Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

Pull networking fixes from David Miller:
 "A quick batch of bug fixes:

  1) Fix build with IPV6 disabled, from Eric Dumazet.

  2) Several more cases of caching SKB data pointers across calls to
     pskb_may_pull(), thus referencing potentially free'd memory.  From
     Li RongQing.

  3) DSA phy code tests operation presence improperly, instead of going:

        if (x->ops->foo)
                r = x->ops->foo(args);

     it was going:

        if (x->ops->foo(args))
                r = x->ops->foo(args);

   Fix from Andew Lunn"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  Net: DSA: Fix checking for get_phy_flags function
  ipv6: fix a potential use after free in sit.c
  ipv6: fix a potential use after free in ip6_offload.c
  ipv4: fix a potential use after free in gre_offload.c
  tcp: fix build error if IPv6 is not enabled

include/net/tcp.h

@@ -730,6 +730,7 @@ struct tcp_skb_cb {
 #define TCP_SKB_CB(__skb)	((struct tcp_skb_cb *)&((__skb)->cb[0]))
 
 
+#if IS_ENABLED(CONFIG_IPV6)
 /* This is the variant of inet6_iif() that must be used by TCP,
  * as TCP moves IP6CB into a different location in skb->cb[]
  */
@@ -737,6 +738,7 @@ static inline int tcp_v6_iif(const struct sk_buff *skb)
 {
 	return TCP_SKB_CB(skb)->header.h6.iif;
 }
+#endif
 
 /* Due to TSO, an SKB can be composed of multiple actual
  * packets.  To keep these tracked properly, we use this.

net/dsa/slave.c

@@ -599,7 +599,7 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
 	netif_carrier_off(slave_dev);
 
 	if (p->phy != NULL) {
-		if (ds->drv->get_phy_flags(ds, port))
+		if (ds->drv->get_phy_flags)
 			p->phy->dev_flags |= ds->drv->get_phy_flags(ds, port);
 
 		phy_attach(slave_dev, dev_name(&p->phy->dev),

net/ipv4/gre_offload.c

@@ -55,13 +55,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 	if (csum)
 		skb->encap_hdr_csum = 1;
 
-	if (unlikely(!pskb_may_pull(skb, ghl)))
-		goto out;
-
 	/* setup inner skb. */
 	skb->protocol = greh->protocol;
 	skb->encapsulation = 0;
 
+	if (unlikely(!pskb_may_pull(skb, ghl)))
+		goto out;
+
 	__skb_pull(skb, ghl);
 	skb_reset_mac_header(skb);
 	skb_set_network_header(skb, skb_inner_network_offset(skb));

net/ipv6/ip6_offload.c

@@ -46,6 +46,7 @@ static int ipv6_gso_pull_exthdrs(struct sk_buff *skb, int proto)
 		if (unlikely(!pskb_may_pull(skb, len)))
 			break;
 
+		opth = (void *)skb->data;
 		proto = opth->nexthdr;
 		__skb_pull(skb, len);
 	}

net/ipv6/sit.c

@@ -485,11 +485,11 @@ static void ipip6_tunnel_uninit(struct net_device *dev)
  */
 static int ipip6_err_gen_icmpv6_unreach(struct sk_buff *skb)
 {
-	const struct iphdr *iph = (const struct iphdr *) skb->data;
+	int ihl = ((const struct iphdr *)skb->data)->ihl*4;
 	struct rt6_info *rt;
 	struct sk_buff *skb2;
 
-	if (!pskb_may_pull(skb, iph->ihl * 4 + sizeof(struct ipv6hdr) + 8))
+	if (!pskb_may_pull(skb, ihl + sizeof(struct ipv6hdr) + 8))
 		return 1;
 
 	skb2 = skb_clone(skb, GFP_ATOMIC);
@@ -498,7 +498,7 @@ static int ipip6_err_gen_icmpv6_unreach(struct sk_buff *skb)
 		return 1;
 
 	skb_dst_drop(skb2);
-	skb_pull(skb2, iph->ihl * 4);
+	skb_pull(skb2, ihl);
 	skb_reset_network_header(skb2);
 
 	rt = rt6_lookup(dev_net(skb->dev), &ipv6_hdr(skb2)->saddr, NULL, 0, 0);