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
14 #include "internal.h"
15
efivarfs_get_inode(struct super_block * sb,const struct inode * dir,int mode,dev_t dev,bool is_removable)16 struct inode *efivarfs_get_inode(struct super_block *sb,
17 const struct inode *dir, int mode,
18 dev_t dev, bool is_removable)
19 {
20 struct inode *inode = new_inode(sb);
21
22 if (inode) {
23 inode->i_ino = get_next_ino();
24 inode->i_mode = mode;
25 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
26 inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
27 switch (mode & S_IFMT) {
28 case S_IFREG:
29 inode->i_fop = &efivarfs_file_operations;
30 break;
31 case S_IFDIR:
32 inode->i_op = &efivarfs_dir_inode_operations;
33 inode->i_fop = &simple_dir_operations;
34 inc_nlink(inode);
35 break;
36 }
37 }
38 return inode;
39 }
40
41 /*
42 * Return true if 'str' is a valid efivarfs filename of the form,
43 *
44 * VariableName-12345678-1234-1234-1234-1234567891bc
45 */
efivarfs_valid_name(const char * str,int len)46 bool efivarfs_valid_name(const char *str, int len)
47 {
48 const char *s = str + len - EFI_VARIABLE_GUID_LEN;
49
50 /*
51 * We need a GUID, plus at least one letter for the variable name,
52 * plus the '-' separator
53 */
54 if (len < EFI_VARIABLE_GUID_LEN + 2)
55 return false;
56
57 /* GUID must be preceded by a '-' */
58 if (*(s - 1) != '-')
59 return false;
60
61 /*
62 * Validate that 's' is of the correct format, e.g.
63 *
64 * 12345678-1234-1234-1234-123456789abc
65 */
66 return uuid_is_valid(s);
67 }
68
efivarfs_create(struct inode * dir,struct dentry * dentry,umode_t mode,bool excl)69 static int efivarfs_create(struct inode *dir, struct dentry *dentry,
70 umode_t mode, bool excl)
71 {
72 struct inode *inode = NULL;
73 struct efivar_entry *var;
74 int namelen, i = 0, err = 0;
75 bool is_removable = false;
76
77 if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
78 return -EINVAL;
79
80 var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
81 if (!var)
82 return -ENOMEM;
83
84 /* length of the variable name itself: remove GUID and separator */
85 namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
86
87 err = guid_parse(dentry->d_name.name + namelen + 1, &var->var.VendorGuid);
88 if (err)
89 goto out;
90
91 if (efivar_variable_is_removable(var->var.VendorGuid,
92 dentry->d_name.name, namelen))
93 is_removable = true;
94
95 inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
96 if (!inode) {
97 err = -ENOMEM;
98 goto out;
99 }
100
101 for (i = 0; i < namelen; i++)
102 var->var.VariableName[i] = dentry->d_name.name[i];
103
104 var->var.VariableName[i] = '\0';
105
106 inode->i_private = var;
107 kmemleak_ignore(var);
108
109 err = efivar_entry_add(var, &efivarfs_list);
110 if (err)
111 goto out;
112
113 d_instantiate(dentry, inode);
114 dget(dentry);
115 out:
116 if (err) {
117 kfree(var);
118 if (inode)
119 iput(inode);
120 }
121 return err;
122 }
123
efivarfs_unlink(struct inode * dir,struct dentry * dentry)124 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
125 {
126 struct efivar_entry *var = d_inode(dentry)->i_private;
127
128 if (efivar_entry_delete(var))
129 return -EINVAL;
130
131 drop_nlink(d_inode(dentry));
132 dput(dentry);
133 return 0;
134 };
135
136 const struct inode_operations efivarfs_dir_inode_operations = {
137 .lookup = simple_lookup,
138 .unlink = efivarfs_unlink,
139 .create = efivarfs_create,
140 };
141