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
efivarfs_get_inode(struct super_block * sb,const struct inode * dir,int mode,dev_t dev,bool is_removable)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
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 */
efivarfs_valid_name(const char * str,int len)50 bool 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
efivarfs_create(struct mnt_idmap * idmap,struct inode * dir,struct dentry * dentry,umode_t mode,bool excl)73 static 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);
123 out:
124 if (err) {
125 kfree(var);
126 if (inode)
127 iput(inode);
128 }
129 return err;
130 }
131
efivarfs_unlink(struct inode * dir,struct dentry * dentry)132 static 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
144 const struct inode_operations efivarfs_dir_inode_operations = {
145 .lookup = simple_lookup,
146 .unlink = efivarfs_unlink,
147 .create = efivarfs_create,
148 };
149
150 static int
efivarfs_fileattr_get(struct dentry * dentry,struct fileattr * fa)151 efivarfs_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
165 static int
efivarfs_fileattr_set(struct mnt_idmap * idmap,struct dentry * dentry,struct fileattr * fa)166 efivarfs_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
185 static const struct inode_operations efivarfs_file_inode_operations = {
186 .fileattr_get = efivarfs_fileattr_get,
187 .fileattr_set = efivarfs_fileattr_set,
188 };
189