[PATCH 4.4 50/65] l2tp: hold tunnel while processing genl delete command

[Greg Kroah-Hartman]

From: Guillaume Nault <g.na...@alphalink.fr>

commit bb0a32ce4389e17e47e198d2cddaf141561581ad upstream.
l2tp_nl_cmd_tunnel_delete() needs to take a reference on the tunnel, to
prevent it from being concurrently freed by l2tp_tunnel_destruct().

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.na...@alphalink.fr>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Giuliano Procida <gproc...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/l2tp/l2tp_netlink.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -280,8 +280,8 @@ static int l2tp_nl_cmd_tunnel_delete(str
        }
        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
 
-       tunnel = l2tp_tunnel_find(net, tunnel_id);
-       if (tunnel == NULL) {
+       tunnel = l2tp_tunnel_get(net, tunnel_id);
+       if (!tunnel) {
                ret = -ENODEV;
                goto out;
        }
@@ -291,6 +291,8 @@ static int l2tp_nl_cmd_tunnel_delete(str
 
        l2tp_tunnel_delete(tunnel);
 
+       l2tp_tunnel_dec_refcount(tunnel);
+
 out:
        return ret;
 }