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(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(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,
75						    &remaining_space,
76						    &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(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(str, name->name, guid))
135		return 1;
136
137	/* Case-insensitive compare for the GUID */
138	return strncasecmp(name->name + guid, 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(s, len))
148		return -EINVAL;
149
150	while (len-- > EFI_VARIABLE_GUID_LEN)
151		hash = partial_name_hash(*s++, hash);
152
153	/* GUID is case-insensitive. */
154	while (len--)
155		hash = partial_name_hash(tolower(*s++), 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(parent, &q);
177	if (err)
178		return ERR_PTR(err);
179
180	d = d_alloc(parent, &q);
181	if (d)
182		return d;
183
184	return ERR_PTR(-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(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
202		return 0;
203
204	entry = kzalloc(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(entry->var.VariableName);
212
213	/* name, plus '-', plus GUID, plus NUL*/
214	name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
215	if (!name)
216		goto fail;
217
218	ucs2_as_utf8(name, entry->var.VariableName, len);
219
220	if (efivar_variable_is_removable(entry->var.VendorGuid, name, len))
221		is_removable = true;
222
223	name[len] = '-';
224
225	efi_guid_to_str(&entry->var.VendorGuid, 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(name, '/', '!');
231
232	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
233				   is_removable);
234	if (!inode)
235		goto fail_name;
236
237	dentry = efivarfs_alloc_dentry(root, name);
238	if (IS_ERR(dentry)) {
239		err = PTR_ERR(dentry);
240		goto fail_inode;
241	}
242
243	__efivar_entry_get(entry, NULL, &size, NULL);
244	__efivar_entry_add(entry, list);
245
246	/* copied by the above to local storage in the dentry. */
247	kfree(name);
248
249	inode_lock(inode);
250	inode->i_private = entry;
251	i_size_write(inode, 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(name);
261fail:
262	kfree(entry);
263	return err;
264}
265
266static int efivarfs_destroy(struct efivar_entry *entry, void *data)
267{
268	efivar_entry_remove(entry);
269	kfree(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, efivarfs_parameters, param, &result);
291	if (opt < 0)
292		return opt;
293
294	switch (opt) {
295	case Opt_uid:
296		opts->uid = make_kuid(current_user_ns(), result.uint_32);
297		if (!uid_valid(opts->uid))
298			return -EINVAL;
299		break;
300	case Opt_gid:
301		opts->gid = make_kgid(current_user_ns(), result.uint_32);
302		if (!gid_valid(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, 0, 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(&efivar_ops_nh, &sfi->nb);
343	if (err)
344		return err;
345
346	return efivar_init(efivarfs_callback, sb, &sfi->efivarfs_list);
347}
348
349static int efivarfs_get_tree(struct fs_context *fc)
350{
351	return get_tree_single(fc, 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(sizeof(*sfi), GFP_KERNEL);
378	if (!sfi)
379		return -ENOMEM;
380
381	INIT_LIST_HEAD(&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(&efivar_ops_nh, &sfi->nb);
396	kill_litter_super(sb);
397
398	/* Remove all entries and destroy */
399	efivar_entry_iter(efivarfs_destroy, &sfi->efivarfs_list, NULL);
400	kfree(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