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,