fs/ecryptfs/messaging.c - kernel/common - Git at Google

 /**
  * eCryptfs: Linux filesystem encryption layer
  *
  * Copyright (C) 2004-2008 International Business Machines Corp.
  *   Author(s): Michael A. Halcrow <[email protected]>
  *		Tyler Hicks <[email protected]>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version
  * 2 as published by the Free Software Foundation.
  *
  * 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/sched.h>
 #include <linux/slab.h>
 #include <linux/user_namespace.h>
 #include <linux/nsproxy.h>
 #include "ecryptfs_kernel.h"

 static LIST_HEAD(ecryptfs_msg_ctx_free_list);
 static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
 static struct mutex ecryptfs_msg_ctx_lists_mux;

 static struct hlist_head *ecryptfs_daemon_hash;
 struct mutex ecryptfs_daemon_hash_mux;
 static int ecryptfs_hash_bits;
 #define ecryptfs_current_euid_hash(uid) \
 	hash_long((unsigned long)from_kuid(&init_user_ns, current_euid()), ecryptfs_hash_bits)

 static u32 ecryptfs_msg_counter;
 static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;

 /**
  * ecryptfs_acquire_free_msg_ctx
  * @msg_ctx: The context that was acquired from the free list
  *
  * Acquires a context element from the free list and locks the mutex
  * on the context.  Sets the msg_ctx task to current.  Returns zero on
  * success; non-zero on error or upon failure to acquire a free
  * context element.  Must be called with ecryptfs_msg_ctx_lists_mux
  * held.
  */
 static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
 {
 	struct list_head *p;
 	int rc;

 	if (list_empty(&ecryptfs_msg_ctx_free_list)) {
 		printk(KERN_WARNING "%s: The eCryptfs free "
 		       "context list is empty.  It may be helpful to "
 		       "specify the ecryptfs_message_buf_len "
 		       "parameter to be greater than the current "
 		       "value of [%d]\n", __func__, ecryptfs_message_buf_len);
 		rc = -ENOMEM;
 		goto out;
 	}
 	list_for_each(p, &ecryptfs_msg_ctx_free_list) {
 		*msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
 		if (mutex_trylock(&(*msg_ctx)->mux)) {
 			(*msg_ctx)->task = current;
 			rc = 0;
 			goto out;
 		}
 	}
 	rc = -ENOMEM;
 out:
 	return rc;
 }

 /**
  * ecryptfs_msg_ctx_free_to_alloc
  * @msg_ctx: The context to move from the free list to the alloc list
  *
  * Must be called with ecryptfs_msg_ctx_lists_mux held.
  */
 static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
 {
 	list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
 	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
 	msg_ctx->counter = ++ecryptfs_msg_counter;
 }

 /**
  * ecryptfs_msg_ctx_alloc_to_free
  * @msg_ctx: The context to move from the alloc list to the free list
  *
  * Must be called with ecryptfs_msg_ctx_lists_mux held.
  */
 void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
 {
 	list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
 	kfree(msg_ctx->msg);
 	msg_ctx->msg = NULL;
 	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
 }

 /**
  * ecryptfs_find_daemon_by_euid
  * @daemon: If return value is zero, points to the desired daemon pointer
  *
  * Must be called with ecryptfs_daemon_hash_mux held.
  *
  * Search the hash list for the current effective user id.
  *
  * Returns zero if the user id exists in the list; non-zero otherwise.
  */
 int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
 {
 	int rc;

 	hlist_for_each_entry(*daemon,
 			    &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
 			    euid_chain) {
 		if (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
 			rc = 0;
 			goto out;
 		}
 	}
 	rc = -EINVAL;
 out:
 	return rc;
 }

