super.c

  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/suspend.h>
 17#include <linux/magic.h>
 18#include <linux/statfs.h>
 19#include <linux/notifier.h>
 20#include <linux/printk.h>
 21#include <linux/namei.h>
 22
 23#include "internal.h"
 24#include "../internal.h"
 25
 26static int efivarfs_ops_notifier(struct notifier_block *nb, unsigned long event,
 27				 void *data)
 28{
 29	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info, nb);
 30
 31	switch (event) {
 32	case EFIVAR_OPS_RDONLY:
 33		sfi->sb->s_flags |= SB_RDONLY;
 34		break;
 35	case EFIVAR_OPS_RDWR:
 36		sfi->sb->s_flags &= ~SB_RDONLY;
 37		break;
 38	default:
 39		return NOTIFY_DONE;
 40	}
 41
 42	return NOTIFY_OK;
 43}
 44
 45static struct inode *efivarfs_alloc_inode(struct super_block *sb)
 46{
 47	struct efivar_entry *entry = kzalloc(sizeof(*entry), GFP_KERNEL);
 48
 49	if (!entry)
 50		return NULL;
 51
 52	inode_init_once(&entry->vfs_inode);
 53	entry->removed = false;
 54
 55	return &entry->vfs_inode;
 56}
 57
 58static void efivarfs_free_inode(struct inode *inode)
 59{
 60	struct efivar_entry *entry = efivar_entry(inode);
 61
 62	kfree(entry);
 63}
 64
 65static int efivarfs_show_options(struct seq_file *m, struct dentry *root)
 66{
 67	struct super_block *sb = root->d_sb;
 68	struct efivarfs_fs_info *sbi = sb->s_fs_info;
 69	struct efivarfs_mount_opts *opts = &sbi->mount_opts;
 70
 71	if (!uid_eq(opts->uid, GLOBAL_ROOT_UID))
 72		seq_printf(m, ",uid=%u",
 73				from_kuid_munged(&init_user_ns, opts->uid));
 74	if (!gid_eq(opts->gid, GLOBAL_ROOT_GID))
 75		seq_printf(m, ",gid=%u",
 76				from_kgid_munged(&init_user_ns, opts->gid));
 77	return 0;
 78}
 79
 80static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 81{
 82	const u32 attr = EFI_VARIABLE_NON_VOLATILE |
 83			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
 84			 EFI_VARIABLE_RUNTIME_ACCESS;
 85	u64 storage_space, remaining_space, max_variable_size;
 86	u64 id = huge_encode_dev(dentry->d_sb->s_dev);
 87	efi_status_t status;
 88
 89	/* Some UEFI firmware does not implement QueryVariableInfo() */
 90	storage_space = remaining_space = 0;
 91	if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
 92		status = efivar_query_variable_info(attr, &storage_space,
 93						    &remaining_space,
 94						    &max_variable_size);
 95		if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
 96			pr_warn_ratelimited("query_variable_info() failed: 0x%lx\n",
 97					    status);
 98	}
 99
100	/*
101	 * This is not a normal filesystem, so no point in pretending it has a block
102	 * size; we declare f_bsize to 1, so that we can then report the exact value
103	 * sent by EFI QueryVariableInfo in f_blocks and f_bfree
104	 */
105	buf->f_bsize	= 1;
106	buf->f_namelen	= NAME_MAX;
107	buf->f_blocks	= storage_space;
108	buf->f_bfree	= remaining_space;
109	buf->f_type	= dentry->d_sb->s_magic;
110	buf->f_fsid	= u64_to_fsid(id);
111
112	/*
113	 * In f_bavail we declare the free space that the kernel will allow writing
114	 * when the storage_paranoia x86 quirk is active. To use more, users
115	 * should boot the kernel with efi_no_storage_paranoia.
