xref: /openbmc/linux/fs/efivarfs/super.c (revision a72b9869) 
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/module.h>
12 #include <linux/pagemap.h>
13 #include <linux/ucs2_string.h>
14 #include <linux/slab.h>
15 #include <linux/magic.h>
16 
17 #include "internal.h"
18 
19 LIST_HEAD(efivarfs_list);
20 
21 static void efivarfs_evict_inode(struct inode *inode)
22 {
23 	clear_inode(inode);
24 }
25 
26 static const struct super_operations efivarfs_ops = {
27 	.statfs = simple_statfs,
28 	.drop_inode = generic_delete_inode,
29 	.evict_inode = efivarfs_evict_inode,
30 };
31 
32 /*
33  * Compare two efivarfs file names.
34  *
35  * An efivarfs filename is composed of two parts,
36  *
37  *	1. A case-sensitive variable name
38  *	2. A case-insensitive GUID
39  *
40  * So we need to perform a case-sensitive match on part 1 and a
41  * case-insensitive match on part 2.
42  */
43 static int efivarfs_d_compare(const struct dentry *dentry,
44 			      unsigned int len, const char *str,
45 			      const struct qstr *name)
46 {
47 	int guid = len - EFI_VARIABLE_GUID_LEN;
48 
49 	if (name->len != len)
50 		return 1;
51 
52 	/* Case-sensitive compare for the variable name */
53 	if (memcmp(str, name->name, guid))
54 		return 1;
55 
56 	/* Case-insensitive compare for the GUID */
57 	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
58 }
59 
60 static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
61 {
62 	unsigned long hash = init_name_hash(dentry);
63 	const unsigned char *s = qstr->name;
64 	unsigned int len = qstr->len;
65 
66 	if (!efivarfs_valid_name(s, len))
67 		return -EINVAL;
68 
69 	while (len-- > EFI_VARIABLE_GUID_LEN)
70 		hash = partial_name_hash(*s++, hash);
71 
72 	/* GUID is case-insensitive. */
73 	while (len--)
74 		hash = partial_name_hash(tolower(*s++), hash);
75 
76 	qstr->hash = end_name_hash(hash);
77 	return 0;
78 }
79 
80 static const struct dentry_operations efivarfs_d_ops = {
81 	.d_compare = efivarfs_d_compare,
82 	.d_hash = efivarfs_d_hash,
83 	.d_delete = always_delete_dentry,
84 };
85 
86 static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
87 {
88 	struct dentry *d;
89 	struct qstr q;
90 	int err;
91 
92 	q.name = name;
93 	q.len = strlen(name);
94 
95 	err = efivarfs_d_hash(parent, &q);
96 	if (err)
97 		return ERR_PTR(err);
98 
99 	d = d_alloc(parent, &q);
100 	if (d)
101 		return d;
102 
103 	return ERR_PTR(-ENOMEM);
104 }
105 
106 static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
107 			     unsigned long name_size, void *data)
108 {
109 	struct super_block *sb = (struct super_block *)data;
110 	struct efivar_entry *entry;
111 	struct inode *inode = NULL;
112 	struct dentry *dentry, *root = sb->s_root;
113 	unsigned long size = 0;
114 	char *name;
115 	int len;
116 	int err = -ENOMEM;
117 	bool is_removable = false;
118 
119 	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
120 		return 0;
121 
122 	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
123 	if (!entry)
124 		return err;
125 
126 	memcpy(entry->var.VariableName, name16, name_size);
127 	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
128 
129 	len = ucs2_utf8size(entry->var.VariableName);
130 
131 	/* name, plus '-', plus GUID, plus NUL*/
132 	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
133 	if (!name)
134 		goto fail;
135 
136 	ucs2_as_utf8(name, entry->var.VariableName, len);
137 
138 	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
139 		is_removable = true;
140 
141 	name[len] = '-';
