/*
   * Pid namespaces
   *
   * Authors:
   *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
   *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
   *     Many thanks to Oleg Nesterov for comments and help
   *
   */
  
  #include <linux/pid.h>
  #include <linux/pid_namespace.h>

  #include <linux/user_namespace.h>

  #include <linux/syscalls.h>

  #include <linux/cred.h>

  #include <linux/err.h>

  #include <linux/acct.h>

  #include <linux/slab.h>

  #include <linux/proc_ns.h>

  #include <linux/reboot.h>

  #include <linux/export.h>

  #include <linux/sched/task.h>

  #include <linux/sched/signal.h>

  #include <linux/idr.h>

  static DEFINE_MUTEX(pid_caches_mutex);
  static struct kmem_cache *pid_ns_cachep;

  /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
  #define MAX_PID_NS_LEVEL 32
  /* Write once array, filled from the beginning. */
  static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];

  
  /*
   * creates the kmem cache to allocate pids from.

   * @level: pid namespace level

   */

  static struct kmem_cache *create_pid_cachep(unsigned int level)

  {

  	/* Level 0 is init_pid_ns.pid_cachep */
  	struct kmem_cache **pkc = &pid_cache[level - 1];
  	struct kmem_cache *kc;
  	char name[4 + 10 + 1];
  	unsigned int len;
  
  	kc = READ_ONCE(*pkc);
  	if (kc)
  		return kc;
  
  	snprintf(name, sizeof(name), "pid_%u", level + 1);
  	len = sizeof(struct pid) + level * sizeof(struct upid);

  	mutex_lock(&pid_caches_mutex);

  	/* Name collision forces to do allocation under mutex. */
  	if (!*pkc)
  		*pkc = kmem_cache_create(name, len, 0, SLAB_HWCACHE_ALIGN, 0);

  	mutex_unlock(&pid_caches_mutex);

  	/* current can fail, but someone else can succeed. */
  	return READ_ONCE(*pkc);

  }

  static void proc_cleanup_work(struct work_struct *work)
  {
  	struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
  	pid_ns_release_proc(ns);
  }

  static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
  {
  	return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
  }
  
  static void dec_pid_namespaces(struct ucounts *ucounts)
  {
  	dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
  }

  static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
  	struct pid_namespace *parent_pid_ns)

  {
  	struct pid_namespace *ns;

  	unsigned int level = parent_pid_ns->level + 1;

  	struct ucounts *ucounts;

  	int err;

  	err = -EINVAL;
  	if (!in_userns(parent_pid_ns->user_ns, user_ns))
  		goto out;

  	err = -ENOSPC;

  	if (level > MAX_PID_NS_LEVEL)
  		goto out;
  	ucounts = inc_pid_namespaces(user_ns);
  	if (!ucounts)

  		goto out;

  	err = -ENOMEM;

  	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);

  	if (ns == NULL)

  		goto out_dec;

  	idr_init(&ns->idr);

  	ns->pid_cachep = create_pid_cachep(level);

  	if (ns->pid_cachep == NULL)

  		goto out_free_idr;

  	err = ns_alloc_inum(&ns->ns);

  	if (err)

  		goto out_free_idr;

  	ns->ns.ops = &pidns_operations;

  	kref_init(&ns->kref);

  	ns->level = level;

  	ns->parent = get_pid_ns(parent_pid_ns);

  	ns->user_ns = get_user_ns(user_ns);

  	ns->ucounts = ucounts;

  	ns->pid_allocated = PIDNS_ADDING;

  	INIT_WORK(&ns->proc_work, proc_cleanup_work);

  	return ns;

  out_free_idr:
  	idr_destroy(&ns->idr);

  	kmem_cache_free(pid_ns_cachep, ns);

  out_dec:
  	dec_pid_namespaces(ucounts);

  out:

  	return ERR_PTR(err);

  }

  static void delayed_free_pidns(struct rcu_head *p)
  {

  	struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
  
  	dec_pid_namespaces(ns->ucounts);
  	put_user_ns(ns->user_ns);
  
  	kmem_cache_free(pid_ns_cachep, ns);

  }

  static void destroy_pid_namespace(struct pid_namespace *ns)
  {

  	ns_free_inum(&ns->ns);

  
  	idr_destroy(&ns->idr);

  	call_rcu(&ns->rcu, delayed_free_pidns);

  }

  struct pid_namespace *copy_pid_ns(unsigned long flags,
  	struct user_namespace *user_ns, struct pid_namespace *old_ns)

  {

  	if (!(flags & CLONE_NEWPID))

  		return get_pid_ns(old_ns);

  	if (task_active_pid_ns(current) != old_ns)
  		return ERR_PTR(-EINVAL);

  	return create_pid_namespace(user_ns, old_ns);

