[PATCH 3.16 159/294] l2tp: hold tunnel while handling genl tunnel updates

[Ben Hutchings]

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

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

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

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.na...@alphalink.fr>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 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
@@ -236,8 +236,8 @@ 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;
        }
@@ -245,6 +245,8 @@ 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;
 }