 /**
  * ecryptfs_spawn_daemon - Create and initialize a new daemon struct
  * @daemon: Pointer to set to newly allocated daemon struct
  * @file: File used when opening /dev/ecryptfs
  *
  * Must be called ceremoniously while in possession of
  * ecryptfs_sacred_daemon_hash_mux
  *
  * Returns zero on success; non-zero otherwise
  */
 int
 ecryptfs_spawn_daemon(struct ecryptfs_daemon **daemon, struct file *file)
 {
 	int rc = 0;

 	(*daemon) = kzalloc(sizeof(**daemon), GFP_KERNEL);
 	if (!(*daemon)) {
 		rc = -ENOMEM;
 		goto out;
 	}
 	(*daemon)->file = file;
 	mutex_init(&(*daemon)->mux);
 	INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
 	init_waitqueue_head(&(*daemon)->wait);
 	(*daemon)->num_queued_msg_ctx = 0;
 	hlist_add_head(&(*daemon)->euid_chain,
 		       &ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
 out:
 	return rc;
 }

 /**
  * ecryptfs_exorcise_daemon - Destroy the daemon struct
  *
  * Must be called ceremoniously while in possession of
  * ecryptfs_daemon_hash_mux and the daemon's own mux.
  */
 int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
 {
 	struct ecryptfs_msg_ctx *msg_ctx, *msg_ctx_tmp;
 	int rc = 0;

 	mutex_lock(&daemon->mux);
 	if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
 	    || (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
 		rc = -EBUSY;
 		mutex_unlock(&daemon->mux);
 		goto out;
 	}
 	list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
 				 &daemon->msg_ctx_out_queue, daemon_out_list) {
 		list_del(&msg_ctx->daemon_out_list);
 		daemon->num_queued_msg_ctx--;
 		printk(KERN_WARNING "%s: Warning: dropping message that is in "
 		       "the out queue of a dying daemon\n", __func__);
 		ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 	}
 	hlist_del(&daemon->euid_chain);
 	mutex_unlock(&daemon->mux);
 	kzfree(daemon);
 out:
 	return rc;
 }

 /**
  * ecryptfs_process_reponse
  * @msg: The ecryptfs message received; the caller should sanity check
  *       msg->data_len and free the memory
  * @seq: The sequence number of the message; must match the sequence
  *       number for the existing message context waiting for this
  *       response
  *
  * Processes a response message after sending an operation request to
  * userspace. Some other process is awaiting this response. Before
  * sending out its first communications, the other process allocated a
  * msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
  * response message contains this index so that we can copy over the
  * response message into the msg_ctx that the process holds a
  * reference to. The other process is going to wake up, check to see
  * that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
  * proceed to read off and process the response message. Returns zero
  * upon delivery to desired context element; non-zero upon delivery
  * failure or error.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
 			      struct ecryptfs_message *msg, u32 seq)
 {
 	struct ecryptfs_msg_ctx *msg_ctx;
 	size_t msg_size;
 	int rc;

 	if (msg->index >= ecryptfs_message_buf_len) {
 		rc = -EINVAL;
 		printk(KERN_ERR "%s: Attempt to reference "
 		       "context buffer at index [%d]; maximum "
 		       "allowable is [%d]\n", __func__, msg->index,
 		       (ecryptfs_message_buf_len - 1));
 		goto out;
 	}
 	msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
 	mutex_lock(&msg_ctx->mux);
 	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
 		rc = -EINVAL;
 		printk(KERN_WARNING "%s: Desired context element is not "
 		       "pending a response\n", __func__);
 		goto unlock;
 	} else if (msg_ctx->counter != seq) {
 		rc = -EINVAL;
 		printk(KERN_WARNING "%s: Invalid message sequence; "
 		       "expected [%d]; received [%d]\n", __func__,
 		       msg_ctx->counter, seq);
 		goto unlock;
 	}
 	msg_size = (sizeof(*msg) + msg->data_len);
 	msg_ctx->msg = kmemdup(msg, msg_size, GFP_KERNEL);
 	if (!msg_ctx->msg) {
 		rc = -ENOMEM;
 		goto unlock;
 	}
 	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
 	wake_up_process(msg_ctx->task);
 	rc = 0;
 unlock:
 	mutex_unlock(&msg_ctx->mux);
 out:
 	return rc;
 }

