From: Andrey Vagin <avagin@openvz.org>
Date: Tue, 6 Sep 2016 07:47:15 +0000 (-0700)
Subject: nsfs: add ioctl to get a parent namespace
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a7306ed8d94af729ecef8b6e37506a1c6fc14788;p=linux-beck.git

nsfs: add ioctl to get a parent namespace

Pid and user namepaces are hierarchical. There is no way to discover
parent-child relationships.

In a future we will use this interface to dump and restore nested
namespaces.

Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Andrei Vagin <avagin@openvz.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---

diff --git a/fs/nsfs.c b/fs/nsfs.c
index 3887da470f7e..fb7b397a1297 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -171,6 +171,10 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 	switch (ioctl) {
 	case NS_GET_USERNS:
 		return open_related_ns(ns, ns_get_owner);
+	case NS_GET_PARENT:
+		if (!ns->ops->get_parent)
+			return -EINVAL;
+		return open_related_ns(ns, ns->ops->get_parent);
 	default:
 		return -ENOTTY;
 	}
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index ca85a4348ffc..12cb8bd81d2d 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -19,6 +19,7 @@ struct proc_ns_operations {
 	void (*put)(struct ns_common *ns);
 	int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);
 	struct user_namespace *(*owner)(struct ns_common *ns);
+	struct ns_common *(*get_parent)(struct ns_common *ns);
 };
 
 extern const struct proc_ns_operations netns_operations;
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
index 5cacd5c1b5d7..3af617230d1b 100644
--- a/include/uapi/linux/nsfs.h
+++ b/include/uapi/linux/nsfs.h
@@ -7,5 +7,7 @@
 
 /* Returns a file descriptor that refers to an owning user namespace */
 #define NS_GET_USERNS	_IO(NSIO, 0x1)
+/* Returns a file descriptor that refers to a parent namespace */
+#define NS_GET_PARENT	_IO(NSIO, 0x2)
 
 #endif /* __LINUX_NSFS_H */
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index c02d744225e1..4fa2d56a936c 100644
--- 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)
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 0ef683a03c20..a58a219b99c6 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -1034,6 +1034,7 @@ const struct proc_ns_operations userns_operations = {
 	.put		= userns_put,
 	.install	= userns_install,
 	.owner		= userns_owner,
+	.get_parent	= ns_get_owner,
 };
 
 static __init int user_namespaces_init(void)