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, 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 };