 /**
  * ecryptfs_send_message_locked
  * @data: The data to send
  * @data_len: The length of data
  * @msg_ctx: The message context allocated for the send
  *
  * Must be called with ecryptfs_daemon_hash_mux held.
  *
  * Returns zero on success; non-zero otherwise
  */
 static int
 ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
 			     struct ecryptfs_msg_ctx **msg_ctx)
 {
 	struct ecryptfs_daemon *daemon;
 	int rc;

 	rc = ecryptfs_find_daemon_by_euid(&daemon);
 	if (rc) {
 		rc = -ENOTCONN;
 		goto out;
 	}
 	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 	rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
 	if (rc) {
 		mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 		printk(KERN_WARNING "%s: Could not claim a free "
 		       "context element\n", __func__);
 		goto out;
 	}
 	ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
 	mutex_unlock(&(*msg_ctx)->mux);
 	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 	rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
 				   daemon);
 	if (rc)
 		printk(KERN_ERR "%s: Error attempting to send message to "
 		       "userspace daemon; rc = [%d]\n", __func__, rc);
 out:
 	return rc;
 }

 /**
  * ecryptfs_send_message
  * @data: The data to send
  * @data_len: The length of data
  * @msg_ctx: The message context allocated for the send
  *
  * Grabs ecryptfs_daemon_hash_mux.
  *
  * Returns zero on success; non-zero otherwise
  */
 int ecryptfs_send_message(char *data, int data_len,
 			  struct ecryptfs_msg_ctx **msg_ctx)
 {
 	int rc;

 	mutex_lock(&ecryptfs_daemon_hash_mux);
 	rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
 					  msg_ctx);
 	mutex_unlock(&ecryptfs_daemon_hash_mux);
 	return rc;
 }

 /**
  * ecryptfs_wait_for_response
  * @msg_ctx: The context that was assigned when sending a message
  * @msg: The incoming message from userspace; not set if rc != 0
  *
  * Sleeps until awaken by ecryptfs_receive_message or until the amount
  * of time exceeds ecryptfs_message_wait_timeout.  If zero is
  * returned, msg will point to a valid message from userspace; a
  * non-zero value is returned upon failure to receive a message or an
  * error occurs. Callee must free @msg on success.
  */
 int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
 			       struct ecryptfs_message **msg)
 {
 	signed long timeout = ecryptfs_message_wait_timeout * HZ;
 	int rc = 0;

 sleep:
 	timeout = schedule_timeout_interruptible(timeout);
 	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 	mutex_lock(&msg_ctx->mux);
 	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
 		if (timeout) {
 			mutex_unlock(&msg_ctx->mux);
 			mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 			goto sleep;
 		}
 		rc = -ENOMSG;
 	} else {
 		*msg = msg_ctx->msg;
 		msg_ctx->msg = NULL;
 	}
 	ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
 	mutex_unlock(&msg_ctx->mux);
 	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 	return rc;
 }

 int __init ecryptfs_init_messaging(void)
 {
 	int i;
 	int rc = 0;

