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 child 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,
  46                 struct cgroup *new_cgroup, struct task_struct *task)
  47 {
  48         struct cgroup *orig;
  49
  50         if (current != task) {
  51                 if (!capable(CAP_SYS_ADMIN))
  52                         return -EPERM;
  53
  54                 if (!cgroup_is_descendant(new_cgroup))
  55                         return -EPERM;
  56         }
  57
  58         if (atomic_read(&new_cgroup->count) != 0)
  59                 return -EPERM;
  60
  61         orig = task_cgroup(task, ns_subsys_id);
  62         if (orig && orig != new_cgroup->parent)
  63                 return -EPERM;
  64
  65         return 0;
  66 }
  67
  68 /*
  69  * Rules: you can only create a cgroup if
  70  *     1. you are capable(CAP_SYS_ADMIN)
  71  *     2. the target cgroup is a descendant of your own cgroup
  72  */
  73 static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
  74                                                 struct cgroup *cgroup)
  75 {
  76         struct ns_cgroup *ns_cgroup;
  77
  78         if (!capable(CAP_SYS_ADMIN))
  79                 return ERR_PTR(-EPERM);
  80         if (!cgroup_is_descendant(cgroup))
  81                 return ERR_PTR(-EPERM);
  82
  83         ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
  84         if (!ns_cgroup)
  85                 return ERR_PTR(-ENOMEM);
  86         return &ns_cgroup->css;
  87 }
  88
  89 static void ns_destroy(struct cgroup_subsys *ss,
  90                         struct cgroup *cgroup)
  91 {
  92         struct ns_cgroup *ns_cgroup;
  93
  94         ns_cgroup = cgroup_to_ns(cgroup);
  95         kfree(ns_cgroup);
  96 }
  97
  98 struct cgroup_subsys ns_subsys = {
  99         .name = "ns",
 100         .can_attach = ns_can_attach,
 101         .create = ns_create,
 102         .destroy  = ns_destroy,
 103         .subsys_id = ns_subsys_id,
 104 };