xref: /linux/fs/efivarfs/inode.c (revision c5dbf04160005e07e8ca7232a7faa77ab1547ae0)
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 
17 static const struct inode_operations efivarfs_file_inode_operations;
18 
19 struct 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 	struct efivarfs_fs_info *fsi = sb->s_fs_info;
25 	struct efivarfs_mount_opts *opts = &fsi->mount_opts;
26 
27 	if (inode) {
28 		inode->i_uid = opts->uid;
29 		inode->i_gid = opts->gid;
30 		inode->i_ino = get_next_ino();
31 		inode->i_mode = mode;
32 		simple_inode_init_ts(inode);
33 		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
34 		switch (mode & S_IFMT) {
35 		case S_IFREG:
36 			inode->i_op = &efivarfs_file_inode_operations;
37 			inode->i_fop = &efivarfs_file_operations;
38 			break;
39 		case S_IFDIR:
40 			inode->i_op = &efivarfs_dir_inode_operations;
41 			inode->i_fop = &simple_dir_operations;
42 			inc_nlink(inode);
43 			break;
44 		}
45 	}
46 	return inode;
47 }
48 
49 /*
50  * Return true if 'str' is a valid efivarfs filename of the form,
51  *
52  *	VariableName-12345678-1234-1234-1234-1234567891bc
53  */
54 bool efivarfs_valid_name(const char *str, int len)
55 {
56 	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
57 
58 	/*
59 	 * We need a GUID, plus at least one letter for the variable name,
60 	 * plus the '-' separator
61 	 */
62 	if (len < EFI_VARIABLE_GUID_LEN + 2)
63 		return false;
64 
65 	/* GUID must be preceded by a '-' */
66 	if (*(s - 1) != '-')
67 		return false;
68 
69 	/*
70 	 * Validate that 's' is of the correct format, e.g.
71 	 *
72 	 *	12345678-1234-1234-1234-123456789abc
73 	 */
74 	return uuid_is_valid(s);
75 }
76 
77 static int efivarfs_create(struct mnt_idmap *idmap, struct inode *dir,
78 			   struct dentry *dentry, umode_t mode, bool excl)
79 {
80 	struct inode *inode = NULL;
81 	struct efivar_entry *var;
82 	int namelen, i = 0, err = 0;
83 	bool is_removable = false;
84 
85 	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
86 		return -EINVAL;
87 
88 	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
89 	if (!var)
90 		return -ENOMEM;
91 
92 	/* length of the variable name itself: remove GUID and separator */
93 	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
94 
95 	err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
96 	if (err)
97 		goto out;
98 	if (guid_equal(&var->var.VendorGuid, &LINUX_EFI_RANDOM_SEED_TABLE_GUID)) {
99 		err = -EPERM;
100 		goto out;
101 	}
102 
103 	if (efivar_variable_is_removable(var->var.VendorGuid,
104 					 dentry->d_name.name, namelen))
105 		is_removable = true;
106 
107 	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
108 	if (!inode) {
109 		err = -ENOMEM;
110 		goto out;
111 	}
112 
113 	for (i = 0; i < namelen; i++)
114 		var->var.VariableName[i] = dentry->d_name.name[i];
115 
116 	var->var.VariableName[i] = '\0';
117 
118 	inode->i_private = var;
119 	kmemleak_ignore(var);
120 
121 	err = efivar_entry_add(var, &efivarfs_list);
122 	if (err)
123 		goto out;
124 
125 	d_instantiate(dentry, inode);
126 	dget(dentry);
127 out:
128 	if (err) {
129 		kfree(var);
130 		if (inode)
131 			iput(inode);
132 	}
133 	return err;
134 }
135 
136 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
137 {
138 	struct efivar_entry *var = d_inode(dentry)->i_private;
139 
140 	if (efivar_entry_delete(var))
141 		return -EINVAL;
142 
143 	drop_nlink(d_inode(dentry));
144 	dput(dentry);
145 	return 0;
146 };
147 
148 const struct inode_operations efivarfs_dir_inode_operations = {
149 	.lookup = simple_lookup,
150 	.unlink = efivarfs_unlink,
151 	.create = efivarfs_create,
152 };
153 
154 static int
155 efivarfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
156 {
157 	unsigned int i_flags;
158 	unsigned int flags = 0;
159 
160 	i_flags = d_inode(dentry)->i_flags;
161 	if (i_flags & S_IMMUTABLE)
162 		flags |= FS_IMMUTABLE_FL;
163 
164 	fileattr_fill_flags(fa, flags);
165 
166 	return 0;
167 }
168 
169 static int
170 efivarfs_fileattr_set(struct mnt_idmap *idmap,
171 		      struct dentry *dentry, struct fileattr *fa)
172 {
173 	unsigned int i_flags = 0;
174 
175 	if (fileattr_has_fsx(fa))
176 		return -EOPNOTSUPP;
177 
178 	if (fa->flags & ~FS_IMMUTABLE_FL)
179 		return -EOPNOTSUPP;
180 
181 	if (fa->flags & FS_IMMUTABLE_FL)
182 		i_flags |= S_IMMUTABLE;
183 
184 	inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
185 
186 	return 0;
187 }
188 
189 static const struct inode_operations efivarfs_file_inode_operations = {
190 	.fileattr_get = efivarfs_fileattr_get,
191 	.fileattr_set = efivarfs_fileattr_set,
192 };
193