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/magic.h>
17 #include <linux/statfs.h>
18 #include <linux/notifier.h>
19 #include <linux/printk.h>
20
21 #include "internal.h"
22
23 static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event,
24 void *data)
25 {
26 struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb);
27
28 switch (event) {
29 case EFIVAR_OPS_RDONLY:
30 sfi->sb->s_flags |= SB_RDONLY;
31 break;
32 case EFIVAR_OPS_RDWR:
33 sfi->sb->s_flags &= ~SB_RDONLY;
34 break;
35 default:
36 return NOTIFY_DONE;
37 }
38
39 return NOTIFY_OK;
40 }
41
42 static void efivarfs_evict_inode(struct inode *inode)
43 {
44 clear_inode(inode);
45 }
46
47 static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
48 {
49 struct super_block *sb = root->d_sb;
50 struct efivarfs_fs_info *sbi = sb->s_fs_info;
51 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
52
53 if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
54 seq_printf(m, ",uid=%u",
55 from_kuid_munged(&init_user_ns, opts->uid));
56 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
57 seq_printf(m, ",gid=%u",
58 from_kgid_munged(&init_user_ns, opts->gid));
59 return 0;
60 }
61
62 static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
63 {
64 const u32 attr = EFI_VARIABLE_NON_VOLATILE |
65 EFI_VARIABLE_BOOTSERVICE_ACCESS |
66 EFI_VARIABLE_RUNTIME_ACCESS;
67 u64 storage_space, remaining_space, max_variable_size;
68 u64 id = huge_encode_dev(dentry->d_sb->s_dev);
69 efi_status_t status;
70
71 /* Some UEFI firmware does not implement QueryVariableInfo() */
72 storage_space = remaining_space = 0;
73 if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
74 status = efivar_query_variable_info(attr, &storage_space,
75 &remaining_space,
76 &max_variable_size);
77 if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
78 pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
79 status);
80 }
81
82 /*
83 * This is not a normal filesystem, so no point in pretending it has a block
84 * size; we declare f_bsize to 1, so that we can then report the exact value
85 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
86 */
87 buf->f_bsize = 1;
88 buf->f_namelen = NAME_MAX;
89 buf->f_blocks = storage_space;
90 buf->f_bfree = remaining_space;
91 buf->f_type = dentry->d_sb->s_magic;
92 buf->f_fsid = u64_to_fsid(id);
93
94 /*
95 * In f_bavail we declare the free space that the kernel will allow writing
96 * when the storage_paranoia x86 quirk is active. To use more, users
97 * should boot the kernel with efi_no_storage_paranoia.
98 */
99 if (remaining_space > efivar_reserved_space())
100 buf->f_bavail = remaining_space - efivar_reserved_space();
101 else
102 buf->f_bavail = 0;
103
104 return 0;
105 }
106 static const struct super_operations efivarfs_ops = {
107 .statfs = efivarfs_statfs,
108 .drop_inode = generic_delete_inode,
109 .evict_inode = efivarfs_evict_inode,
110 .show_options = efivarfs_show_options,
111 };
112
113 /*
114 * Compare two efivarfs file names.
115 *
116 * An efivarfs filename is composed of two parts,
117 *
118 * 1. A case-sensitive variable name
119 * 2. A case-insensitive GUID
120 *
121 * So we need to perform a case-sensitive match on part 1 and a
122 * case-insensitive match on part 2.
