kernel/nsproxy.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright (C) 2006 IBM Corporation
  *
  *  Author: Serge Hallyn <serue@us.ibm.com>
  *
  *  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/time_namespace.h>
 #include <linux/fs_struct.h>
 #include <linux/proc_fs.h>
 #include <linux/proc_ns.h>
 #include <linux/file.h>
 #include <linux/syscalls.h>
 #include <linux/cgroup.h>
 #include <linux/perf_event.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
 #ifdef CONFIG_CGROUPS
 	.cgroup_ns		= &init_cgroup_ns,
 #endif
 #ifdef CONFIG_TIME_NS
 	.time_ns		= &init_time_ns,
 	.time_ns_for_children	= &init_time_ns,
 #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->cgroup_ns = copy_cgroup_ns(flags, user_ns,
 					    tsk->nsproxy->cgroup_ns);
 	if (IS_ERR(new_nsp->cgroup_ns)) {
 		err = PTR_ERR(new_nsp->cgroup_ns);
 		goto out_cgroup;
 	}

 	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;
 	}

 	new_nsp->time_ns_for_children = copy_time_ns(flags, user_ns,
 					tsk->nsproxy->time_ns_for_children);
 	if (IS_ERR(new_nsp->time_ns_for_children)) {
 		err = PTR_ERR(new_nsp->time_ns_for_children);
 		goto out_time;
 	}
 	new_nsp->time_ns = get_time_ns(tsk->nsproxy->time_ns);

 	return new_nsp;

 out_time:
 	put_net(new_nsp->net_ns);
 out_net:
 	put_cgroup_ns(new_nsp->cgroup_ns);
 out_cgroup:
 	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 |
 			      CLONE_NEWCGROUP | CLONE_NEWTIME)))) {
 		if (likely(old_ns->time_ns_for_children == old_ns->time_ns)) {
 			get_nsproxy(old_ns);
 			return 0;
 		}
 	} else 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);

 	timens_on_fork(new_ns, tsk);

 	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);
 	if (ns->time_ns)
 		put_time_ns(ns->time_ns);
 	if (ns->time_ns_for_children)
 		put_time_ns(ns->time_ns_for_children);
 	put_cgroup_ns(ns->cgroup_ns);
 	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 | CLONE_NEWCGROUP |
 			       CLONE_NEWTIME)))
 		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();

 	task_lock(p);
 	ns = p->nsproxy;
 	p->nsproxy = new;
 	task_unlock(p);

 	if (ns)
 		put_nsproxy(ns);
 }

 void exit_task_namespaces(struct task_struct *p)
 {
 	switch_task_namespaces(p, NULL);
 }

 static int check_setns_flags(unsigned long flags)
 {
 	if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 				 CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER |
 				 CLONE_NEWPID | CLONE_NEWCGROUP)))
 		return -EINVAL;

 #ifndef CONFIG_USER_NS
 	if (flags & CLONE_NEWUSER)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_PID_NS
 	if (flags & CLONE_NEWPID)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_UTS_NS
 	if (flags & CLONE_NEWUTS)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_IPC_NS
 	if (flags & CLONE_NEWIPC)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_CGROUPS
 	if (flags & CLONE_NEWCGROUP)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_NET_NS
 	if (flags & CLONE_NEWNET)
 		return -EINVAL;
 #endif
 #ifndef CONFIG_TIME_NS
 	if (flags & CLONE_NEWTIME)
 		return -EINVAL;
 #endif

 	return 0;
 }

 static void put_nsset(struct nsset *nsset)
 {
 	unsigned flags = nsset->flags;

 	if (flags & CLONE_NEWUSER)
 		put_cred(nsset_cred(nsset));
 	/*
 	 * We only created a temporary copy if we attached to more than just
 	 * the mount namespace.
 	 */
 	if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
 		free_fs_struct(nsset->fs);
 	if (nsset->nsproxy)
 		free_nsproxy(nsset->nsproxy);
 }

 static int prepare_nsset(unsigned flags, struct nsset *nsset)
 {
 	struct task_struct *me = current;

 	nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
 	if (IS_ERR(nsset->nsproxy))
 		return PTR_ERR(nsset->nsproxy);

 	if (flags & CLONE_NEWUSER)
 		nsset->cred = prepare_creds();
 	else
 		nsset->cred = current_cred();
 	if (!nsset->cred)
 		goto out;