142 
143 	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
144 
145 	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
146 
147 	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
148 	strreplace(name, '/', '!');
149 
150 	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
151 				   is_removable);
152 	if (!inode)
153 		goto fail_name;
154 
155 	dentry = efivarfs_alloc_dentry(root, name);
156 	if (IS_ERR(dentry)) {
157 		err = PTR_ERR(dentry);
158 		goto fail_inode;
159 	}
160 
161 	__efivar_entry_get(entry, NULL, &size, NULL);
162 	__efivar_entry_add(entry, &efivarfs_list);
163 
164 	/* copied by the above to local storage in the dentry. */
165 	kfree(name);
166 
167 	inode_lock(inode);
168 	inode->i_private = entry;
169 	i_size_write(inode, size + sizeof(entry->var.Attributes));
170 	inode_unlock(inode);
171 	d_add(dentry, inode);
172 
173 	return 0;
174 
175 fail_inode:
176 	iput(inode);
177 fail_name:
178 	kfree(name);
179 fail:
180 	kfree(entry);
181 	return err;
182 }
183 
184 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
185 {
186 	efivar_entry_remove(entry);
187 	kfree(entry);
188 	return 0;
189 }
190 
191 static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
192 {
193 	struct inode *inode = NULL;
194 	struct dentry *root;
195 	int err;
196 
197 	if (!efivar_is_available())
198 		return -EOPNOTSUPP;
199 
200 	sb->s_maxbytes          = MAX_LFS_FILESIZE;
201 	sb->s_blocksize         = PAGE_SIZE;
202 	sb->s_blocksize_bits    = PAGE_SHIFT;
203 	sb->s_magic             = EFIVARFS_MAGIC;
204 	sb->s_op                = &efivarfs_ops;
205 	sb->s_d_op		= &efivarfs_d_ops;
206 	sb->s_time_gran         = 1;
207 
208 	if (!efivar_supports_writes())
209 		sb->s_flags |= SB_RDONLY;
210 
211 	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
212 	if (!inode)
213 		return -ENOMEM;
214 	inode->i_op = &efivarfs_dir_inode_operations;
215 
216 	root = d_make_root(inode);
217 	sb->s_root = root;
218 	if (!root)
219 		return -ENOMEM;
220 
221 	INIT_LIST_HEAD(&efivarfs_list);
222 
223 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
224 	if (err)
225 		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
226 
227 	return err;
228 }
229 
230 static int efivarfs_get_tree(struct fs_context *fc)
231 {
232 	return get_tree_single(fc, efivarfs_fill_super);
233 }
234 
235 static const struct fs_context_operations efivarfs_context_ops = {
236 	.get_tree	= efivarfs_get_tree,
237 };
238 
239 static int efivarfs_init_fs_context(struct fs_context *fc)
240 {
241 	fc->ops = &efivarfs_context_ops;
242 	return 0;
243 }
244 
245 static void efivarfs_kill_sb(struct super_block *sb)
246 {
247 	kill_litter_super(sb);
248 
249 	if (!efivar_is_available())
250 		return;
251 
252 	/* Remove all entries and destroy */
253 	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
254 }
255 
256 static struct file_system_type efivarfs_type = {
257 	.owner   = THIS_MODULE,
258 	.name    = "efivarfs",
259 	.init_fs_context = efivarfs_init_fs_context,
260 	.kill_sb = efivarfs_kill_sb,
261 };
262 
263 static __init int efivarfs_init(void)
264 {
265 	return register_filesystem(&efivarfs_type);
266 }
267 
268 static __exit void efivarfs_exit(void)
269 {
270 	unregister_filesystem(&efivarfs_type);
271 }
272 
273 MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
274 MODULE_DESCRIPTION("EFI Variable Filesystem");
275 MODULE_LICENSE("GPL");
276 MODULE_ALIAS_FS("efivarfs");
277 
278 module_init(efivarfs_init);
279 module_exit(efivarfs_exit);
280