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Source at commit ec7cab4cbb721bff91ec924ec691efd8daf36579 created 12 years 8 months ago. By Maarten ter Huurne, MIPS: JZ4740: A320: Updated quickstart documentation. | |
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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 | |
16 | #include "util.h" |
17 | |
18 | static struct ipc_namespace *create_ipc_ns(struct task_struct *tsk, |
19 | struct ipc_namespace *old_ns) |
20 | { |
21 | struct ipc_namespace *ns; |
22 | int err; |
23 | |
24 | ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL); |
25 | if (ns == NULL) |
26 | return ERR_PTR(-ENOMEM); |
27 | |
28 | atomic_set(&ns->count, 1); |
29 | err = mq_init_ns(ns); |
30 | if (err) { |
31 | kfree(ns); |
32 | return ERR_PTR(err); |
33 | } |
34 | atomic_inc(&nr_ipc_ns); |
35 | |
36 | sem_init_ns(ns); |
37 | msg_init_ns(ns); |
38 | shm_init_ns(ns); |
39 | |
40 | /* |
41 | * msgmni has already been computed for the new ipc ns. |
42 | * Thus, do the ipcns creation notification before registering that |
43 | * new ipcns in the chain. |
44 | */ |
45 | ipcns_notify(IPCNS_CREATED); |
46 | register_ipcns_notifier(ns); |
47 | |
48 | ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns); |
49 | |
50 | return ns; |
51 | } |
52 | |
53 | struct ipc_namespace *copy_ipcs(unsigned long flags, |
54 | struct task_struct *tsk) |
55 | { |
56 | struct ipc_namespace *ns = tsk->nsproxy->ipc_ns; |
57 | |
58 | if (!(flags & CLONE_NEWIPC)) |
59 | return get_ipc_ns(ns); |
60 | return create_ipc_ns(tsk, ns); |
61 | } |
62 | |
63 | /* |
64 | * free_ipcs - free all ipcs of one type |
65 | * @ns: the namespace to remove the ipcs from |
66 | * @ids: the table of ipcs to free |
67 | * @free: the function called to free each individual ipc |
68 | * |
69 | * Called for each kind of ipc when an ipc_namespace exits. |
70 | */ |
71 | void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, |
72 | void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) |
73 | { |
74 | struct kern_ipc_perm *perm; |
75 | int next_id; |
76 | int total, in_use; |
77 | |
78 | down_write(&ids->rw_mutex); |
79 | |
80 | in_use = ids->in_use; |
81 | |
82 | for (total = 0, next_id = 0; total < in_use; next_id++) { |
83 | perm = idr_find(&ids->ipcs_idr, next_id); |
84 | if (perm == NULL) |
85 | continue; |
86 | ipc_lock_by_ptr(perm); |
87 | free(ns, perm); |
88 | total++; |
89 | } |
90 | up_write(&ids->rw_mutex); |
91 | } |
92 | |
93 | static void free_ipc_ns(struct ipc_namespace *ns) |
94 | { |
95 | /* |
96 | * Unregistering the hotplug notifier at the beginning guarantees |
97 | * that the ipc namespace won't be freed while we are inside the |
98 | * callback routine. Since the blocking_notifier_chain_XXX routines |
99 | * hold a rw lock on the notifier list, unregister_ipcns_notifier() |
100 | * won't take the rw lock before blocking_notifier_call_chain() has |
101 | * released the rd lock. |
102 | */ |
103 | unregister_ipcns_notifier(ns); |
104 | sem_exit_ns(ns); |
105 | msg_exit_ns(ns); |
106 | shm_exit_ns(ns); |
107 | atomic_dec(&nr_ipc_ns); |
108 | |
109 | /* |
110 | * Do the ipcns removal notification after decrementing nr_ipc_ns in |
111 | * order to have a correct value when recomputing msgmni. |
112 | */ |
113 | ipcns_notify(IPCNS_REMOVED); |
114 | put_user_ns(ns->user_ns); |
115 | kfree(ns); |
116 | } |
117 | |
118 | /* |
119 | * put_ipc_ns - drop a reference to an ipc namespace. |
120 | * @ns: the namespace to put |
121 | * |
122 | * If this is the last task in the namespace exiting, and |
123 | * it is dropping the refcount to 0, then it can race with |
124 | * a task in another ipc namespace but in a mounts namespace |
125 | * which has this ipcns's mqueuefs mounted, doing some action |
126 | * with one of the mqueuefs files. That can raise the refcount. |
127 | * So dropping the refcount, and raising the refcount when |
128 | * accessing it through the VFS, are protected with mq_lock. |
129 | * |
130 | * (Clearly, a task raising the refcount on its own ipc_ns |
131 | * needn't take mq_lock since it can't race with the last task |
132 | * in the ipcns exiting). |
133 | */ |
134 | void put_ipc_ns(struct ipc_namespace *ns) |
135 | { |
136 | if (atomic_dec_and_lock(&ns->count, &mq_lock)) { |
137 | mq_clear_sbinfo(ns); |
138 | spin_unlock(&mq_lock); |
139 | mq_put_mnt(ns); |
140 | free_ipc_ns(ns); |
141 | } |
142 | } |
143 |
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