/**
   * eCryptfs: Linux filesystem encryption layer
   *
   * Copyright (C) 2004-2008 International Business Machines Corp.
   *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
   *		Tyler Hicks <tyhicks@ou.edu>
   *
   * 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]
  ", __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;
  		printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
  		       "GFP_KERNEL memory
  ", __func__, sizeof(**daemon));
  		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
  ", __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]
  ", __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
  ", __func__);
  		goto unlock;
  	} else if (msg_ctx->counter != seq) {
  		rc = -EINVAL;
  		printk(KERN_WARNING "%s: Invalid message sequence; "
  		       "expected [%d]; received [%d]
  ", __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;
  		printk(KERN_ERR "%s: Failed to allocate [%zd] bytes of "
  		       "GFP_KERNEL memory
  ", __func__, msg_size);
  		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
  ", __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]
  ", __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
  ", __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;
  		printk(KERN_ERR "%s: Failed to allocate memory
  ", __func__);
  		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;
  		printk(KERN_ERR "%s: Failed to allocate memory
  ", __func__);
  		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);
  			if (ecryptfs_msg_ctx_arr[i].msg)
  				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;
  		int i;
  
  		mutex_lock(&ecryptfs_daemon_hash_mux);
  		for (i = 0; i < (1 << ecryptfs_hash_bits); i++) {
  			int rc;
  
  			hlist_for_each_entry(daemon,
  					     &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.
  ",
  					       __func__, rc);
  			}
  		}
  		kfree(ecryptfs_daemon_hash);
  		mutex_unlock(&ecryptfs_daemon_hash_mux);
  	}
  	ecryptfs_destroy_ecryptfs_miscdev();
  	return;
  }