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/slab.h>
11 #include <linux/uuid.h>
12
13 #include "internal.h"
14
efivarfs_get_inode(struct super_block * sb,const struct inode * dir,int mode,dev_t dev,bool is_removable)15 struct inode *efivarfs_get_inode(struct super_block *sb,
16 const struct inode *dir, int mode,
17 dev_t dev, bool is_removable)
18 {
19 struct inode *inode = new_inode(sb);
20
21 if (inode) {
22 inode->i_ino = get_next_ino();
23 inode->i_mode = mode;
24 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
25 inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
26 switch (mode & S_IFMT) {
27 case S_IFREG:
28 inode->i_fop = &efivarfs_file_operations;
29 break;
30 case S_IFDIR:
31 inode->i_op = &efivarfs_dir_inode_operations;
32 inode->i_fop = &simple_dir_operations;
33 inc_nlink(inode);
34 break;
35 }
36 }
37 return inode;
38 }
39
40 /*
41 * Return true if 'str' is a valid efivarfs filename of the form,
42 *
43 * VariableName-12345678-1234-1234-1234-1234567891bc
44 */
efivarfs_valid_name(const char * str,int len)45 bool efivarfs_valid_name(const char *str, int len)
46 {
47 const char *s = str + len - EFI_VARIABLE_GUID_LEN;
48
49 /*
50 * We need a GUID, plus at least one letter for the variable name,
51 * plus the '-' separator
52 */
53 if (len < EFI_VARIABLE_GUID_LEN + 2)
54 return false;
55
56 /* GUID must be preceded by a '-' */
57 if (*(s - 1) != '-')
58 return false;
59
60 /*
61 * Validate that 's' is of the correct format, e.g.
62 *
63 * 12345678-1234-1234-1234-123456789abc
64 */
65 return uuid_is_valid(s);
66 }
67
efivarfs_create(struct inode * dir,struct dentry * dentry,umode_t mode,bool excl)68 static int efivarfs_create(struct inode *dir, struct dentry *dentry,
69 umode_t mode, bool excl)
70 {
71 struct inode *inode = NULL;
72 struct efivar_entry *var;
73 int namelen, i = 0, err = 0;
74 bool is_removable = false;
75
76 if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
77 return -EINVAL;
78
79 var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
80 if (!var)
81 return -ENOMEM;
82
83 /* length of the variable name itself: remove GUID and separator */
84 namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
85
86 err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
87 if (err)
88 goto out;
89
90 if (efivar_variable_is_removable(var->var.VendorGuid,
91 dentry->d_name.name, namelen))
92 is_removable = true;
93
94 inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
95 if (!inode) {
96 err = -ENOMEM;
97 goto out;
98 }
99
100 for (i = 0; i < namelen; i++)
101 var->var.VariableName[i] = dentry->d_name.name[i];
102
103 var->var.VariableName[i] = '\0';
104
105 inode->i_private = var;
106
107 err = efivar_entry_add(var, &efivarfs_list);
108 if (err)
109 goto out;
110
111 d_instantiate(dentry, inode);
112 dget(dentry);
113 out:
114 if (err) {
115 kfree(var);
116 if (inode)
117 iput(inode);
118 }
119 return err;
120 }
121
efivarfs_unlink(struct inode * dir,struct dentry * dentry)122 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
123 {
124 struct efivar_entry *var = d_inode(dentry)->i_private;
125
126 if (efivar_entry_delete(var))
127 return -EINVAL;
128
129 drop_nlink(d_inode(dentry));
130 dput(dentry);
131 return 0;
132 };
133
134 const struct inode_operations efivarfs_dir_inode_operations = {
135 .lookup = simple_lookup,
136 .unlink = efivarfs_unlink,
137 .create = efivarfs_create,
138 };
139