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.
* task's current cgroup is descendent of the target cgroupns-root
cgroup.
* target cgroupns-root is same as or deeper than task's current
cgroupns-root. This is so that the task cannot escape out of its
cgroupns-root. This also ensures that setns() only makes the task
get restricted to a deeper cgroup hierarchy.
Signed-off-by: Aditya Kali <adityak...@google.com>
---
kernel/cgroup_namespace.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 42 insertions(+), 2 deletions(-)
diff --git a/kernel/cgroup_namespace.c b/kernel/cgroup_namespace.c
index c16604f..c612946 100644
--- a/kernel/cgroup_namespace.c
+++ b/kernel/cgroup_namespace.c
@@ -80,8 +80,48 @@ err_out:
static int cgroupns_install(struct nsproxy *nsproxy, void *ns)
{
- pr_info("setns not supported for cgroup namespace");
- return -EINVAL;
+ struct cgroup_namespace *cgroup_ns = ns;
+ struct task_struct *task = current;
+ struct cgroup *cgrp = NULL;
+ int err = 0;
+
+ if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) ||
+ !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /* Prevent cgroup changes for this task. */
+ threadgroup_lock(task);
+
+ cgrp = get_task_cgroup(task);
+
+ err = -EINVAL;
+ if (!cgroup_on_dfl(cgrp))
+ goto out_unlock;
+
+ /* Allow switch only if the task's current cgroup is descendant of the
+ * target cgroup_ns->root_cgrp.
+ */
+ if (!cgroup_is_descendant(cgrp, cgroup_ns->root_cgrp))
+ goto out_unlock;
+
+ /* Only allow setns to a cgroupns root-ed deeper than task's current
+ * cgroupns-root. This will make sure that tasks cannot escape their
+ * cgroupns by attaching to parent cgroupns.
+ */
+ if (!cgroup_is_descendant(cgroup_ns->root_cgrp,
+ task_cgroupns_root(task)))
+ goto out_unlock;
+
+ err = 0;
+ get_cgroup_ns(cgroup_ns);
+ put_cgroup_ns(nsproxy->cgroup_ns);
+ nsproxy->cgroup_ns = cgroup_ns;
+
+out_unlock:
+ threadgroup_unlock(current);
+ if (cgrp)
+ cgroup_put(cgrp);
+ return err;
}
static void *cgroupns_get(struct task_struct *task)
--
2.1.0.rc2.206.gedb03e5
--
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