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
cgroup_to_ns(struct cgroup * cgroup)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
ns_cgroup_clone(struct task_struct * task,struct pid * pid)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 child 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 */
ns_can_attach(struct cgroup_subsys * ss,struct cgroup * new_cgroup,struct task_struct * task)45 static int ns_can_attach(struct cgroup_subsys *ss,
46 struct cgroup *new_cgroup, struct task_struct *task)
47 {
48 struct cgroup *orig;
49
50 if (current != task) {
51 if (!capable(CAP_SYS_ADMIN))
52 return -EPERM;
53
54 if (!cgroup_is_descendant(new_cgroup))
55 return -EPERM;
56 }
57
58 if (atomic_read(&new_cgroup->count) != 0)
59 return -EPERM;
60
61 orig = task_cgroup(task, ns_subsys_id);
62 if (orig && orig != new_cgroup->parent)
63 return -EPERM;
64
65 return 0;
66 }
67
68 /*
69 * Rules: you can only create a cgroup if
70 * 1. you are capable(CAP_SYS_ADMIN)
71 * 2. the target cgroup is a descendant of your own cgroup
72 */
ns_create(struct cgroup_subsys * ss,struct cgroup * cgroup)73 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
74 struct cgroup *cgroup)
75 {
76 struct ns_cgroup *ns_cgroup;
77
78 if (!capable(CAP_SYS_ADMIN))
79 return ERR_PTR(-EPERM);
80 if (!cgroup_is_descendant(cgroup))
81 return ERR_PTR(-EPERM);
82
83 ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
84 if (!ns_cgroup)
85 return ERR_PTR(-ENOMEM);
86 return &ns_cgroup->css;
87 }
88
ns_destroy(struct cgroup_subsys * ss,struct cgroup * cgroup)89 static void ns_destroy(struct cgroup_subsys *ss,
90 struct cgroup *cgroup)
91 {
92 struct ns_cgroup *ns_cgroup;
93
94 ns_cgroup = cgroup_to_ns(cgroup);
95 kfree(ns_cgroup);
96 }
97
98 struct cgroup_subsys ns_subsys = {
99 .name = "ns",
100 .can_attach = ns_can_attach,
101 .create = ns_create,
102 .destroy = ns_destroy,
103 .subsys_id = ns_subsys_id,
104 };
105