  }

  static void free_pid_ns(struct kref *kref)

  {

  	struct pid_namespace *ns;

  
  	ns = container_of(kref, struct pid_namespace, kref);

  	destroy_pid_namespace(ns);

  }

  void put_pid_ns(struct pid_namespace *ns)
  {
  	struct pid_namespace *parent;
  
  	while (ns != &init_pid_ns) {
  		parent = ns->parent;
  		if (!kref_put(&ns->kref, free_pid_ns))
  			break;
  		ns = parent;
  	}

  }

  EXPORT_SYMBOL_GPL(put_pid_ns);

  
  void zap_pid_ns_processes(struct pid_namespace *pid_ns)
  {
  	int nr;
  	int rc;

  	struct task_struct *task, *me = current;

  	int init_pids = thread_group_leader(me) ? 1 : 2;

  	struct pid *pid;

  	/* Don't allow any more processes into the pid namespace */
  	disable_pid_allocation(pid_ns);

  	/*
  	 * Ignore SIGCHLD causing any terminated children to autoreap.
  	 * This speeds up the namespace shutdown, plus see the comment
  	 * below.
  	 */

  	spin_lock_irq(&me->sighand->siglock);
  	me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
  	spin_unlock_irq(&me->sighand->siglock);

  
  	/*
  	 * The last thread in the cgroup-init thread group is terminating.
  	 * Find remaining pid_ts in the namespace, signal and wait for them
  	 * to exit.
  	 *
  	 * Note:  This signals each threads in the namespace - even those that
  	 * 	  belong to the same thread group, To avoid this, we would have
  	 * 	  to walk the entire tasklist looking a processes in this
  	 * 	  namespace, but that could be unnecessarily expensive if the
  	 * 	  pid namespace has just a few processes. Or we need to
  	 * 	  maintain a tasklist for each pid namespace.
  	 *
  	 */

  	rcu_read_lock();

  	read_lock(&tasklist_lock);

  	nr = 2;
  	idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
  		task = pid_task(pid, PIDTYPE_PID);

  		if (task && !__fatal_signal_pending(task))
  			send_sig_info(SIGKILL, SEND_SIG_FORCED, task);

  	}
  	read_unlock(&tasklist_lock);

  	rcu_read_unlock();

  	/*
  	 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.

  	 * kernel_wait4() will also block until our children traced from the

  	 * parent namespace are detached and become EXIT_DEAD.
  	 */

  	do {
  		clear_thread_flag(TIF_SIGPENDING);

  		rc = kernel_wait4(-1, NULL, __WALL, NULL);

  	} while (rc != -ECHILD);

  	/*

  	 * kernel_wait4() above can't reap the EXIT_DEAD children but we do not

  	 * really care, we could reparent them to the global init. We could
  	 * exit and reap ->child_reaper even if it is not the last thread in

  	 * this pid_ns, free_pid(pid_allocated == 0) calls proc_cleanup_work(),

  	 * pid_ns can not go away until proc_kill_sb() drops the reference.
  	 *
  	 * But this ns can also have other tasks injected by setns()+fork().
  	 * Again, ignoring the user visible semantics we do not really need
  	 * to wait until they are all reaped, but they can be reparented to
  	 * us and thus we need to ensure that pid->child_reaper stays valid
  	 * until they all go away. See free_pid()->wake_up_process().
  	 *
  	 * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
  	 * if reparented.

  	 */
  	for (;;) {

  		set_current_state(TASK_INTERRUPTIBLE);

  		if (pid_ns->pid_allocated == init_pids)

  			break;
  		schedule();
  	}

  	__set_current_state(TASK_RUNNING);

  	if (pid_ns->reboot)
  		current->signal->group_exit_code = pid_ns->reboot;

  	acct_exit_ns(pid_ns);

  	return;
  }

  #ifdef CONFIG_CHECKPOINT_RESTORE

  static int pid_ns_ctl_handler(struct ctl_table *table, int write,
  		void __user *buffer, size_t *lenp, loff_t *ppos)
  {

  	struct pid_namespace *pid_ns = task_active_pid_ns(current);

  	struct ctl_table tmp = *table;

  	int ret, next;

  	if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))

  		return -EPERM;
  
  	/*
  	 * Writing directly to ns' last_pid field is OK, since this field
  	 * is volatile in a living namespace anyway and a code writing to
  	 * it should synchronize its usage with external means.
  	 */

  	next = idr_get_cursor(&pid_ns->idr) - 1;
  
  	tmp.data = &next;
  	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
  	if (!ret && write)
  		idr_set_cursor(&pid_ns->idr, next + 1);
  
  	return ret;

  }

  extern int pid_max;
  static int zero = 0;

  static struct ctl_table pid_ns_ctl_table[] = {
  	{
  		.procname = "ns_last_pid",
  		.maxlen = sizeof(int),
  		.mode = 0666, /* permissions are checked in the handler */
  		.proc_handler = pid_ns_ctl_handler,

