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/delay.h>
  12 #include <linux/fs.h>
  13 #include <linux/slab.h>
  14 #include <linux/mount.h>
  15
  16 #include "internal.h"
  17
  18 static ssize_t efivarfs_file_write(struct file *file,
  19                 const char __user *userbuf, size_t count, loff_t *ppos)
  20 {
  21         struct efivar_entry *var = file->private_data;
  22         void *data;
  23         u32 attributes;
  24         struct inode *inode = file->f_mapping->host;
  25         unsigned long datasize = count - sizeof(attributes);
  26         ssize_t bytes;
  27         bool set = false;
  28
  29         if (count < sizeof(attributes))
  30                 return -EINVAL;
  31
  32         if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
  33                 return -EFAULT;
  34
  35         if (attributes & ~(EFI_VARIABLE_MASK))
  36                 return -EINVAL;
  37
  38         data = memdup_user(userbuf + sizeof(attributes), datasize);
  39         if (IS_ERR(data))
  40                 return PTR_ERR(data);
  41
  42         bytes = efivar_entry_set_get_size(var, attributes, &datasize,
  43                                           data, &set);
  44         if (!set && bytes) {
  45                 if (bytes == -ENOENT)
  46                         bytes = -EIO;
  47                 goto out;
  48         }
  49
  50         if (bytes == -ENOENT) {
  51                 drop_nlink(inode);
  52                 d_delete(file->f_path.dentry);
  53                 dput(file->f_path.dentry);
  54         } else {
  55                 inode_lock(inode);
  56                 i_size_write(inode, datasize + sizeof(attributes));
  57                 inode_unlock(inode);
  58         }
  59
  60         bytes = count;
  61
  62 out:
  63         kfree(data);
  64
  65         return bytes;
  66 }
  67
  68 static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
  69                 size_t count, loff_t *ppos)
  70 {
  71         struct efivar_entry *var = file->private_data;
  72         unsigned long datasize = 0;
  73         u32 attributes;
  74         void *data;
  75         ssize_t size = 0;
  76         int err;
  77
  78         while (!__ratelimit(&file->f_cred->user->ratelimit)) {
  79                 if (!msleep_interruptible(50))
  80                         return -EINTR;
  81         }
  82
  83         err = efivar_entry_size(var, &datasize);
  84
  85         /*
  86          * efivarfs represents uncommitted variables with
  87          * zero-length files. Reading them should return EOF.
  88          */
  89         if (err == -ENOENT)
  90                 return 0;
  91         else if (err)
  92                 return err;
  93
  94         data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);
  95
  96         if (!data)
  97                 return -ENOMEM;
  98
  99         size = efivar_entry_get(var, &attributes, &datasize,
 100                                 data + sizeof(attributes));
 101         if (size)
 102                 goto out_free;
 103
 104         memcpy(data, &attributes, sizeof(attributes));
 105         size = simple_read_from_buffer(userbuf, count, ppos,
 106                                        data, datasize + sizeof(attributes));
 107 out_free:
 108         kfree(data);
 109
 110         return size;
 111 }
 112
 113 static int
 114 efivarfs_ioc_getxflags(struct file *file, void __user *arg)
 115 {
 116         struct inode *inode = file->f_mapping->host;
 117         unsigned int i_flags;
 118         unsigned int flags = 0;
 119
 120         i_flags = inode->i_flags;
 121         if (i_flags & S_IMMUTABLE)
 122                 flags |= FS_IMMUTABLE_FL;
 123
 124         if (copy_to_user(arg, &flags, sizeof(flags)))
 125                 return -EFAULT;
 126         return 0;
 127 }
 128
 129 static int
 130 efivarfs_ioc_setxflags(struct file *file, void __user *arg)
 131 {
 132         struct inode *inode = file->f_mapping->host;
 133         unsigned int flags;
 134         unsigned int i_flags = 0;
 135         int error;
 136
 137         if (!inode_owner_or_capable(inode))
 138                 return -EACCES;
 139
 140         if (copy_from_user(&flags, arg, sizeof(flags)))
 141                 return -EFAULT;
 142
 143         if (flags & ~FS_IMMUTABLE_FL)
 144                 return -EOPNOTSUPP;
 145
 146         if (!capable(CAP_LINUX_IMMUTABLE))
 147                 return -EPERM;
 148
 149         if (flags & FS_IMMUTABLE_FL)
 150                 i_flags |= S_IMMUTABLE;
 151
 152
 153         error = mnt_want_write_file(file);
 154         if (error)
 155                 return error;
 156
 157         inode_lock(inode);
 158         inode_set_flags(inode, i_flags, S_IMMUTABLE);
 159         inode_unlock(inode);
 160
 161         mnt_drop_write_file(file);
 162
 163         return 0;
 164 }
 165
 166 static long
 167 efivarfs_file_ioctl(struct file *file, unsigned int cmd, unsigned long p)
 168 {
 169         void __user *arg = (void __user *)p;
 170
 171         switch (cmd) {
 172         case FS_IOC_GETFLAGS:
 173                 return efivarfs_ioc_getxflags(file, arg);
 174         case FS_IOC_SETFLAGS:
 175                 return efivarfs_ioc_setxflags(file, arg);
 176         }
 177
 178         return -ENOTTY;
 179 }
 180
 181 const struct file_operations efivarfs_file_operations = {
 182         .open   = simple_open,
 183         .read   = efivarfs_file_read,
 184         .write  = efivarfs_file_write,
 185         .llseek = no_llseek,
 186         .unlocked_ioctl = efivarfs_file_ioctl,
 187 };