/*
   * linux/ipc/namespace.c
   * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
   */
  
  #include <linux/ipc.h>
  #include <linux/msg.h>
  #include <linux/ipc_namespace.h>
  #include <linux/rcupdate.h>
  #include <linux/nsproxy.h>
  #include <linux/slab.h>

  #include <linux/fs.h>
  #include <linux/mount.h>

  #include <linux/user_namespace.h>

  #include <linux/proc_fs.h>

  
  #include "util.h"

  static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk,
  					   struct ipc_namespace *old_ns)

  {

  	struct ipc_namespace *ns;

  	int err;

  	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  	if (ns == NULL)

  		return ERR_PTR(-ENOMEM);

  	atomic_set(&ns->count, 1);
  	err = mq_init_ns(ns);
  	if (err) {
  		kfree(ns);
  		return ERR_PTR(err);
  	}

  	atomic_inc(&nr_ipc_ns);

  	sem_init_ns(ns);
  	msg_init_ns(ns);
  	shm_init_ns(ns);

  	/*
  	 * msgmni has already been computed for the new ipc ns.
  	 * Thus, do the ipcns creation notification before registering that
  	 * new ipcns in the chain.
  	 */
  	ipcns_notify(IPCNS_CREATED);

  	register_ipcns_notifier(ns);

  	ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);

  	return ns;

  }

  struct ipc_namespace *copy_ipcs(unsigned long flags,
  				struct task_struct *tsk)

  {

  	struct ipc_namespace *ns = tsk->nsproxy->ipc_ns;

  	if (!(flags & CLONE_NEWIPC))

  		return get_ipc_ns(ns);

  	return create_ipc_ns(tsk, ns);

  }

  /*
   * free_ipcs - free all ipcs of one type
   * @ns:   the namespace to remove the ipcs from
   * @ids:  the table of ipcs to free
   * @free: the function called to free each individual ipc
   *
   * Called for each kind of ipc when an ipc_namespace exits.
   */
  void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  	       void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  {
  	struct kern_ipc_perm *perm;
  	int next_id;
  	int total, in_use;
  
  	down_write(&ids->rw_mutex);
  
  	in_use = ids->in_use;
  
  	for (total = 0, next_id = 0; total < in_use; next_id++) {
  		perm = idr_find(&ids->ipcs_idr, next_id);
  		if (perm == NULL)
  			continue;
  		ipc_lock_by_ptr(perm);
  		free(ns, perm);
  		total++;
  	}
  	up_write(&ids->rw_mutex);
  }

  static void free_ipc_ns(struct ipc_namespace *ns)
  {
  	/*
  	 * Unregistering the hotplug notifier at the beginning guarantees
  	 * that the ipc namespace won't be freed while we are inside the
  	 * callback routine. Since the blocking_notifier_chain_XXX routines
  	 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
  	 * won't take the rw lock before blocking_notifier_call_chain() has
  	 * released the rd lock.
  	 */
  	unregister_ipcns_notifier(ns);
  	sem_exit_ns(ns);
  	msg_exit_ns(ns);
  	shm_exit_ns(ns);

  	atomic_dec(&nr_ipc_ns);
  
  	/*
  	 * Do the ipcns removal notification after decrementing nr_ipc_ns in
  	 * order to have a correct value when recomputing msgmni.
  	 */
  	ipcns_notify(IPCNS_REMOVED);

  	put_user_ns(ns->user_ns);

  	kfree(ns);

  }

  /*
   * put_ipc_ns - drop a reference to an ipc namespace.
   * @ns: the namespace to put
   *
   * If this is the last task in the namespace exiting, and
   * it is dropping the refcount to 0, then it can race with
   * a task in another ipc namespace but in a mounts namespace
   * which has this ipcns's mqueuefs mounted, doing some action
   * with one of the mqueuefs files.  That can raise the refcount.
   * So dropping the refcount, and raising the refcount when
   * accessing it through the VFS, are protected with mq_lock.
   *
   * (Clearly, a task raising the refcount on its own ipc_ns
   * needn't take mq_lock since it can't race with the last task
   * in the ipcns exiting).
   */
  void put_ipc_ns(struct ipc_namespace *ns)

  {

  	if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
  		mq_clear_sbinfo(ns);
  		spin_unlock(&mq_lock);
  		mq_put_mnt(ns);
  		free_ipc_ns(ns);
  	}
  }

  
  static void *ipcns_get(struct task_struct *task)
  {
  	struct ipc_namespace *ns = NULL;
  	struct nsproxy *nsproxy;
  
  	rcu_read_lock();
  	nsproxy = task_nsproxy(task);
  	if (nsproxy)
  		ns = get_ipc_ns(nsproxy->ipc_ns);
  	rcu_read_unlock();
  
  	return ns;
  }
  
  static void ipcns_put(void *ns)
  {
  	return put_ipc_ns(ns);
  }
  
  static int ipcns_install(struct nsproxy *nsproxy, void *ns)
  {
  	/* Ditch state from the old ipc namespace */
  	exit_sem(current);
  	put_ipc_ns(nsproxy->ipc_ns);
  	nsproxy->ipc_ns = get_ipc_ns(ns);
  	return 0;
  }
  
  const struct proc_ns_operations ipcns_operations = {
  	.name		= "ipc",
  	.type		= CLONE_NEWIPC,
  	.get		= ipcns_get,
  	.put		= ipcns_put,
  	.install	= ipcns_install,
  };