 	if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
 		ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
 		printk(KERN_WARNING "%s: Specified number of users is "
 		       "too large, defaulting to [%d] users\n", __func__,
 		       ecryptfs_number_of_users);
 	}
 	mutex_init(&ecryptfs_daemon_hash_mux);
 	mutex_lock(&ecryptfs_daemon_hash_mux);
 	ecryptfs_hash_bits = 1;
 	while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
 		ecryptfs_hash_bits++;
 	ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
 					* (1 << ecryptfs_hash_bits)),
 				       GFP_KERNEL);
 	if (!ecryptfs_daemon_hash) {
 		rc = -ENOMEM;
 		mutex_unlock(&ecryptfs_daemon_hash_mux);
 		goto out;
 	}
 	for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
 		INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
 	mutex_unlock(&ecryptfs_daemon_hash_mux);
 	ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
 					* ecryptfs_message_buf_len),
 				       GFP_KERNEL);
 	if (!ecryptfs_msg_ctx_arr) {
 		rc = -ENOMEM;
 		goto out;
 	}
 	mutex_init(&ecryptfs_msg_ctx_lists_mux);
 	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 	ecryptfs_msg_counter = 0;
 	for (i = 0; i < ecryptfs_message_buf_len; i++) {
 		INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
 		INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
 		mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
 		mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 		ecryptfs_msg_ctx_arr[i].index = i;
 		ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
 		ecryptfs_msg_ctx_arr[i].counter = 0;
 		ecryptfs_msg_ctx_arr[i].task = NULL;
 		ecryptfs_msg_ctx_arr[i].msg = NULL;
 		list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
 			      &ecryptfs_msg_ctx_free_list);
 		mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 	}
 	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 	rc = ecryptfs_init_ecryptfs_miscdev();
 	if (rc)
 		ecryptfs_release_messaging();
 out:
 	return rc;
 }

 void ecryptfs_release_messaging(void)
 {
 	if (ecryptfs_msg_ctx_arr) {
 		int i;

 		mutex_lock(&ecryptfs_msg_ctx_lists_mux);
 		for (i = 0; i < ecryptfs_message_buf_len; i++) {
 			mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
 			kfree(ecryptfs_msg_ctx_arr[i].msg);
 			mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
 		}
 		kfree(ecryptfs_msg_ctx_arr);
 		mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
 	}
 	if (ecryptfs_daemon_hash) {
 		struct ecryptfs_daemon *daemon;
 		struct hlist_node *n;
 		int i;

 		mutex_lock(&ecryptfs_daemon_hash_mux);
 		for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
 			int rc;

 			hlist_for_each_entry_safe(daemon, n,
 						  &ecryptfs_daemon_hash[i],
 						  euid_chain) {
 				rc = ecryptfs_exorcise_daemon(daemon);
 				if (rc)
 					printk(KERN_ERR "%s: Error whilst "
 					       "attempting to destroy daemon; "
 					       "rc = [%d]. Dazed and confused, "
 					       "but trying to continue.\n",
 					       __func__, rc);
 			}
 		}
 		kfree(ecryptfs_daemon_hash);
 		mutex_unlock(&ecryptfs_daemon_hash_mux);
 	}
 	ecryptfs_destroy_ecryptfs_miscdev();
 	return;
 }
	/**
	* eCryptfs: Linux filesystem encryption layer
	*
	* Copyright (C) 2004-2008 International Business Machines Corp.
	* Author(s): Michael A. Halcrow <[email protected]>
	* Tyler Hicks <[email protected]>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License version
	* 2 as published by the Free Software Foundation.
	*
	* 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/sched.h>
	#include <linux/slab.h>
	#include <linux/user_namespace.h>
	#include <linux/nsproxy.h>
	#include "ecryptfs_kernel.h"

	static LIST_HEAD(ecryptfs_msg_ctx_free_list);
	static LIST_HEAD(ecryptfs_msg_ctx_alloc_list);
	static struct mutex ecryptfs_msg_ctx_lists_mux;

	static struct hlist_head *ecryptfs_daemon_hash;
	struct mutex ecryptfs_daemon_hash_mux;
	static int ecryptfs_hash_bits;
	#define ecryptfs_current_euid_hash(uid) \
	hash_long((unsigned long)from_kuid(&init_user_ns, current_euid()), ecryptfs_hash_bits)

	static u32 ecryptfs_msg_counter;
	static struct ecryptfs_msg_ctx *ecryptfs_msg_ctx_arr;

