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/slab.h>
  11 #include <linux/nsproxy.h>
  12
  13 struct ns_cgroup {
  14         struct cgroup_subsys_state css;
  15         spinlock_t lock;
  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)
  28 {
  29         return cgroup_clone(task, &ns_subsys);
  30 }
  31
  32 /*
  33  * Rules:
  34  *   1. you can only enter a cgroup which is a child of your current
  35  *     cgroup
  36  *   2. you can only place another process into a cgroup if
  37  *     a. you have CAP_SYS_ADMIN
  38  *     b. your cgroup is an ancestor of task's destination cgroup
  39  *       (hence either you are in the same cgroup as task, or in an
  40  *        ancestor cgroup thereof)
  41  */
  42 static int ns_can_attach(struct cgroup_subsys *ss,
  43                 struct cgroup *new_cgroup, struct task_struct *task)
  44 {
  45         struct cgroup *orig;
  46
  47         if (current != task) {
  48                 if (!capable(CAP_SYS_ADMIN))
  49                         return -EPERM;
  50
  51                 if (!cgroup_is_descendant(new_cgroup))
  52                         return -EPERM;
  53         }
  54
  55         if (atomic_read(&new_cgroup->count) != 0)
  56                 return -EPERM;
  57
  58         orig = task_cgroup(task, ns_subsys_id);
  59         if (orig && orig != new_cgroup->parent)
  60                 return -EPERM;
  61
  62         return 0;
  63 }
  64
  65 /*
  66  * Rules: you can only create a cgroup if
  67  *     1. you are capable(CAP_SYS_ADMIN)
  68  *     2. the target cgroup is a descendant of your own cgroup
  69  */
  70 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
  71                                                 struct cgroup *cgroup)
  72 {
  73         struct ns_cgroup *ns_cgroup;
  74
  75         if (!capable(CAP_SYS_ADMIN))
  76                 return ERR_PTR(-EPERM);
  77         if (!cgroup_is_descendant(cgroup))
  78                 return ERR_PTR(-EPERM);
  79
  80         ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
  81         if (!ns_cgroup)
  82                 return ERR_PTR(-ENOMEM);
  83         spin_lock_init(&ns_cgroup->lock);
  84         return &ns_cgroup->css;
  85 }
  86
  87 static void ns_destroy(struct cgroup_subsys *ss,
  88                         struct cgroup *cgroup)
  89 {
  90         struct ns_cgroup *ns_cgroup;
  91
  92         ns_cgroup = cgroup_to_ns(cgroup);
  93         kfree(ns_cgroup);
  94 }
  95
  96 struct cgroup_subsys ns_subsys = {
  97         .name = "ns",
  98         .can_attach = ns_can_attach,
  99         .create = ns_create,
 100         .destroy  = ns_destroy,
 101         .subsys_id = ns_subsys_id,
 102 };