/**
* eCryptfs: Linux filesystem encryption layer
*
* Copyright (C) 2008 International Business Machines Corp.
* Author(s): Michael A. Halcrow <mahalcro@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/kthread.h>
#include <linux/freezer.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/mount.h>
#include "ecryptfs_kernel.h"
struct kmem_cache *ecryptfs_open_req_cache;
static struct ecryptfs_kthread_ctl {
#define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001
u32 flags;
struct mutex mux;
struct list_head req_list;
wait_queue_head_t wait;
} ecryptfs_kthread_ctl;
static struct task_struct *ecryptfs_kthread;
/**
* ecryptfs_threadfn
* @ignored: ignored
*
* The eCryptfs kernel thread that has the responsibility of getting
* the lower file with RW permissions.
*
* Returns zero on success; non-zero otherwise
*/
static int ecryptfs_threadfn(void *ignored)
{
set_freezable();
while (1) {
struct ecryptfs_open_req *req;
wait_event_freezable(
ecryptfs_kthread_ctl.wait,
(!list_empty(&ecryptfs_kthread_ctl.req_list)
|| kthread_should_stop()));
mutex_lock(&ecryptfs_kthread_ctl.mux);
if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
mutex_unlock(&ecryptfs_kthread_ctl.mux);
goto out;
}
while (!list_empty(&ecryptfs_kthread_ctl.req_list)) {
req = list_first_entry(&ecryptfs_kthread_ctl.req_list,
struct ecryptfs_open_req,
kthread_ctl_list);
mutex_lock(&req->mux);
list_del(&req->kthread_ctl_list);
if (!(req->flags & ECRYPTFS_REQ_ZOMBIE)) {
dget(req->lower_dentry);
mntget(req->lower_mnt);
(*req->lower_file) = dentry_open(
req->lower_dentry, req->lower_mnt,
(O_RDWR | O_LARGEFILE), current_cred());
req->flags |= ECRYPTFS_REQ_PROCESSED;
}
wake_up(&req->wait);
mutex_unlock(&req->mux);
}
mutex_unlock(&ecryptfs_kthread_ctl.mux);
}
out:
return 0;
}
int __init ecryptfs_init_kthread(void)
{
int rc = 0;
mutex_init(&ecryptfs_kthread_ctl.mux);
init_waitqueue_head(&ecryptfs_kthread_ctl.wait);
INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list);
ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL,
"ecryptfs-kthread");
if (IS_ERR(ecryptfs_kthread)) {
rc = PTR_ERR(ecryptfs_kthread);
printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]"
"\n", __func__, rc);
}
return rc;
}
void ecryptfs_destroy_kthread(void)
{
struct ecryptfs_open_req *req;
mutex_lock(&ecryptfs_kthread_ctl.mux);
ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE;
list_for_each_entry(req, &ecryptfs_kthread_ctl.req_list,
kthread_ctl_list) {
mutex_lock(&req->mux);
req->flags |= ECRYPTFS_REQ_ZOMBIE;
wake_up(&req->wait);
mutex_unlock(&req->mux);
}
mutex_unlock(&ecryptfs_kthread_ctl.mux);
kthread_stop(ecryptfs_kthread);
wake_up(&ecryptfs_kthread_ctl.wait);
}
/**
* ecryptfs_privileged_open
* @lower_file: Result of dentry_open by root on lower dentry
* @lower_dentry: Lower dentry for file to open
* @lower_mnt: Lower vfsmount for file to open
*
* This function gets a r/w file opened againt the lower dentry.
*
* Returns zero on success; non-zero otherwise
*/
int ecryptfs_privileged_open(struct file **lower_file,
struct dentry *lower_dentry,
struct vfsmount *lower_mnt,
const struct cred *cred)
{
struct ecryptfs_open_req *req;
int flags = O_LARGEFILE;
int rc = 0;
/* Corresponding dput() and mntput() are done when the
* lower file is fput() when all eCryptfs files for the inode are
* released. */
dget(lower_dentry);
mntget(lower_mnt);
flags |= IS_RDONLY(lower_dentry->d_inode) ? O_RDONLY : O_RDWR;
(*lower_file) = dentry_open(lower_dentry, lower_mnt, flags, cred);
if (!IS_ERR(*lower_file))
goto out;
if ((flags & O_ACCMODE) == O_RDONLY) {
rc = PTR_ERR((*lower_file));
goto out;
}
req = kmem_cache_alloc(ecryptfs_open_req_cache, GFP_KERNEL);
if (!req) {
rc = -ENOMEM;
goto out;
}
mutex_init(&req->mux);
req->lower_file = lower_file;
req->lower_dentry = lower_dentry;
req->lower_mnt = lower_mnt;
init_waitqueue_head(&req->wait);
req->flags = 0;
mutex_lock(&ecryptfs_kthread_ctl.mux);
if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) {
rc = -EIO;
mutex_unlock(&ecryptfs_kthread_ctl.mux);
printk(KERN_ERR "%s: We are in the middle of shutting down; "
"aborting privileged request to open lower file\n",
__func__);
goto out_free;
}
list_add_tail(&req->kthread_ctl_list, &ecryptfs_kthread_ctl.req_list);
mutex_unlock(&ecryptfs_kthread_ctl.mux);
wake_up(&ecryptfs_kthread_ctl.wait);
wait_event(req->wait, (req->flags != 0));
mutex_lock(&req->mux);
BUG_ON(req->flags == 0);
if (req->flags & ECRYPTFS_REQ_DROPPED
|| req->flags & ECRYPTFS_REQ_ZOMBIE) {
rc = -EIO;
printk(KERN_WARNING "%s: Privileged open request dropped\n",
__func__);
goto out_unlock;
}
if (IS_ERR(*req->lower_file))
rc = PTR_ERR(*req->lower_file);
out_unlock:
mutex_unlock(&req->mux);
out_free:
kmem_cache_free(ecryptfs_open_req_cache, req);
out:
return rc;
}
