1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2012 Red Hat, Inc.
4 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
5 */
6
7#include <linux/ctype.h>
8#include <linux/efi.h>
9#include <linux/fs.h>
10#include <linux/fs_context.h>
11#include <linux/fs_parser.h>
12#include <linux/module.h>
13#include <linux/pagemap.h>
14#include <linux/ucs2_string.h>
15#include <linux/slab.h>
16#include <linux/suspend.h>
17#include <linux/magic.h>
18#include <linux/statfs.h>
19#include <linux/notifier.h>
20#include <linux/printk.h>
21#include <linux/namei.h>
22
23#include "internal.h"
24#include "../internal.h"
25
26static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event,
27 void *data)
28{
29 struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb);
30
31 switch (event) {
32 case EFIVAR_OPS_RDONLY:
33 sfi->sb->s_flags |= SB_RDONLY;
34 break;
35 case EFIVAR_OPS_RDWR:
36 sfi->sb->s_flags &= ~SB_RDONLY;
37 break;
38 default:
39 return NOTIFY_DONE;
40 }
41
42 return NOTIFY_OK;
43}
44
45static struct inode *efivarfs_alloc_inode(struct super_block *sb)
46{
47 struct efivar_entry *entry = kzalloc(sizeof(*entry), GFP_KERNEL);
48
49 if (!entry)
50 return NULL;
51
52 inode_init_once(&entry->vfs_inode);
53 entry->removed = false;
54
55 return &entry->vfs_inode;
56}
57
58static void efivarfs_free_inode(struct inode *inode)
59{
60 struct efivar_entry *entry = efivar_entry(inode);
61
62 kfree(objp: entry);
63}
64
65static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
66{
67 struct super_block *sb = root->d_sb;
68 struct efivarfs_fs_info *sbi = sb->s_fs_info;
69 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
70
71 if (!uid_eq(left: opts->uid, GLOBAL_ROOT_UID))
72 seq_printf(m, ",uid=%u",
73 from_kuid_munged(&init_user_ns, opts->uid));
74 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
75 seq_printf(m, ",gid=%u",
76 from_kgid_munged(&init_user_ns, opts->gid));
77 return 0;
78}
79
80static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
81{
82 const u32 attr = EFI_VARIABLE_NON_VOLATILE |
83 EFI_VARIABLE_BOOTSERVICE_ACCESS |
84 EFI_VARIABLE_RUNTIME_ACCESS;
85 u64 storage_space, remaining_space, max_variable_size;
86 u64 id = huge_encode_dev(dev: dentry->d_sb->s_dev);
87 efi_status_t status;
88
89 /* Some UEFI firmware does not implement QueryVariableInfo() */
90 storage_space = remaining_space = 0;
91 if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
92 status = efivar_query_variable_info(attr, storage_space: &storage_space,
93 remaining_space: &remaining_space,
94 max_variable_size: &max_variable_size);
95 if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
96 pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
97 status);
98 }
99
100 /*
101 * This is not a normal filesystem, so no point in pretending it has a block
102 * size; we declare f_bsize to 1, so that we can then report the exact value
103 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
104 */
105 buf->f_bsize = 1;
106 buf->f_namelen = NAME_MAX;
107 buf->f_blocks = storage_space;
108 buf->f_bfree = remaining_space;
109 buf->f_type = dentry->d_sb->s_magic;
110 buf->f_fsid = u64_to_fsid(v: id);
111
112 /*
113 * In f_bavail we declare the free space that the kernel will allow writing
114 * when the storage_paranoia x86 quirk is active. To use more, users
115 * should boot the kernel with efi_no_storage_paranoia.
116 */
117 if (remaining_space > efivar_reserved_space())
118 buf->f_bavail = remaining_space - efivar_reserved_space();
119 else
120 buf->f_bavail = 0;
121
122 return 0;
123}
124
125static int efivarfs_freeze_fs(struct super_block *sb);
126static int efivarfs_unfreeze_fs(struct super_block *sb);
127
128static const struct super_operations efivarfs_ops = {
129 .statfs = efivarfs_statfs,
130 .drop_inode = inode_just_drop,
131 .alloc_inode = efivarfs_alloc_inode,
132 .free_inode = efivarfs_free_inode,
133 .show_options = efivarfs_show_options,
134 .freeze_fs = efivarfs_freeze_fs,
135 .unfreeze_fs = efivarfs_unfreeze_fs,
136};
137
138/*
139 * Compare two efivarfs file names.
