// 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>
#include <linux/nstree.h>

static struct kmem_cache *nsproxy_cachep;

struct nsproxy init_nsproxy = {
        .count                  = REFCOUNT_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)
                refcount_set(&nsproxy->count, 1);
        return nsproxy;
}

static inline void nsproxy_free(struct nsproxy *ns)
{
        put_mnt_ns(ns->mnt_ns);
        put_uts_ns(ns->uts_ns);
        put_ipc_ns(ns->ipc_ns);
        put_pid_ns(ns->pid_ns_for_children);
        put_time_ns(ns->time_ns);
        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);
}

void deactivate_nsproxy(struct nsproxy *ns)
{
        nsproxy_ns_active_put(ns);
        nsproxy_free(ns);
}

/*
 * 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(u64 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:
        put_pid_ns(new_nsp->pid_ns_for_children);
out_pid:
        put_ipc_ns(new_nsp->ipc_ns);
out_ipc:
        put_uts_ns(new_nsp->uts_ns);
out_uts:
        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(u64 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 ((flags & CLONE_VM) ||
                    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);

        if ((flags & CLONE_VM) == 0)
                timens_on_fork(new_ns, tsk);

        nsproxy_ns_active_get(new_ns);
        tsk->nsproxy = new_ns;
        return 0;
}

/*
 * 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();

        if (new)
                nsproxy_ns_active_get(new);

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

        if (ns)
                put_nsproxy(ns);
}

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

void switch_cred_namespaces(const struct cred *old, const struct cred *new)
{
        ns_ref_active_get(new->user_ns);
        ns_ref_active_put(old->user_ns);
}

void get_cred_namespaces(struct task_struct *tsk)
{
        ns_ref_active_get(tsk->real_cred->user_ns);
}

void exit_cred_namespaces(struct task_struct *tsk)
{
        ns_ref_active_put(tsk->real_cred->user_ns);
}

int exec_task_namespaces(void)
{
        struct task_struct *tsk = current;
        struct nsproxy *new;

        if (tsk->nsproxy->time_ns_for_children == tsk->nsproxy->time_ns)
                return 0;

        new = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);
        if (IS_ERR(new))
                return PTR_ERR(new);

        timens_on_fork(new, tsk);
        switch_task_namespaces(tsk, new);
        return 0;
}

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)
                nsproxy_free(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)
{
        CLASS(fd, f)(fd);
        struct ns_common *ns = NULL;
        struct nsset nsset = {};
        int err = 0;

        if (fd_empty(f))
                return -EBADF;

        if (proc_ns_file(fd_file(f))) {
                ns = get_proc_ns(file_inode(fd_file(f)));
                if (flags && (ns->ns_type != flags))
                        err = -EINVAL;
                flags = ns->ns_type;
        } else if (!IS_ERR(pidfd_pid(fd_file(f)))) {
                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(fd_file(f)))
                err = validate_ns(&nsset, ns);
        else
                err = validate_nsset(&nsset, pidfd_pid(fd_file(f)));
        if (!err) {
                commit_nsset(&nsset);
                perf_event_namespaces(current);
        }
        put_nsset(&nsset);
out:
        return err;
}

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