![Tyler Hicks](/assets/img/avatar_default.png)
File operations on /dev/ecryptfs would BUG() when the operations were performed by processes other than the process that originally opened the file. This could happen with open files inherited after fork() or file descriptors passed through IPC mechanisms. Rather than calling BUG(), an error code can be safely returned in most situations. In ecryptfs_miscdev_release(), eCryptfs still needs to handle the release even if the last file reference is being held by a process that didn't originally open the file. ecryptfs_find_daemon_by_euid() will not be successful, so a pointer to the daemon is stored in the file's private_data. The private_data pointer is initialized when the miscdev file is opened and only used when the file is released. https://launchpad.net/bugs/994247 Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Reported-by: Sasha Levin <levinsasha928@gmail.com> Tested-by: Sasha Levin <levinsasha928@gmail.com>
568 lines
17 KiB
C
568 lines
17 KiB
C
/**
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* eCryptfs: Linux filesystem encryption layer
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*
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* Copyright (C) 2008 International Business Machines Corp.
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* Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version
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* 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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* 02111-1307, USA.
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*/
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#include <linux/fs.h>
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#include <linux/hash.h>
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#include <linux/random.h>
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#include <linux/miscdevice.h>
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#include <linux/poll.h>
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#include <linux/slab.h>
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#include <linux/wait.h>
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#include <linux/module.h>
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#include "ecryptfs_kernel.h"
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static atomic_t ecryptfs_num_miscdev_opens;
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/**
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* ecryptfs_miscdev_poll
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* @file: dev file (ignored)
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* @pt: dev poll table (ignored)
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*
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* Returns the poll mask
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*/
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static unsigned int
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ecryptfs_miscdev_poll(struct file *file, poll_table *pt)
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{
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struct ecryptfs_daemon *daemon;
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unsigned int mask = 0;
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uid_t euid = current_euid();
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int rc;
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mutex_lock(&ecryptfs_daemon_hash_mux);
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/* TODO: Just use file->private_data? */
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rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
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if (rc || !daemon) {
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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return -EINVAL;
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}
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mutex_lock(&daemon->mux);
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
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printk(KERN_WARNING "%s: Attempt to poll on zombified "
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"daemon\n", __func__);
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goto out_unlock_daemon;
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}
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if (daemon->flags & ECRYPTFS_DAEMON_IN_READ)
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goto out_unlock_daemon;
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if (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)
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goto out_unlock_daemon;
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daemon->flags |= ECRYPTFS_DAEMON_IN_POLL;
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mutex_unlock(&daemon->mux);
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poll_wait(file, &daemon->wait, pt);
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mutex_lock(&daemon->mux);
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if (!list_empty(&daemon->msg_ctx_out_queue))
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mask |= POLLIN | POLLRDNORM;
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out_unlock_daemon:
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daemon->flags &= ~ECRYPTFS_DAEMON_IN_POLL;
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mutex_unlock(&daemon->mux);
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return mask;
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}
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/**
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* ecryptfs_miscdev_open
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* @inode: inode of miscdev handle (ignored)
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* @file: file for miscdev handle (ignored)
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*
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* Returns zero on success; non-zero otherwise
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*/
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static int
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ecryptfs_miscdev_open(struct inode *inode, struct file *file)
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{
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struct ecryptfs_daemon *daemon = NULL;
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uid_t euid = current_euid();
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int rc;
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mutex_lock(&ecryptfs_daemon_hash_mux);
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rc = try_module_get(THIS_MODULE);
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if (rc == 0) {
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rc = -EIO;
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printk(KERN_ERR "%s: Error attempting to increment module use "
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"count; rc = [%d]\n", __func__, rc);
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goto out_unlock_daemon_list;
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}
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rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
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if (rc || !daemon) {
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rc = ecryptfs_spawn_daemon(&daemon, euid, current_user_ns(),
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task_pid(current));
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if (rc) {
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printk(KERN_ERR "%s: Error attempting to spawn daemon; "
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"rc = [%d]\n", __func__, rc);
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goto out_module_put_unlock_daemon_list;
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}
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}
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mutex_lock(&daemon->mux);
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if (daemon->pid != task_pid(current)) {
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rc = -EINVAL;
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printk(KERN_ERR "%s: pid [0x%p] has registered with euid [%d], "
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"but pid [0x%p] has attempted to open the handle "
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"instead\n", __func__, daemon->pid, daemon->euid,
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task_pid(current));
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goto out_unlock_daemon;
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}
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if (daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN) {
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rc = -EBUSY;
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printk(KERN_ERR "%s: Miscellaneous device handle may only be "
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"opened once per daemon; pid [0x%p] already has this "
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"handle open\n", __func__, daemon->pid);
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goto out_unlock_daemon;
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}
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daemon->flags |= ECRYPTFS_DAEMON_MISCDEV_OPEN;
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file->private_data = daemon;
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atomic_inc(&ecryptfs_num_miscdev_opens);
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out_unlock_daemon:
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mutex_unlock(&daemon->mux);
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out_module_put_unlock_daemon_list:
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if (rc)
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module_put(THIS_MODULE);
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out_unlock_daemon_list:
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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return rc;
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}
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/**
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* ecryptfs_miscdev_release
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* @inode: inode of fs/ecryptfs/euid handle (ignored)
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* @file: file for fs/ecryptfs/euid handle (ignored)
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*
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* This keeps the daemon registered until the daemon sends another
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* ioctl to fs/ecryptfs/ctl or until the kernel module unregisters.
