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
17 #define BITS_PER_PAGE (PAGE_SIZE*8)
18
19 struct pid_cache {
20 int nr_ids;
21 char name[16];
22 struct kmem_cache *cachep;
23 struct list_head list;
24 };
25
26 static LIST_HEAD(pid_caches_lh);
27 static DEFINE_MUTEX(pid_caches_mutex);
28 static struct kmem_cache *pid_ns_cachep;
29
30 /*
31 * creates the kmem cache to allocate pids from.
32 * @nr_ids: the number of numerical ids this pid will have to carry
33 */
34
create_pid_cachep(int nr_ids)35 static struct kmem_cache *create_pid_cachep(int nr_ids)
36 {
37 struct pid_cache *pcache;
38 struct kmem_cache *cachep;
39
40 mutex_lock(&pid_caches_mutex);
41 list_for_each_entry(pcache, &pid_caches_lh, list)
42 if (pcache->nr_ids == nr_ids)
43 goto out;
44
45 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
46 if (pcache == NULL)
47 goto err_alloc;
48
49 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
50 cachep = kmem_cache_create(pcache->name,
51 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
52 0, SLAB_HWCACHE_ALIGN, NULL);
53 if (cachep == NULL)
54 goto err_cachep;
55
56 pcache->nr_ids = nr_ids;
57 pcache->cachep = cachep;
58 list_add(&pcache->list, &pid_caches_lh);
59 out:
60 mutex_unlock(&pid_caches_mutex);
61 return pcache->cachep;
62
63 err_cachep:
64 kfree(pcache);
65 err_alloc:
66 mutex_unlock(&pid_caches_mutex);
67 return NULL;
68 }
69
create_pid_namespace(unsigned int level)70 static struct pid_namespace *create_pid_namespace(unsigned int level)
71 {
72 struct pid_namespace *ns;
73 int i;
74
75 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
76 if (ns == NULL)
77 goto out;
78
79 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
80 if (!ns->pidmap[0].page)
81 goto out_free;
82
83 ns->pid_cachep = create_pid_cachep(level + 1);
84 if (ns->pid_cachep == NULL)
85 goto out_free_map;
86
87 kref_init(&ns->kref);
88 ns->level = level;
89
90 set_bit(0, ns->pidmap[0].page);
91 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
92
93 for (i = 1; i < PIDMAP_ENTRIES; i++)
94 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
95
96 return ns;
97
98 out_free_map:
99 kfree(ns->pidmap[0].page);
100 out_free:
101 kmem_cache_free(pid_ns_cachep, ns);
102 out:
103 return ERR_PTR(-ENOMEM);
104 }
105
destroy_pid_namespace(struct pid_namespace * ns)106 static void destroy_pid_namespace(struct pid_namespace *ns)
107 {
108 int i;
109
110 for (i = 0; i < PIDMAP_ENTRIES; i++)
111 kfree(ns->pidmap[i].page);
112 kmem_cache_free(pid_ns_cachep, ns);
113 }
114
copy_pid_ns(unsigned long flags,struct pid_namespace * old_ns)115 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
116 {
117 struct pid_namespace *new_ns;
118
119 BUG_ON(!old_ns);
120 new_ns = get_pid_ns(old_ns);
121 if (!(flags & CLONE_NEWPID))
122 goto out;
123
124 new_ns = ERR_PTR(-EINVAL);
125 if (flags & CLONE_THREAD)
126 goto out_put;
127
128 new_ns = create_pid_namespace(old_ns->level + 1);
129 if (!IS_ERR(new_ns))
130 new_ns->parent = get_pid_ns(old_ns);
131
132 out_put:
133 put_pid_ns(old_ns);
134 out:
135 return new_ns;
136 }
137
free_pid_ns(struct kref * kref)138 void free_pid_ns(struct kref *kref)
139 {
140 struct pid_namespace *ns, *parent;
141
142 ns = container_of(kref, struct pid_namespace, kref);
143
144 parent = ns->parent;
145 destroy_pid_namespace(ns);
146
147 if (parent != NULL)
148 put_pid_ns(parent);
149 }
150
zap_pid_ns_processes(struct pid_namespace * pid_ns)151 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
152 {
153 int nr;
154 int rc;
155
156 /*
157 * The last thread in the cgroup-init thread group is terminating.
158 * Find remaining pid_ts in the namespace, signal and wait for them
159 * to exit.
160 *
161 * Note: This signals each threads in the namespace - even those that
162 * belong to the same thread group, To avoid this, we would have
163 * to walk the entire tasklist looking a processes in this
164 * namespace, but that could be unnecessarily expensive if the
165 * pid namespace has just a few processes. Or we need to
166 * maintain a tasklist for each pid namespace.
167 *
168 */
169 read_lock(&tasklist_lock);
170 nr = next_pidmap(pid_ns, 1);
171 while (nr > 0) {
172 kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
173 nr = next_pidmap(pid_ns, nr);
174 }
175 read_unlock(&tasklist_lock);
176
177 do {
178 clear_thread_flag(TIF_SIGPENDING);
179 rc = sys_wait4(-1, NULL, __WALL, NULL);
180 } while (rc != -ECHILD);
181
182 acct_exit_ns(pid_ns);
183 return;
184 }
185
pid_namespaces_init(void)186 static __init int pid_namespaces_init(void)
187 {
188 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
189 return 0;
190 }
191
192 __initcall(pid_namespaces_init);
193