xref: /kernel/linux/linux-6.6/fs/efivarfs/super.c (revision 62306a36) 
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/statfs.h>
17#include <linux/printk.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_statfs(struct dentry *dentry, struct kstatfs *buf)
29{
30	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
31			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
32			 EFI_VARIABLE_RUNTIME_ACCESS;
33	u64 storage_space, remaining_space, max_variable_size;
34	efi_status_t status;
35
36	/* Some UEFI firmware does not implement QueryVariableInfo() */
37	storage_space = remaining_space = 0;
38	if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
39		status = efivar_query_variable_info(attr, &storage_space,
40						    &remaining_space,
41						    &max_variable_size);
42		if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
43			pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
44					    status);
45	}
46
47	/*
48	 * This is not a normal filesystem, so no point in pretending it has a block
49	 * size; we declare f_bsize to 1, so that we can then report the exact value
50	 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
51	 */
52	buf->f_bsize	= 1;
53	buf->f_namelen	= NAME_MAX;
54	buf->f_blocks	= storage_space;
55	buf->f_bfree	= remaining_space;
56	buf->f_type	= dentry->d_sb->s_magic;
57
58	/*
59	 * In f_bavail we declare the free space that the kernel will allow writing
60	 * when the storage_paranoia x86 quirk is active. To use more, users
61	 * should boot the kernel with efi_no_storage_paranoia.
62	 */
63	if (remaining_space > efivar_reserved_space())
64		buf->f_bavail = remaining_space - efivar_reserved_space();
65	else
66		buf->f_bavail = 0;
67
68	return 0;
69}
70static const struct super_operations efivarfs_ops = {
71	.statfs = efivarfs_statfs,
72	.drop_inode = generic_delete_inode,
73	.evict_inode = efivarfs_evict_inode,
74};
75
76/*
77 * Compare two efivarfs file names.
78 *
79 * An efivarfs filename is composed of two parts,
80 *
81 *	1. A case-sensitive variable name
82 *	2. A case-insensitive GUID
83 *
84 * So we need to perform a case-sensitive match on part 1 and a
85 * case-insensitive match on part 2.
86 */
87static int efivarfs_d_compare(const struct dentry *dentry,
88			      unsigned int len, const char *str,
89			      const struct qstr *name)
90{
91	int guid = len - EFI_VARIABLE_GUID_LEN;
92
93	if (name->len != len)
94		return 1;
95
96	/* Case-sensitive compare for the variable name */
97	if (memcmp(str, name->name, guid))
98		return 1;
99
100	/* Case-insensitive compare for the GUID */
101	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
102}
103
104static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
105{
106	unsigned long hash = init_name_hash(dentry);
107	const unsigned char *s = qstr->name;
108	unsigned int len = qstr->len;
109
110	if (!efivarfs_valid_name(s, len))
111		return -EINVAL;
112
113	while (len-- > EFI_VARIABLE_GUID_LEN)
114		hash = partial_name_hash(*s++, hash);
115
116	/* GUID is case-insensitive. */
117	while (len--)
118		hash = partial_name_hash(tolower(*s++), hash);
119
120	qstr->hash = end_name_hash(hash);
121	return 0;
122}
123
124static const struct dentry_operations efivarfs_d_ops = {
125	.d_compare = efivarfs_d_compare,
126	.d_hash = efivarfs_d_hash,
127	.d_delete = always_delete_dentry,
128};
129
130static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
131{
132	struct dentry *d;
133	struct qstr q;
134	int err;
135
136	q.name = name;
137	q.len = strlen(name);
138
139	err = efivarfs_d_hash(parent, &q);
140	if (err)
141		return ERR_PTR(err);
142
143	d = d_alloc(parent, &q);
144	if (d)
145		return d;
146
147	return ERR_PTR(-ENOMEM);
148}
149
150static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
151			     unsigned long name_size, void *data)
152{
153	struct super_block *sb = (struct super_block *)data;
154	struct efivar_entry *entry;
155	struct inode *inode = NULL;
156	struct dentry *dentry, *root = sb->s_root;
157	unsigned long size = 0;
158	char *name;
159	int len;
160	int err = -ENOMEM;
161	bool is_removable = false;
162
163	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
164		return 0;
165
166	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
167	if (!entry)
168		return err;