	/**
	* ecryptfs_acquire_free_msg_ctx
	* @msg_ctx: The context that was acquired from the free list
	*
	* Acquires a context element from the free list and locks the mutex
	* on the context. Sets the msg_ctx task to current. Returns zero on
	* success; non-zero on error or upon failure to acquire a free
	* context element. Must be called with ecryptfs_msg_ctx_lists_mux
	* held.
	*/
	static int ecryptfs_acquire_free_msg_ctx(struct ecryptfs_msg_ctx **msg_ctx)
	{
	struct list_head *p;
	int rc;

	if (list_empty(&ecryptfs_msg_ctx_free_list)) {
	printk(KERN_WARNING "%s: The eCryptfs free "
	"context list is empty. It may be helpful to "
	"specify the ecryptfs_message_buf_len "
	"parameter to be greater than the current "
	"value of [%d]\n", __func__, ecryptfs_message_buf_len);
	rc = -ENOMEM;
	goto out;
	}
	list_for_each(p, &ecryptfs_msg_ctx_free_list) {
	*msg_ctx = list_entry(p, struct ecryptfs_msg_ctx, node);
	if (mutex_trylock(&(*msg_ctx)->mux)) {
	(*msg_ctx)->task = current;
	rc = 0;
	goto out;
	}
	}
	rc = -ENOMEM;
	out:
	return rc;
	}

	/**
	* ecryptfs_msg_ctx_free_to_alloc
	* @msg_ctx: The context to move from the free list to the alloc list
	*
	* Must be called with ecryptfs_msg_ctx_lists_mux held.
	*/
	static void ecryptfs_msg_ctx_free_to_alloc(struct ecryptfs_msg_ctx *msg_ctx)
	{
	list_move(&msg_ctx->node, &ecryptfs_msg_ctx_alloc_list);
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_PENDING;
	msg_ctx->counter = ++ecryptfs_msg_counter;
	}

	/**
	* ecryptfs_msg_ctx_alloc_to_free
	* @msg_ctx: The context to move from the alloc list to the free list
	*
	* Must be called with ecryptfs_msg_ctx_lists_mux held.
	*/
	void ecryptfs_msg_ctx_alloc_to_free(struct ecryptfs_msg_ctx *msg_ctx)
	{
	list_move(&(msg_ctx->node), &ecryptfs_msg_ctx_free_list);
	kfree(msg_ctx->msg);
	msg_ctx->msg = NULL;
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_FREE;
	}

	/**
	* ecryptfs_find_daemon_by_euid
	* @daemon: If return value is zero, points to the desired daemon pointer
	*
	* Must be called with ecryptfs_daemon_hash_mux held.
	*
	* Search the hash list for the current effective user id.
	*
	* Returns zero if the user id exists in the list; non-zero otherwise.
	*/
	int ecryptfs_find_daemon_by_euid(struct ecryptfs_daemon **daemon)
	{
	int rc;

	hlist_for_each_entry(*daemon,
	&ecryptfs_daemon_hash[ecryptfs_current_euid_hash()],
	euid_chain) {
	if (uid_eq((*daemon)->file->f_cred->euid, current_euid())) {
	rc = 0;
	goto out;
	}
	}
	rc = -EINVAL;
	out:
	return rc;
	}

	/**
	* ecryptfs_spawn_daemon - Create and initialize a new daemon struct
	* @daemon: Pointer to set to newly allocated daemon struct
	* @file: File used when opening /dev/ecryptfs
	*
	* Must be called ceremoniously while in possession of
	* ecryptfs_sacred_daemon_hash_mux
	*
	* Returns zero on success; non-zero otherwise
	*/
	int
	ecryptfs_spawn_daemon(struct ecryptfs_daemon *daemon, struct file file)
	{
	int rc = 0;

