xref: /kernel/linux/linux-6.6/fs/efivarfs/inode.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/efi.h>
8#include <linux/fs.h>
9#include <linux/ctype.h>
10#include <linux/kmemleak.h>
11#include <linux/slab.h>
12#include <linux/uuid.h>
13#include <linux/fileattr.h>
14
15#include "internal.h"
16
17static const struct inode_operations efivarfs_file_inode_operations;
18
19struct inode *efivarfs_get_inode(struct super_block *sb,
20				const struct inode *dir, int mode,
21				dev_t dev, bool is_removable)
22{
23	struct inode *inode = new_inode(sb);
24
25	if (inode) {
26		inode->i_ino = get_next_ino();
27		inode->i_mode = mode;
28		inode->i_atime = inode->i_mtime = inode_set_ctime_current(inode);
29		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
30		switch (mode & S_IFMT) {
31		case S_IFREG:
32			inode->i_op = &efivarfs_file_inode_operations;
33			inode->i_fop = &efivarfs_file_operations;
34			break;
35		case S_IFDIR:
36			inode->i_op = &efivarfs_dir_inode_operations;
37			inode->i_fop = &simple_dir_operations;
38			inc_nlink(inode);
39			break;
40		}
41	}
42	return inode;
43}
44
45/*
46 * Return true if 'str' is a valid efivarfs filename of the form,
47 *
48 *	VariableName-12345678-1234-1234-1234-1234567891bc
49 */
50bool efivarfs_valid_name(const char *str, int len)
51{
52	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
53
54	/*
55	 * We need a GUID, plus at least one letter for the variable name,
56	 * plus the '-' separator
57	 */
58	if (len < EFI_VARIABLE_GUID_LEN + 2)
59		return false;
60
61	/* GUID must be preceded by a '-' */
62	if (*(s - 1) != '-')
63		return false;
64
65	/*
66	 * Validate that 's' is of the correct format, e.g.
67	 *
68	 *	12345678-1234-1234-1234-123456789abc
69	 */
70	return uuid_is_valid(s);
71}
72
73static int efivarfs_create(struct mnt_idmap *idmap, struct inode *dir,
74			   struct dentry *dentry, umode_t mode, bool excl)
75{
76	struct inode *inode = NULL;
77	struct efivar_entry *var;
78	int namelen, i = 0, err = 0;
79	bool is_removable = false;
80
81	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
82		return -EINVAL;
83
84	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
85	if (!var)
86		return -ENOMEM;
87
88	/* length of the variable name itself: remove GUID and separator */
89	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
90
91	err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
92	if (err)
93		goto out;
94	if (guid_equal(&var->var.VendorGuid, &LINUX_EFI_RANDOM_SEED_TABLE_GUID)) {
95		err = -EPERM;
96		goto out;
97	}
98
99	if (efivar_variable_is_removable(var->var.VendorGuid,
100					 dentry->d_name.name, namelen))
101		is_removable = true;
102
103	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
104	if (!inode) {
105		err = -ENOMEM;
106		goto out;
107	}
108
109	for (i = 0; i < namelen; i++)
110		var->var.VariableName[i] = dentry->d_name.name[i];
111
112	var->var.VariableName[i] = '\0';
113
114	inode->i_private = var;
115	kmemleak_ignore(var);
116
117	err = efivar_entry_add(var, &efivarfs_list);
118	if (err)
119		goto out;
120
121	d_instantiate(dentry, inode);
122	dget(dentry);
123out:
124	if (err) {
125		kfree(var);
126		if (inode)
127			iput(inode);
128	}
129	return err;
130}
131
132static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
133{
134	struct efivar_entry *var = d_inode(dentry)->i_private;
135
136	if (efivar_entry_delete(var))
137		return -EINVAL;
138
139	drop_nlink(d_inode(dentry));
140	dput(dentry);
141	return 0;
142};
143
144const struct inode_operations efivarfs_dir_inode_operations = {
145	.lookup = simple_lookup,
146	.unlink = efivarfs_unlink,
147	.create = efivarfs_create,
148};
149
150static int
151efivarfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
152{
153	unsigned int i_flags;
154	unsigned int flags = 0;
155
156	i_flags = d_inode(dentry)->i_flags;
157	if (i_flags & S_IMMUTABLE)
158		flags |= FS_IMMUTABLE_FL;
159
160	fileattr_fill_flags(fa, flags);
161
162	return 0;
163}
164
165static int
166efivarfs_fileattr_set(struct mnt_idmap *idmap,
167		      struct dentry *dentry, struct fileattr *fa)
168{
169	unsigned int i_flags = 0;
170
171	if (fileattr_has_fsx(fa))
172		return -EOPNOTSUPP;
173
174	if (fa->flags & ~FS_IMMUTABLE_FL)
175		return -EOPNOTSUPP;
176
177	if (fa->flags & FS_IMMUTABLE_FL)
178		i_flags |= S_IMMUTABLE;
179
180	inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
181
182	return 0;
183}
184
185static const struct inode_operations efivarfs_file_inode_operations = {
186	.fileattr_get = efivarfs_fileattr_get,
187	.fileattr_set = efivarfs_fileattr_set,
188};
189