diff options
Diffstat (limited to 'fs/ecryptfs/kthread.c')
| -rw-r--r-- | fs/ecryptfs/kthread.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c new file mode 100644 index 000000000000..c440c6b58b2d --- /dev/null +++ b/fs/ecryptfs/kthread.c @@ -0,0 +1,203 @@ +/** + * 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/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 persistent 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)); + req->flags |= ECRYPTFS_REQ_PROCESSED; + } + wake_up(&req->wait); + mutex_unlock(&req->mux); + } + mutex_unlock(&ecryptfs_kthread_ctl.mux); + } +out: + return 0; +} + +int 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) +{ + struct ecryptfs_open_req *req; + int rc = 0; + + /* Corresponding dput() and mntput() are done when the + * persistent file is fput() when the eCryptfs inode is + * destroyed. */ + dget(lower_dentry); + mntget(lower_mnt); + (*lower_file) = dentry_open(lower_dentry, lower_mnt, + (O_RDWR | O_LARGEFILE)); + if (!IS_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); + dget(lower_dentry); + mntget(lower_mnt); + (*lower_file) = dentry_open(lower_dentry, lower_mnt, + (O_RDONLY | O_LARGEFILE)); + if (IS_ERR(*lower_file)) { + rc = PTR_ERR(*req->lower_file); + (*lower_file) = NULL; + printk(KERN_WARNING "%s: Error attempting privileged " + "open of lower file with either RW or RO " + "perms; rc = [%d]. Giving up.\n", + __func__, rc); + } + } +out_unlock: + mutex_unlock(&req->mux); +out_free: + kmem_cache_free(ecryptfs_open_req_cache, req); +out: + return rc; +} |