	(daemon) = kzalloc(sizeof(*daemon), GFP_KERNEL);
	if (!(*daemon)) {
	rc = -ENOMEM;
	goto out;
	}
	(*daemon)->file = file;
	mutex_init(&(*daemon)->mux);
	INIT_LIST_HEAD(&(*daemon)->msg_ctx_out_queue);
	init_waitqueue_head(&(*daemon)->wait);
	(*daemon)->num_queued_msg_ctx = 0;
	hlist_add_head(&(*daemon)->euid_chain,
	&ecryptfs_daemon_hash[ecryptfs_current_euid_hash()]);
	out:
	return rc;
	}

	/**
	* ecryptfs_exorcise_daemon - Destroy the daemon struct
	*
	* Must be called ceremoniously while in possession of
	* ecryptfs_daemon_hash_mux and the daemon's own mux.
	*/
	int ecryptfs_exorcise_daemon(struct ecryptfs_daemon *daemon)
	{
	struct ecryptfs_msg_ctx msg_ctx, msg_ctx_tmp;
	int rc = 0;

	mutex_lock(&daemon->mux);
	if ((daemon->flags & ECRYPTFS_DAEMON_IN_READ)
	\|\| (daemon->flags & ECRYPTFS_DAEMON_IN_POLL)) {
	rc = -EBUSY;
	mutex_unlock(&daemon->mux);
	goto out;
	}
	list_for_each_entry_safe(msg_ctx, msg_ctx_tmp,
	&daemon->msg_ctx_out_queue, daemon_out_list) {
	list_del(&msg_ctx->daemon_out_list);
	daemon->num_queued_msg_ctx--;
	printk(KERN_WARNING "%s: Warning: dropping message that is in "
	"the out queue of a dying daemon\n", __func__);
	ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
	}
	hlist_del(&daemon->euid_chain);
	mutex_unlock(&daemon->mux);
	kzfree(daemon);
	out:
	return rc;
	}

	/**
	* ecryptfs_process_reponse
	* @msg: The ecryptfs message received; the caller should sanity check
	* msg->data_len and free the memory
	* @seq: The sequence number of the message; must match the sequence
	* number for the existing message context waiting for this
	* response
	*
	* Processes a response message after sending an operation request to
	* userspace. Some other process is awaiting this response. Before
	* sending out its first communications, the other process allocated a
	* msg_ctx from the ecryptfs_msg_ctx_arr at a particular index. The
	* response message contains this index so that we can copy over the
	* response message into the msg_ctx that the process holds a
	* reference to. The other process is going to wake up, check to see
	* that msg_ctx->state == ECRYPTFS_MSG_CTX_STATE_DONE, and then
	* proceed to read off and process the response message. Returns zero
	* upon delivery to desired context element; non-zero upon delivery
	* failure or error.
	*
	* Returns zero on success; non-zero otherwise
	*/
	int ecryptfs_process_response(struct ecryptfs_daemon *daemon,
	struct ecryptfs_message *msg, u32 seq)
	{
	struct ecryptfs_msg_ctx *msg_ctx;
	size_t msg_size;
	int rc;

	if (msg->index >= ecryptfs_message_buf_len) {
	rc = -EINVAL;
	printk(KERN_ERR "%s: Attempt to reference "
	"context buffer at index [%d]; maximum "
	"allowable is [%d]\n", __func__, msg->index,
	(ecryptfs_message_buf_len - 1));
	goto out;
	}
	msg_ctx = &ecryptfs_msg_ctx_arr[msg->index];
	mutex_lock(&msg_ctx->mux);
	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_PENDING) {
	rc = -EINVAL;
	printk(KERN_WARNING "%s: Desired context element is not "
	"pending a response\n", __func__);
	goto unlock;
	} else if (msg_ctx->counter != seq) {
	rc = -EINVAL;
	printk(KERN_WARNING "%s: Invalid message sequence; "
	"expected [%d]; received [%d]\n", __func__,
	msg_ctx->counter, seq);
	goto unlock;
	}
	msg_size = (sizeof(*msg) + msg->data_len);
	msg_ctx->msg = kmemdup(msg, msg_size, GFP_KERNEL);
	if (!msg_ctx->msg) {
	rc = -ENOMEM;
	goto unlock;
	}
	msg_ctx->state = ECRYPTFS_MSG_CTX_STATE_DONE;
	wake_up_process(msg_ctx->task);
	rc = 0;
	unlock:
	mutex_unlock(&msg_ctx->mux);
	out:
	return rc;
	}

