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
23static 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
42static void efivarfs_evict_inode(struct inode *inode)
43{
44 clear_inode(inode);
45}
46
47static 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(left: 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
62static 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(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: &storage_space,
75 remaining_space: &remaining_space,
76 max_variable_size: &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(v: 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}
106static 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 */
124static 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(p: str, q: name->name, size: guid))
135 return 1;
136
137 /* Case-insensitive compare for the GUID */
138 return strncasecmp(s1: name->name + guid, s2: str + guid, EFI_VARIABLE_GUID_LEN);
139}
140
141static 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(str: s, len))
148 return -EINVAL;
149
150 while (len-- > EFI_VARIABLE_GUID_LEN)
151 hash = partial_name_hash(c: *s++, prevhash: hash);
152
153 /* GUID is case-insensitive. */
154 while (len--)
155 hash = partial_name_hash(tolower(*s++), prevhash: hash);
156
157 qstr->hash = end_name_hash(hash);
158 return 0;
159}
160
161static 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
167static 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(dentry: parent, qstr: &q);
177 if (err)
178 return ERR_PTR(error: err);
179
180 d = d_alloc(parent, &q);
181 if (d)
182 return d;
183
184 return ERR_PTR(error: -ENOMEM);
185}
186
187static 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(u1: &vendor, u2: &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
202 return 0;
203
204 entry = kzalloc(size: 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(src: entry->var.VariableName);
212
213 /* name, plus '-', plus GUID, plus NUL*/
214 name = kmalloc(size: len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
215 if (!name)
216 goto fail;
217
218 ucs2_as_utf8(dest: name, src: entry->var.VariableName, maxlength: len);
219
220 if (efivar_variable_is_removable(vendor: entry->var.VendorGuid, name, len))
221 is_removable = true;
222
223 name[len] = '-';
224
225 efi_guid_to_str(guid: &entry->var.VendorGuid, out: 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(str: name, old: '/', new: '!');
231
232 inode = efivarfs_get_inode(sb, dir: d_inode(dentry: root), S_IFREG | 0644, dev: 0,
233 is_removable);
234 if (!inode)
235 goto fail_name;
236
237 dentry = efivarfs_alloc_dentry(parent: root, name);
238 if (IS_ERR(ptr: dentry)) {
239 err = PTR_ERR(ptr: dentry);
240 goto fail_inode;
241 }
242
243 __efivar_entry_get(entry, NULL, size: &size, NULL);
244 __efivar_entry_add(entry, head: list);
245
246 /* copied by the above to local storage in the dentry. */
247 kfree(objp: name);
248
249 inode_lock(inode);
250 inode->i_private = entry;
251 i_size_write(inode, i_size: size + sizeof(entry->var.Attributes));
252 inode_unlock(inode);
253 d_add(dentry, inode);
254
255 return 0;
256
257fail_inode:
258 iput(inode);
259fail_name:
260 kfree(objp: name);
261fail:
262 kfree(objp: entry);
263 return err;
264}
265
266static int efivarfs_destroy(struct efivar_entry *entry, void *data)
267{
268 efivar_entry_remove(entry);
269 kfree(objp: entry);
270 return 0;
271}
272
273enum {
274 Opt_uid, Opt_gid,
275};
276
277static const struct fs_parameter_spec efivarfs_parameters[] = {
278 fsparam_u32("uid", Opt_uid),
279 fsparam_u32("gid", Opt_gid),
280 {},
281};
282
283static 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, desc: efivarfs_parameters, param, result: &result);
