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