	/**
	* ecryptfs_send_message_locked
	* @data: The data to send
	* @data_len: The length of data
	* @msg_ctx: The message context allocated for the send
	*
	* Must be called with ecryptfs_daemon_hash_mux held.
	*
	* Returns zero on success; non-zero otherwise
	*/
	static int
	ecryptfs_send_message_locked(char *data, int data_len, u8 msg_type,
	struct ecryptfs_msg_ctx **msg_ctx)
	{
	struct ecryptfs_daemon *daemon;
	int rc;

	rc = ecryptfs_find_daemon_by_euid(&daemon);
	if (rc) {
	rc = -ENOTCONN;
	goto out;
	}
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_acquire_free_msg_ctx(msg_ctx);
	if (rc) {
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	printk(KERN_WARNING "%s: Could not claim a free "
	"context element\n", __func__);
	goto out;
	}
	ecryptfs_msg_ctx_free_to_alloc(*msg_ctx);
	mutex_unlock(&(*msg_ctx)->mux);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_send_miscdev(data, data_len, *msg_ctx, msg_type, 0,
	daemon);
	if (rc)
	printk(KERN_ERR "%s: Error attempting to send message to "
	"userspace daemon; rc = [%d]\n", __func__, rc);
	out:
	return rc;
	}

	/**
	* ecryptfs_send_message
	* @data: The data to send
	* @data_len: The length of data
	* @msg_ctx: The message context allocated for the send
	*
	* Grabs ecryptfs_daemon_hash_mux.
	*
	* Returns zero on success; non-zero otherwise
	*/
	int ecryptfs_send_message(char *data, int data_len,
	struct ecryptfs_msg_ctx **msg_ctx)
	{
	int rc;

	mutex_lock(&ecryptfs_daemon_hash_mux);
	rc = ecryptfs_send_message_locked(data, data_len, ECRYPTFS_MSG_REQUEST,
	msg_ctx);
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	return rc;
	}

	/**
	* ecryptfs_wait_for_response
	* @msg_ctx: The context that was assigned when sending a message
	* @msg: The incoming message from userspace; not set if rc != 0
	*
	* Sleeps until awaken by ecryptfs_receive_message or until the amount
	* of time exceeds ecryptfs_message_wait_timeout. If zero is
	* returned, msg will point to a valid message from userspace; a
	* non-zero value is returned upon failure to receive a message or an
	* error occurs. Callee must free @msg on success.
	*/
	int ecryptfs_wait_for_response(struct ecryptfs_msg_ctx *msg_ctx,
	struct ecryptfs_message **msg)
	{
	signed long timeout = ecryptfs_message_wait_timeout * HZ;
	int rc = 0;

	sleep:
	timeout = schedule_timeout_interruptible(timeout);
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	mutex_lock(&msg_ctx->mux);
	if (msg_ctx->state != ECRYPTFS_MSG_CTX_STATE_DONE) {
	if (timeout) {
	mutex_unlock(&msg_ctx->mux);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	goto sleep;
	}
	rc = -ENOMSG;
	} else {
	*msg = msg_ctx->msg;
	msg_ctx->msg = NULL;
	}
	ecryptfs_msg_ctx_alloc_to_free(msg_ctx);
	mutex_unlock(&msg_ctx->mux);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	return rc;
	}

	int __init ecryptfs_init_messaging(void)
	{
	int i;
	int rc = 0;

