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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_ns.h> | |
16 | ||
17 | #include "util.h" | |
18 | ||
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 = ns_alloc_inum(&ns->ns); | |
30 | if (err) { | |
31 | kfree(ns); | |
32 | return ERR_PTR(err); | |
33 | } | |
34 | ns->ns.ops = &ipcns_operations; | |
35 | ||
36 | atomic_set(&ns->count, 1); | |
37 | err = mq_init_ns(ns); | |
38 | if (err) { | |
39 | ns_free_inum(&ns->ns); | |
40 | kfree(ns); | |
41 | return ERR_PTR(err); | |
42 | } | |
43 | atomic_inc(&nr_ipc_ns); | |
44 | ||
45 | sem_init_ns(ns); | |
46 | msg_init_ns(ns); | |
47 | shm_init_ns(ns); | |
48 | ||
49 | ns->user_ns = get_user_ns(user_ns); | |
50 | ||
51 | return ns; | |
52 | } | |
53 | ||
54 | struct ipc_namespace *copy_ipcs(unsigned long flags, | |
55 | struct user_namespace *user_ns, struct ipc_namespace *ns) | |
56 | { | |
57 | if (!(flags & CLONE_NEWIPC)) | |
58 | return get_ipc_ns(ns); | |
59 | return create_ipc_ns(user_ns, ns); | |
60 | } | |
61 | ||
62 | /* | |
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 | |
67 | * | |
68 | * Called for each kind of ipc when an ipc_namespace exits. | |
69 | */ | |
70 | void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, | |
71 | void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) | |
72 | { | |
73 | struct kern_ipc_perm *perm; | |
74 | int next_id; | |
75 | int total, in_use; | |
76 | ||
77 | down_write(&ids->rwsem); | |
78 | ||
79 | in_use = ids->in_use; | |
80 | ||
81 | for (total = 0, next_id = 0; total < in_use; next_id++) { | |
82 | perm = idr_find(&ids->ipcs_idr, next_id); | |
83 | if (perm == NULL) | |
84 | continue; | |
85 | rcu_read_lock(); | |
86 | ipc_lock_object(perm); | |
87 | free(ns, perm); | |
88 | total++; | |
89 | } | |
90 | up_write(&ids->rwsem); | |
91 | } | |
92 | ||
93 | static void free_ipc_ns(struct ipc_namespace *ns) | |
94 | { | |
95 | sem_exit_ns(ns); | |
96 | msg_exit_ns(ns); | |
97 | shm_exit_ns(ns); | |
98 | atomic_dec(&nr_ipc_ns); | |
99 | ||
100 | put_user_ns(ns->user_ns); | |
101 | ns_free_inum(&ns->ns); | |
102 | kfree(ns); | |
103 | } | |
104 | ||
105 | /* | |
106 | * put_ipc_ns - drop a reference to an ipc namespace. | |
107 | * @ns: the namespace to put | |
108 | * | |
109 | * If this is the last task in the namespace exiting, and | |
110 | * it is dropping the refcount to 0, then it can race with | |
111 | * a task in another ipc namespace but in a mounts namespace | |
112 | * which has this ipcns's mqueuefs mounted, doing some action | |
113 | * with one of the mqueuefs files. That can raise the refcount. | |
114 | * So dropping the refcount, and raising the refcount when | |
115 | * accessing it through the VFS, are protected with mq_lock. | |
116 | * | |
117 | * (Clearly, a task raising the refcount on its own ipc_ns | |
118 | * needn't take mq_lock since it can't race with the last task | |
119 | * in the ipcns exiting). | |
120 | */ | |
121 | void put_ipc_ns(struct ipc_namespace *ns) | |
122 | { | |
123 | if (atomic_dec_and_lock(&ns->count, &mq_lock)) { | |
124 | mq_clear_sbinfo(ns); | |
125 | spin_unlock(&mq_lock); | |
126 | mq_put_mnt(ns); | |
127 | free_ipc_ns(ns); | |
128 | } | |
129 | } | |
130 | ||
131 | static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) | |
132 | { | |
133 | return container_of(ns, struct ipc_namespace, ns); | |
134 | } | |
135 | ||
136 | static struct ns_common *ipcns_get(struct task_struct *task) | |
137 | { | |
138 | struct ipc_namespace *ns = NULL; | |
139 | struct nsproxy *nsproxy; | |
140 | ||
141 | task_lock(task); | |
142 | nsproxy = task->nsproxy; | |
143 | if (nsproxy) | |
144 | ns = get_ipc_ns(nsproxy->ipc_ns); | |
145 | task_unlock(task); | |
146 | ||
147 | return ns ? &ns->ns : NULL; | |
148 | } | |
149 | ||
150 | static void ipcns_put(struct ns_common *ns) | |
151 | { | |
152 | return put_ipc_ns(to_ipc_ns(ns)); | |
153 | } | |
154 | ||
155 | static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new) | |
156 | { | |
157 | struct ipc_namespace *ns = to_ipc_ns(new); | |
158 | if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || | |
159 | !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) | |
160 | return -EPERM; | |
161 | ||
162 | /* Ditch state from the old ipc namespace */ | |
163 | exit_sem(current); | |
164 | put_ipc_ns(nsproxy->ipc_ns); | |
165 | nsproxy->ipc_ns = get_ipc_ns(ns); | |
166 | return 0; | |
167 | } | |
168 | ||
169 | const struct proc_ns_operations ipcns_operations = { | |
170 | .name = "ipc", | |
171 | .type = CLONE_NEWIPC, | |
172 | .get = ipcns_get, | |
173 | .put = ipcns_put, | |
174 | .install = ipcns_install, | |
175 | }; |