kernel/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;
  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 = memdup_user(userbuf + sizeof(attributes), datasize);
  37         if (IS_ERR(data))
  38                 return PTR_ERR(data);
  39
  40         bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  41                                           data, &set);
  42         if (!set && bytes) {
  43                 if (bytes == -ENOENT)
  44                         bytes = -EIO;
  45                 goto out;
  46         }
  47
  48         if (bytes == -ENOENT) {
  49                 drop_nlink(inode);
  50                 d_delete(file->f_path.dentry);
  51                 dput(file->f_path.dentry);
  52         } else {
  53                 mutex_lock(&inode->i_mutex);
  54                 i_size_write(inode, datasize + sizeof(attributes));
  55                 mutex_unlock(&inode->i_mutex);
  56         }
  57
  58         bytes = count;
  59
  60 out:
  61         kfree(data);
  62
  63         return bytes;
  64 }
  65
  66 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  67                 size_t count, loff_t *ppos)
  68 {
  69         struct efivar_entry *var = file->private_data;
  70         unsigned long datasize = 0;
  71         u32 attributes;
  72         void *data;
  73         ssize_t size = 0;
  74         int err;
  75
  76         err = efivar_entry_size(var, &datasize);
  77
  78         /*
  79          * efivarfs represents uncommitted variables with
  80          * zero-length files. Reading them should return EOF.
  81          */
  82         if (err == -ENOENT)
  83                 return 0;
  84         else if (err)
  85                 return err;
  86
  87         data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  88
  89         if (!data)
  90                 return -ENOMEM;
  91
  92         size = efivar_entry_get(var, &attributes, &datasize,
  93                                 data + sizeof(attributes));
  94         if (size)
  95                 goto out_free;
  96
  97         memcpy(data, &attributes, sizeof(attributes));
  98         size = simple_read_from_buffer(userbuf, count, ppos,
  99                                        data, datasize + sizeof(attributes));
 100 out_free:
 101         kfree(data);
 102
 103         return size;
 104 }
 105
 106 const struct file_operations efivarfs_file_operations = {
 107         .open   = simple_open,
 108         .read   = efivarfs_file_read,
 109         .write  = efivarfs_file_write,
 110         .llseek = no_llseek,
 111 };