123 */
124 static int efivarfs_d_compare(const struct dentry *dentry,
125 unsigned int len, const char *str,
126 const struct qstr *name)
127 {
128 int guid = len - EFI_VARIABLE_GUID_LEN;
129
130 if (name->len != len)
131 return 1;
132
133 /* Case-sensitive compare for the variable name */
134 if (memcmp(str, name->name, guid))
135 return 1;
136
137 /* Case-insensitive compare for the GUID */
138 return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
139 }
140
141 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
142 {
143 unsigned long hash = init_name_hash(dentry);
144 const unsigned char *s = qstr->name;
145 unsigned int len = qstr->len;
146
147 if (!efivarfs_valid_name(s, len))
148 return -EINVAL;
149
150 while (len-- > EFI_VARIABLE_GUID_LEN)
151 hash = partial_name_hash(*s++, hash);
152
153 /* GUID is case-insensitive. */
154 while (len--)
155 hash = partial_name_hash(tolower(*s++), hash);
156
157 qstr->hash = end_name_hash(hash);
158 return 0;
159 }
160
161 static const struct dentry_operations efivarfs_d_ops = {
162 .d_compare = efivarfs_d_compare,
163 .d_hash = efivarfs_d_hash,
164 .d_delete = always_delete_dentry,
165 };
166
167 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
168 {
169 struct dentry *d;
170 struct qstr q;
171 int err;
172
173 q.name = name;
174 q.len = strlen(name);
175
176 err = efivarfs_d_hash(parent, &q);
177 if (err)
178 return ERR_PTR(err);
179
180 d = d_alloc(parent, &q);
181 if (d)
182 return d;
183
184 return ERR_PTR(-ENOMEM);
185 }
186
187 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
188 unsigned long name_size, void *data,
189 struct list_head *list)
190 {
191 struct super_block *sb = (struct super_block *)data;
192 struct efivar_entry *entry;
193 struct inode *inode = NULL;
194 struct dentry *dentry, *root = sb->s_root;
195 unsigned long size = 0;
196 char *name;
197 int len;
198 int err = -ENOMEM;
199 bool is_removable = false;
200
201 if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
202 return 0;
203
204 entry = kzalloc(sizeof(*entry), GFP_KERNEL);
205 if (!entry)
206 return err;
207
208 memcpy(entry->var.VariableName, name16, name_size);
209 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
210
211 len = ucs2_utf8size(entry->var.VariableName);
212
213 /* name, plus '-', plus GUID, plus NUL*/
214 name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
215 if (!name)
216 goto fail;
217
218 ucs2_as_utf8(name, entry->var.VariableName, len);
219
220 if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
221 is_removable = true;
222
223 name[len] = '-';
224
225 efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
226
227 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
228
229 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
230 strreplace(name, '/', '!');
231
232 inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
233 is_removable);
234 if (!inode)
235 goto fail_name;
236
237 dentry = efivarfs_alloc_dentry(root, name);
238 if (IS_ERR(dentry)) {
239 err = PTR_ERR(dentry);
240 goto fail_inode;
241 }
242
243 __efivar_entry_get(entry, NULL, &size, NULL);
244 __efivar_entry_add(entry, list);
245
246 /* copied by the above to local storage in the dentry. */
247 kfree(name);
248
249 inode_lock(inode);
250 inode->i_private = entry;
251 i_size_write(inode, size + sizeof(entry->var.Attributes));
252 inode_unlock(inode);
253 d_add(dentry, inode);
254
255 return 0;
256
257 fail_inode:
258 iput(inode);
259 fail_name:
260 kfree(name);
261 fail:
262 kfree(entry);
263 return err;
264 }
265
266 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
267 {
268 efivar_entry_remove(entry);
269 kfree(entry);
270 return 0;
271 }
272
273 enum {
274 Opt_uid, Opt_gid,
275 };
276
277 static const struct fs_parameter_spec efivarfs_parameters[] = {