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*
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* Returns zero on success; non-zero otherwise
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*/
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static int
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ecryptfs_miscdev_release(struct inode *inode, struct file *file)
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{
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struct ecryptfs_daemon *daemon = NULL;
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uid_t euid = current_euid();
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int rc;
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mutex_lock(&ecryptfs_daemon_hash_mux);
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rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
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if (rc || !daemon)
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daemon = file->private_data;
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mutex_lock(&daemon->mux);
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BUG_ON(!(daemon->flags & ECRYPTFS_DAEMON_MISCDEV_OPEN));
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daemon->flags &= ~ECRYPTFS_DAEMON_MISCDEV_OPEN;
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atomic_dec(&ecryptfs_num_miscdev_opens);
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mutex_unlock(&daemon->mux);
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rc = ecryptfs_exorcise_daemon(daemon);
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if (rc) {
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printk(KERN_CRIT "%s: Fatal error whilst attempting to "
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"shut down daemon; rc = [%d]. Please report this "
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"bug.\n", __func__, rc);
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BUG();
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}
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module_put(THIS_MODULE);
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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return rc;
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}
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/**
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* ecryptfs_send_miscdev
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* @data: Data to send to daemon; may be NULL
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* @data_size: Amount of data to send to daemon
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* @msg_ctx: Message context, which is used to handle the reply. If
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* this is NULL, then we do not expect a reply.
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* @msg_type: Type of message
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* @msg_flags: Flags for message
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* @daemon: eCryptfs daemon object
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*
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* Add msg_ctx to queue and then, if it exists, notify the blocked
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* miscdevess about the data being available. Must be called with
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* ecryptfs_daemon_hash_mux held.
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*
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* Returns zero on success; non-zero otherwise
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*/
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int ecryptfs_send_miscdev(char *data, size_t data_size,
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struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
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u16 msg_flags, struct ecryptfs_daemon *daemon)
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{
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struct ecryptfs_message *msg;
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msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
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if (!msg) {
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printk(KERN_ERR "%s: Out of memory whilst attempting "
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"to kmalloc(%zd, GFP_KERNEL)\n", __func__,
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(sizeof(*msg) + data_size));
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return -ENOMEM;
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}
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mutex_lock(&msg_ctx->mux);
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msg_ctx->msg = msg;
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msg_ctx->msg->index = msg_ctx->index;
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msg_ctx->msg->data_len = data_size;
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msg_ctx->type = msg_type;
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memcpy(msg_ctx->msg->data, data, data_size);
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msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
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list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
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mutex_unlock(&msg_ctx->mux);
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mutex_lock(&daemon->mux);
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daemon->num_queued_msg_ctx++;
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wake_up_interruptible(&daemon->wait);
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mutex_unlock(&daemon->mux);
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return 0;
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}
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/*
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* miscdevfs packet format:
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* Octet 0: Type
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* Octets 1-4: network byte order msg_ctx->counter
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* Octets 5-N0: Size of struct ecryptfs_message to follow
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* Octets N0-N1: struct ecryptfs_message (including data)
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*
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* Octets 5-N1 not written if the packet type does not include a message
