[PATCH 4/7] cgroup: cgroup namespace setns support

serge.hallyn
2015-12-07T23:06:33Z

From: Aditya Kali <adityakali@google.com>

setns on a cgroup namespace is allowed only if
task has CAP_SYS_ADMIN in its current user-namespace and
over the user-namespace associated with target cgroupns.
No implicit cgroup changes happen with attaching to another
cgroupns. It is expected that the somone moves the attaching
process under the target cgroupns-root.

Signed-off-by: Aditya Kali <adityakali@google.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
---
kernel/cgroup.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4fd07b5a..a5ab74d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5907,10 +5907,28 @@ err_out:
return ERR_PTR(err);
}

-static int cgroupns_install(struct nsproxy *nsproxy, void *ns)
+static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
{
- pr_info("setns not supported for cgroup namespace");
- return -EINVAL;
+ return container_of(ns, struct cgroup_namespace, ns);
+}
+
+static int cgroupns_install(struct nsproxy *nsproxy, struct ns_common *ns)
+{
+ struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
+
+ if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) ||
+ !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /* Don't need to do anything if we are attaching to our own cgroupns. */
+ if (cgroup_ns == nsproxy->cgroup_ns)
+ return 0;
+
+ get_cgroup_ns(cgroup_ns);
+ put_cgroup_ns(nsproxy->cgroup_ns);
+ nsproxy->cgroup_ns = cgroup_ns;
+
+ return 0;
}

static struct ns_common *cgroupns_get(struct task_struct *task)
--
1.7.9.5