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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 | #include <linux/slab.h> |
17 | |
18 | #define BITS_PER_PAGE (PAGE_SIZE*8) |
19 | |
20 | struct pid_cache { |
21 | int nr_ids; |
22 | char name[16]; |
23 | struct kmem_cache *cachep; |
24 | struct list_head list; |
25 | }; |
26 | |
27 | static LIST_HEAD(pid_caches_lh); |
28 | static DEFINE_MUTEX(pid_caches_mutex); |
29 | static 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 | |
36 | static 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); |
60 | out: |
61 | mutex_unlock(&pid_caches_mutex); |
62 | return pcache->cachep; |
63 | |
64 | err_cachep: |
65 | kfree(pcache); |
66 | err_alloc: |
67 | mutex_unlock(&pid_caches_mutex); |
68 | return NULL; |
69 | } |
70 | |
71 | static 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 | |
101 | out_free_map: |
102 | kfree(ns->pidmap[0].page); |
103 | out_free: |
104 | kmem_cache_free(pid_ns_cachep, ns); |
105 | out: |
106 | return ERR_PTR(-ENOMEM); |
107 | } |
108 | |
109 | static 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 | |
118 | struct 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 | |
127 | void 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 | |
140 | void 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 | |
187 | static __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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