linux/fs/efivarfs/inode.c
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   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
  17struct 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 */
  45bool 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
  82static 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
 102static 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);
 138out:
 139        if (err) {
 140                kfree(var);
 141                iput(inode);
 142        }
 143        return err;
 144}
 145
 146static 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
 158const struct inode_operations efivarfs_dir_inode_operations = {
 159        .lookup = simple_lookup,
 160        .unlink = efivarfs_unlink,
 161        .create = efivarfs_create,
 162};
 163
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