/** * 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; }