116	 */
117	if (remaining_space > efivar_reserved_space())
118		buf->f_bavail = remaining_space - efivar_reserved_space();
119	else
120		buf->f_bavail = 0;
121
122	return 0;
123}
124
125static int efivarfs_freeze_fs(struct super_block *sb);
126static int efivarfs_unfreeze_fs(struct super_block *sb);
127
128static const struct super_operations efivarfs_ops = {
129	.statfs = efivarfs_statfs,
130	.drop_inode = inode_just_drop,
131	.alloc_inode = efivarfs_alloc_inode,
132	.free_inode = efivarfs_free_inode,
133	.show_options = efivarfs_show_options,
134	.freeze_fs = efivarfs_freeze_fs,
135	.unfreeze_fs = efivarfs_unfreeze_fs,
136};
137
138/*
139 * Compare two efivarfs file names.
140 *
141 * An efivarfs filename is composed of two parts,
142 *
143 *	1. A case-sensitive variable name
144 *	2. A case-insensitive GUID
145 *
146 * So we need to perform a case-sensitive match on part 1 and a
147 * case-insensitive match on part 2.
148 */
149static int efivarfs_d_compare(const struct dentry *dentry,
150			      unsigned int len, const char *str,
151			      const struct qstr *name)
152{
153	int guid = len - EFI_VARIABLE_GUID_LEN;
154
155	/* Parallel lookups may produce a temporary invalid filename */
156	if (guid <= 0)
157		return 1;
158
159	if (name->len != len)
160		return 1;
161
162	/* Case-sensitive compare for the variable name */
163	if (memcmp(str, name->name, guid))
164		return 1;
165
166	/* Case-insensitive compare for the GUID */
167	return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
168}
169
170static int efivarfs_d_hash(const struct dentry *dentry, struct qstr *qstr)
171{
172	unsigned long hash = init_name_hash(dentry);
173	const unsigned char *s = qstr->name;
174	unsigned int len = qstr->len;
175
176	while (len-- > EFI_VARIABLE_GUID_LEN)
177		hash = partial_name_hash(*s++, hash);
178
179	/* GUID is case-insensitive. */
180	while (len--)
181		hash = partial_name_hash(tolower(*s++), hash);
182
183	qstr->hash = end_name_hash(hash);
184	return 0;
185}
186
187static const struct dentry_operations efivarfs_d_ops = {
188	.d_compare = efivarfs_d_compare,
189	.d_hash = efivarfs_d_hash,
190};
191
192static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
193{
194	struct dentry *d;
195	struct qstr q;
196	int err;
197
198	q.name = name;
199	q.len = strlen(name);
200
201	err = efivarfs_d_hash(parent, &q);
202	if (err)
203		return ERR_PTR(err);
204
205	d = d_alloc(parent, &q);
206	if (d)
207		return d;
208
209	return ERR_PTR(-ENOMEM);
210}
211
212bool efivarfs_variable_is_present(efi_char16_t *variable_name,
213				  efi_guid_t *vendor, void *data)
214{
215	char *name = efivar_get_utf8name(variable_name, vendor);
216	struct super_block *sb = data;
217	struct dentry *dentry;
218
219	if (!name)
220		/*
221		 * If the allocation failed there'll already be an
222		 * error in the log (and likely a huge and growing
223		 * number of them since they system will be under
224		 * extreme memory pressure), so simply assume
225		 * collision for safety but don't add to the log
226		 * flood.
