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
19#include "internal.h"
20
21LIST_HEAD(efivarfs_list);
22
23static void efivarfs_evict_inode(struct inode *inode)
24{
25 clear_inode(inode);
26}
27
28static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
29{
30 struct super_block *sb = root->d_sb;
31 struct efivarfs_fs_info *sbi = sb->s_fs_info;
32 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
33
34 if (!uid_eq(left: opts->uid, GLOBAL_ROOT_UID))
35 seq_printf(m, ",uid=%u",
36 from_kuid_munged(&init_user_ns, opts->uid));
37 if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
38 seq_printf(m, ",gid=%u",
39 from_kgid_munged(&init_user_ns, opts->gid));
40 return 0;
41}
42
43static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
44{
45 const u32 attr = EFI_VARIABLE_NON_VOLATILE |
46 EFI_VARIABLE_BOOTSERVICE_ACCESS |
47 EFI_VARIABLE_RUNTIME_ACCESS;
48 u64 storage_space, remaining_space, max_variable_size;
49 u64 id = huge_encode_dev(dev: dentry->d_sb->s_dev);
50 efi_status_t status;
51
52 /* Some UEFI firmware does not implement QueryVariableInfo() */
53 storage_space = remaining_space = 0;
54 if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
55 status = efivar_query_variable_info(attr, storage_space: &storage_space,
56 remaining_space: &remaining_space,
57 max_variable_size: &max_variable_size);
58 if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
59 pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
60 status);
61 }
62
63 /*
64 * This is not a normal filesystem, so no point in pretending it has a block
65 * size; we declare f_bsize to 1, so that we can then report the exact value
66 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
67 */
68 buf->f_bsize = 1;
69 buf->f_namelen = NAME_MAX;
70 buf->f_blocks = storage_space;
71 buf->f_bfree = remaining_space;
72 buf->f_type = dentry->d_sb->s_magic;
73 buf->f_fsid = u64_to_fsid(v: id);
74
75 /*
76 * In f_bavail we declare the free space that the kernel will allow writing
77 * when the storage_paranoia x86 quirk is active. To use more, users
78 * should boot the kernel with efi_no_storage_paranoia.
79 */
80 if (remaining_space > efivar_reserved_space())
81 buf->f_bavail = remaining_space - efivar_reserved_space();
82 else
83 buf->f_bavail = 0;
84
85 return 0;
86}
87static const struct super_operations efivarfs_ops = {
88 .statfs = efivarfs_statfs,
89 .drop_inode = generic_delete_inode,
90 .evict_inode = efivarfs_evict_inode,
91 .show_options = efivarfs_show_options,
92};
93
94/*
95 * Compare two efivarfs file names.
96 *
97 * An efivarfs filename is composed of two parts,
98 *
99 * 1. A case-sensitive variable name
100 * 2. A case-insensitive GUID
101 *
102 * So we need to perform a case-sensitive match on part 1 and a
103 * case-insensitive match on part 2.