	if (ecryptfs_number_of_users > ECRYPTFS_MAX_NUM_USERS) {
	ecryptfs_number_of_users = ECRYPTFS_MAX_NUM_USERS;
	printk(KERN_WARNING "%s: Specified number of users is "
	"too large, defaulting to [%d] users\n", __func__,
	ecryptfs_number_of_users);
	}
	mutex_init(&ecryptfs_daemon_hash_mux);
	mutex_lock(&ecryptfs_daemon_hash_mux);
	ecryptfs_hash_bits = 1;
	while (ecryptfs_number_of_users >> ecryptfs_hash_bits)
	ecryptfs_hash_bits++;
	ecryptfs_daemon_hash = kmalloc((sizeof(struct hlist_head)
	* (1 << ecryptfs_hash_bits)),
	GFP_KERNEL);
	if (!ecryptfs_daemon_hash) {
	rc = -ENOMEM;
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	goto out;
	}
	for (i = 0; i < (1 << ecryptfs_hash_bits); i++)
	INIT_HLIST_HEAD(&ecryptfs_daemon_hash[i]);
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	ecryptfs_msg_ctx_arr = kmalloc((sizeof(struct ecryptfs_msg_ctx)
	* ecryptfs_message_buf_len),
	GFP_KERNEL);
	if (!ecryptfs_msg_ctx_arr) {
	rc = -ENOMEM;
	goto out;
	}
	mutex_init(&ecryptfs_msg_ctx_lists_mux);
	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	ecryptfs_msg_counter = 0;
	for (i = 0; i < ecryptfs_message_buf_len; i++) {
	INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].node);
	INIT_LIST_HEAD(&ecryptfs_msg_ctx_arr[i].daemon_out_list);
	mutex_init(&ecryptfs_msg_ctx_arr[i].mux);
	mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
	ecryptfs_msg_ctx_arr[i].index = i;
	ecryptfs_msg_ctx_arr[i].state = ECRYPTFS_MSG_CTX_STATE_FREE;
	ecryptfs_msg_ctx_arr[i].counter = 0;
	ecryptfs_msg_ctx_arr[i].task = NULL;
	ecryptfs_msg_ctx_arr[i].msg = NULL;
	list_add_tail(&ecryptfs_msg_ctx_arr[i].node,
	&ecryptfs_msg_ctx_free_list);
	mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
	}
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	rc = ecryptfs_init_ecryptfs_miscdev();
	if (rc)
	ecryptfs_release_messaging();
	out:
	return rc;
	}

	void ecryptfs_release_messaging(void)
	{
	if (ecryptfs_msg_ctx_arr) {
	int i;

	mutex_lock(&ecryptfs_msg_ctx_lists_mux);
	for (i = 0; i < ecryptfs_message_buf_len; i++) {
	mutex_lock(&ecryptfs_msg_ctx_arr[i].mux);
	kfree(ecryptfs_msg_ctx_arr[i].msg);
	mutex_unlock(&ecryptfs_msg_ctx_arr[i].mux);
	}
	kfree(ecryptfs_msg_ctx_arr);
	mutex_unlock(&ecryptfs_msg_ctx_lists_mux);
	}
	if (ecryptfs_daemon_hash) {
	struct ecryptfs_daemon *daemon;
	struct hlist_node *n;
	int i;

	mutex_lock(&ecryptfs_daemon_hash_mux);
	for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
	int rc;

	hlist_for_each_entry_safe(daemon, n,
	&ecryptfs_daemon_hash[i],
	euid_chain) {
	rc = ecryptfs_exorcise_daemon(daemon);
	if (rc)
	printk(KERN_ERR "%s: Error whilst "
	"attempting to destroy daemon; "
	"rc = [%d]. Dazed and confused, "
	"but trying to continue.\n",
	__func__, rc);
	}
	}
	kfree(ecryptfs_daemon_hash);
	mutex_unlock(&ecryptfs_daemon_hash_mux);
	}
	ecryptfs_destroy_ecryptfs_miscdev();
	return;
	}