bridge: Fix possibly wrong MLD queries' ethernet source address

The ipv6_dev_get_saddr() is currently called with an uninitialized
destination address. Although in tests it usually seemed to nevertheless
always fetch the right source address, there seems to be a possible race
condition.

Therefore this commit changes this, first setting the destination
address and only after that fetching the source address.

Reported-by: Jan Beulich <JBeulich@novell.com>
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
index 030a002ff8eee31230c02bad9c1584f5f94931aa..f61eb2eff3fdd387b83d9fab642bb610dde1ad69 100644 (file)
--- a/net/bridge/br_multicast.c
+++ b/net/bridge/br_multicast.c
@@ -445,9 +445,9 @@ static struct sk_buff *br_ip6_multicast_alloc_query(struct net_bridge *br,
        ip6h->payload_len = htons(8 + sizeof(*mldq));
        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);
-       ipv6_addr_set(&ip6h->daddr, htonl(0xff020000), 0, 0, htonl(1));
        ipv6_eth_mc_map(&ip6h->daddr, eth->h_dest);
 
        hopopt = (u8 *)(ip6h + 1);