140 *
141 * An efivarfs filename is composed of two parts,
142 *
143 * 1. A case-sensitive variable name
144 * 2. A case-insensitive GUID
145 *
146 * So we need to perform a case-sensitive match on part 1 and a
147 * case-insensitive match on part 2.
148 */
149static int efivarfs_d_compare(const struct dentry *dentry,
150 unsigned int len, const char *str,
151 const struct qstr *name)
152{
153 int guid = len - EFI_VARIABLE_GUID_LEN;
154
155 /* Parallel lookups may produce a temporary invalid filename */
156 if (guid <= 0)
157 return 1;
158
159 if (name->len != len)
160 return 1;
161
162 /* Case-sensitive compare for the variable name */
163 if (memcmp(str, name->name, guid))
164 return 1;
165
166 /* Case-insensitive compare for the GUID */
167 return strncasecmp(s1: name->name + guid, s2: str + guid, EFI_VARIABLE_GUID_LEN);
168}
169
170static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
171{
172 unsigned long hash = init_name_hash(dentry);
173 const unsigned char *s = qstr->name;
174 unsigned int len = qstr->len;
175
176 while (len-- > EFI_VARIABLE_GUID_LEN)
177 hash = partial_name_hash(c: *s++, prevhash: hash);
178
179 /* GUID is case-insensitive. */
180 while (len--)
181 hash = partial_name_hash(tolower(*s++), prevhash: hash);
182
183 qstr->hash = end_name_hash(hash);
184 return 0;
185}
186
187static const struct dentry_operations efivarfs_d_ops = {
188 .d_compare = efivarfs_d_compare,
189 .d_hash = efivarfs_d_hash,
190};
191
192static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
193{
194 struct dentry *d;
195 struct qstr q;
196 int err;
197
198 q.name = name;
199 q.len = strlen(name);
200
201 err = efivarfs_d_hash(dentry: parent, qstr: &q);
202 if (err)
203 return ERR_PTR(error: err);
204
205 d = d_alloc(parent, &q);
206 if (d)
207 return d;
208
209 return ERR_PTR(error: -ENOMEM);
210}
211
212bool efivarfs_variable_is_present(efi_char16_t *variable_name,
213 efi_guid_t *vendor, void *data)
214{
215 char *name = efivar_get_utf8name(name16: variable_name, vendor);
216 struct super_block *sb = data;
217 struct dentry *dentry;
218
219 if (!name)
220 /*
221 * If the allocation failed there'll already be an
222 * error in the log (and likely a huge and growing
223 * number of them since they system will be under
224 * extreme memory pressure), so simply assume
225 * collision for safety but don't add to the log
226 * flood.