291 if (opt < 0)
292 return opt;
293
294 switch (opt) {
295 case Opt_uid:
296 opts->uid = make_kuid(current_user_ns(), uid: result.uint_32);
297 if (!uid_valid(uid: opts->uid))
298 return -EINVAL;
299 break;
300 case Opt_gid:
301 opts->gid = make_kgid(current_user_ns(), gid: result.uint_32);
302 if (!gid_valid(gid: opts->gid))
303 return -EINVAL;
304 break;
305 default:
306 return -EINVAL;
307 }
308
309 return 0;
310}
311
312static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
313{
314 struct efivarfs_fs_info *sfi = sb->s_fs_info;
315 struct inode *inode = NULL;
316 struct dentry *root;
317 int err;
318
319 sb->s_maxbytes = MAX_LFS_FILESIZE;
320 sb->s_blocksize = PAGE_SIZE;
321 sb->s_blocksize_bits = PAGE_SHIFT;
322 sb->s_magic = EFIVARFS_MAGIC;
323 sb->s_op = &efivarfs_ops;
324 sb->s_d_op = &efivarfs_d_ops;
325 sb->s_time_gran = 1;
326
327 if (!efivar_supports_writes())
328 sb->s_flags |= SB_RDONLY;
329
330 inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, dev: 0, is_removable: true);
331 if (!inode)
332 return -ENOMEM;
333 inode->i_op = &efivarfs_dir_inode_operations;
334
335 root = d_make_root(inode);
336 sb->s_root = root;
337 if (!root)
338 return -ENOMEM;
339
340 sfi->sb = sb;
341 sfi->nb.notifier_call = efivarfs_ops_notifier;
342 err = blocking_notifier_chain_register(nh: &efivar_ops_nh, nb: &sfi->nb);
343 if (err)
344 return err;
345
346 return efivar_init(func: efivarfs_callback, data: sb, head: &sfi->efivarfs_list);
347}
348
349static int efivarfs_get_tree(struct fs_context *fc)
350{
351 return get_tree_single(fc, fill_super: efivarfs_fill_super);
352}
353
354static int efivarfs_reconfigure(struct fs_context *fc)
355{
356 if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
357 pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
358 return -EINVAL;
359 }
360
361 return 0;
362}
363
364static const struct fs_context_operations efivarfs_context_ops = {
365 .get_tree = efivarfs_get_tree,
366 .parse_param = efivarfs_parse_param,
367 .reconfigure = efivarfs_reconfigure,
368};
369
370static int efivarfs_init_fs_context(struct fs_context *fc)
371{
372 struct efivarfs_fs_info *sfi;
373
374 if (!efivar_is_available())
375 return -EOPNOTSUPP;
376
377 sfi = kzalloc(size: sizeof(*sfi), GFP_KERNEL);
378 if (!sfi)
379 return -ENOMEM;
380
381 INIT_LIST_HEAD(list: &sfi->efivarfs_list);
382
383 sfi->mount_opts.uid = GLOBAL_ROOT_UID;
384 sfi->mount_opts.gid = GLOBAL_ROOT_GID;
385
386 fc->s_fs_info = sfi;
387 fc->ops = &efivarfs_context_ops;
388 return 0;
389}
390
391static void efivarfs_kill_sb(struct super_block *sb)
392{
393 struct efivarfs_fs_info *sfi = sb->s_fs_info;
394
395 blocking_notifier_chain_unregister(nh: &efivar_ops_nh, nb: &sfi->nb);
396 kill_litter_super(sb);
397
398 /* Remove all entries and destroy */
399 efivar_entry_iter(func: efivarfs_destroy, head: &sfi->efivarfs_list, NULL);
400 kfree(objp: sfi);
401}
402
403static struct file_system_type efivarfs_type = {
404 .owner = THIS_MODULE,
405 .name = "efivarfs",
406 .init_fs_context = efivarfs_init_fs_context,
407 .kill_sb = efivarfs_kill_sb,
408 .parameters = efivarfs_parameters,
409};
410
411static __init int efivarfs_init(void)
412{
413 return register_filesystem(&efivarfs_type);
414}
415
416static __exit void efivarfs_exit(void)
417{
418 unregister_filesystem(&efivarfs_type);
419}
420
421MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
422MODULE_DESCRIPTION("EFI Variable Filesystem");
423MODULE_LICENSE("GPL");
424MODULE_ALIAS_FS("efivarfs");
425
426module_init(efivarfs_init);
427module_exit(efivarfs_exit);
428

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