IB/mthca: Set cleaned CQEs back to HW ownership when cleaning CQ

mthca_cq_clean() updates the CQ consumer index without moving CQEs
back to HW ownership.  As a result, the same WRID might get reported
twice, resulting in a use-after-free.  This was observed in IPoIB CM.
Fix by moving all freed CQEs to HW ownership.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=617>
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_cq.c

@@ -284,7 +284,7 @@ void mthca_cq_clean(struct mthca_dev *dev, struct mthca_cq *cq, u32 qpn,
 {
 	struct mthca_cqe *cqe;
 	u32 prod_index;
-	int nfreed = 0;
+	int i, nfreed = 0;
 
 	spin_lock_irq(&cq->lock);
 
@@ -321,6 +321,8 @@ void mthca_cq_clean(struct mthca_dev *dev, struct mthca_cq *cq, u32 qpn,
 	}
 
 	if (nfreed) {
+		for (i = 0; i < nfreed; ++i)
+			set_cqe_hw(get_cqe(cq, (cq->cons_index + i) & cq->ibcq.cqe));
 		wmb();
 		cq->cons_index += nfreed;
 		update_cons_index(dev, cq, nfreed);