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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_fs.h> |
16 | |
17 | #include "util.h" |
18 | |
19 | static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk, |
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 | atomic_set(&ns->count, 1); |
30 | err = mq_init_ns(ns); |
31 | if (err) { |
32 | kfree(ns); |
33 | return ERR_PTR(err); |
34 | } |
35 | atomic_inc(&nr_ipc_ns); |
36 | |
37 | sem_init_ns(ns); |
38 | msg_init_ns(ns); |
39 | shm_init_ns(ns); |
40 | |
41 | /* |
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. |
45 | */ |
46 | ipcns_notify(IPCNS_CREATED); |
47 | register_ipcns_notifier(ns); |
48 | |
49 | ns->user_ns = get_user_ns(task_cred_xxx(tsk, user_ns)); |
50 | |
51 | return ns; |
52 | } |
53 | |
54 | struct ipc_namespace *copy_ipcs(unsigned long flags, |
55 | struct task_struct *tsk) |
56 | { |
57 | struct ipc_namespace *ns = tsk->nsproxy->ipc_ns; |
58 | |
59 | if (!(flags & CLONE_NEWIPC)) |
60 | return get_ipc_ns(ns); |
61 | return create_ipc_ns(tsk, ns); |
62 | } |
63 | |
64 | /* |
65 | * free_ipcs - free all ipcs of one type |
66 | * @ns: the namespace to remove the ipcs from |
67 | * @ids: the table of ipcs to free |
68 | * @free: the function called to free each individual ipc |
69 | * |
70 | * Called for each kind of ipc when an ipc_namespace exits. |
71 | */ |
72 | void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, |
73 | void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) |
74 | { |
75 | struct kern_ipc_perm *perm; |
76 | int next_id; |
77 | int total, in_use; |
78 | |
79 | down_write(&ids->rw_mutex); |
80 | |
81 | in_use = ids->in_use; |
82 | |
83 | for (total = 0, next_id = 0; total < in_use; next_id++) { |
84 | perm = idr_find(&ids->ipcs_idr, next_id); |
85 | if (perm == NULL) |
86 | continue; |
87 | ipc_lock_by_ptr(perm); |
88 | free(ns, perm); |
89 | total++; |
90 | } |
91 | up_write(&ids->rw_mutex); |
92 | } |
93 | |
94 | static void free_ipc_ns(struct ipc_namespace *ns) |
95 | { |
96 | /* |
97 | * Unregistering the hotplug notifier at the beginning guarantees |
98 | * that the ipc namespace won't be freed while we are inside the |
99 | * callback routine. Since the blocking_notifier_chain_XXX routines |
100 | * hold a rw lock on the notifier list, unregister_ipcns_notifier() |
101 | * won't take the rw lock before blocking_notifier_call_chain() has |
102 | * released the rd lock. |
103 | */ |
104 | unregister_ipcns_notifier(ns); |
105 | sem_exit_ns(ns); |
106 | msg_exit_ns(ns); |
107 | shm_exit_ns(ns); |
108 | atomic_dec(&nr_ipc_ns); |
109 | |
110 | /* |
111 | * Do the ipcns removal notification after decrementing nr_ipc_ns in |
112 | * order to have a correct value when recomputing msgmni. |
113 | */ |
114 | ipcns_notify(IPCNS_REMOVED); |
115 | put_user_ns(ns->user_ns); |
116 | kfree(ns); |
117 | } |
118 | |
119 | /* |
120 | * put_ipc_ns - drop a reference to an ipc namespace. |
121 | * @ns: the namespace to put |
122 | * |
123 | * If this is the last task in the namespace exiting, and |
124 | * it is dropping the refcount to 0, then it can race with |
125 | * a task in another ipc namespace but in a mounts namespace |
126 | * which has this ipcns's mqueuefs mounted, doing some action |
127 | * with one of the mqueuefs files. That can raise the refcount. |
128 | * So dropping the refcount, and raising the refcount when |
129 | * accessing it through the VFS, are protected with mq_lock. |
130 | * |
131 | * (Clearly, a task raising the refcount on its own ipc_ns |
132 | * needn't take mq_lock since it can't race with the last task |
133 | * in the ipcns exiting). |
134 | */ |
135 | void put_ipc_ns(struct ipc_namespace *ns) |
136 | { |
137 | if (atomic_dec_and_lock(&ns->count, &mq_lock)) { |
138 | mq_clear_sbinfo(ns); |
139 | spin_unlock(&mq_lock); |
140 | mq_put_mnt(ns); |
141 | free_ipc_ns(ns); |
142 | } |
143 | } |
144 | |
145 | static void *ipcns_get(struct task_struct *task) |
146 | { |
147 | struct ipc_namespace *ns = NULL; |
148 | struct nsproxy *nsproxy; |
149 | |
150 | rcu_read_lock(); |
151 | nsproxy = task_nsproxy(task); |
152 | if (nsproxy) |
153 | ns = get_ipc_ns(nsproxy->ipc_ns); |
154 | rcu_read_unlock(); |
155 | |
156 | return ns; |
157 | } |
158 | |
159 | static void ipcns_put(void *ns) |
160 | { |
161 | return put_ipc_ns(ns); |
162 | } |
163 | |
164 | static int ipcns_install(struct nsproxy *nsproxy, void *ns) |
165 | { |
166 | /* Ditch state from the old ipc namespace */ |
167 | exit_sem(current); |
168 | put_ipc_ns(nsproxy->ipc_ns); |
169 | nsproxy->ipc_ns = get_ipc_ns(ns); |
170 | return 0; |
171 | } |
172 | |
173 | const struct proc_ns_operations ipcns_operations = { |
174 | .name = "ipc", |
175 | .type = CLONE_NEWIPC, |
176 | .get = ipcns_get, |
177 | .put = ipcns_put, |
178 | .install = ipcns_install, |
179 | }; |
180 |
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