l2tp: hold tunnel used while creating sessions with netlink

commit e702c1204eb57788ef189c839c8c779368267d70 upstream.

Use l2tp_tunnel_get() to retrieve tunnel, so that it can't go away on
us. Otherwise l2tp_tunnel_destruct() might release the last reference
count concurrently, thus freeing the tunnel while we're using it.

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 8f39086..5ea5d3f 100644 (file)
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -510,8 +510,9 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
                ret = -EINVAL;
                goto out;
        }
+
        tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]);
-       tunnel = l2tp_tunnel_find(net, tunnel_id);
+       tunnel = l2tp_tunnel_get(net, tunnel_id);
        if (!tunnel) {
                ret = -ENODEV;
                goto out;
@@ -519,24 +520,24 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 
        if (!info->attrs[L2TP_ATTR_SESSION_ID]) {
                ret = -EINVAL;
-               goto out;
+               goto out_tunnel;
        }
        session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]);
 
        if (!info->attrs[L2TP_ATTR_PEER_SESSION_ID]) {
                ret = -EINVAL;
-               goto out;
+               goto out_tunnel;
        }
        peer_session_id = nla_get_u32(info->attrs[L2TP_ATTR_PEER_SESSION_ID]);
 
        if (!info->attrs[L2TP_ATTR_PW_TYPE]) {
                ret = -EINVAL;
-               goto out;
+               goto out_tunnel;
        }
        cfg.pw_type = nla_get_u16(info->attrs[L2TP_ATTR_PW_TYPE]);
        if (cfg.pw_type >= __L2TP_PWTYPE_MAX) {
                ret = -EINVAL;
-               goto out;
+               goto out_tunnel;
        }
 
        if (tunnel->version > 2) {
@@ -555,7 +556,7 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
                        u16 len = nla_len(info->attrs[L2TP_ATTR_COOKIE]);
                        if (len > 8) {
                                ret = -EINVAL;
-                               goto out;
+                               goto out_tunnel;
                        }
                        cfg.cookie_len = len;
                        memcpy(&cfg.cookie[0], nla_data(info->attrs[L2TP_ATTR_COOKIE]), len);
@@ -564,7 +565,7 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
                        u16 len = nla_len(info->attrs[L2TP_ATTR_PEER_COOKIE]);
                        if (len > 8) {
                                ret = -EINVAL;
-                               goto out;
+                               goto out_tunnel;
                        }
                        cfg.peer_cookie_len = len;
                        memcpy(&cfg.peer_cookie[0], nla_data(info->attrs[L2TP_ATTR_PEER_COOKIE]), len);
@@ -607,7 +608,7 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
        if ((l2tp_nl_cmd_ops[cfg.pw_type] == NULL) ||
            (l2tp_nl_cmd_ops[cfg.pw_type]->session_create == NULL)) {
                ret = -EPROTONOSUPPORT;
-               goto out;
+               goto out_tunnel;
        }
 
        /* Check that pseudowire-specific params are present */
@@ -617,7 +618,7 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
        case L2TP_PWTYPE_ETH_VLAN:
                if (!info->attrs[L2TP_ATTR_VLAN_ID]) {
                        ret = -EINVAL;
-                       goto out;
+                       goto out_tunnel;
                }
                break;
        case L2TP_PWTYPE_ETH:
@@ -645,6 +646,8 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
                }
        }
 
+out_tunnel:
+       l2tp_tunnel_dec_refcount(tunnel);
 out:
        return ret;
 }