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/*
* 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/fs.h>
#include <linux/mount.h>
#include <linux/user_namespace.h>
#include <linux/proc_fs.h>

#include "util.h"

static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk,
struct ipc_namespace *old_ns)
{
struct ipc_namespace *ns;
int err;

ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
if (ns == NULL)
return ERR_PTR(-ENOMEM);

atomic_set(&ns->count, 1);
err = mq_init_ns(ns);
if (err) {
kfree(ns);
return ERR_PTR(err);
}
atomic_inc(&nr_ipc_ns);

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

/*
* msgmni has already been computed for the new ipc ns.
* Thus, do the ipcns creation notification before registering that
* new ipcns in the chain.
*/
ipcns_notify(IPCNS_CREATED);
register_ipcns_notifier(ns);

ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);

return ns;
}

struct ipc_namespace *copy_ipcs(unsigned long flags,
struct task_struct *tsk)
{
struct ipc_namespace *ns = tsk->nsproxy->ipc_ns;

if (!(flags & CLONE_NEWIPC))
return get_ipc_ns(ns);
return create_ipc_ns(tsk, 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->rw_mutex);

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;
ipc_lock_by_ptr(perm);
free(ns, perm);
total++;
}
up_write(&ids->rw_mutex);
}

static void free_ipc_ns(struct ipc_namespace *ns)
{
/*
* Unregistering the hotplug notifier at the beginning guarantees
* that the ipc namespace won't be freed while we are inside the
* callback routine. Since the blocking_notifier_chain_XXX routines
* hold a rw lock on the notifier list, unregister_ipcns_notifier()
* won't take the rw lock before blocking_notifier_call_chain() has
* released the rd lock.
*/
unregister_ipcns_notifier(ns);
sem_exit_ns(ns);
msg_exit_ns(ns);
shm_exit_ns(ns);
atomic_dec(&nr_ipc_ns);

/*
* Do the ipcns removal notification after decrementing nr_ipc_ns in
* order to have a correct value when recomputing msgmni.
*/
ipcns_notify(IPCNS_REMOVED);
put_user_ns(ns->user_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 (atomic_dec_and_lock(&ns->count, &mq_lock)) {
mq_clear_sbinfo(ns);
spin_unlock(&mq_lock);
mq_put_mnt(ns);
free_ipc_ns(ns);
}
}

static void *ipcns_get(struct task_struct *task)
{
struct ipc_namespace *ns = NULL;
struct nsproxy *nsproxy;

rcu_read_lock();
nsproxy = task_nsproxy(task);
if (nsproxy)
ns = get_ipc_ns(nsproxy->ipc_ns);
rcu_read_unlock();

return ns;
}

static void ipcns_put(void *ns)
{
return put_ipc_ns(ns);
}

static int ipcns_install(struct nsproxy *nsproxy, void *ns)
{
/* 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;
}

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