diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 48b4ff0294f6..c035a96fba3a 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1175,14 +1175,16 @@ static void ip6gre_tnl_link_config_route(struct ip6_tnl *t, int set_mtu,
 				dev->needed_headroom = dst_len;
 
 			if (set_mtu) {
-				dev->mtu = rt->dst.dev->mtu - t_hlen;
-				if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
-					dev->mtu -= 8;
-				if (dev->type == ARPHRD_ETHER)
-					dev->mtu -= ETH_HLEN;
+				int mtu = rt->dst.dev->mtu - t_hlen;
 
-				if (dev->mtu < IPV6_MIN_MTU)
-					dev->mtu = IPV6_MIN_MTU;
+				if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
+					mtu -= 8;
+				if (dev->type == ARPHRD_ETHER)
+					mtu -= ETH_HLEN;
+
+				if (mtu < IPV6_MIN_MTU)
+					mtu = IPV6_MIN_MTU;
+				WRITE_ONCE(dev->mtu, mtu);
 			}
 		}
 		ip6_rt_put(rt);
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index cc5d5e75b658..2fb4c6ad7243 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1450,8 +1450,8 @@ static void ip6_tnl_link_config(struct ip6_tnl *t)
 	struct net_device *tdev = NULL;
 	struct __ip6_tnl_parm *p = &t->parms;
 	struct flowi6 *fl6 = &t->fl.u.ip6;
-	unsigned int mtu;
 	int t_hlen;
+	int mtu;
 
 	__dev_addr_set(dev, &p->laddr, sizeof(struct in6_addr));
 	memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));
@@ -1498,12 +1498,13 @@ static void ip6_tnl_link_config(struct ip6_tnl *t)
 			dev->hard_header_len = tdev->hard_header_len + t_hlen;
 			mtu = min_t(unsigned int, tdev->mtu, IP6_MAX_MTU);
 
-			dev->mtu = mtu - t_hlen;
+			mtu = mtu - t_hlen;
 			if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
-				dev->mtu -= 8;
+				mtu -= 8;
 
-			if (dev->mtu < IPV6_MIN_MTU)
-				dev->mtu = IPV6_MIN_MTU;
+			if (mtu < IPV6_MIN_MTU)
+				mtu = IPV6_MIN_MTU;
+			WRITE_ONCE(dev->mtu, mtu);
 		}
 	}
 }
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index d27683e3fc97..5703d3cbea9b 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1124,10 +1124,12 @@ static void ipip6_tunnel_bind_dev(struct net_device *dev)
 
 	if (tdev && !netif_is_l3_master(tdev)) {
 		int t_hlen = tunnel->hlen + sizeof(struct iphdr);
+		int mtu;
 
-		dev->mtu = tdev->mtu - t_hlen;
-		if (dev->mtu < IPV6_MIN_MTU)
-			dev->mtu = IPV6_MIN_MTU;
+		mtu = tdev->mtu - t_hlen;
+		if (mtu < IPV6_MIN_MTU)
+			mtu = IPV6_MIN_MTU;
+		WRITE_ONCE(dev->mtu, mtu);
 	}
 }