[PATCH 4.4 51/65] l2tp: hold tunnel while handling genl tunnel updates

From: Greg Kroah-Hartman
Date: Tue May 26 2020 - 14:57:24 EST


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: Giuliano Procida <gprocida@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -310,8 +310,8 @@ 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;
}
@@ -322,6 +322,8 @@ static int l2tp_nl_cmd_tunnel_modify(str
ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
tunnel, L2TP_CMD_TUNNEL_MODIFY);

+ l2tp_tunnel_dec_refcount(tunnel);
+
out:
return ret;
}