xref: /openbmc/linux/fs/efivarfs/inode.c (revision b34e08d5)
1 /*
2  * Copyright (C) 2012 Red Hat, Inc.
3  * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License version 2 as
7  * published by the Free Software Foundation.
8  */
9 
10 #include <linux/efi.h>
11 #include <linux/fs.h>
12 #include <linux/ctype.h>
13 #include <linux/slab.h>
14 
15 #include "internal.h"
16 
17 struct inode *efivarfs_get_inode(struct super_block *sb,
18 				const struct inode *dir, int mode, dev_t dev)
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;
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  */
45 bool efivarfs_valid_name(const char *str, int len)
46 {
47 	static const char dashes[EFI_VARIABLE_GUID_LEN] = {
48 		[8] = 1, [13] = 1, [18] = 1, [23] = 1
49 	};
50 	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
51 	int i;
52 
53 	/*
54 	 * We need a GUID, plus at least one letter for the variable name,
55 	 * plus the '-' separator
56 	 */
57 	if (len < EFI_VARIABLE_GUID_LEN + 2)
58 		return false;
59 
60 	/* GUID must be preceded by a '-' */
61 	if (*(s - 1) != '-')
62 		return false;
63 
64 	/*
65 	 * Validate that 's' is of the correct format, e.g.
66 	 *
67 	 *	12345678-1234-1234-1234-123456789abc
68 	 */
69 	for (i = 0; i < EFI_VARIABLE_GUID_LEN; i++) {
70 		if (dashes[i]) {
71 			if (*s++ != '-')
72 				return false;
73 		} else {
74 			if (!isxdigit(*s++))
75 				return false;
76 		}
77 	}
78 
79 	return true;
80 }
81 
82 static void efivarfs_hex_to_guid(const char *str, efi_guid_t *guid)
83 {
84 	guid->b[0] = hex_to_bin(str[6]) << 4 | hex_to_bin(str[7]);
85 	guid->b[1] = hex_to_bin(str[4]) << 4 | hex_to_bin(str[5]);
86 	guid->b[2] = hex_to_bin(str[2]) << 4 | hex_to_bin(str[3]);
87 	guid->b[3] = hex_to_bin(str[0]) << 4 | hex_to_bin(str[1]);
88 	guid->b[4] = hex_to_bin(str[11]) << 4 | hex_to_bin(str[12]);
89 	guid->b[5] = hex_to_bin(str[9]) << 4 | hex_to_bin(str[10]);
90 	guid->b[6] = hex_to_bin(str[16]) << 4 | hex_to_bin(str[17]);
91 	guid->b[7] = hex_to_bin(str[14]) << 4 | hex_to_bin(str[15]);
92 	guid->b[8] = hex_to_bin(str[19]) << 4 | hex_to_bin(str[20]);
93 	guid->b[9] = hex_to_bin(str[21]) << 4 | hex_to_bin(str[22]);
94 	guid->b[10] = hex_to_bin(str[24]) << 4 | hex_to_bin(str[25]);
95 	guid->b[11] = hex_to_bin(str[26]) << 4 | hex_to_bin(str[27]);
96 	guid->b[12] = hex_to_bin(str[28]) << 4 | hex_to_bin(str[29]);
97 	guid->b[13] = hex_to_bin(str[30]) << 4 | hex_to_bin(str[31]);
98 	guid->b[14] = hex_to_bin(str[32]) << 4 | hex_to_bin(str[33]);
99 	guid->b[15] = hex_to_bin(str[34]) << 4 | hex_to_bin(str[35]);
100 }
101 
102 static int efivarfs_create(struct inode *dir, struct dentry *dentry,
103 			  umode_t mode, bool excl)
104 {
105 	struct inode *inode;
106 	struct efivar_entry *var;
107 	int namelen, i = 0, err = 0;
108 
109 	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
110 		return -EINVAL;
111 
112 	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0);
113 	if (!inode)
114 		return -ENOMEM;
115 
116 	var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
117 	if (!var) {
118 		err = -ENOMEM;
119 		goto out;
120 	}
121 
122 	/* length of the variable name itself: remove GUID and separator */
123 	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
124 
125 	efivarfs_hex_to_guid(dentry->d_name.name + namelen + 1,
126 			&var->var.VendorGuid);
127 
128 	for (i = 0; i < namelen; i++)
129 		var->var.VariableName[i] = dentry->d_name.name[i];
130 
131 	var->var.VariableName[i] = '\0';
132 
133 	inode->i_private = var;
134 
135 	efivar_entry_add(var, &efivarfs_list);
136 	d_instantiate(dentry, inode);
137 	dget(dentry);
138 out:
139 	if (err) {
140 		kfree(var);
141 		iput(inode);
142 	}
143 	return err;
144 }
145 
146 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
147 {
148 	struct efivar_entry *var = dentry->d_inode->i_private;
149 
150 	if (efivar_entry_delete(var))
151 		return -EINVAL;
152 
153 	drop_nlink(dentry->d_inode);
154 	dput(dentry);
155 	return 0;
156 };
157 
158 const struct inode_operations efivarfs_dir_inode_operations = {
159 	.lookup = simple_lookup,
160 	.unlink = efivarfs_unlink,
161 	.create = efivarfs_create,
162 };
163