169
170	memcpy(entry->var.VariableName, name16, name_size);
171	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
172
173	len = ucs2_utf8size(entry->var.VariableName);
174
175	/* name, plus '-', plus GUID, plus NUL*/
176	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
177	if (!name)
178		goto fail;
179
180	ucs2_as_utf8(name, entry->var.VariableName, len);
181
182	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
183		is_removable = true;
184
185	name[len] = '-';
186
187	efi_guid_to_str(&entry->var.VendorGuid, name + len + 1);
188
189	name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';
190
191	/* replace invalid slashes like kobject_set_name_vargs does for /sys/firmware/efi/vars. */
192	strreplace(name, '/', '!');
193
194	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
195				   is_removable);
196	if (!inode)
197		goto fail_name;
198
199	dentry = efivarfs_alloc_dentry(root, name);
200	if (IS_ERR(dentry)) {
201		err = PTR_ERR(dentry);
202		goto fail_inode;
203	}
204
205	__efivar_entry_get(entry, NULL, &size, NULL);
206	__efivar_entry_add(entry, &efivarfs_list);
207
208	/* copied by the above to local storage in the dentry. */
209	kfree(name);
210
211	inode_lock(inode);
212	inode->i_private = entry;
213	i_size_write(inode, size + sizeof(entry->var.Attributes));
214	inode_unlock(inode);
215	d_add(dentry, inode);
216
217	return 0;
218
219fail_inode:
220	iput(inode);
221fail_name:
222	kfree(name);
223fail:
224	kfree(entry);
225	return err;
226}
227
228static int efivarfs_destroy(struct efivar_entry *entry, void *data)
229{
230	efivar_entry_remove(entry);
231	kfree(entry);
232	return 0;
233}
234
235static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
236{
237	struct inode *inode = NULL;
238	struct dentry *root;
239	int err;
240
241	if (!efivar_is_available())
242		return -EOPNOTSUPP;
243
244	sb->s_maxbytes          = MAX_LFS_FILESIZE;
245	sb->s_blocksize         = PAGE_SIZE;
246	sb->s_blocksize_bits    = PAGE_SHIFT;
247	sb->s_magic             = EFIVARFS_MAGIC;
248	sb->s_op                = &efivarfs_ops;
249	sb->s_d_op		= &efivarfs_d_ops;
250	sb->s_time_gran         = 1;
251
252	if (!efivar_supports_writes())
253		sb->s_flags |= SB_RDONLY;
254
255	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
256	if (!inode)
257		return -ENOMEM;
258	inode->i_op = &efivarfs_dir_inode_operations;
259
260	root = d_make_root(inode);
261	sb->s_root = root;
262	if (!root)
263		return -ENOMEM;
264
265	INIT_LIST_HEAD(&efivarfs_list);
266
267	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
268	if (err)
269		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
270
271	return err;
272}
273
274static int efivarfs_get_tree(struct fs_context *fc)
275{
276	return get_tree_single(fc, efivarfs_fill_super);
277}
278
279static int efivarfs_reconfigure(struct fs_context *fc)
280{
281	if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
282		pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
283		return -EINVAL;
284	}
285
286	return 0;
287}
288
289static const struct fs_context_operations efivarfs_context_ops = {
290	.get_tree	= efivarfs_get_tree,
291	.reconfigure	= efivarfs_reconfigure,
292};
293
294static int efivarfs_init_fs_context(struct fs_context *fc)
295{
296	fc->ops = &efivarfs_context_ops;
297	return 0;
298}
299
300static void efivarfs_kill_sb(struct super_block *sb)
301{
302	struct efivarfs_fs_info *sfi = sb->s_fs_info;
303
304	kill_litter_super(sb);
305
306	if (!efivar_is_available())
307		return;
308
309	/* Remove all entries and destroy */
310	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
311	kfree(sfi);
312}
313
314static struct file_system_type efivarfs_type = {
315	.owner   = THIS_MODULE,
316	.name    = "efivarfs",
317	.init_fs_context = efivarfs_init_fs_context,
318	.kill_sb = efivarfs_kill_sb,
319};
320
321static __init int efivarfs_init(void)
322{
323	return register_filesystem(&efivarfs_type);
324}
325
326static __exit void efivarfs_exit(void)
327{
328	unregister_filesystem(&efivarfs_type);
329}
330
331MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
332MODULE_DESCRIPTION("EFI Variable Filesystem");
333MODULE_LICENSE("GPL");
334MODULE_ALIAS_FS("efivarfs");
335
336module_init(efivarfs_init);
337module_exit(efivarfs_exit);
338