LXR linux/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
  18struct 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(inode);
  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 */
  48bool 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
  71static 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        err = efivar_entry_add(var, &efivarfs_list);
 109        if (err)
 110                goto out;
 111
 112        d_instantiate(dentry, inode);
 113        dget(dentry);
 114out:
 115        if (err) {
 116                kfree(var);
 117                if (inode)
 118                        iput(inode);
 119        }
 120        return err;
 121}
 122
 123static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
 124{
 125        struct efivar_entry *var = d_inode(dentry)->i_private;
 126
 127        if (efivar_entry_delete(var))
 128                return -EINVAL;
 129
 130        drop_nlink(d_inode(dentry));
 131        dput(dentry);
 132        return 0;
 133};
 134
 135const struct inode_operations efivarfs_dir_inode_operations = {
 136        .lookup = simple_lookup,
 137        .unlink = efivarfs_unlink,
 138        .create = efivarfs_create,
 139};
 140