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
  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, 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  */
  79 static 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
  95 static 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
 104 struct 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 };