1 /*
2 * linux/ipc/namespace.c
3 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
4 */
5
6 #include <linux/ipc.h>
7 #include <linux/msg.h>
8 #include <linux/ipc_namespace.h>
9 #include <linux/rcupdate.h>
10 #include <linux/nsproxy.h>
11 #include <linux/slab.h>
12 #include <linux/fs.h>
13 #include <linux/mount.h>
14 #include <linux/user_namespace.h>
15 #include <linux/proc_ns.h>
16
17 #include "util.h"
18
create_ipc_ns(struct user_namespace * user_ns,struct ipc_namespace * old_ns)19 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
20 struct ipc_namespace *old_ns)
21 {
22 struct ipc_namespace *ns;
23 int err;
24
25 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
26 if (ns == NULL)
27 return ERR_PTR(-ENOMEM);
28
29 err = proc_alloc_inum(&ns->proc_inum);
30 if (err) {
31 kfree(ns);
32 return ERR_PTR(err);
33 }
34
35 atomic_set(&ns->count, 1);
36 err = mq_init_ns(ns);
37 if (err) {
38 proc_free_inum(ns->proc_inum);
39 kfree(ns);
40 return ERR_PTR(err);
41 }
42 atomic_inc(&nr_ipc_ns);
43
44 sem_init_ns(ns);
45 msg_init_ns(ns);
46 shm_init_ns(ns);
47
48 /*
49 * msgmni has already been computed for the new ipc ns.
50 * Thus, do the ipcns creation notification before registering that
51 * new ipcns in the chain.
52 */
53 ipcns_notify(IPCNS_CREATED);
54 register_ipcns_notifier(ns);
55
56 ns->user_ns = get_user_ns(user_ns);
57
58 return ns;
59 }
60
copy_ipcs(unsigned long flags,struct user_namespace * user_ns,struct ipc_namespace * ns)61 struct ipc_namespace *copy_ipcs(unsigned long flags,
62 struct user_namespace *user_ns, struct ipc_namespace *ns)
63 {
64 if (!(flags & CLONE_NEWIPC))
65 return get_ipc_ns(ns);
66 return create_ipc_ns(user_ns, ns);
67 }
68
69 /*
70 * free_ipcs - free all ipcs of one type
71 * @ns: the namespace to remove the ipcs from
72 * @ids: the table of ipcs to free
73 * @free: the function called to free each individual ipc
74 *
75 * Called for each kind of ipc when an ipc_namespace exits.
76 */
free_ipcs(struct ipc_namespace * ns,struct ipc_ids * ids,void (* free)(struct ipc_namespace *,struct kern_ipc_perm *))77 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
78 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
79 {
80 struct kern_ipc_perm *perm;
81 int next_id;
82 int total, in_use;
83
84 down_write(&ids->rw_mutex);
85
86 in_use = ids->in_use;
87
88 for (total = 0, next_id = 0; total < in_use; next_id++) {
89 perm = idr_find(&ids->ipcs_idr, next_id);
90 if (perm == NULL)
91 continue;
92 ipc_lock_by_ptr(perm);
93 free(ns, perm);
94 total++;
95 }
96 up_write(&ids->rw_mutex);
97 }
98
free_ipc_ns(struct ipc_namespace * ns)99 static void free_ipc_ns(struct ipc_namespace *ns)
100 {
101 /*
102 * Unregistering the hotplug notifier at the beginning guarantees
103 * that the ipc namespace won't be freed while we are inside the
104 * callback routine. Since the blocking_notifier_chain_XXX routines
105 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
106 * won't take the rw lock before blocking_notifier_call_chain() has
107 * released the rd lock.
108 */
109 unregister_ipcns_notifier(ns);
110 sem_exit_ns(ns);
111 msg_exit_ns(ns);
112 shm_exit_ns(ns);
113 atomic_dec(&nr_ipc_ns);
114
115 /*
116 * Do the ipcns removal notification after decrementing nr_ipc_ns in
117 * order to have a correct value when recomputing msgmni.
118 */
119 ipcns_notify(IPCNS_REMOVED);
120 put_user_ns(ns->user_ns);
121 proc_free_inum(ns->proc_inum);
122 kfree(ns);
123 }
124
125 /*
126 * put_ipc_ns - drop a reference to an ipc namespace.
127 * @ns: the namespace to put
128 *
129 * If this is the last task in the namespace exiting, and
130 * it is dropping the refcount to 0, then it can race with
131 * a task in another ipc namespace but in a mounts namespace
132 * which has this ipcns's mqueuefs mounted, doing some action
133 * with one of the mqueuefs files. That can raise the refcount.
134 * So dropping the refcount, and raising the refcount when
135 * accessing it through the VFS, are protected with mq_lock.
136 *
137 * (Clearly, a task raising the refcount on its own ipc_ns
138 * needn't take mq_lock since it can't race with the last task
139 * in the ipcns exiting).
140 */
put_ipc_ns(struct ipc_namespace * ns)141 void put_ipc_ns(struct ipc_namespace *ns)
142 {
143 if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
144 mq_clear_sbinfo(ns);
145 spin_unlock(&mq_lock);
146 mq_put_mnt(ns);
147 free_ipc_ns(ns);
148 }
149 }
150
ipcns_get(struct task_struct * task)151 static void *ipcns_get(struct task_struct *task)
152 {
153 struct ipc_namespace *ns = NULL;
154 struct nsproxy *nsproxy;
155
156 rcu_read_lock();
157 nsproxy = task_nsproxy(task);
158 if (nsproxy)
159 ns = get_ipc_ns(nsproxy->ipc_ns);
160 rcu_read_unlock();
161
162 return ns;
163 }
164
ipcns_put(void * ns)165 static void ipcns_put(void *ns)
166 {
167 return put_ipc_ns(ns);
168 }
169
ipcns_install(struct nsproxy * nsproxy,void * new)170 static int ipcns_install(struct nsproxy *nsproxy, void *new)
171 {
172 struct ipc_namespace *ns = new;
173 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
174 !nsown_capable(CAP_SYS_ADMIN))
175 return -EPERM;
176
177 /* Ditch state from the old ipc namespace */
178 exit_sem(current);
179 put_ipc_ns(nsproxy->ipc_ns);
180 nsproxy->ipc_ns = get_ipc_ns(ns);
181 return 0;
182 }
183
ipcns_inum(void * vp)184 static unsigned int ipcns_inum(void *vp)
185 {
186 struct ipc_namespace *ns = vp;
187
188 return ns->proc_inum;
189 }
190
191 const struct proc_ns_operations ipcns_operations = {
192 .name = "ipc",
193 .type = CLONE_NEWIPC,
194 .get = ipcns_get,
195 .put = ipcns_put,
196 .install = ipcns_install,
197 .inum = ipcns_inum,
198 };
199