fs/efivarfs/file.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/slab.h>
  13 #include <linux/mount.h>
  14
  15 #include "internal.h"
  16
  17 static ssize_t efivarfs_file_write(struct file *file,
  18                 const char __user *userbuf, size_t count, loff_t *ppos)
  19 {
  20         struct efivar_entry *var = file->private_data;
  21         void *data;
  22         u32 attributes;
  23         struct inode *inode = file->f_mapping->host;
  24         unsigned long datasize = count - sizeof(attributes);
  25         ssize_t bytes;
  26         bool set = false;
  27
  28         if (count < sizeof(attributes))
  29                 return -EINVAL;
  30
  31         if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
  32                 return -EFAULT;
  33
  34         if (attributes & ~(EFI_VARIABLE_MASK))
  35                 return -EINVAL;
  36
  37         data = memdup_user(userbuf + sizeof(attributes), datasize);
  38         if (IS_ERR(data))
  39                 return PTR_ERR(data);
  40
  41         bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  42                                           data, &set);
  43         if (!set && bytes) {
  44                 if (bytes == -ENOENT)
  45                         bytes = -EIO;
  46                 goto out;
  47         }
  48
  49         if (bytes == -ENOENT) {
  50                 drop_nlink(inode);
  51                 d_delete(file->f_path.dentry);
  52                 dput(file->f_path.dentry);
  53         } else {
  54                 mutex_lock(&inode->i_mutex);
  55                 i_size_write(inode, datasize + sizeof(attributes));
  56                 mutex_unlock(&inode->i_mutex);
  57         }
  58
  59         bytes = count;
  60
  61 out:
  62         kfree(data);
  63
  64         return bytes;
  65 }
  66
  67 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  68                 size_t count, loff_t *ppos)
  69 {
  70         struct efivar_entry *var = file->private_data;
  71         unsigned long datasize = 0;
  72         u32 attributes;
  73         void *data;
  74         ssize_t size = 0;
  75         int err;
  76
  77         err = efivar_entry_size(var, &datasize);
  78
  79         /*
  80          * efivarfs represents uncommitted variables with
  81          * zero-length files. Reading them should return EOF.
  82          */
  83         if (err == -ENOENT)
  84                 return 0;
  85         else if (err)
  86                 return err;
  87
  88         data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  89
  90         if (!data)
  91                 return -ENOMEM;
  92
  93         size = efivar_entry_get(var, &attributes, &datasize,
  94                                 data + sizeof(attributes));
  95         if (size)
  96                 goto out_free;
  97
  98         memcpy(data, &attributes, sizeof(attributes));
  99         size = simple_read_from_buffer(userbuf, count, ppos,
 100                                        data, datasize + sizeof(attributes));
 101 out_free:
 102         kfree(data);
 103
 104         return size;
 105 }
 106
 107 static int
 108 efivarfs_ioc_getxflags(struct file *file, void __user *arg)
 109 {
 110         struct inode *inode = file->f_mapping->host;
 111         unsigned int i_flags;
 112         unsigned int flags = 0;
 113
 114         i_flags = inode->i_flags;
 115         if (i_flags & S_IMMUTABLE)
 116                 flags |= FS_IMMUTABLE_FL;
 117
 118         if (copy_to_user(arg, &flags, sizeof(flags)))
 119                 return -EFAULT;
 120         return 0;
 121 }
 122
 123 static int
 124 efivarfs_ioc_setxflags(struct file *file, void __user *arg)
 125 {
 126         struct inode *inode = file->f_mapping->host;
 127         unsigned int flags;
 128         unsigned int i_flags = 0;
 129         int error;
 130
 131         if (!inode_owner_or_capable(inode))
 132                 return -EACCES;
 133
 134         if (copy_from_user(&flags, arg, sizeof(flags)))
 135                 return -EFAULT;
 136
 137         if (flags & ~FS_IMMUTABLE_FL)
 138                 return -EOPNOTSUPP;
 139
 140         if (!capable(CAP_LINUX_IMMUTABLE))
 141                 return -EPERM;
 142
 143         if (flags & FS_IMMUTABLE_FL)
 144                 i_flags |= S_IMMUTABLE;
 145
 146
 147         error = mnt_want_write_file(file);
 148         if (error)
 149                 return error;
 150
 151         mutex_lock(&inode->i_mutex);
 152         inode_set_flags(inode, i_flags, S_IMMUTABLE);
 153         mutex_unlock(&inode->i_mutex);
 154
 155         mnt_drop_write_file(file);
 156
 157         return 0;
 158 }
 159
 160 long
 161 efivarfs_file_ioctl(struct file *file, unsigned int cmd, unsigned long p)
 162 {
 163         void __user *arg = (void __user *)p;
 164
 165         switch (cmd) {
 166         case FS_IOC_GETFLAGS:
 167                 return efivarfs_ioc_getxflags(file, arg);
 168         case FS_IOC_SETFLAGS:
 169                 return efivarfs_ioc_setxflags(file, arg);
 170         }
 171
 172         return -ENOTTY;
 173 }
 174
 175 const struct file_operations efivarfs_file_operations = {
 176         .open   = simple_open,
 177         .read   = efivarfs_file_read,
 178         .write  = efivarfs_file_write,
 179         .llseek = no_llseek,
 180         .unlocked_ioctl = efivarfs_file_ioctl,
 181 };