 	/* Only create a temporary copy of fs_struct if we really need to. */
 	if (flags == CLONE_NEWNS) {
 		nsset->fs = me->fs;
 	} else if (flags & CLONE_NEWNS) {
 		nsset->fs = copy_fs_struct(me->fs);
 		if (!nsset->fs)
 			goto out;
 	}

 	nsset->flags = flags;
 	return 0;

 out:
 	put_nsset(nsset);
 	return -ENOMEM;
 }

 static inline int validate_ns(struct nsset *nsset, struct ns_common *ns)
 {
 	return ns->ops->install(nsset, ns);
 }

 /*
  * This is the inverse operation to unshare().
  * Ordering is equivalent to the standard ordering used everywhere else
  * during unshare and process creation. The switch to the new set of
  * namespaces occurs at the point of no return after installation of
  * all requested namespaces was successful in commit_nsset().
  */
 static int validate_nsset(struct nsset *nsset, struct pid *pid)
 {
 	int ret = 0;
 	unsigned flags = nsset->flags;
 	struct user_namespace *user_ns = NULL;
 	struct pid_namespace *pid_ns = NULL;
 	struct nsproxy *nsp;
 	struct task_struct *tsk;

 	/* Take a "snapshot" of the target task's namespaces. */
 	rcu_read_lock();
 	tsk = pid_task(pid, PIDTYPE_PID);
 	if (!tsk) {
 		rcu_read_unlock();
 		return -ESRCH;
 	}

 	if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
 		rcu_read_unlock();
 		return -EPERM;
 	}

 	task_lock(tsk);
 	nsp = tsk->nsproxy;
 	if (nsp)
 		get_nsproxy(nsp);
 	task_unlock(tsk);
 	if (!nsp) {
 		rcu_read_unlock();
 		return -ESRCH;
 	}

 #ifdef CONFIG_PID_NS
 	if (flags & CLONE_NEWPID) {
 		pid_ns = task_active_pid_ns(tsk);
 		if (unlikely(!pid_ns)) {
 			rcu_read_unlock();
 			ret = -ESRCH;
 			goto out;
 		}
 		get_pid_ns(pid_ns);
 	}
 #endif

 #ifdef CONFIG_USER_NS
 	if (flags & CLONE_NEWUSER)
 		user_ns = get_user_ns(__task_cred(tsk)->user_ns);
 #endif
 	rcu_read_unlock();

 	/*
 	 * Install requested namespaces. The caller will have
 	 * verified earlier that the requested namespaces are
 	 * supported on this kernel. We don't report errors here
 	 * if a namespace is requested that isn't supported.
 	 */
 #ifdef CONFIG_USER_NS
 	if (flags & CLONE_NEWUSER) {
 		ret = validate_ns(nsset, &user_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 	if (flags & CLONE_NEWNS) {
 		ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
 		if (ret)
 			goto out;
 	}

 #ifdef CONFIG_UTS_NS
 	if (flags & CLONE_NEWUTS) {
 		ret = validate_ns(nsset, &nsp->uts_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 #ifdef CONFIG_IPC_NS
 	if (flags & CLONE_NEWIPC) {
 		ret = validate_ns(nsset, &nsp->ipc_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 #ifdef CONFIG_PID_NS
 	if (flags & CLONE_NEWPID) {
 		ret = validate_ns(nsset, &pid_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 #ifdef CONFIG_CGROUPS
 	if (flags & CLONE_NEWCGROUP) {
 		ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 #ifdef CONFIG_NET_NS
 	if (flags & CLONE_NEWNET) {
 		ret = validate_ns(nsset, &nsp->net_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 #ifdef CONFIG_TIME_NS
 	if (flags & CLONE_NEWTIME) {
 		ret = validate_ns(nsset, &nsp->time_ns->ns);
 		if (ret)
 			goto out;
 	}
 #endif

 out:
 	if (pid_ns)
 		put_pid_ns(pid_ns);
 	if (nsp)
 		put_nsproxy(nsp);
 	put_user_ns(user_ns);

 	return ret;
 }

 /*
  * This is the point of no return. There are just a few namespaces
  * that do some actual work here and it's sufficiently minimal that
  * a separate ns_common operation seems unnecessary for now.
  * Unshare is doing the same thing. If we'll end up needing to do
  * more in a given namespace or a helper here is ultimately not
  * exported anymore a simple commit handler for each namespace
  * should be added to ns_common.
  */
 static void commit_nsset(struct nsset *nsset)
 {
 	unsigned flags = nsset->flags;
 	struct task_struct *me = current;

