benet: Avoid potential null deref in be_cmd_get_seeprom_data()

Found by: Jesper Juhl <jj@chaosbits.net>

Signed-off-by: Ajit Khaparde <ajit.khaparde@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/benet/be_cmds.c

@@ -1786,6 +1786,10 @@ int be_cmd_get_seeprom_data(struct be_adapter *adapter,
 	spin_lock_bh(&adapter->mcc_lock);
 
 	wrb = wrb_from_mccq(adapter);
+	if (!wrb) {
+		status = -EBUSY;
+		goto err;
+	}
 	req = nonemb_cmd->va;
 	sge = nonembedded_sgl(wrb);
 
@@ -1801,6 +1805,7 @@ int be_cmd_get_seeprom_data(struct be_adapter *adapter,
 
 	status = be_mcc_notify_wait(adapter);
 
+err:
 	spin_unlock_bh(&adapter->mcc_lock);
 	return status;
 }