nsfs: add ioctl to get a parent namespace

[mirror_ubuntu-zesty-kernel.git] / kernel / pid_namespace.c

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index c02d744225e1989d1bdbcac1b88e1537d203e34b..4fa2d56a936cfd76d9322e2c98dd253f28702839 100644 (file)
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -388,6 +388,24 @@ static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
        return 0;
 }
 
+static struct ns_common *pidns_get_parent(struct ns_common *ns)
+{
+       struct pid_namespace *active = task_active_pid_ns(current);
+       struct pid_namespace *pid_ns, *p;
+
+       /* See if the parent is in the current namespace */
+       pid_ns = p = to_pid_ns(ns)->parent;
+       for (;;) {
+               if (!p)
+                       return ERR_PTR(-EPERM);
+               if (p == active)
+                       break;
+               p = p->parent;
+       }
+
+       return &get_pid_ns(pid_ns)->ns;
+}
+
 static struct user_namespace *pidns_owner(struct ns_common *ns)
 {
        return to_pid_ns(ns)->user_ns;
@@ -400,6 +418,7 @@ const struct proc_ns_operations pidns_operations = {
        .put            = pidns_put,
        .install        = pidns_install,
        .owner          = pidns_owner,
+       .get_parent     = pidns_get_parent,
 };
 
 static __init int pid_namespaces_init(void)