/*
   *  Copyright (C) 2006 IBM Corporation
   *
   *  Author: Serge Hallyn <serue@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, version 2 of the
   *  License.

   *
   *  Jun 2006 - namespaces support
   *             OpenVZ, SWsoft Inc.
   *             Pavel Emelianov <xemul@openvz.org>

   */

  #include <linux/slab.h>

  #include <linux/export.h>

  #include <linux/nsproxy.h>

  #include <linux/init_task.h>

  #include <linux/mnt_namespace.h>

  #include <linux/utsname.h>

  #include <linux/pid_namespace.h>

  #include <net/net_namespace.h>

  #include <linux/ipc_namespace.h>

  #include <linux/proc_ns.h>

  #include <linux/file.h>
  #include <linux/syscalls.h>

  static struct kmem_cache *nsproxy_cachep;

  struct nsproxy init_nsproxy = {

  	.count			= ATOMIC_INIT(1),
  	.uts_ns			= &init_uts_ns,

  #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)

  	.ipc_ns			= &init_ipc_ns,

  #endif

  	.mnt_ns			= NULL,
  	.pid_ns_for_children	= &init_pid_ns,

  #ifdef CONFIG_NET

  	.net_ns			= &init_net,

  #endif
  };

  static inline struct nsproxy *create_nsproxy(void)

  {

  	struct nsproxy *nsproxy;

  	nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
  	if (nsproxy)
  		atomic_set(&nsproxy->count, 1);
  	return nsproxy;

  }
  
  /*

   * Create new nsproxy and all of its the associated namespaces.
   * Return the newly created nsproxy.  Do not attach this to the task,
   * leave it to the caller to do proper locking and attach it to task.

   */

  static struct nsproxy *create_new_namespaces(unsigned long flags,

  	struct task_struct *tsk, struct user_namespace *user_ns,
  	struct fs_struct *new_fs)

  {

  	struct nsproxy *new_nsp;

  	int err;

  	new_nsp = create_nsproxy();

  	if (!new_nsp)
  		return ERR_PTR(-ENOMEM);

  	new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, user_ns, new_fs);

  	if (IS_ERR(new_nsp->mnt_ns)) {
  		err = PTR_ERR(new_nsp->mnt_ns);

  		goto out_ns;

  	}

  	new_nsp->uts_ns = copy_utsname(flags, user_ns, tsk->nsproxy->uts_ns);

  	if (IS_ERR(new_nsp->uts_ns)) {
  		err = PTR_ERR(new_nsp->uts_ns);

  		goto out_uts;

  	}

  	new_nsp->ipc_ns = copy_ipcs(flags, user_ns, tsk->nsproxy->ipc_ns);

  	if (IS_ERR(new_nsp->ipc_ns)) {
  		err = PTR_ERR(new_nsp->ipc_ns);

  		goto out_ipc;

  	}

  	new_nsp->pid_ns_for_children =
  		copy_pid_ns(flags, user_ns, tsk->nsproxy->pid_ns_for_children);
  	if (IS_ERR(new_nsp->pid_ns_for_children)) {
  		err = PTR_ERR(new_nsp->pid_ns_for_children);

  		goto out_pid;

  	}

  	new_nsp->net_ns = copy_net_ns(flags, user_ns, tsk->nsproxy->net_ns);

  	if (IS_ERR(new_nsp->net_ns)) {
  		err = PTR_ERR(new_nsp->net_ns);
  		goto out_net;
  	}

  	return new_nsp;

  out_net:

  	if (new_nsp->pid_ns_for_children)
  		put_pid_ns(new_nsp->pid_ns_for_children);

  out_pid:
  	if (new_nsp->ipc_ns)
  		put_ipc_ns(new_nsp->ipc_ns);
  out_ipc:
  	if (new_nsp->uts_ns)
  		put_uts_ns(new_nsp->uts_ns);
  out_uts:
  	if (new_nsp->mnt_ns)
  		put_mnt_ns(new_nsp->mnt_ns);
  out_ns:

  	kmem_cache_free(nsproxy_cachep, new_nsp);

  	return ERR_PTR(err);

  }
  
  /*
   * called from clone.  This now handles copy for nsproxy and all
   * namespaces therein.
   */

  int copy_namespaces(unsigned long flags, struct task_struct *tsk)

