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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiyu Yang <xiyuyang19@fudan.edu.cn>,
        Xin Tan <tanxin.ctf@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 23/80] net: netrom: Fix potential nr_neigh refcnt leak in nr_add_node
Date:   Fri,  1 May 2020 15:21:17 +0200
Message-Id: <20200501131521.948479586@linuxfoundation.org>
In-Reply-To: <20200501131513.810761598@linuxfoundation.org>
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From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

[ Upstream commit d03f228470a8c0a22b774d1f8d47071e0de4f6dd ]

nr_add_node() invokes nr_neigh_get_dev(), which returns a local
reference of the nr_neigh object to "nr_neigh" with increased refcnt.

When nr_add_node() returns, "nr_neigh" becomes invalid, so the refcount
should be decreased to keep refcount balanced.

The issue happens in one normal path of nr_add_node(), which forgets to
decrease the refcnt increased by nr_neigh_get_dev() and causes a refcnt
leak. It should decrease the refcnt before the function returns like
other normal paths do.

Fix this issue by calling nr_neigh_put() before the nr_add_node()
returns.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netrom/nr_route.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netrom/nr_route.c
+++ b/net/netrom/nr_route.c
@@ -199,6 +199,7 @@ static int __must_check nr_add_node(ax25
 		/* refcount initialized at 1 */
 		spin_unlock_bh(&nr_node_list_lock);
 
+		nr_neigh_put(nr_neigh);
 		return 0;
 	}
 	nr_node_lock(nr_node);