ns proc: Add support for the uts namespace

Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

fs/proc/namespaces.c

@@ -19,6 +19,9 @@ static const struct proc_ns_operations *ns_entries[] = {
 #ifdef CONFIG_NET_NS
 	&netns_operations,
 #endif
+#ifdef CONFIG_UTS_NS
+	&utsns_operations,
+#endif
 };
 
 static const struct file_operations ns_file_operations = {

include/linux/proc_fs.h

@@ -266,6 +266,7 @@ struct proc_ns_operations {
 	int (*install)(struct nsproxy *nsproxy, void *ns);
 };
 extern const struct proc_ns_operations netns_operations;
+extern const struct proc_ns_operations utsns_operations;
 
 union proc_op {
 	int (*proc_get_link)(struct inode *, struct path *);

kernel/utsname.c

@@ -15,6 +15,7 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/user_namespace.h>
+#include <linux/proc_fs.h>
 
 static struct uts_namespace *create_uts_ns(void)
 {
@@ -79,3 +80,41 @@ void free_uts_ns(struct kref *kref)
 	put_user_ns(ns->user_ns);
 	kfree(ns);
 }
+
+static void *utsns_get(struct task_struct *task)
+{
+	struct uts_namespace *ns = NULL;
+	struct nsproxy *nsproxy;
+
+	rcu_read_lock();
+	nsproxy = task_nsproxy(task);
+	if (nsproxy) {
+		ns = nsproxy->uts_ns;
+		get_uts_ns(ns);
+	}
+	rcu_read_unlock();
+
+	return ns;
+}
+
+static void utsns_put(void *ns)
+{
+	put_uts_ns(ns);
+}
+
+static int utsns_install(struct nsproxy *nsproxy, void *ns)
+{
+	get_uts_ns(ns);
+	put_uts_ns(nsproxy->uts_ns);
+	nsproxy->uts_ns = ns;
+	return 0;
+}
+
+const struct proc_ns_operations utsns_operations = {
+	.name		= "uts",
+	.type		= CLONE_NEWUTS,
+	.get		= utsns_get,
+	.put		= utsns_put,
+	.install	= utsns_install,
+};
+