278 fsparam_uid("uid", Opt_uid),
279 fsparam_gid("gid", Opt_gid),
280 {},
281 };
282
283 static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
284 {
285 struct efivarfs_fs_info *sbi = fc->s_fs_info;
286 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
287 struct fs_parse_result result;
288 int opt;
289
290 opt = fs_parse(fc, efivarfs_parameters, param, &result);
291 if (opt < 0)
292 return opt;
293
294 switch (opt) {
295 case Opt_uid:
296 opts->uid = result.uid;
297 break;
298 case Opt_gid:
299 opts->gid = result.gid;
300 break;
301 default:
302 return -EINVAL;
303 }
304
305 return 0;
306 }
307
308 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
309 {
310 struct efivarfs_fs_info *sfi = sb->s_fs_info;
311 struct inode *inode = NULL;
312 struct dentry *root;
313 int err;
314
315 sb->s_maxbytes = MAX_LFS_FILESIZE;
316 sb->s_blocksize = PAGE_SIZE;
317 sb->s_blocksize_bits = PAGE_SHIFT;
318 sb->s_magic = EFIVARFS_MAGIC;
319 sb->s_op = &efivarfs_ops;
320 sb->s_d_op = &efivarfs_d_ops;
321 sb->s_time_gran = 1;
322
323 if (!efivar_supports_writes())
324 sb->s_flags |= SB_RDONLY;
325
326 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
327 if (!inode)
328 return -ENOMEM;
329 inode->i_op = &efivarfs_dir_inode_operations;
330
331 root = d_make_root(inode);
332 sb->s_root = root;
333 if (!root)
334 return -ENOMEM;
335
336 sfi->sb = sb;
337 sfi->nb.notifier_call = efivarfs_ops_notifier;
338 err = blocking_notifier_chain_register(&efivar_ops_nh, &sfi->nb);
339 if (err)
340 return err;
341
342 return efivar_init(efivarfs_callback, sb, &sfi->efivarfs_list);
343 }
344
345 static int efivarfs_get_tree(struct fs_context *fc)
346 {
347 return get_tree_single(fc, efivarfs_fill_super);
348 }
349
350 static int efivarfs_reconfigure(struct fs_context *fc)
351 {
352 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
353 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
354 return -EINVAL;
355 }
356
357 return 0;
358 }
359
360 static const struct fs_context_operations efivarfs_context_ops = {
361 .get_tree = efivarfs_get_tree,
362 .parse_param = efivarfs_parse_param,
363 .reconfigure = efivarfs_reconfigure,
364 };
365
366 static int efivarfs_init_fs_context(struct fs_context *fc)
367 {
368 struct efivarfs_fs_info *sfi;
369
370 if (!efivar_is_available())
371 return -EOPNOTSUPP;
372
373 sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
374 if (!sfi)
375 return -ENOMEM;
376
377 INIT_LIST_HEAD(&sfi->efivarfs_list);
378
379 sfi->mount_opts.uid = GLOBAL_ROOT_UID;
380 sfi->mount_opts.gid = GLOBAL_ROOT_GID;
381
382 fc->s_fs_info = sfi;
383 fc->ops = &efivarfs_context_ops;
384 return 0;
385 }
386
387 static void efivarfs_kill_sb(struct super_block *sb)
388 {
389 struct efivarfs_fs_info *sfi = sb->s_fs_info;
390
391 blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
392 kill_litter_super(sb);
393
394 /* Remove all entries and destroy */
395 efivar_entry_iter(efivarfs_destroy, &sfi->efivarfs_list, NULL);
396 kfree(sfi);
397 }
398
399 static struct file_system_type efivarfs_type = {
400 .owner = THIS_MODULE,
401 .name = "efivarfs",
402 .init_fs_context = efivarfs_init_fs_context,
403 .kill_sb = efivarfs_kill_sb,
404 .parameters = efivarfs_parameters,
405 };
406
407 static __init int efivarfs_init(void)
408 {
409 return register_filesystem(&efivarfs_type);
410 }
411
412 static __exit void efivarfs_exit(void)
413 {
414 unregister_filesystem(&efivarfs_type);
415 }
416
417 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
418 MODULE_DESCRIPTION("EFI Variable Filesystem");
419 MODULE_LICENSE("GPL");
420 MODULE_ALIAS_FS("efivarfs");
421
422 module_init(efivarfs_init);
423 module_exit(efivarfs_exit);
424
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