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*/
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#define PKT_TYPE_SIZE 1
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#define PKT_CTR_SIZE 4
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#define MIN_NON_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE)
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#define MIN_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \
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+ ECRYPTFS_MIN_PKT_LEN_SIZE)
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/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */
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#define MAX_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \
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+ ECRYPTFS_MAX_PKT_LEN_SIZE \
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+ sizeof(struct ecryptfs_message) \
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+ 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)
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#define PKT_TYPE_OFFSET 0
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#define PKT_CTR_OFFSET PKT_TYPE_SIZE
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#define PKT_LEN_OFFSET (PKT_TYPE_SIZE + PKT_CTR_SIZE)
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/**
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* ecryptfs_miscdev_read - format and send message from queue
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* @file: fs/ecryptfs/euid miscdevfs handle (ignored)
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* @buf: User buffer into which to copy the next message on the daemon queue
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* @count: Amount of space available in @buf
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* @ppos: Offset in file (ignored)
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*
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* Pulls the most recent message from the daemon queue, formats it for
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* being sent via a miscdevfs handle, and copies it into @buf
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*
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* Returns the number of bytes copied into the user buffer
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*/
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static ssize_t
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ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count,
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loff_t *ppos)
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{
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struct ecryptfs_daemon *daemon;
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struct ecryptfs_msg_ctx *msg_ctx;
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size_t packet_length_size;
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char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE];
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size_t i;
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size_t total_length;
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uid_t euid = current_euid();
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int rc;
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mutex_lock(&ecryptfs_daemon_hash_mux);
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/* TODO: Just use file->private_data? */
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rc = ecryptfs_find_daemon_by_euid(&daemon, euid, current_user_ns());
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if (rc || !daemon) {
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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return -EINVAL;
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}
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mutex_lock(&daemon->mux);
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if (task_pid(current) != daemon->pid) {
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mutex_unlock(&daemon->mux);
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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return -EPERM;
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}
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if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
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rc = 0;
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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printk(KERN_WARNING "%s: Attempt to read from zombified "
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"daemon\n", __func__);
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goto out_unlock_daemon;
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}
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if (daemon->flags & ECRYPTFS_DAEMON_IN_READ) {
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rc = 0;
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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goto out_unlock_daemon;
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}
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/* This daemon will not go away so long as this flag is set */
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daemon->flags |= ECRYPTFS_DAEMON_IN_READ;
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mutex_unlock(&ecryptfs_daemon_hash_mux);
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check_list:
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if (list_empty(&daemon->msg_ctx_out_queue)) {
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mutex_unlock(&daemon->mux);
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rc = wait_event_interruptible(
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daemon->wait, !list_empty(&daemon->msg_ctx_out_queue));
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mutex_lock(&daemon->mux);
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if (rc < 0) {
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rc = 0;
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goto out_unlock_daemon;
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}
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}
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if (daemon->flags & ECRYPTFS_DAEMON_ZOMBIE) {
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rc = 0;
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goto out_unlock_daemon;
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}
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if (list_empty(&daemon->msg_ctx_out_queue)) {