 #ifdef CONFIG_USER_NS
 	if (flags & CLONE_NEWUSER) {
 		/* transfer ownership */
 		commit_creds(nsset_cred(nsset));
 		nsset->cred = NULL;
 	}
 #endif

 	/* We only need to commit if we have used a temporary fs_struct. */
 	if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
 		set_fs_root(me->fs, &nsset->fs->root);
 		set_fs_pwd(me->fs, &nsset->fs->pwd);
 	}

 #ifdef CONFIG_IPC_NS
 	if (flags & CLONE_NEWIPC)
 		exit_sem(me);
 #endif

 #ifdef CONFIG_TIME_NS
 	if (flags & CLONE_NEWTIME)
 		timens_commit(me, nsset->nsproxy->time_ns);
 #endif

 	/* transfer ownership */
 	switch_task_namespaces(me, nsset->nsproxy);
 	nsset->nsproxy = NULL;
 }

 SYSCALL_DEFINE2(setns, int, fd, int, flags)
 {
 	struct file *file;
 	struct ns_common *ns = NULL;
 	struct nsset nsset = {};
 	int err = 0;

 	file = fget(fd);
 	if (!file)
 		return -EBADF;

 	if (proc_ns_file(file)) {
 		ns = get_proc_ns(file_inode(file));
 		if (flags && (ns->ops->type != flags))
 			err = -EINVAL;
 		flags = ns->ops->type;
 	} else if (!IS_ERR(pidfd_pid(file))) {
 		err = check_setns_flags(flags);
 	} else {
 		err = -EINVAL;
 	}
 	if (err)
 		goto out;

 	err = prepare_nsset(flags, &nsset);
 	if (err)
 		goto out;

 	if (proc_ns_file(file))
 		err = validate_ns(&nsset, ns);
 	else
 		err = validate_nsset(&nsset, file->private_data);
 	if (!err) {
 		commit_nsset(&nsset);
 		perf_event_namespaces(current);
 	}
 	put_nsset(&nsset);
 out:
 	fput(file);
 	return err;
 }

 int __init nsproxy_cache_init(void)
 {
 	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC|SLAB_ACCOUNT);
 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2006 IBM Corporation
	*
	* Author: Serge Hallyn <serue@us.ibm.com>
	*
	* 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/time_namespace.h>
	#include <linux/fs_struct.h>
	#include <linux/proc_fs.h>
	#include <linux/proc_ns.h>
	#include <linux/file.h>
	#include <linux/syscalls.h>
	#include <linux/cgroup.h>
	#include <linux/perf_event.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
	#ifdef CONFIG_CGROUPS
	.cgroup_ns = &init_cgroup_ns,
	#endif
	#ifdef CONFIG_TIME_NS
	.time_ns = &init_time_ns,
	.time_ns_for_children = &init_time_ns,
	#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->cgroup_ns = copy_cgroup_ns(flags, user_ns,
	tsk->nsproxy->cgroup_ns);
	if (IS_ERR(new_nsp->cgroup_ns)) {
	err = PTR_ERR(new_nsp->cgroup_ns);
	goto out_cgroup;
	}

	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;
	}

	new_nsp->time_ns_for_children = copy_time_ns(flags, user_ns,
	tsk->nsproxy->time_ns_for_children);
	if (IS_ERR(new_nsp->time_ns_for_children)) {
	err = PTR_ERR(new_nsp->time_ns_for_children);
	goto out_time;
	}
	new_nsp->time_ns = get_time_ns(tsk->nsproxy->time_ns);

	return new_nsp;

	out_time:
	put_net(new_nsp->net_ns);
	out_net:
	put_cgroup_ns(new_nsp->cgroup_ns);
	out_cgroup:
	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 \|
	CLONE_NEWCGROUP \| CLONE_NEWTIME)))) {
	if (likely(old_ns->time_ns_for_children == old_ns->time_ns)) {
	get_nsproxy(old_ns);
	return 0;
	}
	} else 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);

	timens_on_fork(new_ns, tsk);

	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);
	if (ns->time_ns)
	put_time_ns(ns->time_ns);
	if (ns->time_ns_for_children)
	put_time_ns(ns->time_ns_for_children);
	put_cgroup_ns(ns->cgroup_ns);
	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 \| CLONE_NEWCGROUP \|
	CLONE_NEWTIME)))
	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();

	task_lock(p);
	ns = p->nsproxy;
	p->nsproxy = new;
	task_unlock(p);

	if (ns)
	put_nsproxy(ns);
	}

	void exit_task_namespaces(struct task_struct *p)
	{
	switch_task_namespaces(p, NULL);
	}

	static int check_setns_flags(unsigned long flags)
	{
	if (!flags \|\| (flags & ~(CLONE_NEWNS \| CLONE_NEWUTS \| CLONE_NEWIPC \|
	CLONE_NEWNET \| CLONE_NEWTIME \| CLONE_NEWUSER \|
	CLONE_NEWPID \| CLONE_NEWCGROUP)))
	return -EINVAL;