227 */
228 return true;
229
230 dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
231 kfree(objp: name);
232 if (!IS_ERR_OR_NULL(ptr: dentry))
233 dput(dentry);
234
235 return dentry != NULL;
236}
237
238static int efivarfs_create_dentry(struct super_block *sb, efi_char16_t *name16,
239 unsigned long name_size, efi_guid_t vendor,
240 char *name)
241{
242 struct efivar_entry *entry;
243 struct inode *inode;
244 struct dentry *dentry, *root = sb->s_root;
245 unsigned long size = 0;
246 int len;
247 int err = -ENOMEM;
248 bool is_removable = false;
249
250 /* length of the variable name itself: remove GUID and separator */
251 len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1;
252
253 if (efivar_variable_is_removable(vendor, name, len))
254 is_removable = true;
255
256 inode = efivarfs_get_inode(sb, dir: d_inode(dentry: root), S_IFREG | 0644, dev: 0,
257 is_removable);
258 if (!inode)
259 goto fail_name;
260
261 entry = efivar_entry(inode);
262
263 memcpy(to: entry->var.VariableName, from: name16, len: name_size);
264 memcpy(to: &(entry->var.VendorGuid), from: &vendor, len: sizeof(efi_guid_t));
265
266 dentry = efivarfs_alloc_dentry(parent: root, name);
267 if (IS_ERR(ptr: dentry)) {
268 err = PTR_ERR(ptr: dentry);
269 goto fail_inode;
270 }
271
272 __efivar_entry_get(entry, NULL, size: &size, NULL);
273
274 /* copied by the above to local storage in the dentry. */
275 kfree(objp: name);
276
277 inode_lock(inode);
278 inode->i_private = entry;
279 i_size_write(inode, i_size: size + sizeof(__u32)); /* attributes + data */
280 inode_unlock(inode);
281 d_add(dentry, inode);
282
283 return 0;
284
285fail_inode:
286 iput(inode);
287fail_name:
288 kfree(objp: name);
289
290 return err;
291}
292
293static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
294 unsigned long name_size, void *data)
295{
296 struct super_block *sb = (struct super_block *)data;
297 char *name;
298
299 if (guid_equal(u1: &vendor, u2: &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
300 return 0;
301
302 name = efivar_get_utf8name(name16, vendor: &vendor);
303 if (!name)
304 return -ENOMEM;
305
306 return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
307}
308
309enum {
310 Opt_uid, Opt_gid,
311};
312
313static const struct fs_parameter_spec efivarfs_parameters[] = {
314 fsparam_uid("uid", Opt_uid),
315 fsparam_gid("gid", Opt_gid),
316 {},
317};
318
319static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
320{
321 struct efivarfs_fs_info *sbi = fc->s_fs_info;
322 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
323 struct fs_parse_result result;
324 int opt;
325
326 opt = fs_parse(fc, desc: efivarfs_parameters, param, result: &result);
327 if (opt < 0)
328 return opt;
329
330 switch (opt) {
331 case Opt_uid:
332 opts->uid = result.uid;
333 break;
334 case Opt_gid:
335 opts->gid = result.gid;
336 break;
337 default:
338 return -EINVAL;
339 }
340
341 return 0;
342}
343
344static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
345{
346 struct efivarfs_fs_info *sfi = sb->s_fs_info;
347 struct inode *inode = NULL;
348 struct dentry *root;
349 int err;
350
351 sb->s_maxbytes = MAX_LFS_FILESIZE;
352 sb->s_blocksize = PAGE_SIZE;
353 sb->s_blocksize_bits = PAGE_SHIFT;
354 sb->s_magic = EFIVARFS_MAGIC;
355 sb->s_op = &efivarfs_ops;
356 set_default_d_op(sb, &efivarfs_d_ops);
357 sb->s_d_flags |= DCACHE_DONTCACHE;
358 sb->s_time_gran = 1;
359
360 if (!efivar_supports_writes())
361 sb->s_flags |= SB_RDONLY;
362
363 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, dev: 0, is_removable: true);
364 if (!inode)
365 return -ENOMEM;
366 inode->i_op = &efivarfs_dir_inode_operations;
367
368 root = d_make_root(inode);
369 sb->s_root = root;
370 if (!root)
371 return -ENOMEM;
372
373 sfi->sb = sb;
374 sfi->nb.notifier_call = efivarfs_ops_notifier;
375 err = blocking_notifier_chain_register(nh: &efivar_ops_nh, nb: &sfi->nb);
376 if (err)
377 return err;
378
379 return efivar_init(func: efivarfs_callback, data: sb, duplicate_check: true);
380}
381
382static int efivarfs_get_tree(struct fs_context *fc)
383{
384 return get_tree_single(fc, fill_super: efivarfs_fill_super);
385}
386
387static int efivarfs_reconfigure(struct fs_context *fc)
388{
389 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
390 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
391 return -EINVAL;
392 }
393
394 return 0;
395}
396
397static void efivarfs_free(struct fs_context *fc)
398{
399 kfree(objp: fc->s_fs_info);
400}
401
402static const struct fs_context_operations efivarfs_context_ops = {
403 .get_tree = efivarfs_get_tree,
404 .parse_param = efivarfs_parse_param,
405 .reconfigure = efivarfs_reconfigure,
406 .free = efivarfs_free,
407};
408
409static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
410 unsigned long name_size, void *data)
411{
412 char *name;
413 struct super_block *sb = data;
414 struct dentry *dentry;
415 int err;
416
417 if (guid_equal(u1: &vendor, u2: &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
418 return 0;
419
420 name = efivar_get_utf8name(name16, vendor: &vendor);
421 if (!name)
422 return -ENOMEM;
423
424 dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
425 if (IS_ERR(ptr: dentry)) {
426 err = PTR_ERR(ptr: dentry);
427 goto out;
428 }
429
430 if (!dentry) {
431 /* found missing entry */
432 pr_info("efivarfs: creating variable %s\n", name);
433 return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
434 }
435
436 dput(dentry);
437 err = 0;
438
439 out:
440 kfree(objp: name);
441
442 return err;
443}
444
445static struct file_system_type efivarfs_type;
446
447static int efivarfs_freeze_fs(struct super_block *sb)
448{
449 /* Nothing for us to do. */
450 return 0;
451}
452
453static int efivarfs_unfreeze_fs(struct super_block *sb)
454{
455 struct dentry *child = NULL;
456
457 /*
458 * Unconditionally resync the variable state on a thaw request.
