[PATCH 3.2 061/147] l2tp: hold tunnel while handling genl tunnel updates

[Ben Hutchings]

3.2.95-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Guillaume Nault <g.nault@xxxxxxxxxxxx>

commit 8c0e421525c9eb50d68e8f633f703ca31680b746 upstream.

We need to make sure the tunnel is not going to be destroyed by
l2tp_tunnel_destruct() concurrently.

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.nault@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 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
@@ -211,8 +211,8 @@ static int l2tp_nl_cmd_tunnel_modify(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;
 	}
@@ -220,6 +220,8 @@ static int l2tp_nl_cmd_tunnel_modify(str
 	if (info->attrs[L2TP_ATTR_DEBUG])
 		tunnel->debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
 
+	l2tp_tunnel_dec_refcount(tunnel);
+
 out:
 	return ret;
 }