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[mirror_ubuntu-zesty-kernel.git] / kernel / ns_cgroup.c
1 /*
2 * ns_cgroup.c - namespace cgroup subsystem
3 *
4 * Copyright 2006, 2007 IBM Corp
5 */
6
7 #include <linux/module.h>
8 #include <linux/cgroup.h>
9 #include <linux/fs.h>
10 #include <linux/proc_fs.h>
11 #include <linux/slab.h>
12 #include <linux/nsproxy.h>
13
14 struct ns_cgroup {
15 struct cgroup_subsys_state css;
16 };
17
18 struct cgroup_subsys ns_subsys;
19
20 static inline struct ns_cgroup *cgroup_to_ns(
21 struct cgroup *cgroup)
22 {
23 return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
24 struct ns_cgroup, css);
25 }
26
27 int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
28 {
29 char name[PROC_NUMBUF];
30
31 snprintf(name, PROC_NUMBUF, "%d", pid_vnr(pid));
32 return cgroup_clone(task, &ns_subsys, name);
33 }
34
35 /*
36 * Rules:
37 * 1. you can only enter a cgroup which is a descendant of your current
38 * cgroup
39 * 2. you can only place another process into a cgroup if
40 * a. you have CAP_SYS_ADMIN
41 * b. your cgroup is an ancestor of task's destination cgroup
42 * (hence either you are in the same cgroup as task, or in an
43 * ancestor cgroup thereof)
44 */
45 static int ns_can_attach(struct cgroup_subsys *ss, struct cgroup *new_cgroup,
46 struct task_struct *task, bool threadgroup)
47 {
48 if (current != task) {
49 if (!capable(CAP_SYS_ADMIN))
50 return -EPERM;
51
52 if (!cgroup_is_descendant(new_cgroup, current))
53 return -EPERM;
54 }
55
56 if (!cgroup_is_descendant(new_cgroup, task))
57 return -EPERM;
58
59 if (threadgroup) {
60 struct task_struct *c;
61 rcu_read_lock();
62 list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
63 if (!cgroup_is_descendant(new_cgroup, c)) {
64 rcu_read_unlock();
65 return -EPERM;
66 }
67 }
68 rcu_read_unlock();
69 }
70
71 return 0;
72 }
73
74 /*
75 * Rules: you can only create a cgroup if
76 * 1. you are capable(CAP_SYS_ADMIN)
77 * 2. the target cgroup is a descendant of your own cgroup
78 */
79 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
80 struct cgroup *cgroup)
81 {
82 struct ns_cgroup *ns_cgroup;
83
84 if (!capable(CAP_SYS_ADMIN))
85 return ERR_PTR(-EPERM);
86 if (!cgroup_is_descendant(cgroup, current))
87 return ERR_PTR(-EPERM);
88
89 ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
90 if (!ns_cgroup)
91 return ERR_PTR(-ENOMEM);
92 return &ns_cgroup->css;
93 }
94
95 static void ns_destroy(struct cgroup_subsys *ss,
96 struct cgroup *cgroup)
97 {
98 struct ns_cgroup *ns_cgroup;
99
100 ns_cgroup = cgroup_to_ns(cgroup);
101 kfree(ns_cgroup);
102 }
103
104 struct cgroup_subsys ns_subsys = {
105 .name = "ns",
106 .can_attach = ns_can_attach,
107 .create = ns_create,
108 .destroy = ns_destroy,
109 .subsys_id = ns_subsys_id,
110 };