linux/fs/ecryptfs/super.c
Tyler Hicks 332ab16f83 eCryptfs: Add reference counting to lower files
For any given lower inode, eCryptfs keeps only one lower file open and
multiplexes all eCryptfs file operations through that lower file. The
lower file was considered "persistent" and stayed open from the first
lookup through the lifetime of the inode.

This patch keeps the notion of a single, per-inode lower file, but adds
reference counting around the lower file so that it is closed when not
currently in use. If the reference count is at 0 when an operation (such
as open, create, etc.) needs to use the lower file, a new lower file is
opened. Since the file is no longer persistent, all references to the
term persistent file are changed to lower file.

Locking is added around the sections of code that opens the lower file
and assign the pointer in the inode info, as well as the code the fputs
the lower file when all eCryptfs users are done with it.

This patch is needed to fix issues, when mounted on top of the NFSv3
client, where the lower file is left silly renamed until the eCryptfs
inode is destroyed.

Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
2011-04-25 18:32:37 -05:00

198 lines
6.2 KiB
C

/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 1997-2003 Erez Zadok
* Copyright (C) 2001-2003 Stony Brook University
* Copyright (C) 2004-2006 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
* Michael C. Thompson <mcthomps@us.ibm.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
* 02111-1307, USA.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/key.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/file.h>
#include <linux/crypto.h>
#include "ecryptfs_kernel.h"
struct kmem_cache *ecryptfs_inode_info_cache;
/**
* ecryptfs_alloc_inode - allocate an ecryptfs inode
* @sb: Pointer to the ecryptfs super block
*
* Called to bring an inode into existence.
*
* Only handle allocation, setting up structures should be done in
* ecryptfs_read_inode. This is because the kernel, between now and
* then, will 0 out the private data pointer.
*
* Returns a pointer to a newly allocated inode, NULL otherwise
*/
static struct inode *ecryptfs_alloc_inode(struct super_block *sb)
{
struct ecryptfs_inode_info *inode_info;
struct inode *inode = NULL;
inode_info = kmem_cache_alloc(ecryptfs_inode_info_cache, GFP_KERNEL);
if (unlikely(!inode_info))
goto out;
ecryptfs_init_crypt_stat(&inode_info->crypt_stat);
mutex_init(&inode_info->lower_file_mutex);
atomic_set(&inode_info->lower_file_count, 0);
inode_info->lower_file = NULL;
inode = &inode_info->vfs_inode;
out:
return inode;
}
static void ecryptfs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
struct ecryptfs_inode_info *inode_info;
inode_info = ecryptfs_inode_to_private(inode);
INIT_LIST_HEAD(&inode->i_dentry);
kmem_cache_free(ecryptfs_inode_info_cache, inode_info);
}
/**
* ecryptfs_destroy_inode
* @inode: The ecryptfs inode
*
* This is used during the final destruction of the inode. All
* allocation of memory related to the inode, including allocated
* memory in the crypt_stat struct, will be released here.
* There should be no chance that this deallocation will be missed.
*/
static void ecryptfs_destroy_inode(struct inode *inode)
{
struct ecryptfs_inode_info *inode_info;
inode_info = ecryptfs_inode_to_private(inode);
BUG_ON(inode_info->lower_file);
ecryptfs_destroy_crypt_stat(&inode_info->crypt_stat);
call_rcu(&inode->i_rcu, ecryptfs_i_callback);
}
/**
* ecryptfs_init_inode
* @inode: The ecryptfs inode
*
* Set up the ecryptfs inode.
*/
void ecryptfs_init_inode(struct inode *inode, struct inode *lower_inode)
{
ecryptfs_set_inode_lower(inode, lower_inode);
inode->i_ino = lower_inode->i_ino;
inode->i_version++;
inode->i_op = &ecryptfs_main_iops;
inode->i_fop = &ecryptfs_main_fops;
inode->i_mapping->a_ops = &ecryptfs_aops;
}
/**
* ecryptfs_statfs
* @sb: The ecryptfs super block
* @buf: The struct kstatfs to fill in with stats
*
* Get the filesystem statistics. Currently, we let this pass right through
* to the lower filesystem and take no action ourselves.
*/
static int ecryptfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
if (!lower_dentry->d_sb->s_op->statfs)
return -ENOSYS;
return lower_dentry->d_sb->s_op->statfs(lower_dentry, buf);
}
/**
* ecryptfs_evict_inode
* @inode - The ecryptfs inode
*
* Called by iput() when the inode reference count reached zero
* and the inode is not hashed anywhere. Used to clear anything
* that needs to be, before the inode is completely destroyed and put
* on the inode free list. We use this to drop out reference to the
* lower inode.
*/
static void ecryptfs_evict_inode(struct inode *inode)
{
truncate_inode_pages(&inode->i_data, 0);
end_writeback(inode);
iput(ecryptfs_inode_to_lower(inode));
}
/**
* ecryptfs_show_options
*
* Prints the mount options for a given superblock.
* Returns zero; does not fail.
*/
static int ecryptfs_show_options(struct seq_file *m, struct vfsmount *mnt)
{
struct super_block *sb = mnt->mnt_sb;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(sb)->mount_crypt_stat;
struct ecryptfs_global_auth_tok *walker;
mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
list_for_each_entry(walker,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
if (walker->flags & ECRYPTFS_AUTH_TOK_FNEK)
seq_printf(m, ",ecryptfs_fnek_sig=%s", walker->sig);
else
seq_printf(m, ",ecryptfs_sig=%s", walker->sig);
}
mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
seq_printf(m, ",ecryptfs_cipher=%s",
mount_crypt_stat->global_default_cipher_name);
if (mount_crypt_stat->global_default_cipher_key_size)
seq_printf(m, ",ecryptfs_key_bytes=%zd",
mount_crypt_stat->global_default_cipher_key_size);
if (mount_crypt_stat->flags & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)
seq_printf(m, ",ecryptfs_passthrough");
if (mount_crypt_stat->flags & ECRYPTFS_XATTR_METADATA_ENABLED)
seq_printf(m, ",ecryptfs_xattr_metadata");
if (mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
seq_printf(m, ",ecryptfs_encrypted_view");
if (mount_crypt_stat->flags & ECRYPTFS_UNLINK_SIGS)
seq_printf(m, ",ecryptfs_unlink_sigs");
if (mount_crypt_stat->flags & ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY)
seq_printf(m, ",ecryptfs_mount_auth_tok_only");
return 0;
}
const struct super_operations ecryptfs_sops = {
.alloc_inode = ecryptfs_alloc_inode,
.destroy_inode = ecryptfs_destroy_inode,
.drop_inode = generic_drop_inode,
.statfs = ecryptfs_statfs,
.remount_fs = NULL,
.evict_inode = ecryptfs_evict_inode,
.show_options = ecryptfs_show_options
};