Root/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
14struct ns_cgroup {
15    struct cgroup_subsys_state css;
16};
17
18struct cgroup_subsys ns_subsys;
19
20static 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
27int 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 */
45static 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 */
79static 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
95static 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
104struct 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};
111

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