Root/ipc/namespace.c

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
19static 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
61struct 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 */
77void 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->rwsem);
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        rcu_read_lock();
93        ipc_lock_object(perm);
94        free(ns, perm);
95        total++;
96    }
97    up_write(&ids->rwsem);
98}
99
100static void free_ipc_ns(struct ipc_namespace *ns)
101{
102    /*
103     * Unregistering the hotplug notifier at the beginning guarantees
104     * that the ipc namespace won't be freed while we are inside the
105     * callback routine. Since the blocking_notifier_chain_XXX routines
106     * hold a rw lock on the notifier list, unregister_ipcns_notifier()
107     * won't take the rw lock before blocking_notifier_call_chain() has
108     * released the rd lock.
109     */
110    unregister_ipcns_notifier(ns);
111    sem_exit_ns(ns);
112    msg_exit_ns(ns);
113    shm_exit_ns(ns);
114    atomic_dec(&nr_ipc_ns);
115
116    /*
117     * Do the ipcns removal notification after decrementing nr_ipc_ns in
118     * order to have a correct value when recomputing msgmni.
119     */
120    ipcns_notify(IPCNS_REMOVED);
121    put_user_ns(ns->user_ns);
122    proc_free_inum(ns->proc_inum);
123    kfree(ns);
124}
125
126/*
127 * put_ipc_ns - drop a reference to an ipc namespace.
128 * @ns: the namespace to put
129 *
130 * If this is the last task in the namespace exiting, and
131 * it is dropping the refcount to 0, then it can race with
132 * a task in another ipc namespace but in a mounts namespace
133 * which has this ipcns's mqueuefs mounted, doing some action
134 * with one of the mqueuefs files. That can raise the refcount.
135 * So dropping the refcount, and raising the refcount when
136 * accessing it through the VFS, are protected with mq_lock.
137 *
138 * (Clearly, a task raising the refcount on its own ipc_ns
139 * needn't take mq_lock since it can't race with the last task
140 * in the ipcns exiting).
141 */
142void put_ipc_ns(struct ipc_namespace *ns)
143{
144    if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
145        mq_clear_sbinfo(ns);
146        spin_unlock(&mq_lock);
147        mq_put_mnt(ns);
148        free_ipc_ns(ns);
149    }
150}
151
152static void *ipcns_get(struct task_struct *task)
153{
154    struct ipc_namespace *ns = NULL;
155    struct nsproxy *nsproxy;
156
157    rcu_read_lock();
158    nsproxy = task_nsproxy(task);
159    if (nsproxy)
160        ns = get_ipc_ns(nsproxy->ipc_ns);
161    rcu_read_unlock();
162
163    return ns;
164}
165
166static void ipcns_put(void *ns)
167{
168    return put_ipc_ns(ns);
169}
170
171static int ipcns_install(struct nsproxy *nsproxy, void *new)
172{
173    struct ipc_namespace *ns = new;
174    if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
175        !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
176        return -EPERM;
177
178    /* Ditch state from the old ipc namespace */
179    exit_sem(current);
180    put_ipc_ns(nsproxy->ipc_ns);
181    nsproxy->ipc_ns = get_ipc_ns(ns);
182    return 0;
183}
184
185static unsigned int ipcns_inum(void *vp)
186{
187    struct ipc_namespace *ns = vp;
188
189    return ns->proc_inum;
190}
191
192const struct proc_ns_operations ipcns_operations = {
193    .name = "ipc",
194    .type = CLONE_NEWIPC,
195    .get = ipcns_get,
196    .put = ipcns_put,
197    .install = ipcns_install,
198    .inum = ipcns_inum,
199};
200

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