releases/3.10.38/pid_namespace-pidns_get-should-check-task_active_pid_ns-null.patch

From d23082257d83e4bc89727d5aedee197e907999d2 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 2 Apr 2014 17:45:05 +0200
Subject: pid_namespace: pidns_get() should check task_active_pid_ns() != NULL

From: Oleg Nesterov <oleg@redhat.com>

commit d23082257d83e4bc89727d5aedee197e907999d2 upstream.

pidns_get()->get_pid_ns() can hit ns == NULL. This task_struct can't
go away, but task_active_pid_ns(task) is NULL if release_task(task)
was already called. Alternatively we could change get_pid_ns(ns) to
check ns != NULL, but it seems that other callers are fine.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman ebiederm@xmission.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/pid_namespace.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -312,7 +312,9 @@ static void *pidns_get(struct task_struc
 	struct pid_namespace *ns;
 
 	rcu_read_lock();
-	ns = get_pid_ns(task_active_pid_ns(task));
+	ns = task_active_pid_ns(task);
+	if (ns)
+		get_pid_ns(ns);
 	rcu_read_unlock();
 
 	return ns;