From: Oleg Nesterov <oleg@redhat.com>
Date: Wed, 2 Apr 2014 15:45:05 +0000 (+0200)
Subject: pid_namespace: pidns_get() should check task_active_pid_ns() != NULL
X-Git-Tag: v4.9.8~6656
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d23082257d83e4bc89727d5aedee197e907999d2;p=platform%2Fkernel%2Flinux-rpi3.git

pid_namespace: pidns_get() should check task_active_pid_ns() != NULL

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>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 06c62de..db95d8e 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -318,7 +318,9 @@ static void *pidns_get(struct task_struct *task)
 	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;