bridge: check return value of ipv6_dev_get_saddr()

otherwise source IPv6 address of ICMPV6_MGM_QUERY packet
might be random junk if IPv6 is disabled on interface or
link-local address is not yet ready (DAD).

Signed-off-by: Ulrich Weber <ulrich.weber@sophos.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_multicast.c

@@ -446,8 +446,11 @@ static struct sk_buff *br_ip6_multicast_alloc_query(struct net_bridge *br,
 	ip6h->nexthdr = IPPROTO_HOPOPTS;
 	ip6h->hop_limit = 1;
 	ipv6_addr_set(&ip6h->daddr, htonl(0xff020000), 0, 0, htonl(1));
-	ipv6_dev_get_saddr(dev_net(br->dev), br->dev, &ip6h->daddr, 0,
-			   &ip6h->saddr);
+	if (ipv6_dev_get_saddr(dev_net(br->dev), br->dev, &ip6h->daddr, 0,
+			       &ip6h->saddr)) {
+		kfree_skb(skb);
+		return NULL;
+	}
 	ipv6_eth_mc_map(&ip6h->daddr, eth->h_dest);
 
 	hopopt = (u8 *)(ip6h + 1);