  		.extra1 = &zero,
  		.extra2 = &pid_max,

  	},
  	{ }
  };

  static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };

  #endif	/* CONFIG_CHECKPOINT_RESTORE */

  int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
  {
  	if (pid_ns == &init_pid_ns)
  		return 0;
  
  	switch (cmd) {
  	case LINUX_REBOOT_CMD_RESTART2:
  	case LINUX_REBOOT_CMD_RESTART:
  		pid_ns->reboot = SIGHUP;
  		break;
  
  	case LINUX_REBOOT_CMD_POWER_OFF:
  	case LINUX_REBOOT_CMD_HALT:
  		pid_ns->reboot = SIGINT;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	read_lock(&tasklist_lock);
  	force_sig(SIGKILL, pid_ns->child_reaper);
  	read_unlock(&tasklist_lock);
  
  	do_exit(0);
  
  	/* Not reached */
  	return 0;
  }

  static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
  {
  	return container_of(ns, struct pid_namespace, ns);
  }

  static struct ns_common *pidns_get(struct task_struct *task)

  {
  	struct pid_namespace *ns;
  
  	rcu_read_lock();

  	ns = task_active_pid_ns(task);
  	if (ns)
  		get_pid_ns(ns);

  	rcu_read_unlock();

  	return ns ? &ns->ns : NULL;

  }

  static struct ns_common *pidns_for_children_get(struct task_struct *task)
  {
  	struct pid_namespace *ns = NULL;
  
  	task_lock(task);
  	if (task->nsproxy) {
  		ns = task->nsproxy->pid_ns_for_children;
  		get_pid_ns(ns);
  	}
  	task_unlock(task);
  
  	if (ns) {
  		read_lock(&tasklist_lock);
  		if (!ns->child_reaper) {
  			put_pid_ns(ns);
  			ns = NULL;
  		}
  		read_unlock(&tasklist_lock);
  	}
  
  	return ns ? &ns->ns : NULL;
  }

  static void pidns_put(struct ns_common *ns)

  {

  	put_pid_ns(to_pid_ns(ns));

  }

  static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)

  {
  	struct pid_namespace *active = task_active_pid_ns(current);

  	struct pid_namespace *ancestor, *new = to_pid_ns(ns);

  	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||

  	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))

  		return -EPERM;
  
  	/*
  	 * Only allow entering the current active pid namespace
  	 * or a child of the current active pid namespace.
  	 *
  	 * This is required for fork to return a usable pid value and
  	 * this maintains the property that processes and their
  	 * children can not escape their current pid namespace.
  	 */
  	if (new->level < active->level)
  		return -EINVAL;
  
  	ancestor = new;
  	while (ancestor->level > active->level)
  		ancestor = ancestor->parent;
  	if (ancestor != active)
  		return -EINVAL;

  	put_pid_ns(nsproxy->pid_ns_for_children);
  	nsproxy->pid_ns_for_children = get_pid_ns(new);

  	return 0;
  }

  static struct ns_common *pidns_get_parent(struct ns_common *ns)
  {
  	struct pid_namespace *active = task_active_pid_ns(current);
  	struct pid_namespace *pid_ns, *p;
  
  	/* See if the parent is in the current namespace */
  	pid_ns = p = to_pid_ns(ns)->parent;
  	for (;;) {
  		if (!p)
  			return ERR_PTR(-EPERM);
  		if (p == active)
  			break;
  		p = p->parent;
  	}
  
  	return &get_pid_ns(pid_ns)->ns;
  }

  static struct user_namespace *pidns_owner(struct ns_common *ns)
  {
  	return to_pid_ns(ns)->user_ns;
  }

  const struct proc_ns_operations pidns_operations = {
  	.name		= "pid",
  	.type		= CLONE_NEWPID,
  	.get		= pidns_get,
  	.put		= pidns_put,
  	.install	= pidns_install,

  	.owner		= pidns_owner,

  	.get_parent	= pidns_get_parent,

  };

  const struct proc_ns_operations pidns_for_children_operations = {
  	.name		= "pid_for_children",
  	.real_ns_name	= "pid",
  	.type		= CLONE_NEWPID,
  	.get		= pidns_for_children_get,
  	.put		= pidns_put,
  	.install	= pidns_install,
  	.owner		= pidns_owner,
  	.get_parent	= pidns_get_parent,
  };

  static __init int pid_namespaces_init(void)
  {
  	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);

  
  #ifdef CONFIG_CHECKPOINT_RESTORE

  	register_sysctl_paths(kern_path, pid_ns_ctl_table);

  #endif

  	return 0;
  }
  
  __initcall(pid_namespaces_init);