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
  11 struct ns_cgroup {
  12         struct cgroup_subsys_state css;
  13         spinlock_t lock;
  14 };
  15
  16 struct cgroup_subsys ns_subsys;
  17
  18 static inline struct ns_cgroup *cgroup_to_ns(
  19                 struct cgroup *cgroup)
  20 {
  21         return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
  22                             struct ns_cgroup, css);
  23 }
  24
  25 int ns_cgroup_clone(struct task_struct *task)
  26 {
  27         return cgroup_clone(task, &ns_subsys);
  28 }
  29
  30 /*
  31  * Rules:
  32  *   1. you can only enter a cgroup which is a child of your current
  33  *     cgroup
  34  *   2. you can only place another process into a cgroup if
  35  *     a. you have CAP_SYS_ADMIN
  36  *     b. your cgroup is an ancestor of task's destination cgroup
  37  *       (hence either you are in the same cgroup as task, or in an
  38  *        ancestor cgroup thereof)
  39  */
  40 static int ns_can_attach(struct cgroup_subsys *ss,
  41                 struct cgroup *new_cgroup, struct task_struct *task)
  42 {
  43         struct cgroup *orig;
  44
  45         if (current != task) {
  46                 if (!capable(CAP_SYS_ADMIN))
  47                         return -EPERM;
  48
  49                 if (!cgroup_is_descendant(new_cgroup))
  50                         return -EPERM;
  51         }
  52
  53         if (atomic_read(&new_cgroup->count) != 0)
  54                 return -EPERM;
  55
  56         orig = task_cgroup(task, ns_subsys_id);
  57         if (orig && orig != new_cgroup->parent)
  58                 return -EPERM;
  59
  60         return 0;
  61 }
  62
  63 /*
  64  * Rules: you can only create a cgroup if
  65  *     1. you are capable(CAP_SYS_ADMIN)
  66  *     2. the target cgroup is a descendant of your own cgroup
  67  */
  68 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
  69                                                 struct cgroup *cgroup)
  70 {
  71         struct ns_cgroup *ns_cgroup;
  72
  73         if (!capable(CAP_SYS_ADMIN))
  74                 return ERR_PTR(-EPERM);
  75         if (!cgroup_is_descendant(cgroup))
  76                 return ERR_PTR(-EPERM);
  77
  78         ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
  79         if (!ns_cgroup)
  80                 return ERR_PTR(-ENOMEM);
  81         spin_lock_init(&ns_cgroup->lock);
  82         return &ns_cgroup->css;
  83 }
  84
  85 static void ns_destroy(struct cgroup_subsys *ss,
  86                         struct cgroup *cgroup)
  87 {
  88         struct ns_cgroup *ns_cgroup;
  89
  90         ns_cgroup = cgroup_to_ns(cgroup);
  91         kfree(ns_cgroup);
  92 }
  93
  94 struct cgroup_subsys ns_subsys = {
  95         .name = "ns",
  96         .can_attach = ns_can_attach,
  97         .create = ns_create,
  98         .destroy  = ns_destroy,
  99         .subsys_id = ns_subsys_id,
 100 };