netdev - [PATCH] net_namespace: fixed net

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Message-ID: <CAJD3hpUgNJPOqGmAp7tEaY2+EnOasG=W6VLOMbEhDRgr8M5v8A@mail.gmail.com>
Date:   Wed, 7 Sep 2016 18:55:52 -0700
From:   Jojy Varghese <jojy.varghese@...il.com>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net
Subject: [PATCH] net_namespace: fixed net_device reference leak

During namespace cleanup, if ‘dst’ subsystem is holding
a reference to the loopback interface in the namespace, it does not get
released. This is because in the case where the net_device held by 'dst'
is same as the namespace's loopback net_device, current code first
does a ’dev_hold’ on the same device followed by a ‘dev_put’ on the
same device resulting in a no-op.

This change fixes this leak by assigning the initial namespace’s loopback
device to the ‘dst’’ before releasing the reference to the network device
being unregistered.

Additional reference: https://github.com/docker/docker/issues/5618

Signed-off-by: Jojy G Varghese <jojy.varghese@...il.com>
---
 net/core/dst.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dst.c b/net/core/dst.c
index a1656e3..a18e8ea 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -433,7 +433,7 @@ static void dst_ifdown(struct dst_entry *dst,
struct net_device *dev,
                dst->input = dst_discard;
                dst->output = dst_discard_out;
        } else {
-               dst->dev = dev_net(dst->dev)->loopback_dev;
+               dst->dev = init_net.loopback_dev;
                dev_hold(dst->dev);
                dev_put(dev);
        }
-- 
1.8.3.1