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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, Eyal Birger <eyal.birger@gmail.com>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.14 002/165] vti6: fix PMTU caching and reporting on xmit
Date:   Mon,  3 Sep 2018 18:54:48 +0200
Message-Id: <20180903165655.128471631@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Eyal Birger <eyal.birger@gmail.com>

[ Upstream commit d6990976af7c5d8f55903bfb4289b6fb030bf754 ]

When setting the skb->dst before doing the MTU check, the route PMTU
caching and reporting is done on the new dst which is about to be
released.

Instead, PMTU handling should be done using the original dst.

This is aligned with IPv4 VTI.

Fixes: ccd740cbc6 ("vti6: Add pmtu handling to vti6_xmit.")
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/ip6_vti.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -480,10 +480,6 @@ vti6_xmit(struct sk_buff *skb, struct ne
 		goto tx_err_dst_release;
 	}
 
-	skb_scrub_packet(skb, !net_eq(t->net, dev_net(dev)));
-	skb_dst_set(skb, dst);
-	skb->dev = skb_dst(skb)->dev;
-
 	mtu = dst_mtu(dst);
 	if (!skb->ignore_df && skb->len > mtu) {
 		skb_dst_update_pmtu(skb, mtu);
@@ -498,9 +494,14 @@ vti6_xmit(struct sk_buff *skb, struct ne
 				  htonl(mtu));
 		}
 
-		return -EMSGSIZE;
+		err = -EMSGSIZE;
+		goto tx_err_dst_release;
 	}
 
+	skb_scrub_packet(skb, !net_eq(t->net, dev_net(dev)));
+	skb_dst_set(skb, dst);
+	skb->dev = skb_dst(skb)->dev;
+
 	err = dst_output(t->net, skb->sk, skb);
 	if (net_xmit_eval(err) == 0) {
 		struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats);