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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Guillaume Nault <gnault@redhat.com>,
        Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 5.16 0991/1039] gre: Dont accidentally set RTO_ONLINK in gre_fill_metadata_dst()
Date:   Mon, 24 Jan 2022 19:46:20 +0100
Message-Id: <20220124184158.599754506@linuxfoundation.org>
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From: Guillaume Nault <gnault@redhat.com>

commit f7716b318568b22fbf0e3be99279a979e217cf71 upstream.

Mask the ECN bits before initialising ->flowi4_tos. The tunnel key may
have the last ECN bit set, which will interfere with the route lookup
process as ip_route_output_key_hash() interpretes this bit specially
(to restrict the route scope).

Found by code inspection, compile tested only.

Fixes: 962924fa2b7a ("ip_gre: Refactor collect metatdata mode tunnel xmit to ip_md_tunnel_xmit")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/ip_gre.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -604,8 +604,9 @@ static int gre_fill_metadata_dst(struct
 
 	key = &info->key;
 	ip_tunnel_init_flow(&fl4, IPPROTO_GRE, key->u.ipv4.dst, key->u.ipv4.src,
-			    tunnel_id_to_key32(key->tun_id), key->tos, 0,
-			    skb->mark, skb_get_hash(skb));
+			    tunnel_id_to_key32(key->tun_id),
+			    key->tos & ~INET_ECN_MASK, 0, skb->mark,
+			    skb_get_hash(skb));
 	rt = ip_route_output_key(dev_net(dev), &fl4);
 	if (IS_ERR(rt))
 		return PTR_ERR(rt);