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/* Something else jumped in since the
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* wait_event_interruptable() and removed the
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* message from the queue; try again */
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goto check_list;
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}
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msg_ctx = list_first_entry(&daemon->msg_ctx_out_queue,
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struct ecryptfs_msg_ctx, daemon_out_list);
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BUG_ON(!msg_ctx);
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mutex_lock(&msg_ctx->mux);
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if (msg_ctx->msg) {
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rc = ecryptfs_write_packet_length(packet_length,
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msg_ctx->msg_size,
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&packet_length_size);
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if (rc) {
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rc = 0;
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printk(KERN_WARNING "%s: Error writing packet length; "
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"rc = [%d]\n", __func__, rc);
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goto out_unlock_msg_ctx;
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}
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} else {
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packet_length_size = 0;
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msg_ctx->msg_size = 0;
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}
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total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size
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+ msg_ctx->msg_size);
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if (count < total_length) {
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rc = 0;
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printk(KERN_WARNING "%s: Only given user buffer of "
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"size [%zd], but we need [%zd] to read the "
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"pending message\n", __func__, count, total_length);
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goto out_unlock_msg_ctx;
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}
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rc = -EFAULT;
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if (put_user(msg_ctx->type, buf))
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goto out_unlock_msg_ctx;
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if (put_user(cpu_to_be32(msg_ctx->counter),
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(__be32 __user *)(&buf[PKT_CTR_OFFSET])))
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goto out_unlock_msg_ctx;
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i = PKT_TYPE_SIZE + PKT_CTR_SIZE;
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if (msg_ctx->msg) {
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if (copy_to_user(&buf[i], packet_length, packet_length_size))
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goto out_unlock_msg_ctx;
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i += packet_length_size;
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if (copy_to_user(&buf[i], msg_ctx->msg, msg_ctx->msg_size))
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goto out_unlock_msg_ctx;
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i += msg_ctx->msg_size;
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}
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rc = i;
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list_del(&msg_ctx->daemon_out_list);
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kfree(msg_ctx->msg);
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msg_ctx->msg = NULL;
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/* We do not expect a reply from the userspace daemon for any
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* message type other than ECRYPTFS_MSG_REQUEST */
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if (msg_ctx->type != ECRYPTFS_MSG_REQUEST)
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ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
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out_unlock_msg_ctx:
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mutex_unlock(&msg_ctx->mux);
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out_unlock_daemon:
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daemon->flags &= ~ECRYPTFS_DAEMON_IN_READ;
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mutex_unlock(&daemon->mux);
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return rc;
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}
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/**
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* ecryptfs_miscdev_response - miscdevess response to message previously sent to daemon
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* @data: Bytes comprising struct ecryptfs_message
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* @data_size: sizeof(struct ecryptfs_message) + data len
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* @euid: Effective user id of miscdevess sending the miscdev response
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* @user_ns: The namespace in which @euid applies
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* @pid: Miscdevess id of miscdevess sending the miscdev response
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* @seq: Sequence number for miscdev response packet
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*
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* Returns zero on success; non-zero otherwise
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*/
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static int ecryptfs_miscdev_response(char *data, size_t data_size,
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uid_t euid, struct user_namespace *user_ns,
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struct pid *pid, u32 seq)
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{
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struct ecryptfs_message *msg = (struct ecryptfs_message *)data;
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int rc;
