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
  14 #include "internal.h"
  15
  16 static ssize_t efivarfs_file_write(struct file *file,
  17                 const char __user *userbuf, size_t count, loff_t *ppos)
  18 {
  19         struct efivar_entry *var = file->private_data;
  20         void *data;
  21         u32 attributes;
  22         struct inode *inode = file->f_mapping->host;
  23         unsigned long datasize = count - sizeof(attributes);
  24         ssize_t bytes = 0;
  25         bool set = false;
  26
  27         if (count < sizeof(attributes))
  28                 return -EINVAL;
  29
  30         if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
  31                 return -EFAULT;
  32
  33         if (attributes & ~(EFI_VARIABLE_MASK))
  34                 return -EINVAL;
  35
  36         data = kmalloc(datasize, GFP_KERNEL);
  37         if (!data)
  38                 return -ENOMEM;
  39
  40         if (copy_from_user(data, userbuf + sizeof(attributes), datasize)) {
  41                 bytes = -EFAULT;
  42                 goto out;
  43         }
  44
  45         bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  46                                           data, &set);
  47         if (!set && bytes) {
  48                 if (bytes == -ENOENT)
  49                         bytes = -EIO;
  50                 goto out;
  51         }
  52
  53         if (bytes == -ENOENT) {
  54                 drop_nlink(inode);
  55                 d_delete(file->f_dentry);
  56                 dput(file->f_dentry);
  57         } else {
  58                 mutex_lock(&inode->i_mutex);
  59                 i_size_write(inode, datasize + sizeof(attributes));
  60                 mutex_unlock(&inode->i_mutex);
  61         }
  62
  63         bytes = count;
  64
  65 out:
  66         kfree(data);
  67
  68         return bytes;
  69 }
  70
  71 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  72                 size_t count, loff_t *ppos)
  73 {
  74         struct efivar_entry *var = file->private_data;
  75         unsigned long datasize = 0;
  76         u32 attributes;
  77         void *data;
  78         ssize_t size = 0;
  79         int err;
  80
  81         err = efivar_entry_size(var, &datasize);
  82
  83         /*
  84          * efivarfs represents uncommitted variables with
  85          * zero-length files. Reading them should return EOF.
  86          */
  87         if (err == -ENOENT)
  88                 return 0;
  89         else if (err)
  90                 return err;
  91
  92         data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  93
  94         if (!data)
  95                 return -ENOMEM;
  96
  97         size = efivar_entry_get(var, &attributes, &datasize,
  98                                 data + sizeof(attributes));
  99         if (size)
 100                 goto out_free;
 101
 102         memcpy(data, &attributes, sizeof(attributes));
 103         size = simple_read_from_buffer(userbuf, count, ppos,
 104                                        data, datasize + sizeof(attributes));
 105 out_free:
 106         kfree(data);
 107
 108         return size;
 109 }
 110
 111 const struct file_operations efivarfs_file_operations = {
 112         .open   = simple_open,
 113         .read   = efivarfs_file_read,
 114         .write  = efivarfs_file_write,
 115         .llseek = no_llseek,
 116 };