2 * linux/ipc/namespace.c
3 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
8 #include <linux/ipc_namespace.h>
9 #include <linux/rcupdate.h>
10 #include <linux/nsproxy.h>
11 #include <linux/slab.h>
13 #include <linux/mount.h>
14 #include <linux/user_namespace.h>
15 #include <linux/proc_fs.h>
19 static struct ipc_namespace
*create_ipc_ns(struct user_namespace
*user_ns
,
20 struct ipc_namespace
*old_ns
)
22 struct ipc_namespace
*ns
;
25 ns
= kmalloc(sizeof(struct ipc_namespace
), GFP_KERNEL
);
27 return ERR_PTR(-ENOMEM
);
29 atomic_set(&ns
->count
, 1);
35 atomic_inc(&nr_ipc_ns
);
42 * msgmni has already been computed for the new ipc ns.
43 * Thus, do the ipcns creation notification before registering that
44 * new ipcns in the chain.
46 ipcns_notify(IPCNS_CREATED
);
47 register_ipcns_notifier(ns
);
49 ns
->user_ns
= get_user_ns(user_ns
);
54 struct ipc_namespace
*copy_ipcs(unsigned long flags
,
55 struct user_namespace
*user_ns
, struct ipc_namespace
*ns
)
57 if (!(flags
& CLONE_NEWIPC
))
58 return get_ipc_ns(ns
);
59 return create_ipc_ns(user_ns
, ns
);
63 * free_ipcs - free all ipcs of one type
64 * @ns: the namespace to remove the ipcs from
65 * @ids: the table of ipcs to free
66 * @free: the function called to free each individual ipc
68 * Called for each kind of ipc when an ipc_namespace exits.
70 void free_ipcs(struct ipc_namespace
*ns
, struct ipc_ids
*ids
,
71 void (*free
)(struct ipc_namespace
*, struct kern_ipc_perm
*))
73 struct kern_ipc_perm
*perm
;
77 down_write(&ids
->rw_mutex
);
81 for (total
= 0, next_id
= 0; total
< in_use
; next_id
++) {
82 perm
= idr_find(&ids
->ipcs_idr
, next_id
);
85 ipc_lock_by_ptr(perm
);
89 up_write(&ids
->rw_mutex
);
92 static void free_ipc_ns(struct ipc_namespace
*ns
)
95 * Unregistering the hotplug notifier at the beginning guarantees
96 * that the ipc namespace won't be freed while we are inside the
97 * callback routine. Since the blocking_notifier_chain_XXX routines
98 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
99 * won't take the rw lock before blocking_notifier_call_chain() has
100 * released the rd lock.
102 unregister_ipcns_notifier(ns
);
106 atomic_dec(&nr_ipc_ns
);
109 * Do the ipcns removal notification after decrementing nr_ipc_ns in
110 * order to have a correct value when recomputing msgmni.
112 ipcns_notify(IPCNS_REMOVED
);
113 put_user_ns(ns
->user_ns
);
118 * put_ipc_ns - drop a reference to an ipc namespace.
119 * @ns: the namespace to put
121 * If this is the last task in the namespace exiting, and
122 * it is dropping the refcount to 0, then it can race with
123 * a task in another ipc namespace but in a mounts namespace
124 * which has this ipcns's mqueuefs mounted, doing some action
125 * with one of the mqueuefs files. That can raise the refcount.
126 * So dropping the refcount, and raising the refcount when
127 * accessing it through the VFS, are protected with mq_lock.
129 * (Clearly, a task raising the refcount on its own ipc_ns
130 * needn't take mq_lock since it can't race with the last task
131 * in the ipcns exiting).
133 void put_ipc_ns(struct ipc_namespace
*ns
)
135 if (atomic_dec_and_lock(&ns
->count
, &mq_lock
)) {
137 spin_unlock(&mq_lock
);
143 static void *ipcns_get(struct task_struct
*task
)
145 struct ipc_namespace
*ns
= NULL
;
146 struct nsproxy
*nsproxy
;
149 nsproxy
= task_nsproxy(task
);
151 ns
= get_ipc_ns(nsproxy
->ipc_ns
);
157 static void ipcns_put(void *ns
)
159 return put_ipc_ns(ns
);
162 static int ipcns_install(struct nsproxy
*nsproxy
, void *new)
164 struct ipc_namespace
*ns
= new;
165 if (!ns_capable(ns
->user_ns
, CAP_SYS_ADMIN
))
168 /* Ditch state from the old ipc namespace */
170 put_ipc_ns(nsproxy
->ipc_ns
);
171 nsproxy
->ipc_ns
= get_ipc_ns(ns
);
175 const struct proc_ns_operations ipcns_operations
= {
177 .type
= CLONE_NEWIPC
,
180 .install
= ipcns_install
,