104 */
105static int efivarfs_d_compare(const struct dentry *dentry,
106 unsigned int len, const char *str,
107 const struct qstr *name)
108{
109 int guid = len - EFI_VARIABLE_GUID_LEN;
110
111 if (name->len != len)
112 return 1;
113
114 /* Case-sensitive compare for the variable name */
115 if (memcmp(p: str, q: name->name, size: guid))
116 return 1;
117
118 /* Case-insensitive compare for the GUID */
119 return strncasecmp(s1: name->name + guid, s2: str + guid, EFI_VARIABLE_GUID_LEN);
120}
121
122static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
123{
124 unsigned long hash = init_name_hash(dentry);
125 const unsigned char *s = qstr->name;
126 unsigned int len = qstr->len;
127
128 if (!efivarfs_valid_name(str: s, len))
129 return -EINVAL;
130
131 while (len-- > EFI_VARIABLE_GUID_LEN)
132 hash = partial_name_hash(c: *s++, prevhash: hash);
133
134 /* GUID is case-insensitive. */
135 while (len--)
136 hash = partial_name_hash(tolower(*s++), prevhash: hash);
137
138 qstr->hash = end_name_hash(hash);
139 return 0;
140}
141
142static const struct dentry_operations efivarfs_d_ops = {
143 .d_compare = efivarfs_d_compare,
144 .d_hash = efivarfs_d_hash,
145 .d_delete = always_delete_dentry,
146};
147
148static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
149{
150 struct dentry *d;
151 struct qstr q;
152 int err;
153
154 q.name = name;
155 q.len = strlen(name);
156
157 err = efivarfs_d_hash(dentry: parent, qstr: &q);
158 if (err)
159 return ERR_PTR(error: err);
160
161 d = d_alloc(parent, &q);
162 if (d)
163 return d;
164
165 return ERR_PTR(error: -ENOMEM);
166}
167
168static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
169 unsigned long name_size, void *data)
170{
171 struct super_block *sb = (struct super_block *)data;
172 struct efivar_entry *entry;
173 struct inode *inode = NULL;
174 struct dentry *dentry, *root = sb->s_root;
175 unsigned long size = 0;
176 char *name;
177 int len;
178 int err = -ENOMEM;
179 bool is_removable = false;
180
181 if (guid_equal(u1: &vendor, u2: &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
182 return 0;
183
184 entry = kzalloc(size: sizeof(*entry), GFP_KERNEL);
185 if (!entry)
186 return err;
187
188 memcpy(entry->var.VariableName, name16, name_size);
189 memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
190
191 len = ucs2_utf8size(src: entry->var.VariableName);
192
193 /* name, plus '-', plus GUID, plus NUL*/
194 name = kmalloc(size: len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
195 if (!name)
196 goto fail;
197
198 ucs2_as_utf8(dest: name, src: entry->var.VariableName, maxlength: len);
199
200 if (efivar_variable_is_removable(vendor: entry->var.VendorGuid, name, len))
201 is_removable = true;
202
203 name[len] = '-';
204
205 efi_guid_to_str(guid: &entry->var.VendorGuid, out: name + len + 1);
206
207 name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
208
209 /* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
210 strreplace(str: name, old: '/', new: '!');
211
212 inode = efivarfs_get_inode(sb, dir: d_inode(dentry: root), S_IFREG | 0644, dev: 0,
213 is_removable);
214 if (!inode)
215 goto fail_name;
216
217 dentry = efivarfs_alloc_dentry(parent: root, name);
218 if (IS_ERR(ptr: dentry)) {
219 err = PTR_ERR(ptr: dentry);
220 goto fail_inode;
221 }
222
223 __efivar_entry_get(entry, NULL, size: &size, NULL);
224 __efivar_entry_add(entry, head: &efivarfs_list);
225
226 /* copied by the above to local storage in the dentry. */
227 kfree(objp: name);
228
229 inode_lock(inode);
230 inode->i_private = entry;
231 i_size_write(inode, i_size: size + sizeof(entry->var.Attributes));
232 inode_unlock(inode);
233 d_add(dentry, inode);
234
235 return 0;
236
237fail_inode:
238 iput(inode);
239fail_name:
240 kfree(objp: name);
241fail:
242 kfree(objp: entry);
