From d6990976af7c5d8f55903bfb4289b6fb030bf754 Mon Sep 17 00:00:00 2001
From: Eyal Birger <eyal.birger@gmail.com>
Date: Thu, 7 Jun 2018 10:11:02 +0300
Subject: [PATCH] vti6: fix PMTU caching and reporting on xmit
Git-commit: d6990976af7c5d8f55903bfb4289b6fb030bf754
Patch-mainline: v4.18-rc8
References: bsc#1051510

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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(skb)->ops->update_pmtu(dst, NULL, 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);