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