net/smc: use a constant for control message length

The sizeof(struct smc_cdc_msg) evaluates to 48 bytes instead of the
required 44 bytes. We need to use the constant value of
SMC_WR_TX_SIZE to set and check the control message length.

Signed-off-by: Karsten Graul <kgraul@linux.vnet.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 3cd086e..b42395d 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -269,7 +269,7 @@ static void smc_cdc_rx_handler(struct ib_wc *wc, void *buf)
 
 	if (wc->byte_len < offsetof(struct smc_cdc_msg, reserved))
 		return; /* short message */
-	if (cdc->len != sizeof(*cdc))
+	if (cdc->len != SMC_WR_TX_SIZE)
 		return; /* invalid message */
 	smc_cdc_msg_recv(cdc, link, wc->wr_id);
 }