_guid,
						 variable_name_size);
				status = EFI_NOT_FOUND;
			} else {
				err = func(variable_name, vendor_guid,
					   variable_name_size, data, head);
				if (err)
					status = EFI_NOT_FOUND;
			}
			break;
		case EFI_UNSUPPORTED:
			err = -EOPNOTSUPP;
			status = EFI_NOT_FOUND;
			break;
		case EFI_NOT_FOUND:
			break;
		case EFI_BUFFER_TOO_SMALL:
			pr_warn("efivars: Variable name size exceeds maximum (%lu > 512)\n",
				variable_name_size);
			status = EFI_NOT_FOUND;
			break;
		default:
			pr_warn("efivars: get_next_variable: status=%lx\n", status);
			status = EFI_NOT_FOUND;
			break;
		}

	} while (status != EFI_NOT_FOUND);

	efivar_unlock();
free:
	kfree(variable_name);

	return err;
}

/**
 * efivar_entry_add - add entry to variable list
 * @entry: entry to add to list
 * @head: list head
 *
 * Returns 0 on success, or a kernel error code on failure.
 */
int efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
{
	int err;

	err = efivar_lock();
	if (err)
		return err;
	list_add(&entry->list, head);
	efivar_unlock();

	return 0;
}

/**
 * __efivar_entry_add - add entry to variable list
 * @entry: entry to add to list
 * @head: list head
 */
void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head)
{
	list_add(&entry->list, head);
}

/**
 * efivar_entry_remove - remove entry from variable list
 * @entry: entry to remove from list
 *
 * Returns 0 on success, or a kernel error code on failure.
 */
void efivar_entry_remove(struct efivar_entry *entry)
{
	list_del(&entry->list);
}

/*
 * efivar_entry_list_del_unlock - remove entry from variable list
 * @entry: entry to remove
 *
 * Remove @entry from the variable list and release the list lock.
 *
 * NOTE: slightly weird locking semantics here - we expect to be
 * called with the efivars lock already held, and we release it before
 * returning. This is because this function is usually called after
 * set_variable() while the lock is still held.
 */
static void efivar_entry_list_del_unlock(struct efivar_entry *entry)
{
	list_del(&entry->list);
	efivar_unlock();
}

/**
 * efivar_entry_delete - delete variable and remove entry from list
 * @entry: entry containing variable to delete
 *
 * Delete the variable from the firmware and remove @entry from the
 * variable list. It is the caller's responsibility to free @entry
 * once we return.
 *
 * Returns 0 on success, -EINTR if we can't grab the semaphore,
 * converted EFI status code if set_variable() fails.
 */
int efivar_entry_delete(struct efivar_entry *entry)
{
	efi_status_t status;
	int err;

	err = efivar_lock();
	if (err)
		return err;

	status = efivar_set_variable_locked(entry->var.VariableName,
					    &entry->var.VendorGuid,
					    0, 0, NULL, false);
	if (!(status == EFI_SUCCESS || status == EFI_NOT_FOUND)) {
		efivar_unlock();
		return efi_status_to_err(status);
	}

	efivar_entry_list_del_unlock(entry);
	return 0;
}

/**
 * efivar_entry_size - obtain the size of a variable
 * @entry: entry for this variable
 * @size: location to store the variable's size
 */
int efivar_entry_size(struct efivar_entry *entry, unsigned long *size)
{
	efi_status_t status;
	int err;

	*size = 0;

	err = efivar_lock();
	if (err)
		return err;

	status = efivar_get_variable(entry->var.VariableName,
				     &entry->var.VendorGuid, NULL, size, NULL);
	efivar_unlock();

	if (status != EFI_BUFFER_TOO_SMALL)
		return efi_status_to_err(status);

	return 0;
}

/**
 * __efivar_entry_get - call get_variable()
 * @entry: read data for this variable
 * @attributes: variable attributes
 * @size: size of @data buffer
 * @data: buffer to store variable data
 *
 * The caller MUST call efivar_entry_iter_begin() and
 * efivar_entry_iter_end() before and after the invocation of this
 * function, respectively.
 */
int __efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
		       unsigned long *size, void *data)
{
	efi_status_t status;

