linux-hardened/kernel/ns_cgroup.c
Grzegorz Nosek 313e924c08 cgroups: relax ns_can_attach checks to allow attaching to grandchild cgroups
The ns_proxy cgroup allows moving processes to child cgroups only one
level deep at a time.  This commit relaxes this restriction and makes it
possible to attach tasks directly to grandchild cgroups, e.g.:

($pid is in the root cgroup)
echo $pid > /cgroup/CG1/CG2/tasks

Previously this operation would fail with -EPERM and would have to be
performed as two steps:
echo $pid > /cgroup/CG1/tasks
echo $pid > /cgroup/CG1/CG2/tasks

Also, the target cgroup no longer needs to be empty to move a task there.

Signed-off-by: Grzegorz Nosek <root@localdomain.pl>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-02 19:04:53 -07:00

98 lines
2.2 KiB
C

/*
* ns_cgroup.c - namespace cgroup subsystem
*
* Copyright 2006, 2007 IBM Corp
*/
#include <linux/module.h>
#include <linux/cgroup.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/nsproxy.h>
struct ns_cgroup {
struct cgroup_subsys_state css;
};
struct cgroup_subsys ns_subsys;
static inline struct ns_cgroup *cgroup_to_ns(
struct cgroup *cgroup)
{
return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
struct ns_cgroup, css);
}
int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
{
char name[PROC_NUMBUF];
snprintf(name, PROC_NUMBUF, "%d", pid_vnr(pid));
return cgroup_clone(task, &ns_subsys, name);
}
/*
* Rules:
* 1. you can only enter a cgroup which is a descendant of your current
* cgroup
* 2. you can only place another process into a cgroup if
* a. you have CAP_SYS_ADMIN
* b. your cgroup is an ancestor of task's destination cgroup
* (hence either you are in the same cgroup as task, or in an
* ancestor cgroup thereof)
*/
static int ns_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup, struct task_struct *task)
{
if (current != task) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!cgroup_is_descendant(new_cgroup, current))
return -EPERM;
}
if (!cgroup_is_descendant(new_cgroup, task))
return -EPERM;
return 0;
}
/*
* Rules: you can only create a cgroup if
* 1. you are capable(CAP_SYS_ADMIN)
* 2. the target cgroup is a descendant of your own cgroup
*/
static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct ns_cgroup *ns_cgroup;
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
if (!cgroup_is_descendant(cgroup, current))
return ERR_PTR(-EPERM);
ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
if (!ns_cgroup)
return ERR_PTR(-ENOMEM);
return &ns_cgroup->css;
}
static void ns_destroy(struct cgroup_subsys *ss,
struct cgroup *cgroup)
{
struct ns_cgroup *ns_cgroup;
ns_cgroup = cgroup_to_ns(cgroup);
kfree(ns_cgroup);
}
struct cgroup_subsys ns_subsys = {
.name = "ns",
.can_attach = ns_can_attach,
.create = ns_create,
.destroy = ns_destroy,
.subsys_id = ns_subsys_id,
};