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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 | |
15 | #include "util.h" |
16 | |
17 | static struct ipc_namespace *create_ipc_ns(void) |
18 | { |
19 | struct ipc_namespace *ns; |
20 | int err; |
21 | |
22 | ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL); |
23 | if (ns == NULL) |
24 | return ERR_PTR(-ENOMEM); |
25 | |
26 | atomic_set(&ns->count, 1); |
27 | err = mq_init_ns(ns); |
28 | if (err) { |
29 | kfree(ns); |
30 | return ERR_PTR(err); |
31 | } |
32 | atomic_inc(&nr_ipc_ns); |
33 | |
34 | sem_init_ns(ns); |
35 | msg_init_ns(ns); |
36 | shm_init_ns(ns); |
37 | |
38 | /* |
39 | * msgmni has already been computed for the new ipc ns. |
40 | * Thus, do the ipcns creation notification before registering that |
41 | * new ipcns in the chain. |
42 | */ |
43 | ipcns_notify(IPCNS_CREATED); |
44 | register_ipcns_notifier(ns); |
45 | |
46 | return ns; |
47 | } |
48 | |
49 | struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns) |
50 | { |
51 | if (!(flags & CLONE_NEWIPC)) |
52 | return get_ipc_ns(ns); |
53 | return create_ipc_ns(); |
54 | } |
55 | |
56 | /* |
57 | * free_ipcs - free all ipcs of one type |
58 | * @ns: the namespace to remove the ipcs from |
59 | * @ids: the table of ipcs to free |
60 | * @free: the function called to free each individual ipc |
61 | * |
62 | * Called for each kind of ipc when an ipc_namespace exits. |
63 | */ |
64 | void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, |
65 | void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) |
66 | { |
67 | struct kern_ipc_perm *perm; |
68 | int next_id; |
69 | int total, in_use; |
70 | |
71 | down_write(&ids->rw_mutex); |
72 | |
73 | in_use = ids->in_use; |
74 | |
75 | for (total = 0, next_id = 0; total < in_use; next_id++) { |
76 | perm = idr_find(&ids->ipcs_idr, next_id); |
77 | if (perm == NULL) |
78 | continue; |
79 | ipc_lock_by_ptr(perm); |
80 | free(ns, perm); |
81 | total++; |
82 | } |
83 | up_write(&ids->rw_mutex); |
84 | } |
85 | |
86 | static void free_ipc_ns(struct ipc_namespace *ns) |
87 | { |
88 | /* |
89 | * Unregistering the hotplug notifier at the beginning guarantees |
90 | * that the ipc namespace won't be freed while we are inside the |
91 | * callback routine. Since the blocking_notifier_chain_XXX routines |
92 | * hold a rw lock on the notifier list, unregister_ipcns_notifier() |
93 | * won't take the rw lock before blocking_notifier_call_chain() has |
94 | * released the rd lock. |
95 | */ |
96 | unregister_ipcns_notifier(ns); |
97 | sem_exit_ns(ns); |
98 | msg_exit_ns(ns); |
99 | shm_exit_ns(ns); |
100 | kfree(ns); |
101 | atomic_dec(&nr_ipc_ns); |
102 | |
103 | /* |
104 | * Do the ipcns removal notification after decrementing nr_ipc_ns in |
105 | * order to have a correct value when recomputing msgmni. |
106 | */ |
107 | ipcns_notify(IPCNS_REMOVED); |
108 | } |
109 | |
110 | /* |
111 | * put_ipc_ns - drop a reference to an ipc namespace. |
112 | * @ns: the namespace to put |
113 | * |
114 | * If this is the last task in the namespace exiting, and |
115 | * it is dropping the refcount to 0, then it can race with |
116 | * a task in another ipc namespace but in a mounts namespace |
117 | * which has this ipcns's mqueuefs mounted, doing some action |
118 | * with one of the mqueuefs files. That can raise the refcount. |
119 | * So dropping the refcount, and raising the refcount when |
120 | * accessing it through the VFS, are protected with mq_lock. |
121 | * |
122 | * (Clearly, a task raising the refcount on its own ipc_ns |
123 | * needn't take mq_lock since it can't race with the last task |
124 | * in the ipcns exiting). |
125 | */ |
126 | void put_ipc_ns(struct ipc_namespace *ns) |
127 | { |
128 | if (atomic_dec_and_lock(&ns->count, &mq_lock)) { |
129 | mq_clear_sbinfo(ns); |
130 | spin_unlock(&mq_lock); |
131 | mq_put_mnt(ns); |
132 | free_ipc_ns(ns); |
133 | } |
134 | } |
135 |
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