fs/efivarfs/inode.c

   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 };