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>
18 static struct ipc_namespace *create_ipc_ns(struct ipc_namespace *old_ns)
20 struct ipc_namespace *ns;
23 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
25 return ERR_PTR(-ENOMEM);
27 atomic_set(&ns->count, 1);
33 atomic_inc(&nr_ipc_ns);
40 * msgmni has already been computed for the new ipc ns.
41 * Thus, do the ipcns creation notification before registering that
42 * new ipcns in the chain.
44 ipcns_notify(IPCNS_CREATED);
45 register_ipcns_notifier(ns);
47 ns->user_ns = old_ns->user_ns;
48 get_user_ns(ns->user_ns);
53 struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
55 if (!(flags & CLONE_NEWIPC))
56 return get_ipc_ns(ns);
57 return create_ipc_ns(ns);
61 * free_ipcs - free all ipcs of one type
62 * @ns: the namespace to remove the ipcs from
63 * @ids: the table of ipcs to free
64 * @free: the function called to free each individual ipc
66 * Called for each kind of ipc when an ipc_namespace exits.
68 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
69 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
71 struct kern_ipc_perm *perm;
75 down_write(&ids->rw_mutex);
79 for (total = 0, next_id = 0; total < in_use; next_id++) {
80 perm = idr_find(&ids->ipcs_idr, next_id);
83 ipc_lock_by_ptr(perm);
87 up_write(&ids->rw_mutex);
90 static void free_ipc_ns(struct ipc_namespace *ns)
93 * Unregistering the hotplug notifier at the beginning guarantees
94 * that the ipc namespace won't be freed while we are inside the
95 * callback routine. Since the blocking_notifier_chain_XXX routines
96 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
97 * won't take the rw lock before blocking_notifier_call_chain() has
98 * released the rd lock.
100 unregister_ipcns_notifier(ns);
105 atomic_dec(&nr_ipc_ns);
108 * Do the ipcns removal notification after decrementing nr_ipc_ns in
109 * order to have a correct value when recomputing msgmni.
111 ipcns_notify(IPCNS_REMOVED);
112 put_user_ns(ns->user_ns);
116 * put_ipc_ns - drop a reference to an ipc namespace.
117 * @ns: the namespace to put
119 * If this is the last task in the namespace exiting, and
120 * it is dropping the refcount to 0, then it can race with
121 * a task in another ipc namespace but in a mounts namespace
122 * which has this ipcns's mqueuefs mounted, doing some action
123 * with one of the mqueuefs files. That can raise the refcount.
124 * So dropping the refcount, and raising the refcount when
125 * accessing it through the VFS, are protected with mq_lock.
127 * (Clearly, a task raising the refcount on its own ipc_ns
128 * needn't take mq_lock since it can't race with the last task
129 * in the ipcns exiting).
131 void put_ipc_ns(struct ipc_namespace *ns)
133 if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
135 spin_unlock(&mq_lock);