/*
 *  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_fs.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 = &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 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, 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, tsk);
        if (IS_ERR(new_nsp->uts_ns)) {
                err = PTR_ERR(new_nsp->uts_ns);
                goto out_uts;
        }

        new_nsp->ipc_ns = copy_ipcs(flags, tsk);
        if (IS_ERR(new_nsp->ipc_ns)) {
                err = PTR_ERR(new_nsp->ipc_ns);
                goto out_ipc;
        }

        new_nsp->pid_ns = copy_pid_ns(flags, task_active_pid_ns(tsk));
        if (IS_ERR(new_nsp->pid_ns)) {
                err = PTR_ERR(new_nsp->pid_ns);
                goto out_pid;
        }

        new_nsp->net_ns = copy_net_ns(flags, 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)
                put_pid_ns(new_nsp->pid_ns);
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 nsproxy *new_ns;
        int err = 0;

        if (!old_ns)
                return 0;

        get_nsproxy(old_ns);

        if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
                                CLONE_NEWPID | CLONE_NEWNET)))
                return 0;

        if (!capable(CAP_SYS_ADMIN)) {
                err = -EPERM;
                goto out;
        }

        /*
         * 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) && (flags & CLONE_SYSVSEM)) {
                err = -EINVAL;
                goto out;
        }

        new_ns = create_new_namespaces(flags, tsk, tsk->fs);
        if (IS_ERR(new_ns)) {
                err = PTR_ERR(new_ns);
                goto out;
        }

        tsk->nsproxy = new_ns;

out:
        put_nsproxy(old_ns);
        return err;
}

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)
                put_pid_ns(ns->pid_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 fs_struct *new_fs)
{
        int err = 0;

        if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
                               CLONE_NEWNET)))
                return 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        *new_nsp = create_new_namespaces(unshare_flags, current,
                                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_inode *ei;
        struct file *file;
        int err;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        file = proc_ns_fget(fd);
        if (IS_ERR(file))
                return PTR_ERR(file);

        err = -EINVAL;
        ei = PROC_I(file->f_dentry->d_inode);
        ops = ei->ns_ops;
        if (nstype && (ops->type != nstype))
                goto out;

        new_nsproxy = create_new_namespaces(0, tsk, 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;
}