	status = efivar_get_variable(entry->var.VariableName,
				     &entry->var.VendorGuid,
				     attributes, size, data);

	return efi_status_to_err(status);
}

/**
 * efivar_entry_get - call get_variable()
 * @entry: read data for this variable
 * @attributes: variable attributes
 * @size: size of @data buffer
 * @data: buffer to store variable data
 */
int efivar_entry_get(struct efivar_entry *entry, u32 *attributes,
		     unsigned long *size, void *data)
{
	int err;

	err = efivar_lock();
	if (err)
		return err;
	err = __efivar_entry_get(entry, attributes, size, data);
	efivar_unlock();

	return 0;
}

/**
 * efivar_entry_set_get_size - call set_variable() and get new size (atomic)
 * @entry: entry containing variable to set and get
 * @attributes: attributes of variable to be written
 * @size: size of data buffer
 * @data: buffer containing data to write
 * @set: did the set_variable() call succeed?
 *
 * This is a pretty special (complex) function. See efivarfs_file_write().
 *
 * Atomically call set_variable() for @entry and if the call is
 * successful, return the new size of the variable from get_variable()
 * in @size. The success of set_variable() is indicated by @set.
 *
 * Returns 0 on success, -EINVAL if the variable data is invalid,
 * -ENOSPC if the firmware does not have enough available space, or a
 * converted EFI status code if either of set_variable() or
 * get_variable() fail.
 *
 * If the EFI variable does not exist when calling set_variable()
 * (EFI_NOT_FOUND), @entry is removed from the variable list.
 */
int efivar_entry_set_get_size(struct efivar_entry *entry, u32 attributes,
			      unsigned long *size, void *data, bool *set)
{
	efi_char16_t *name = entry->var.VariableName;
	efi_guid_t *vendor = &entry->var.VendorGuid;
	efi_status_t status;
	int err;

	*set = false;

	if (efivar_validate(*vendor, name, data, *size) == false)
		return -EINVAL;

	/*
	 * The lock here protects the get_variable call, the conditional
	 * set_variable call, and removal of the variable from the efivars
	 * list (in the case of an authenticated delete).
	 */
	err = efivar_lock();
	if (err)
		return err;

	status = efivar_set_variable_locked(name, vendor, attributes, *size,
					    data, false);
	if (status != EFI_SUCCESS) {
		err = efi_status_to_err(status);
		goto out;
	}

	*set = true;

	/*
	 * Writing to the variable may have caused a change in size (which
	 * could either be an append or an overwrite), or the variable to be
	 * deleted. Perform a GetVariable() so we can tell what actually
	 * happened.
	 */
	*size = 0;
	status = efivar_get_variable(entry->var.VariableName,
				    &entry->var.VendorGuid,
				    NULL, size, NULL);

	if (status == EFI_NOT_FOUND)
		efivar_entry_list_del_unlock(entry);
	else
		efivar_unlock();

	if (status && status != EFI_BUFFER_TOO_SMALL)
		return efi_status_to_err(status);

	return 0;

out:
	efivar_unlock();
	return err;

}

/**
 * efivar_entry_iter - iterate over variable list
 * @func: callback function
 * @head: head of variable list
 * @data: function-specific data to pass to callback
 *
 * Iterate over the list of EFI variables and call @func with every
 * entry on the list. It is safe for @func to remove entries in the
 * list via efivar_entry_delete() while iterating.
 *
 * Some notes for the callback function:
 *  - a non-zero return value indicates an error and terminates the loop
 *  - @func is called from atomic context
 */
int efivar_entry_iter(int (*func)(struct efivar_entry *, void *),
		      struct list_head *head, void *data)
{
	struct efivar_entry *entry, *n;
	int err = 0;

	err = efivar_lock();
	if (err)
		return err;

	list_for_each_entry_safe(entry, n, head, list) {
		err = func(entry, data);
		if (err)
			break;
	}
	efivar_unlock();

	return err;
}