time/namespace: Fix time_for_children symlink

Looking at the contents of the /proc/PID/ns/time_for_children symlink shows
an anomaly:

$ ls -l /proc/self/ns/* |awk '{print $9, $10, $11}'
...
/proc/self/ns/pid -> pid:[4026531836]
/proc/self/ns/pid_for_children -> pid:[4026531836]
/proc/self/ns/time -> time:[4026531834]
/proc/self/ns/time_for_children -> time_for_children:[4026531834]
/proc/self/ns/user -> user:[4026531837]
...

The reference for 'time_for_children' should be a 'time' namespace, just as
the reference for 'pid_for_children' is a 'pid' namespace.  In other words,
the above time_for_children link should read:

/proc/self/ns/time_for_children -> time:[4026531834]

Fixes: 769071a ("ns: Introduce Time Namespace")
Signed-off-by: Michael Kerrisk <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Dmitry Safonov <[email protected]>
Acked-by: Christian Brauner <[email protected]>
Acked-by: Andrei Vagin <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

Author: mkerrisk

kernel/time/namespace.c

@@ -447,6 +447,7 @@ const struct proc_ns_operations timens_operations = {
 
 const struct proc_ns_operations timens_for_children_operations = {
 	.name		= "time_for_children",
+	.real_ns_name	= "time",
 	.type		= CLONE_NEWTIME,
 	.get		= timens_for_children_get,
 	.put		= timens_put,