Root/kernel/pid_namespace.c

1/*
2 * Pid namespaces
3 *
4 * Authors:
5 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
6 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
7 * Many thanks to Oleg Nesterov for comments and help
8 *
9 */
10
11#include <linux/pid.h>
12#include <linux/pid_namespace.h>
13#include <linux/syscalls.h>
14#include <linux/err.h>
15#include <linux/acct.h>
16#include <linux/slab.h>
17
18#define BITS_PER_PAGE (PAGE_SIZE*8)
19
20struct pid_cache {
21    int nr_ids;
22    char name[16];
23    struct kmem_cache *cachep;
24    struct list_head list;
25};
26
27static LIST_HEAD(pid_caches_lh);
28static DEFINE_MUTEX(pid_caches_mutex);
29static struct kmem_cache *pid_ns_cachep;
30
31/*
32 * creates the kmem cache to allocate pids from.
33 * @nr_ids: the number of numerical ids this pid will have to carry
34 */
35
36static struct kmem_cache *create_pid_cachep(int nr_ids)
37{
38    struct pid_cache *pcache;
39    struct kmem_cache *cachep;
40
41    mutex_lock(&pid_caches_mutex);
42    list_for_each_entry(pcache, &pid_caches_lh, list)
43        if (pcache->nr_ids == nr_ids)
44            goto out;
45
46    pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
47    if (pcache == NULL)
48        goto err_alloc;
49
50    snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
51    cachep = kmem_cache_create(pcache->name,
52            sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
53            0, SLAB_HWCACHE_ALIGN, NULL);
54    if (cachep == NULL)
55        goto err_cachep;
56
57    pcache->nr_ids = nr_ids;
58    pcache->cachep = cachep;
59    list_add(&pcache->list, &pid_caches_lh);
60out:
61    mutex_unlock(&pid_caches_mutex);
62    return pcache->cachep;
63
64err_cachep:
65    kfree(pcache);
66err_alloc:
67    mutex_unlock(&pid_caches_mutex);
68    return NULL;
69}
70
71static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
72{
73    struct pid_namespace *ns;
74    unsigned int level = parent_pid_ns->level + 1;
75    int i;
76
77    ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
78    if (ns == NULL)
79        goto out;
80
81    ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
82    if (!ns->pidmap[0].page)
83        goto out_free;
84
85    ns->pid_cachep = create_pid_cachep(level + 1);
86    if (ns->pid_cachep == NULL)
87        goto out_free_map;
88
89    kref_init(&ns->kref);
90    ns->level = level;
91    ns->parent = get_pid_ns(parent_pid_ns);
92
93    set_bit(0, ns->pidmap[0].page);
94    atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
95
96    for (i = 1; i < PIDMAP_ENTRIES; i++)
97        atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
98
99    return ns;
100
101out_free_map:
102    kfree(ns->pidmap[0].page);
103out_free:
104    kmem_cache_free(pid_ns_cachep, ns);
105out:
106    return ERR_PTR(-ENOMEM);
107}
108
109static void destroy_pid_namespace(struct pid_namespace *ns)
110{
111    int i;
112
113    for (i = 0; i < PIDMAP_ENTRIES; i++)
114        kfree(ns->pidmap[i].page);
115    kmem_cache_free(pid_ns_cachep, ns);
116}
117
118struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
119{
120    if (!(flags & CLONE_NEWPID))
121        return get_pid_ns(old_ns);
122    if (flags & (CLONE_THREAD|CLONE_PARENT))
123        return ERR_PTR(-EINVAL);
124    return create_pid_namespace(old_ns);
125}
126
127void free_pid_ns(struct kref *kref)
128{
129    struct pid_namespace *ns, *parent;
130
131    ns = container_of(kref, struct pid_namespace, kref);
132
133    parent = ns->parent;
134    destroy_pid_namespace(ns);
135
136    if (parent != NULL)
137        put_pid_ns(parent);
138}
139
140void zap_pid_ns_processes(struct pid_namespace *pid_ns)
141{
142    int nr;
143    int rc;
144    struct task_struct *task;
145
146    /*
147     * The last thread in the cgroup-init thread group is terminating.
148     * Find remaining pid_ts in the namespace, signal and wait for them
149     * to exit.
150     *
151     * Note: This signals each threads in the namespace - even those that
152     * belong to the same thread group, To avoid this, we would have
153     * to walk the entire tasklist looking a processes in this
154     * namespace, but that could be unnecessarily expensive if the
155     * pid namespace has just a few processes. Or we need to
156     * maintain a tasklist for each pid namespace.
157     *
158     */
159    read_lock(&tasklist_lock);
160    nr = next_pidmap(pid_ns, 1);
161    while (nr > 0) {
162        rcu_read_lock();
163
164        /*
165         * Any nested-container's init processes won't ignore the
166         * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
167         */
168        task = pid_task(find_vpid(nr), PIDTYPE_PID);
169        if (task)
170            send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);
171
172        rcu_read_unlock();
173
174        nr = next_pidmap(pid_ns, nr);
175    }
176    read_unlock(&tasklist_lock);
177
178    do {
179        clear_thread_flag(TIF_SIGPENDING);
180        rc = sys_wait4(-1, NULL, __WALL, NULL);
181    } while (rc != -ECHILD);
182
183    acct_exit_ns(pid_ns);
184    return;
185}
186
187static __init int pid_namespaces_init(void)
188{
189    pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
190    return 0;
191}
192
193__initcall(pid_namespaces_init);
194

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