	#ifndef CONFIG_USER_NS
	if (flags & CLONE_NEWUSER)
	return -EINVAL;
	#endif
	#ifndef CONFIG_PID_NS
	if (flags & CLONE_NEWPID)
	return -EINVAL;
	#endif
	#ifndef CONFIG_UTS_NS
	if (flags & CLONE_NEWUTS)
	return -EINVAL;
	#endif
	#ifndef CONFIG_IPC_NS
	if (flags & CLONE_NEWIPC)
	return -EINVAL;
	#endif
	#ifndef CONFIG_CGROUPS
	if (flags & CLONE_NEWCGROUP)
	return -EINVAL;
	#endif
	#ifndef CONFIG_NET_NS
	if (flags & CLONE_NEWNET)
	return -EINVAL;
	#endif
	#ifndef CONFIG_TIME_NS
	if (flags & CLONE_NEWTIME)
	return -EINVAL;
	#endif

	return 0;
	}

	static void put_nsset(struct nsset *nsset)
	{
	unsigned flags = nsset->flags;

	if (flags & CLONE_NEWUSER)
	put_cred(nsset_cred(nsset));
	/*
	* We only created a temporary copy if we attached to more than just
	* the mount namespace.
	*/
	if (nsset->fs && (flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS))
	free_fs_struct(nsset->fs);
	if (nsset->nsproxy)
	free_nsproxy(nsset->nsproxy);
	}

	static int prepare_nsset(unsigned flags, struct nsset *nsset)
	{
	struct task_struct *me = current;

	nsset->nsproxy = create_new_namespaces(0, me, current_user_ns(), me->fs);
	if (IS_ERR(nsset->nsproxy))
	return PTR_ERR(nsset->nsproxy);

	if (flags & CLONE_NEWUSER)
	nsset->cred = prepare_creds();
	else
	nsset->cred = current_cred();
	if (!nsset->cred)
	goto out;

	/* Only create a temporary copy of fs_struct if we really need to. */
	if (flags == CLONE_NEWNS) {
	nsset->fs = me->fs;
	} else if (flags & CLONE_NEWNS) {
	nsset->fs = copy_fs_struct(me->fs);
	if (!nsset->fs)
	goto out;
	}

	nsset->flags = flags;
	return 0;

	out:
	put_nsset(nsset);
	return -ENOMEM;
	}

	static inline int validate_ns(struct nsset nsset, struct ns_common ns)
	{
	return ns->ops->install(nsset, ns);
	}

	/*
	* This is the inverse operation to unshare().
	* Ordering is equivalent to the standard ordering used everywhere else
	* during unshare and process creation. The switch to the new set of
	* namespaces occurs at the point of no return after installation of
	* all requested namespaces was successful in commit_nsset().
	*/
	static int validate_nsset(struct nsset nsset, struct pid pid)
	{
	int ret = 0;
	unsigned flags = nsset->flags;
	struct user_namespace *user_ns = NULL;
	struct pid_namespace *pid_ns = NULL;
	struct nsproxy *nsp;
	struct task_struct *tsk;

	/* Take a "snapshot" of the target task's namespaces. */
	rcu_read_lock();
	tsk = pid_task(pid, PIDTYPE_PID);
	if (!tsk) {
	rcu_read_unlock();
	return -ESRCH;
	}

	if (!ptrace_may_access(tsk, PTRACE_MODE_READ_REALCREDS)) {
	rcu_read_unlock();
	return -EPERM;
	}

	task_lock(tsk);
	nsp = tsk->nsproxy;
	if (nsp)
	get_nsproxy(nsp);
	task_unlock(tsk);
	if (!nsp) {
	rcu_read_unlock();
	return -ESRCH;
	}

	#ifdef CONFIG_PID_NS
	if (flags & CLONE_NEWPID) {
	pid_ns = task_active_pid_ns(tsk);
	if (unlikely(!pid_ns)) {
	rcu_read_unlock();
	ret = -ESRCH;
	goto out;
	}
	get_pid_ns(pid_ns);
	}
	#endif

