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_fs.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->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
99static 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 */
141void 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
151static 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
165static void ipcns_put(void *ns)
166{
167    return put_ipc_ns(ns);
168}
169
170static 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
184static unsigned int ipcns_inum(void *vp)
185{
186    struct ipc_namespace *ns = vp;
187
188    return ns->proc_inum;
189}
190
191const 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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