xref: /linux/fs/efivarfs/super.c (revision d642ef71) 
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 
21 LIST_HEAD(efivarfs_list);
22 
23 static void efivarfs_evict_inode(struct inode *inode)
24 {
25 	clear_inode(inode);
26 }
27 
28 static 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(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 
43 static 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(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,
56 						    &remaining_space,
57 						    &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(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 }
87 static 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  */
105 static 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(str, name->name, guid))
116 		return 1;
117 
118 	/* Case-insensitive compare for the GUID */
119 	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
120 }
121 
122 static 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(s, len))
129 		return -EINVAL;
130 
131 	while (len-- > EFI_VARIABLE_GUID_LEN)
132 		hash = partial_name_hash(*s++, hash);
133 
134 	/* GUID is case-insensitive. */
135 	while (len--)
136 		hash = partial_name_hash(tolower(*s++), hash);
137 
138 	qstr->hash = end_name_hash(hash);
139 	return 0;
140 }
141 
142 static 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 
148 static 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(parent, &q);
158 	if (err)
159 		return ERR_PTR(err);
160 
161 	d = d_alloc(parent, &q);
162 	if (d)
163 		return d;
164 
165 	return ERR_PTR(-ENOMEM);
166 }
167 
168 static 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(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
182 		return 0;
183 
184 	entry = kzalloc(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(entry->var.VariableName);
192 
193 	/* name, plus '-', plus GUID, plus NUL*/
194 	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
195 	if (!name)
196 		goto fail;
197 
198 	ucs2_as_utf8(name, entry->var.VariableName, len);
199 
200 	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
201 		is_removable = true;
202 
203 	name[len] = '-';
204 
205 	efi_guid_to_str(&entry->var.VendorGuid, 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(name, '/', '!');
211 
212 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
213 				   is_removable);
214 	if (!inode)
215 		goto fail_name;
216 
217 	dentry = efivarfs_alloc_dentry(root, name);
218 	if (IS_ERR(dentry)) {
219 		err = PTR_ERR(dentry);
220 		goto fail_inode;
221 	}
222 
223 	__efivar_entry_get(entry, NULL, &size, NULL);
224 	__efivar_entry_add(entry, &efivarfs_list);
225 
226 	/* copied by the above to local storage in the dentry. */
227 	kfree(name);
228 
229 	inode_lock(inode);
230 	inode->i_private = entry;
231 	i_size_write(inode, size + sizeof(entry->var.Attributes));
232 	inode_unlock(inode);
233 	d_add(dentry, inode);
234 
235 	return 0;
236 
237 fail_inode:
238 	iput(inode);
239 fail_name:
240 	kfree(name);
241 fail:
242 	kfree(entry);
243 	return err;
244 }
245 
246 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
247 {
248 	efivar_entry_remove(entry);
249 	kfree(entry);
250 	return 0;
251 }
252 
253 enum {
254 	Opt_uid, Opt_gid,
255 };
256 
257 static const struct fs_parameter_spec efivarfs_parameters[] = {
258 	fsparam_u32("uid", Opt_uid),
259 	fsparam_u32("gid", Opt_gid),
260 	{},
261 };
262 
263 static 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, efivarfs_parameters, param, &result);
271 	if (opt < 0)
272 		return opt;
273 
274 	switch (opt) {
275 	case Opt_uid:
276 		opts->uid = make_kuid(current_user_ns(), result.uint_32);
277 		if (!uid_valid(opts->uid))
278 			return -EINVAL;
279 		break;
280 	case Opt_gid:
281 		opts->gid = make_kgid(current_user_ns(), result.uint_32);
282 		if (!gid_valid(opts->gid))
283 			return -EINVAL;
284 		break;
285 	default:
286 		return -EINVAL;
287 	}
288 
289 	return 0;
290 }
291 
292 static 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, 0, 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(&efivarfs_list);
323 
324 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
325 	if (err)
326 		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
327 
328 	return err;
329 }
330 
331 static int efivarfs_get_tree(struct fs_context *fc)
332 {
333 	return get_tree_single(fc, efivarfs_fill_super);
334 }
335 
336 static const struct fs_context_operations efivarfs_context_ops = {
337 	.get_tree	= efivarfs_get_tree,
338 	.parse_param	= efivarfs_parse_param,
339 };
340 
341 static int efivarfs_init_fs_context(struct fs_context *fc)
342 {
343 	struct efivarfs_fs_info *sfi;
344 
345 	sfi = kzalloc(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 
357 static 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(efivarfs_destroy, &efivarfs_list, NULL);
366 }
367 
368 static 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 
376 static __init int efivarfs_init(void)
377 {
378 	return register_filesystem(&efivarfs_type);
379 }
380 
381 static __exit void efivarfs_exit(void)
382 {
383 	unregister_filesystem(&efivarfs_type);
384 }
385 
386 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
387 MODULE_DESCRIPTION("EFI Variable Filesystem");
388 MODULE_LICENSE("GPL");
389 MODULE_ALIAS_FS("efivarfs");
390 
391 module_init(efivarfs_init);
392 module_exit(efivarfs_exit);
393