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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 
create_ipc_ns(struct user_namespace * user_ns,struct ipc_namespace * old_ns)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 
copy_ipcs(unsigned long flags,struct user_namespace * user_ns,struct ipc_namespace * ns)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  */
free_ipcs(struct ipc_namespace * ns,struct ipc_ids * ids,void (* free)(struct ipc_namespace *,struct kern_ipc_perm *))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 
free_ipc_ns(struct ipc_namespace * ns)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  */
put_ipc_ns(struct ipc_namespace * ns)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 
to_ipc_ns(struct ns_common * ns)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 
ipcns_get(struct task_struct * task)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 
ipcns_put(struct ns_common * ns)150 static void ipcns_put(struct ns_common *ns)
151 {
152 	return put_ipc_ns(to_ipc_ns(ns));
153 }
154 
ipcns_install(struct nsproxy * nsproxy,struct ns_common * new)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 };
176