227		 */
228		return true;
229
230	dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
231	kfree(name);
232	if (!IS_ERR_OR_NULL(dentry))
233		dput(dentry);
234
235	return dentry != NULL;
236}
237
238static int efivarfs_create_dentry(struct super_block *sb, efi_char16_t *name16,
239				  unsigned long name_size, efi_guid_t vendor,
240				  char *name)
241{
242	struct efivar_entry *entry;
243	struct inode *inode;
244	struct dentry *dentry, *root = sb->s_root;
245	unsigned long size = 0;
246	int len;
247	int err = -ENOMEM;
248	bool is_removable = false;
249
250	/* length of the variable name itself: remove GUID and separator */
251	len = strlen(name) - EFI_VARIABLE_GUID_LEN - 1;
252
253	if (efivar_variable_is_removable(vendor, name, len))
254		is_removable = true;
255
256	inode = efivarfs_get_inode(sb, d_inode(root), S_IFREG | 0644, 0,
257				   is_removable);
258	if (!inode)
259		goto fail_name;
260
261	entry = efivar_entry(inode);
262
263	memcpy(entry->var.VariableName, name16, name_size);
264	memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));
265
266	dentry = efivarfs_alloc_dentry(root, name);
267	if (IS_ERR(dentry)) {
268		err = PTR_ERR(dentry);
269		goto fail_inode;
270	}
271
272	__efivar_entry_get(entry, NULL, &size, NULL);
273
274	/* copied by the above to local storage in the dentry. */
275	kfree(name);
276
277	inode_lock(inode);
278	inode->i_private = entry;
279	i_size_write(inode, size + sizeof(__u32)); /* attributes + data */
280	inode_unlock(inode);
281	d_make_persistent(dentry, inode);
282	dput(dentry);
283
284	return 0;
285
286fail_inode:
287	iput(inode);
288fail_name:
289	kfree(name);
290
291	return err;
292}
293
294static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
295			     unsigned long name_size, void *data)
296{
297	struct super_block *sb = (struct super_block *)data;
298	char *name;
299
300	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
301		return 0;
302
303	name = efivar_get_utf8name(name16, &vendor);
304	if (!name)
305		return -ENOMEM;
306
307	return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
308}
309
310enum {
311	Opt_uid, Opt_gid,
312};
313
314static const struct fs_parameter_spec efivarfs_parameters[] = {
315	fsparam_uid("uid", Opt_uid),
316	fsparam_gid("gid", Opt_gid),
317	{},
318};
319
320static int efivarfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
321{
322	struct efivarfs_fs_info *sbi = fc->s_fs_info;
323	struct efivarfs_mount_opts *opts = &sbi->mount_opts;
324	struct fs_parse_result result;
325	int opt;
326
327	opt = fs_parse(fc, efivarfs_parameters, param, &result);
328	if (opt < 0)
329		return opt;
330
331	switch (opt) {
332	case Opt_uid:
333		opts->uid = result.uid;
334		break;
335	case Opt_gid:
336		opts->gid = result.gid;
337		break;
338	default:
339		return -EINVAL;
340	}
341
342	return 0;
343}
344
345static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
346{
347	struct efivarfs_fs_info *sfi = sb->s_fs_info;
348	struct inode *inode = NULL;
349	struct dentry *root;
350	int err;
351
352	sb->s_maxbytes          = MAX_LFS_FILESIZE;
353	sb->s_blocksize         = PAGE_SIZE;
354	sb->s_blocksize_bits    = PAGE_SHIFT;
355	sb->s_magic             = EFIVARFS_MAGIC;
356	sb->s_op                = &efivarfs_ops;
357	set_default_d_op(sb, &efivarfs_d_ops);
358	sb->s_d_flags |= DCACHE_DONTCACHE;
359	sb->s_time_gran         = 1;
360
361	if (!efivar_supports_writes())
362		sb->s_flags |= SB_RDONLY;
363
364	inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0, true);
365	if (!inode)
366		return -ENOMEM;
367	inode->i_op = &efivarfs_dir_inode_operations;
368
369	root = d_make_root(inode);
370	sb->s_root = root;
371	if (!root)
372		return -ENOMEM;
373
374	sfi->sb = sb;
375	sfi->nb.notifier_call = efivarfs_ops_notifier;
376	err = blocking_notifier_chain_register(&efivar_ops_nh, &sfi->nb);
377	if (err)
378		return err;
379
380	return efivar_init(efivarfs_callback, sb, true);
381}
382
383static int efivarfs_get_tree(struct fs_context *fc)
384{
385	return get_tree_single(fc, efivarfs_fill_super);
386}
387
388static int efivarfs_reconfigure(struct fs_context *fc)
389{
390	if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) {
391		pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n");
392		return -EINVAL;
393	}
394
395	return 0;
396}
397
398static void efivarfs_free(struct fs_context *fc)
399{
400	kfree(fc->s_fs_info);
401}
402
403static const struct fs_context_operations efivarfs_context_ops = {
404	.get_tree	= efivarfs_get_tree,
405	.parse_param	= efivarfs_parse_param,
406	.reconfigure	= efivarfs_reconfigure,
407	.free		= efivarfs_free,
408};
409
410static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
411				  unsigned long name_size, void *data)
412{
413	char *name;
414	struct super_block *sb = data;
415	struct dentry *dentry;
416	int err;
417
418	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
419		return 0;
420
421	name = efivar_get_utf8name(name16, &vendor);
422	if (!name)
423		return -ENOMEM;
424
425	dentry = try_lookup_noperm(&QSTR(name), sb->s_root);
426	if (IS_ERR(dentry)) {
427		err = PTR_ERR(dentry);
428		goto out;
429	}
430
431	if (!dentry) {
432		/* found missing entry */
433		pr_info("efivarfs: creating variable %s\n", name);
434		return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
435	}
436
437	dput(dentry);
438	err = 0;
439
440 out:
441	kfree(name);
442
443	return err;
444}
445
446static struct file_system_type efivarfs_type;
447
448static int efivarfs_freeze_fs(struct super_block *sb)
449{
450	/* Nothing for us to do. */
451	return 0;
452}
453
454static int efivarfs_unfreeze_fs(struct super_block *sb)
455{
456	struct dentry *child = NULL;
457
458	/*
459	 * Unconditionally resync the variable state on a thaw request.
