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,
46 struct cgroup *new_cgroup, struct task_struct *task)
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 return 0;
60 }
61
62 /*
63 * Rules: you can only create a cgroup if
64 * 1. you are capable(CAP_SYS_ADMIN)
65 * 2. the target cgroup is a descendant of your own cgroup
66 */
67 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
68 struct cgroup *cgroup)
69 {
70 struct ns_cgroup *ns_cgroup;
71
72 if (!capable(CAP_SYS_ADMIN))
73 return ERR_PTR(-EPERM);
74 if (!cgroup_is_descendant(cgroup, current))
75 return ERR_PTR(-EPERM);
76
77 ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
78 if (!ns_cgroup)
79 return ERR_PTR(-ENOMEM);
80 return &ns_cgroup->css;
81 }
82
83 static void ns_destroy(struct cgroup_subsys *ss,
84 struct cgroup *cgroup)
85 {
86 struct ns_cgroup *ns_cgroup;
87
88 ns_cgroup = cgroup_to_ns(cgroup);
89 kfree(ns_cgroup);
90 }
91
92 struct cgroup_subsys ns_subsys = {
93 .name = "ns",
94 .can_attach = ns_can_attach,
95 .create = ns_create,
96 .destroy = ns_destroy,
97 .subsys_id = ns_subsys_id,
98 };
99
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