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, 19 dev_t dev, bool is_removable) 20 { 21 struct inode *inode = new_inode(sb); 22 23 if (inode) { 24 inode->i_ino = get_next_ino(); 25 inode->i_mode = mode; 26 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; 27 inode->i_flags = is_removable ? 0 : S_IMMUTABLE; 28 switch (mode & S_IFMT) { 29 case S_IFREG: 30 inode->i_fop = &efivarfs_file_operations; 31 break; 32 case S_IFDIR: 33 inode->i_op = &efivarfs_dir_inode_operations; 34 inode->i_fop = &simple_dir_operations; 35 inc_nlink(inode); 36 break; 37 } 38 } 39 return inode; 40 } 41 42 /* 43 * Return true if 'str' is a valid efivarfs filename of the form, 44 * 45 * VariableName-12345678-1234-1234-1234-1234567891bc 46 */ 47 bool efivarfs_valid_name(const char *str, int len) 48 { 49 static const char dashes[EFI_VARIABLE_GUID_LEN] = { 50 [8] = 1, [13] = 1, [18] = 1, [23] = 1 51 }; 52 const char *s = str + len - EFI_VARIABLE_GUID_LEN; 53 int i; 54 55 /* 56 * We need a GUID, plus at least one letter for the variable name, 57 * plus the '-' separator 58 */ 59 if (len < EFI_VARIABLE_GUID_LEN + 2) 60 return false; 61 62 /* GUID must be preceded by a '-' */ 63 if (*(s - 1) != '-') 64 return false; 65 66 /* 67 * Validate that 's' is of the correct format, e.g. 68 * 69 * 12345678-1234-1234-1234-123456789abc 70 */ 71 for (i = 0; i < EFI_VARIABLE_GUID_LEN; i++) { 72 if (dashes[i]) { 73 if (*s++ != '-') 74 return false; 75 } else { 76 if (!isxdigit(*s++)) 77 return false; 78 } 79 } 80 81 return true; 82 } 83 84 static void efivarfs_hex_to_guid(const char *str, efi_guid_t *guid) 85 { 86 guid->b[0] = hex_to_bin(str[6]) << 4 | hex_to_bin(str[7]); 87 guid->b[1] = hex_to_bin(str[4]) << 4 | hex_to_bin(str[5]); 88 guid->b[2] = hex_to_bin(str[2]) << 4 | hex_to_bin(str[3]); 89 guid->b[3] = hex_to_bin(str[0]) << 4 | hex_to_bin(str[1]); 90 guid->b[4] = hex_to_bin(str[11]) << 4 | hex_to_bin(str[12]); 91 guid->b[5] = hex_to_bin(str[9]) << 4 | hex_to_bin(str[10]); 92 guid->b[6] = hex_to_bin(str[16]) << 4 | hex_to_bin(str[17]); 93 guid->b[7] = hex_to_bin(str[14]) << 4 | hex_to_bin(str[15]); 94 guid->b[8] = hex_to_bin(str[19]) << 4 | hex_to_bin(str[20]); 95 guid->b[9] = hex_to_bin(str[21]) << 4 | hex_to_bin(str[22]); 96 guid->b[10] = hex_to_bin(str[24]) << 4 | hex_to_bin(str[25]); 97 guid->b[11] = hex_to_bin(str[26]) << 4 | hex_to_bin(str[27]); 98 guid->b[12] = hex_to_bin(str[28]) << 4 | hex_to_bin(str[29]); 99 guid->b[13] = hex_to_bin(str[30]) << 4 | hex_to_bin(str[31]); 100 guid->b[14] = hex_to_bin(str[32]) << 4 | hex_to_bin(str[33]); 101 guid->b[15] = hex_to_bin(str[34]) << 4 | hex_to_bin(str[35]); 102 } 103 104 static int efivarfs_create(struct inode *dir, struct dentry *dentry, 105 umode_t mode, bool excl) 106 { 107 struct inode *inode = NULL; 108 struct efivar_entry *var; 109 int namelen, i = 0, err = 0; 110 bool is_removable = false; 111 112 if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len)) 113 return -EINVAL; 114 115 var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL); 116 if (!var) 117 return -ENOMEM; 118 119 /* length of the variable name itself: remove GUID and separator */ 120 namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1; 121 122 efivarfs_hex_to_guid(dentry->d_name.name + namelen + 1, 123 &var->var.VendorGuid); 124 125 if (efivar_variable_is_removable(var->var.VendorGuid, 126 dentry->d_name.name, namelen)) 127 is_removable = true; 128 129 inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable); 130 if (!inode) { 131 err = -ENOMEM; 132 goto out; 133 } 134 135 for (i = 0; i < namelen; i++) 136 var->var.VariableName[i] = dentry->d_name.name[i]; 137 138 var->var.VariableName[i] = '\0'; 139 140 inode->i_private = var; 141 142 efivar_entry_add(var, &efivarfs_list); 143 d_instantiate(dentry, inode); 144 dget(dentry); 145 out: 146 if (err) { 147 kfree(var); 148 if (inode) 149 iput(inode); 150 } 151 return err; 152 } 153 154 static int efivarfs_unlink(struct inode *dir, struct dentry *dentry) 155 { 156 struct efivar_entry *var = d_inode(dentry)->i_private; 157 158 if (efivar_entry_delete(var)) 159 return -EINVAL; 160 161 drop_nlink(d_inode(dentry)); 162 dput(dentry); 163 return 0; 164 }; 165 166 const struct inode_operations efivarfs_dir_inode_operations = { 167 .lookup = simple_lookup, 168 .unlink = efivarfs_unlink, 169 .create = efivarfs_create, 170 }; 171