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if ((sizeof(*msg) + msg->data_len) != data_size) {
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printk(KERN_WARNING "%s: (sizeof(*msg) + msg->data_len) = "
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"[%zd]; data_size = [%zd]. Invalid packet.\n", __func__,
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(sizeof(*msg) + msg->data_len), data_size);
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rc = -EINVAL;
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goto out;
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}
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rc = ecryptfs_process_response(msg, euid, user_ns, pid, seq);
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if (rc)
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printk(KERN_ERR
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"Error processing response message; rc = [%d]\n", rc);
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out:
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return rc;
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}
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/**
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* ecryptfs_miscdev_write - handle write to daemon miscdev handle
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* @file: File for misc dev handle (ignored)
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* @buf: Buffer containing user data
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* @count: Amount of data in @buf
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* @ppos: Pointer to offset in file (ignored)
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*
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* Returns the number of bytes read from @buf
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*/
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static ssize_t
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ecryptfs_miscdev_write(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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__be32 counter_nbo;
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u32 seq;
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size_t packet_size, packet_size_length;
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char *data;
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uid_t euid = current_euid();
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unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE];
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ssize_t rc;
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if (count == 0) {
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return 0;
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} else if (count == MIN_NON_MSG_PKT_SIZE) {
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/* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
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goto memdup;
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} else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) {
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printk(KERN_WARNING "%s: Acceptable packet size range is "
|
|
"[%d-%zu], but amount of data written is [%zu].",
|
|
__func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET],
|
|
sizeof(packet_size_peek))) {
|
|
printk(KERN_WARNING "%s: Error while inspecting packet size\n",
|
|
__func__);
|
|
return -EFAULT;
|
|
}
|
|
|
|
rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
|
|
&packet_size_length);
|
|
if (rc) {
|
|
printk(KERN_WARNING "%s: Error parsing packet length; "
|
|
"rc = [%zd]\n", __func__, rc);
|
|
return rc;
|
|
}
|
|
|
|
if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size)
|
|
!= count) {
|
|
printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
|
|
packet_size);
|
|
return -EINVAL;
|
|
}
|
|
|
|
memdup:
|
|
data = memdup_user(buf, count);
|
|
if (IS_ERR(data)) {
|
|
printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
|
|
__func__, PTR_ERR(data));
|
|
return PTR_ERR(data);
|
|
}
|
|
switch (data[PKT_TYPE_OFFSET]) {
|
|
case ECRYPTFS_MSG_RESPONSE:
|
|
if (count < (MIN_MSG_PKT_SIZE
|
|
+ sizeof(struct ecryptfs_message))) {
|
|
printk(KERN_WARNING "%s: Minimum acceptable packet "
|
|
"size is [%zd], but amount of data written is "
|
|
"only [%zd]. Discarding response packet.\n",
|
|
__func__,
|
|
(MIN_MSG_PKT_SIZE
|
|
+ sizeof(struct ecryptfs_message)), count);
|
|
rc = -EINVAL;
|
|
goto out_free;
|
|
}
|
|
memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE);
|
|
seq = be32_to_cpu(counter_nbo);
|
|
rc = ecryptfs_miscdev_response(
|
|
&data[PKT_LEN_OFFSET + packet_size_length],
|
|
packet_size, euid, current_user_ns(),
|
|
task_pid(current), seq);
|
|
if (rc) {
|
|
printk(KERN_WARNING "%s: Failed to deliver miscdev "
|
|
"response to requesting operation; rc = [%zd]\n",
|
|
__func__, rc);
|
|
goto out_free;
|
|
}
|
|
break;
|
|
case ECRYPTFS_MSG_HELO:
|
|
case ECRYPTFS_MSG_QUIT:
|
|
break;
|
|
default:
|
|
ecryptfs_printk(KERN_WARNING, "Dropping miscdev "
|
|
"message of unrecognized type [%d]\n",
|
|
data[0]);
|
|
rc = -EINVAL;
|
|
goto out_free;
|
|
}
|
|
rc = count;
|
|
out_free:
|
|
kfree(data);
|
|
return rc;
|
|
}
|
|
|
|
|
|
static const struct file_operations ecryptfs_miscdev_fops = {
|
|
.open = ecryptfs_miscdev_open,
|
|
.poll = ecryptfs_miscdev_poll,
|
|
.read = ecryptfs_miscdev_read,
|
|
.write = ecryptfs_miscdev_write,
|
|
.release = ecryptfs_miscdev_release,
|
|
.llseek = noop_llseek,
|
|
};
|
|
|
|
static struct miscdevice ecryptfs_miscdev = {
|
|
.minor = MISC_DYNAMIC_MINOR,
|
|
.name = "ecryptfs",
|
|
.fops = &ecryptfs_miscdev_fops
|
|
};
|
|
|
|
/**
|
|
* ecryptfs_init_ecryptfs_miscdev
|
|
*
|
|
* Messages sent to the userspace daemon from the kernel are placed on
|
|
* a queue associated with the daemon. The next read against the
|
|
* miscdev handle by that daemon will return the oldest message placed
|
|
* on the message queue for the daemon.
|
|
*
|
|
* Returns zero on success; non-zero otherwise
|
|
*/
|
|
int __init ecryptfs_init_ecryptfs_miscdev(void)
|
|
{
|
|
int rc;
|
|
|
|
atomic_set(&ecryptfs_num_miscdev_opens, 0);
|
|
rc = misc_register(&ecryptfs_miscdev);
|
|
if (rc)
|
|
printk(KERN_ERR "%s: Failed to register miscellaneous device "
|
|
"for communications with userspace daemons; rc = [%d]\n",
|
|
__func__, rc);
|
|
return rc;
|
|
}
|
|
|
|
/**
|
|
* ecryptfs_destroy_ecryptfs_miscdev
|
|
*
|
|
* All of the daemons must be exorcised prior to calling this
|
|
* function.
|
|
*/
|
|
void ecryptfs_destroy_ecryptfs_miscdev(void)
|
|
{
|
|
BUG_ON(atomic_read(&ecryptfs_num_miscdev_opens) != 0);
|
|
misc_deregister(&ecryptfs_miscdev);
|
|
}
|