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
 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(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
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(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(name, name16, len);
240
241	name[len] = '-';
242
243	efi_guid_to_str(vendor, 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(name, '/', '!');
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(var_name);
262	utf8_name = kmalloc(utf8_size + 1, GFP_KERNEL);
263	if (!utf8_name)
264		return false;
265
266	ucs2_as_utf8(utf8_name, var_name, 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(vendor, variable_validate[i].vendor))
274			continue;
275
276		if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
277			if (variable_validate[i].validate == NULL)
278				break;
279			kfree(utf8_name);
280			return variable_validate[i].validate(var_name, match,
281							     data, data_size);
282		}
283	}
284	kfree(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(variable_validate[i].vendor, vendor))
301			continue;
302
303		if (variable_matches(var_name, len,
304				     variable_validate[i].name, &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(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(&variable_name_size,
404						  variable_name,
405						  &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_guid, data)) {
422				dup_variable_bug(variable_name, &vendor_guid,
423						 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(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(entry->var.VariableName,
479					    &entry->var.VendorGuid,
480					    0, 0, NULL, 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(entry->var.VariableName,
505				     &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(entry->var.VariableName,
531				     &entry->var.VendorGuid,
532				     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, name, data, *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, attributes, *size,
602					    data, 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(entry->var.VariableName,
618				    &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}