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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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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); |