xref: /kernel/linux/linux-5.10/fs/efivarfs/super.c (revision 8c2ecf20) 
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#include <linux/printk.h>
17
18#include "internal.h"
19
20LIST_HEAD(efivarfs_list);
21
22static void efivarfs_evict_inode(struct inode *inode)
23{
24	clear_inode(inode);
25}
26
27static const struct super_operations efivarfs_ops = {
28	.statfs = simple_statfs,
29	.drop_inode = generic_delete_inode,
30	.evict_inode = efivarfs_evict_inode,
31};
32
33/*
34 * Compare two efivarfs file names.
35 *
36 * An efivarfs filename is composed of two parts,
37 *
38 *	1. A case-sensitive variable name
39 *	2. A case-insensitive GUID
40 *
41 * So we need to perform a case-sensitive match on part 1 and a
42 * case-insensitive match on part 2.
43 */
44static int efivarfs_d_compare(const struct dentry *dentry,
45			      unsigned int len, const char *str,
46			      const struct qstr *name)
47{
48	int guid = len - EFI_VARIABLE_GUID_LEN;
49
50	if (name->len != len)
51		return 1;
52
53	/* Case-sensitive compare for the variable name */
54	if (memcmp(str, name->name, guid))
55		return 1;
56
57	/* Case-insensitive compare for the GUID */
58	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
59}
60
61static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
62{
63	unsigned long hash = init_name_hash(dentry);
64	const unsigned char *s = qstr->name;
65	unsigned int len = qstr->len;
66
67	if (!efivarfs_valid_name(s, len))
68		return -EINVAL;
69
70	while (len-- > EFI_VARIABLE_GUID_LEN)
71		hash = partial_name_hash(*s++, hash);
72
73	/* GUID is case-insensitive. */
74	while (len--)
75		hash = partial_name_hash(tolower(*s++), hash);
76
77	qstr->hash = end_name_hash(hash);
78	return 0;
79}
80
81static const struct dentry_operations efivarfs_d_ops = {
82	.d_compare = efivarfs_d_compare,
83	.d_hash = efivarfs_d_hash,
84	.d_delete = always_delete_dentry,
85};
86
87static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
88{
89	struct dentry *d;
90	struct qstr q;
91	int err;
92
93	q.name = name;
94	q.len = strlen(name);
95
96	err = efivarfs_d_hash(parent, &q);
97	if (err)
98		return ERR_PTR(err);
99
100	d = d_alloc(parent, &q);
101	if (d)
102		return d;
103
104	return ERR_PTR(-ENOMEM);
105}
106
107static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
108			     unsigned long name_size, void *data)
109{
110	struct super_block *sb = (struct super_block *)data;
111	struct efivar_entry *entry;
112	struct inode *inode = NULL;
113	struct dentry *dentry, *root = sb->s_root;
114	unsigned long size = 0;
115	char *name;
116	int len;
117	int err = -ENOMEM;
118	bool is_removable = false;
119
120	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
121	if (!entry)
122		return err;
123
124	memcpy(entry->var.VariableName, name16, name_size);
125	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
126
127	len = ucs2_utf8size(entry->var.VariableName);
128
129	/* name, plus '-', plus GUID, plus NUL*/
130	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
131	if (!name)
132		goto fail;
133
134	ucs2_as_utf8(name, entry->var.VariableName, len);
135
136	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
137		is_removable = true;
138
139	name[len] = '-';
140
141	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
142
143	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
144
145	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
146	strreplace(name, '/', '!');
147
148	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
149				   is_removable);
150	if (!inode)
151		goto fail_name;
152
153	dentry = efivarfs_alloc_dentry(root, name);
154	if (IS_ERR(dentry)) {
155		err = PTR_ERR(dentry);
156		goto fail_inode;
157	}
158
159	efivar_entry_size(entry, &size);
160	err = efivar_entry_add(entry, &efivarfs_list);
161	if (err)
162		goto fail_inode;
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
175fail_inode:
176	iput(inode);
177fail_name:
178	kfree(name);
179fail:
180	kfree(entry);
181	return err;
182}
183
184static int efivarfs_destroy(struct efivar_entry *entry, void *data)
185{
186	int err = efivar_entry_remove(entry);
187
188	if (err)
189		return err;
190	kfree(entry);
191	return 0;
192}
193
194static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
195{
196	struct inode *inode = NULL;
197	struct dentry *root;
198	int err;
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, NULL);
226
227	return err;
228}
229
230static int efivarfs_get_tree(struct fs_context *fc)
231{
232	return get_tree_single(fc, efivarfs_fill_super);
233}
234
235static int efivarfs_reconfigure(struct fs_context *fc)
236{
237	if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
238		pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
239		return -EINVAL;
240	}
241
242	return 0;
243}
244
245static const struct fs_context_operations efivarfs_context_ops = {
246	.get_tree	= efivarfs_get_tree,
247	.reconfigure	= efivarfs_reconfigure,
248};
249
250static int efivarfs_init_fs_context(struct fs_context *fc)
251{
252	fc->ops = &efivarfs_context_ops;
253	return 0;
254}
255
256static void efivarfs_kill_sb(struct super_block *sb)
257{
258	kill_litter_super(sb);
259
260	/* Remove all entries and destroy */
261	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
262}
263
264static struct file_system_type efivarfs_type = {
265	.owner   = THIS_MODULE,
266	.name    = "efivarfs",
267	.init_fs_context = efivarfs_init_fs_context,
268	.kill_sb = efivarfs_kill_sb,
269};
270
271static __init int efivarfs_init(void)
272{
273	if (!efivars_kobject())
274		return -ENODEV;
275
276	return register_filesystem(&efivarfs_type);
277}
278
279static __exit void efivarfs_exit(void)
280{
281	unregister_filesystem(&efivarfs_type);
282}
283
284MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
285MODULE_DESCRIPTION("EFI Variable Filesystem");
286MODULE_LICENSE("GPL");
287MODULE_ALIAS_FS("efivarfs");
288
289module_init(efivarfs_init);
290module_exit(efivarfs_exit);
291