459 * Given the size of efivarfs it really doesn't matter to simply
460 * iterate through all of the entries and resync. Freeze/thaw
461 * requests are rare enough for that to not matter and the
462 * number of entries is pretty low too. So we really don't care.
463 */
464 pr_info("efivarfs: resyncing variable state\n");
465 for (;;) {
466 int err;
467 unsigned long size = 0;
468 struct inode *inode;
469 struct efivar_entry *entry;
470
471 child = find_next_child(parent: sb->s_root, prev: child);
472 if (!child)
473 break;
474
475 inode = d_inode(dentry: child);
476 entry = efivar_entry(inode);
477
478 err = efivar_entry_size(entry, size: &size);
479 if (err)
480 size = 0;
481 else
482 size += sizeof(__u32);
483
484 inode_lock(inode);
485 i_size_write(inode, i_size: size);
486 inode_unlock(inode);
487
488 /* The variable doesn't exist anymore, delete it. */
489 if (!size) {
490 pr_info("efivarfs: removing variable %pd\n", child);
491 simple_recursive_removal(child, NULL);
492 }
493 }
494
495 efivar_init(func: efivarfs_check_missing, data: sb, duplicate_check: false);
496 pr_info("efivarfs: finished resyncing variable state\n");
497 return 0;
498}
499
500static int efivarfs_init_fs_context(struct fs_context *fc)
501{
502 struct efivarfs_fs_info *sfi;
503
504 if (!efivar_is_available())
505 return -EOPNOTSUPP;
506
507 sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
508 if (!sfi)
509 return -ENOMEM;
510
511 sfi->mount_opts.uid = GLOBAL_ROOT_UID;
512 sfi->mount_opts.gid = GLOBAL_ROOT_GID;
513
514 fc->s_fs_info = sfi;
515 fc->ops = &efivarfs_context_ops;
516
517 return 0;
518}
519
520static void efivarfs_kill_sb(struct super_block *sb)
521{
522 struct efivarfs_fs_info *sfi = sb->s_fs_info;
523
524 blocking_notifier_chain_unregister(nh: &efivar_ops_nh, nb: &sfi->nb);
525 kill_litter_super(sb);
526
527 kfree(objp: sfi);
528}
529
530static struct file_system_type efivarfs_type = {
531 .owner = THIS_MODULE,
532 .name = "efivarfs",
533 .init_fs_context = efivarfs_init_fs_context,
534 .kill_sb = efivarfs_kill_sb,
535 .parameters = efivarfs_parameters,
536};
537
538static __init int efivarfs_init(void)
539{
540 return register_filesystem(&efivarfs_type);
541}
542
543static __exit void efivarfs_exit(void)
544{
545 unregister_filesystem(&efivarfs_type);
546}
547
548MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
549MODULE_DESCRIPTION("EFI Variable Filesystem");
550MODULE_LICENSE("GPL");
551MODULE_ALIAS_FS("efivarfs");
552
553module_init(efivarfs_init);
554module_exit(efivarfs_exit);
555