	#ifdef CONFIG_USER_NS
	if (flags & CLONE_NEWUSER)
	user_ns = get_user_ns(__task_cred(tsk)->user_ns);
	#endif
	rcu_read_unlock();

	/*
	* Install requested namespaces. The caller will have
	* verified earlier that the requested namespaces are
	* supported on this kernel. We don't report errors here
	* if a namespace is requested that isn't supported.
	*/
	#ifdef CONFIG_USER_NS
	if (flags & CLONE_NEWUSER) {
	ret = validate_ns(nsset, &user_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	if (flags & CLONE_NEWNS) {
	ret = validate_ns(nsset, from_mnt_ns(nsp->mnt_ns));
	if (ret)
	goto out;
	}

	#ifdef CONFIG_UTS_NS
	if (flags & CLONE_NEWUTS) {
	ret = validate_ns(nsset, &nsp->uts_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	#ifdef CONFIG_IPC_NS
	if (flags & CLONE_NEWIPC) {
	ret = validate_ns(nsset, &nsp->ipc_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	#ifdef CONFIG_PID_NS
	if (flags & CLONE_NEWPID) {
	ret = validate_ns(nsset, &pid_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	#ifdef CONFIG_CGROUPS
	if (flags & CLONE_NEWCGROUP) {
	ret = validate_ns(nsset, &nsp->cgroup_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	#ifdef CONFIG_NET_NS
	if (flags & CLONE_NEWNET) {
	ret = validate_ns(nsset, &nsp->net_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	#ifdef CONFIG_TIME_NS
	if (flags & CLONE_NEWTIME) {
	ret = validate_ns(nsset, &nsp->time_ns->ns);
	if (ret)
	goto out;
	}
	#endif

	out:
	if (pid_ns)
	put_pid_ns(pid_ns);
	if (nsp)
	put_nsproxy(nsp);
	put_user_ns(user_ns);

	return ret;
	}

	/*
	* This is the point of no return. There are just a few namespaces
	* that do some actual work here and it's sufficiently minimal that
	* a separate ns_common operation seems unnecessary for now.
	* Unshare is doing the same thing. If we'll end up needing to do
	* more in a given namespace or a helper here is ultimately not
	* exported anymore a simple commit handler for each namespace
	* should be added to ns_common.
	*/
	static void commit_nsset(struct nsset *nsset)
	{
	unsigned flags = nsset->flags;
	struct task_struct *me = current;

	#ifdef CONFIG_USER_NS
	if (flags & CLONE_NEWUSER) {
	/* transfer ownership */
	commit_creds(nsset_cred(nsset));
	nsset->cred = NULL;
	}
	#endif

	/* We only need to commit if we have used a temporary fs_struct. */
	if ((flags & CLONE_NEWNS) && (flags & ~CLONE_NEWNS)) {
	set_fs_root(me->fs, &nsset->fs->root);
	set_fs_pwd(me->fs, &nsset->fs->pwd);
	}

	#ifdef CONFIG_IPC_NS
	if (flags & CLONE_NEWIPC)
	exit_sem(me);
	#endif

	#ifdef CONFIG_TIME_NS
	if (flags & CLONE_NEWTIME)
	timens_commit(me, nsset->nsproxy->time_ns);
	#endif

	/* transfer ownership */
	switch_task_namespaces(me, nsset->nsproxy);
	nsset->nsproxy = NULL;
	}

	SYSCALL_DEFINE2(setns, int, fd, int, flags)
	{
	struct file *file;
	struct ns_common *ns = NULL;
	struct nsset nsset = {};
	int err = 0;

	file = fget(fd);
	if (!file)
	return -EBADF;

	if (proc_ns_file(file)) {
	ns = get_proc_ns(file_inode(file));
	if (flags && (ns->ops->type != flags))
	err = -EINVAL;
	flags = ns->ops->type;
	} else if (!IS_ERR(pidfd_pid(file))) {
	err = check_setns_flags(flags);
	} else {
	err = -EINVAL;
	}
	if (err)
	goto out;

	err = prepare_nsset(flags, &nsset);
	if (err)
	goto out;

	if (proc_ns_file(file))
	err = validate_ns(&nsset, ns);
	else
	err = validate_nsset(&nsset, file->private_data);
	if (!err) {
	commit_nsset(&nsset);
	perf_event_namespaces(current);
	}
	put_nsset(&nsset);
	out:
	fput(file);
	return err;
	}

	int __init nsproxy_cache_init(void)
	{
	nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC\|SLAB_ACCOUNT);
	return 0;
	}