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         spinlock_t lock;
  17 };
  18
  19 struct cgroup_subsys ns_subsys;
  20
  21 static inline struct ns_cgroup *cgroup_to_ns(
  22                 struct cgroup *cgroup)
  23 {
  24         return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
  25                             struct ns_cgroup, css);
  26 }
  27
  28 int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
  29 {
  30         char name[PROC_NUMBUF];
  31
  32         snprintf(name, PROC_NUMBUF, "%d", pid_vnr(pid));
  33         return cgroup_clone(task, &ns_subsys, name);
  34 }
  35
  36 /*
  37  * Rules:
  38  *   1. you can only enter a cgroup which is a child of your current
  39  *     cgroup
  40  *   2. you can only place another process into a cgroup if
  41  *     a. you have CAP_SYS_ADMIN
  42  *     b. your cgroup is an ancestor of task's destination cgroup
  43  *       (hence either you are in the same cgroup as task, or in an
  44  *        ancestor cgroup thereof)
  45  */
  46 static int ns_can_attach(struct cgroup_subsys *ss,
  47                 struct cgroup *new_cgroup, struct task_struct *task)
  48 {
  49         struct cgroup *orig;
  50
  51         if (current != task) {
  52                 if (!capable(CAP_SYS_ADMIN))
  53                         return -EPERM;
  54
  55                 if (!cgroup_is_descendant(new_cgroup))
  56                         return -EPERM;
  57         }
  58
  59         if (atomic_read(&new_cgroup->count) != 0)
  60                 return -EPERM;
  61
  62         orig = task_cgroup(task, ns_subsys_id);
  63         if (orig && orig != new_cgroup->parent)
  64                 return -EPERM;
  65
  66         return 0;
  67 }
  68
  69 /*
  70  * Rules: you can only create a cgroup if
  71  *     1. you are capable(CAP_SYS_ADMIN)
  72  *     2. the target cgroup is a descendant of your own cgroup
  73  */
  74 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
  75                                                 struct cgroup *cgroup)
  76 {
  77         struct ns_cgroup *ns_cgroup;
  78
  79         if (!capable(CAP_SYS_ADMIN))
  80                 return ERR_PTR(-EPERM);
  81         if (!cgroup_is_descendant(cgroup))
  82                 return ERR_PTR(-EPERM);
  83
  84         ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
  85         if (!ns_cgroup)
  86                 return ERR_PTR(-ENOMEM);
  87         spin_lock_init(&ns_cgroup->lock);
  88         return &ns_cgroup->css;
  89 }
  90
  91 static void ns_destroy(struct cgroup_subsys *ss,
  92                         struct cgroup *cgroup)
  93 {
  94         struct ns_cgroup *ns_cgroup;
  95
  96         ns_cgroup = cgroup_to_ns(cgroup);
  97         kfree(ns_cgroup);
  98 }
  99
 100 struct cgroup_subsys ns_subsys = {
 101         .name = "ns",
 102         .can_attach = ns_can_attach,
 103         .create = ns_create,
 104         .destroy  = ns_destroy,
 105         .subsys_id = ns_subsys_id,
 106 };