blob: aead4d69f62b80f0cf648eb8213bc633caf6d8de [file] [log] [blame]
Serge E. Hallyn858d72e2007-10-18 23:39:45 -07001/*
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
11struct ns_cgroup {
12 struct cgroup_subsys_state css;
13 spinlock_t lock;
14};
15
16struct cgroup_subsys ns_subsys;
17
18static inline struct ns_cgroup *cgroup_to_ns(
19 struct cgroup *cgroup)
20{
21 return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
22 struct ns_cgroup, css);
23}
24
25int ns_cgroup_clone(struct task_struct *task)
26{
27 return cgroup_clone(task, &ns_subsys);
28}
29
30/*
31 * Rules:
32 * 1. you can only enter a cgroup which is a child of your current
33 * cgroup
34 * 2. you can only place another process into a cgroup if
35 * a. you have CAP_SYS_ADMIN
36 * b. your cgroup is an ancestor of task's destination cgroup
37 * (hence either you are in the same cgroup as task, or in an
38 * ancestor cgroup thereof)
39 */
40static int ns_can_attach(struct cgroup_subsys *ss,
41 struct cgroup *new_cgroup, struct task_struct *task)
42{
43 struct cgroup *orig;
44
45 if (current != task) {
46 if (!capable(CAP_SYS_ADMIN))
47 return -EPERM;
48
49 if (!cgroup_is_descendant(new_cgroup))
50 return -EPERM;
51 }
52
53 if (atomic_read(&new_cgroup->count) != 0)
54 return -EPERM;
55
56 orig = task_cgroup(task, ns_subsys_id);
57 if (orig && orig != new_cgroup->parent)
58 return -EPERM;
59
60 return 0;
61}
62
63/*
64 * Rules: you can only create a cgroup if
65 * 1. you are capable(CAP_SYS_ADMIN)
66 * 2. the target cgroup is a descendant of your own cgroup
67 */
68static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
69 struct cgroup *cgroup)
70{
71 struct ns_cgroup *ns_cgroup;
72
73 if (!capable(CAP_SYS_ADMIN))
74 return ERR_PTR(-EPERM);
75 if (!cgroup_is_descendant(cgroup))
76 return ERR_PTR(-EPERM);
77
78 ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
79 if (!ns_cgroup)
80 return ERR_PTR(-ENOMEM);
81 spin_lock_init(&ns_cgroup->lock);
82 return &ns_cgroup->css;
83}
84
85static void ns_destroy(struct cgroup_subsys *ss,
86 struct cgroup *cgroup)
87{
88 struct ns_cgroup *ns_cgroup;
89
90 ns_cgroup = cgroup_to_ns(cgroup);
91 kfree(ns_cgroup);
92}
93
94struct cgroup_subsys ns_subsys = {
95 .name = "ns",
96 .can_attach = ns_can_attach,
97 .create = ns_create,
98 .destroy = ns_destroy,
99 .subsys_id = ns_subsys_id,
100};