460	 * Given the size of efivarfs it really doesn't matter to simply
461	 * iterate through all of the entries and resync. Freeze/thaw
462	 * requests are rare enough for that to not matter and the
463	 * number of entries is pretty low too. So we really don't care.
464	 */
465	pr_info("efivarfs: resyncing variable state\n");
466	for (;;) {
467		int err;
468		unsigned long size = 0;
469		struct inode *inode;
470		struct efivar_entry *entry;
471
472		child = find_next_child(sb->s_root, child);
473		if (!child)
474			break;
475
476		inode = d_inode(child);
477		entry = efivar_entry(inode);
478
479		err = efivar_entry_size(entry, &size);
480		if (err)
481			size = 0;
482		else
483			size += sizeof(__u32);
484
485		inode_lock(inode);
486		i_size_write(inode, size);
487		inode_unlock(inode);
488
489		/* The variable doesn't exist anymore, delete it. */
490		if (!size) {
491			pr_info("efivarfs: removing variable %pd\n", child);
492			simple_recursive_removal(child, NULL);
493		}
494	}
495
496	efivar_init(efivarfs_check_missing, sb, false);
497	pr_info("efivarfs: finished resyncing variable state\n");
498	return 0;
499}
500
501static int efivarfs_init_fs_context(struct fs_context *fc)
502{
503	struct efivarfs_fs_info *sfi;
504
505	if (!efivar_is_available())
506		return -EOPNOTSUPP;
507
508	sfi = kzalloc(sizeof(*sfi), GFP_KERNEL);
509	if (!sfi)
510		return -ENOMEM;
511
512	sfi->mount_opts.uid = GLOBAL_ROOT_UID;
513	sfi->mount_opts.gid = GLOBAL_ROOT_GID;
514
515	fc->s_fs_info = sfi;
516	fc->ops = &efivarfs_context_ops;
517
518	return 0;
519}
520
521static void efivarfs_kill_sb(struct super_block *sb)
522{
523	struct efivarfs_fs_info *sfi = sb->s_fs_info;
524
525	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
526	kill_anon_super(sb);
527
528	kfree(sfi);
529}
530
531static struct file_system_type efivarfs_type = {
532	.owner   = THIS_MODULE,
533	.name    = "efivarfs",
534	.init_fs_context = efivarfs_init_fs_context,
535	.kill_sb = efivarfs_kill_sb,
536	.parameters = efivarfs_parameters,
537	.fs_flags = FS_POWER_FREEZE,
538};
539
540static __init int efivarfs_init(void)
541{
542	return register_filesystem(&efivarfs_type);
543}
544
545static __exit void efivarfs_exit(void)
546{
547	unregister_filesystem(&efivarfs_type);
548}
549
550MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
551MODULE_DESCRIPTION("EFI Variable Filesystem");
552MODULE_LICENSE("GPL");
553MODULE_ALIAS_FS("efivarfs");
554
555module_init(efivarfs_init);
556module_exit(efivarfs_exit);