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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org, greg@kroah.com
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Guillaume Nault <g.nault@alphalink.fr>,
        "David S. Miller" <davem@davemloft.net>,
        Giuliano Procida <gprocida@google.com>
Subject: [PATCH 4.9 38/64] l2tp: hold tunnel while processing genl delete command
Date:   Tue, 26 May 2020 20:53:07 +0200
Message-Id: <20200526183925.705310414@linuxfoundation.org>
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From: Guillaume Nault <g.nault@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.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>
---
 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;
 }