IB/hfi1: Unsafe PSN checking for TID RDMA READ Resp packet

When processing a TID RDMA READ RESP packet that causes KDETH EFLAGS
errors, the packet's IB PSN is checked against qp->s_last_psn and
qp->s_psn without the protection of qp->s_lock, which is not safe.

This patch fixes the issue by acquiring qp->s_lock first.

Fixes: 9905bf06 ("IB/hfi1: Add functions to receive TID RDMA READ response")
Cc: <stable@vger.kernel.org>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Link: https://lore.kernel.org/r/20190815192039.105923.7852.stgit@awfm-01.aw.intel.comSigned-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/tid_rdma.c

@@ -2687,12 +2687,12 @@ static bool handle_read_kdeth_eflags(struct hfi1_ctxtdata *rcd,
 	u32 fpsn;
 
 	lockdep_assert_held(&qp->r_lock);
+	spin_lock(&qp->s_lock);
 	/* If the psn is out of valid range, drop the packet */
 	if (cmp_psn(ibpsn, qp->s_last_psn) < 0 ||
 	    cmp_psn(ibpsn, qp->s_psn) > 0)
-		return ret;
+		goto s_unlock;
 
-	spin_lock(&qp->s_lock);
 	/*
 	 * Note that NAKs implicitly ACK outstanding SEND and RDMA write
 	 * requests and implicitly NAK RDMA read and atomic requests issued