net/neighbour: fix crash at dumping device-agnostic proxy entries

commit 6adc5fd6 upstream.

Proxy entries could have null pointer to net-device.
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Fixes: 84920c14 ("net: Allow ipv6 proxies and arp proxies be shown with iproute2")
Signed-off-by: David S. Miller <davem@davemloft.net>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>

net/core/neighbour.c

@@ -2186,7 +2186,7 @@ static int pneigh_fill_info(struct sk_buff *skb, struct pneigh_entry *pn,
 	ndm->ndm_pad2    = 0;
 	ndm->ndm_flags	 = pn->flags | NTF_PROXY;
 	ndm->ndm_type	 = NDA_DST;
-	ndm->ndm_ifindex = pn->dev->ifindex;
+	ndm->ndm_ifindex = pn->dev ? pn->dev->ifindex : 0;
 	ndm->ndm_state	 = NUD_NONE;
 
 	NLA_PUT(skb, NDA_DST, tbl->key_len, pn->key);
@@ -2259,7 +2259,7 @@ static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
 		if (h > s_h)
 			s_idx = 0;
 		for (n = tbl->phash_buckets[h], idx = 0; n; n = n->next) {
-			if (dev_net(n->dev) != net)
+			if (pneigh_net(n) != net)
 				continue;
 			if (idx < s_idx)
 				goto next;