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

#include "util.h"

/*
 * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
 */
static void free_ipc(struct work_struct *unused);
static DECLARE_WORK(free_ipc_work, free_ipc);

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;
 again:
        ucounts = inc_ipc_namespaces(user_ns);
        if (!ucounts) {
                /*
                 * IPC namespaces are freed asynchronously, by free_ipc_work.
                 * If frees were pending, flush_work will wait, and
                 * return true. Fail the allocation if no frees are pending.
                 */
                if (flush_work(&free_ipc_work))
                        goto again;
                goto fail;
        }

        err = -ENOMEM;
        ns = kzalloc_obj(struct ipc_namespace, GFP_KERNEL_ACCOUNT);
        if (ns == NULL)
                goto fail_dec;

        err = ns_common_init(ns);
        if (err)
                goto fail_free;

        ns_tree_gen_id(ns);
        ns->user_ns = get_user_ns(user_ns);
        ns->ucounts = ucounts;

        err = mq_init_ns(ns);
        if (err)
                goto fail_put;

        err = -ENOMEM;
        if (!setup_mq_sysctls(ns))
                goto fail_mq_mount;

        if (!setup_ipc_sysctls(ns))
                goto fail_mq_sysctls;

        err = msg_init_ns(ns);
        if (err)
                goto fail_ipc;

        sem_init_ns(ns);
        shm_init_ns(ns);
        ns_tree_add_raw(ns);

        return ns;

fail_ipc:
        retire_ipc_sysctls(ns);
fail_mq_sysctls:
        retire_mq_sysctls(ns);
fail_mq_mount:
        mntput(ns->mq_mnt);
fail_put:
        put_user_ns(ns->user_ns);
        ns_common_free(ns);
fail_free:
        kfree(ns);
fail_dec:
        dec_ipc_namespaces(ucounts);
fail:
        return ERR_PTR(err);
}

struct ipc_namespace *copy_ipcs(u64 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)
{
        /*
         * Caller needs to wait for an RCU grace period to have passed
         * after making the mount point inaccessible to new accesses.
         */
        mntput(ns->mq_mnt);
        sem_exit_ns(ns);
        msg_exit_ns(ns);
        shm_exit_ns(ns);

        retire_mq_sysctls(ns);
        retire_ipc_sysctls(ns);

        dec_ipc_namespaces(ns->ucounts);
        put_user_ns(ns->user_ns);
        ns_common_free(ns);
        kfree(ns);
}

static LLIST_HEAD(free_ipc_list);
static void free_ipc(struct work_struct *unused)
{
        struct llist_node *node = llist_del_all(&free_ipc_list);
        struct ipc_namespace *n, *t;

        llist_for_each_entry_safe(n, t, node, mnt_llist)
                mnt_make_shortterm(n->mq_mnt);

        /* Wait for any last users to have gone away. */
        synchronize_rcu();

        llist_for_each_entry_safe(n, t, node, mnt_llist)
                free_ipc_ns(n);
}

/*
 * 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 (ns_ref_put_and_lock(ns, &mq_lock)) {
                mq_clear_sbinfo(ns);
                spin_unlock(&mq_lock);

                ns_tree_remove(ns);
                if (llist_add(&ns->mnt_llist, &free_ipc_list))
                        schedule_work(&free_ipc_work);
        }
}

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 nsset *nsset, struct ns_common *new)
{
        struct nsproxy *nsproxy = nsset->nsproxy;
        struct ipc_namespace *ns = to_ipc_ns(new);
        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
            !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
                return -EPERM;

        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",
        .get            = ipcns_get,
        .put            = ipcns_put,
        .install        = ipcns_install,
        .owner          = ipcns_owner,
};