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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 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 | |
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 | */ |
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 | |
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 | */ |
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 | |
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 | |
165 | static void ipcns_put(void *ns) |
166 | { |
167 | return put_ipc_ns(ns); |
168 | } |
169 | |
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 | |
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 |
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