  {
  	struct nsproxy *old_ns = tsk->nsproxy;

  	struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns);

  	struct nsproxy *new_ns;

  	if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
  			      CLONE_NEWPID | CLONE_NEWNET)))) {
  		get_nsproxy(old_ns);

  		return 0;

  	}

  	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
  		return -EPERM;

  	/*
  	 * CLONE_NEWIPC must detach from the undolist: after switching
  	 * to a new ipc namespace, the semaphore arrays from the old
  	 * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
  	 * means share undolist with parent, so we must forbid using
  	 * it along with CLONE_NEWIPC.
  	 */

  	if ((flags & (CLONE_NEWIPC | CLONE_SYSVSEM)) ==

  		(CLONE_NEWIPC | CLONE_SYSVSEM)) 
  		return -EINVAL;

  	new_ns = create_new_namespaces(flags, tsk, user_ns, tsk->fs);

  	if (IS_ERR(new_ns))
  		return  PTR_ERR(new_ns);

  	tsk->nsproxy = new_ns;

  	return 0;

  }
  
  void free_nsproxy(struct nsproxy *ns)
  {

  	if (ns->mnt_ns)
  		put_mnt_ns(ns->mnt_ns);
  	if (ns->uts_ns)
  		put_uts_ns(ns->uts_ns);
  	if (ns->ipc_ns)
  		put_ipc_ns(ns->ipc_ns);

  	if (ns->pid_ns_for_children)
  		put_pid_ns(ns->pid_ns_for_children);

  	put_net(ns->net_ns);

  	kmem_cache_free(nsproxy_cachep, ns);

  }

  
  /*
   * Called from unshare. Unshare all the namespaces part of nsproxy.

   * On success, returns the new nsproxy.

   */
  int unshare_nsproxy_namespaces(unsigned long unshare_flags,

  	struct nsproxy **new_nsp, struct cred *new_cred, struct fs_struct *new_fs)

  {

  	struct user_namespace *user_ns;

  	int err = 0;

  	if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |

  			       CLONE_NEWNET | CLONE_NEWPID)))

  		return 0;

  	user_ns = new_cred ? new_cred->user_ns : current_user_ns();
  	if (!ns_capable(user_ns, CAP_SYS_ADMIN))

  		return -EPERM;

  	*new_nsp = create_new_namespaces(unshare_flags, current, user_ns,

  					 new_fs ? new_fs : current->fs);

  	if (IS_ERR(*new_nsp)) {

  		err = PTR_ERR(*new_nsp);

  		goto out;
  	}

  out:

  	return err;
  }

  void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
  {
  	struct nsproxy *ns;
  
  	might_sleep();
  
  	ns = p->nsproxy;
  
  	rcu_assign_pointer(p->nsproxy, new);
  
  	if (ns && atomic_dec_and_test(&ns->count)) {
  		/*
  		 * wait for others to get what they want from this nsproxy.
  		 *
  		 * cannot release this nsproxy via the call_rcu() since
  		 * put_mnt_ns() will want to sleep
  		 */
  		synchronize_rcu();
  		free_nsproxy(ns);
  	}
  }
  
  void exit_task_namespaces(struct task_struct *p)
  {
  	switch_task_namespaces(p, NULL);
  }

  SYSCALL_DEFINE2(setns, int, fd, int, nstype)
  {
  	const struct proc_ns_operations *ops;
  	struct task_struct *tsk = current;
  	struct nsproxy *new_nsproxy;

  	struct proc_ns *ei;

  	struct file *file;
  	int err;

  	file = proc_ns_fget(fd);
  	if (IS_ERR(file))
  		return PTR_ERR(file);
  
  	err = -EINVAL;

  	ei = get_proc_ns(file_inode(file));

  	ops = ei->ns_ops;
  	if (nstype && (ops->type != nstype))
  		goto out;

  	new_nsproxy = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);

  	if (IS_ERR(new_nsproxy)) {
  		err = PTR_ERR(new_nsproxy);
  		goto out;
  	}
  
  	err = ops->install(new_nsproxy, ei->ns);
  	if (err) {
  		free_nsproxy(new_nsproxy);
  		goto out;
  	}
  	switch_task_namespaces(tsk, new_nsproxy);
  out:
  	fput(file);
  	return err;
  }

  int __init nsproxy_cache_init(void)

  {

  	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);

  	return 0;
  }