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