// SPDX-License-Identifier: GPL-2.0

  /*
   * 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/cred.h>

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

  #include <linux/user_namespace.h>

  #include <linux/proc_ns.h>

  #include <linux/sched/task.h>

  
  #include "util.h"

  static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  {
  	return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  }
  
  static void dec_ipc_namespaces(struct ucounts *ucounts)
  {
  	dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  }

  static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,

  					   struct ipc_namespace *old_ns)

  {

  	struct ipc_namespace *ns;

  	struct ucounts *ucounts;

  	int err;

  	err = -ENOSPC;

  	ucounts = inc_ipc_namespaces(user_ns);
  	if (!ucounts)
  		goto fail;
  
  	err = -ENOMEM;

  	ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL);

  	if (ns == NULL)

  		goto fail_dec;

  	err = ns_alloc_inum(&ns->ns);

  	if (err)
  		goto fail_free;

  	ns->ns.ops = &ipcns_operations;

  	refcount_set(&ns->count, 1);

  	ns->user_ns = get_user_ns(user_ns);

  	ns->ucounts = ucounts;

  	err = mq_init_ns(ns);

  	if (err)
  		goto fail_put;

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

  	return ns;

  
  fail_put:
  	put_user_ns(ns->user_ns);
  	ns_free_inum(&ns->ns);
  fail_free:
  	kfree(ns);
  fail_dec:
  	dec_ipc_namespaces(ucounts);
  fail:
  	return ERR_PTR(err);

  }

  struct ipc_namespace *copy_ipcs(unsigned long flags,

  	struct user_namespace *user_ns, struct ipc_namespace *ns)

  {

  	if (!(flags & CLONE_NEWIPC))

  		return get_ipc_ns(ns);

  	return create_ipc_ns(user_ns, 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->rwsem);

  
  	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;

  		rcu_read_lock();
  		ipc_lock_object(perm);

  		free(ns, perm);
  		total++;
  	}

  	up_write(&ids->rwsem);

  }

  static void free_ipc_ns(struct ipc_namespace *ns)
  {

  	sem_exit_ns(ns);
  	msg_exit_ns(ns);
  	shm_exit_ns(ns);

  	dec_ipc_namespaces(ns->ucounts);

  	put_user_ns(ns->user_ns);

  	ns_free_inum(&ns->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 (refcount_dec_and_lock(&ns->count, &mq_lock)) {

  		mq_clear_sbinfo(ns);
  		spin_unlock(&mq_lock);
  		mq_put_mnt(ns);
  		free_ipc_ns(ns);
  	}
  }

  static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
  {
  	return container_of(ns, struct ipc_namespace, ns);
  }

  static struct ns_common *ipcns_get(struct task_struct *task)

  {
  	struct ipc_namespace *ns = NULL;
  	struct nsproxy *nsproxy;

  	task_lock(task);
  	nsproxy = task->nsproxy;

  	if (nsproxy)
  		ns = get_ipc_ns(nsproxy->ipc_ns);

  	task_unlock(task);

  	return ns ? &ns->ns : NULL;

  }

  static void ipcns_put(struct ns_common *ns)

  {

  	return put_ipc_ns(to_ipc_ns(ns));

  }

  static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)

  {

  	struct ipc_namespace *ns = to_ipc_ns(new);

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

  	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))

  		return -EPERM;

  	/* 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;
  }

  static struct user_namespace *ipcns_owner(struct ns_common *ns)
  {
  	return to_ipc_ns(ns)->user_ns;
  }

  const struct proc_ns_operations ipcns_operations = {
  	.name		= "ipc",
  	.type		= CLONE_NEWIPC,
  	.get		= ipcns_get,
  	.put		= ipcns_put,
  	.install	= ipcns_install,

  	.owner		= ipcns_owner,

  };