IPoIB: Check multicast address format

Check that the format of multicast link addresses is correct before
taking them from dev->mc_list to priv->multicast_list.  This way we
never try to send a bogus address to the SA, which prevents badness
from erronous 'ip maddr addr add', broken bonding drivers, etc.
Signed-off-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -760,6 +760,20 @@ void ipoib_mcast_dev_flush(struct net_device *dev)
 	}
 }
 
+static int ipoib_mcast_addr_is_valid(const u8 *addr, unsigned int addrlen,
+				     const u8 *broadcast)
+{
+	if (addrlen != INFINIBAND_ALEN)
+		return 0;
+	/* reserved QPN, prefix, scope */
+	if (memcmp(addr, broadcast, 6))
+		return 0;
+	/* signature lower, pkey */
+	if (memcmp(addr + 7, broadcast + 7, 3))
+		return 0;
+	return 1;
+}
+
 void ipoib_mcast_restart_task(struct work_struct *work)
 {
 	struct ipoib_dev_priv *priv =
@@ -793,6 +807,11 @@ void ipoib_mcast_restart_task(struct work_struct *work)
 	for (mclist = dev->mc_list; mclist; mclist = mclist->next) {
 		union ib_gid mgid;
 
+		if (!ipoib_mcast_addr_is_valid(mclist->dmi_addr,
+					       mclist->dmi_addrlen,
+					       dev->broadcast))
+			continue;
+
 		memcpy(mgid.raw, mclist->dmi_addr + 4, sizeof mgid);
 
 		mcast = __ipoib_mcast_find(dev, &mgid);