243 return err;
244}
245
246static int efivarfs_destroy(struct efivar_entry *entry, void *data)
247{
248 efivar_entry_remove(entry);
249 kfree(objp: entry);
250 return 0;
251}
252
253enum {
254 Opt_uid, Opt_gid,
255};
256
257static const struct fs_parameter_spec efivarfs_parameters[] = {
258 fsparam_u32("uid", Opt_uid),
259 fsparam_u32("gid", Opt_gid),
260 {},
261};
262
263static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
264{
265 struct efivarfs_fs_info *sbi = fc->s_fs_info;
266 struct efivarfs_mount_opts *opts = &sbi->mount_opts;
267 struct fs_parse_result result;
268 int opt;
269
270 opt = fs_parse(fc, desc: efivarfs_parameters, param, result: &result);
271 if (opt < 0)
272 return opt;
273
274 switch (opt) {
275 case Opt_uid:
276 opts->uid = make_kuid(current_user_ns(), uid: result.uint_32);
277 if (!uid_valid(uid: opts->uid))
278 return -EINVAL;
279 break;
280 case Opt_gid:
281 opts->gid = make_kgid(current_user_ns(), gid: result.uint_32);
282 if (!gid_valid(gid: opts->gid))
283 return -EINVAL;
284 break;
285 default:
286 return -EINVAL;
287 }
288
289 return 0;
290}
291
292static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
293{
294 struct inode *inode = NULL;
295 struct dentry *root;
296 int err;
297
298 if (!efivar_is_available())
299 return -EOPNOTSUPP;
300
301 sb->s_maxbytes = MAX_LFS_FILESIZE;
302 sb->s_blocksize = PAGE_SIZE;
303 sb->s_blocksize_bits = PAGE_SHIFT;
304 sb->s_magic = EFIVARFS_MAGIC;
305 sb->s_op = &efivarfs_ops;
306 sb->s_d_op = &efivarfs_d_ops;
307 sb->s_time_gran = 1;
308
309 if (!efivar_supports_writes())
310 sb->s_flags |= SB_RDONLY;
311
312 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, dev: 0, is_removable: true);
313 if (!inode)
314 return -ENOMEM;
315 inode->i_op = &efivarfs_dir_inode_operations;
316
317 root = d_make_root(inode);
318 sb->s_root = root;
319 if (!root)
320 return -ENOMEM;
321
322 INIT_LIST_HEAD(list: &efivarfs_list);
323
324 err = efivar_init(func: efivarfs_callback, data: (void *)sb, duplicates: true, head: &efivarfs_list);
325 if (err)
326 efivar_entry_iter(func: efivarfs_destroy, head: &efivarfs_list, NULL);
327
328 return err;
329}
330
331static int efivarfs_get_tree(struct fs_context *fc)
332{
333 return get_tree_single(fc, fill_super: efivarfs_fill_super);
334}
335
336static const struct fs_context_operations efivarfs_context_ops = {
337 .get_tree = efivarfs_get_tree,
338 .parse_param = efivarfs_parse_param,
339};
340
341static int efivarfs_init_fs_context(struct fs_context *fc)
342{
343 struct efivarfs_fs_info *sfi;
344
345 sfi = kzalloc(size: sizeof(*sfi), GFP_KERNEL);
346 if (!sfi)
347 return -ENOMEM;
348
349 sfi->mount_opts.uid = GLOBAL_ROOT_UID;
350 sfi->mount_opts.gid = GLOBAL_ROOT_GID;
351
352 fc->s_fs_info = sfi;
353 fc->ops = &efivarfs_context_ops;
354 return 0;
355}
356
357static void efivarfs_kill_sb(struct super_block *sb)
358{
359 kill_litter_super(sb);
360
361 if (!efivar_is_available())
362 return;
363
364 /* Remove all entries and destroy */
365 efivar_entry_iter(func: efivarfs_destroy, head: &efivarfs_list, NULL);
366}
367
368static struct file_system_type efivarfs_type = {
369 .owner = THIS_MODULE,
370 .name = "efivarfs",
371 .init_fs_context = efivarfs_init_fs_context,
372 .kill_sb = efivarfs_kill_sb,
373 .parameters = efivarfs_parameters,
374};
375
376static __init int efivarfs_init(void)
377{
378 return register_filesystem(&efivarfs_type);
379}
380
381static __exit void efivarfs_exit(void)
382{
383 unregister_filesystem(&efivarfs_type);
384}
385
386MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
387MODULE_DESCRIPTION("EFI Variable Filesystem");
388MODULE_LICENSE("GPL");
389MODULE_ALIAS_FS("efivarfs");
390
391module_init(efivarfs_init);
392module_exit(efivarfs_exit);
393

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