IPoIB: Close race in setting mcast->ah

ipoib_mcast_send() tests mcast->ah twice.  If this value is changed
between these two points, we leak an skb.  However,
ipoib_mcast_join_finish() sets mcast->ah with no locking, so it could
race against ipoib_mcast_send().

As a solution, take priv->lock around assignment to mcast->ah thus
making sure ipoib_mcast_send() (which also takes priv->lock) is not in
flight.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index a2408d7ec598..e5dc2a034530 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -213,6 +213,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 {
         struct net_device *dev = mcast->dev;
         struct ipoib_dev_priv *priv = netdev_priv(dev);
+        struct ipoib_ah *ah;
         int ret;
 
         mcast->mcmember = *mcmember;
@@ -269,8 +270,8 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
                                 av.static_rate, priv->local_rate,
                                 ib_sa_rate_enum_to_int(mcast->mcmember.rate));
 
-                mcast->ah = ipoib_create_ah(dev, priv->pd, &av);
-                if (!mcast->ah) {
+                ah = ipoib_create_ah(dev, priv->pd, &av);
+                if (!ah) {
                         ipoib_warn(priv, "ib_address_create failed\n");
                 } else {
                         ipoib_dbg_mcast(priv, "MGID " IPOIB_GID_FMT
@@ -280,6 +281,10 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
                                         be16_to_cpu(mcast->mcmember.mlid),
                                         mcast->mcmember.sl);
                 }
+
+                spin_lock_irq(&priv->lock);
+                mcast->ah = ah;
+                spin_unlock_irq(&priv->lock);
         }
 
         /* actually send any queued packets */