iwlwifi: pcie: don't crash on invalid RX interrupt

If for some reason the device gives us an RX interrupt before we're
ready for it, perhaps during device power-on with misconfigured IRQ
causes mapping or so, we can crash trying to access the queues.

Prevent that by checking that we actually have RXQs and that they
were properly allocated.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/pcie/rx.c

@@ -1429,10 +1429,15 @@ static struct iwl_rx_mem_buffer *iwl_pcie_get_rxb(struct iwl_trans *trans,
 static void iwl_pcie_rx_handle(struct iwl_trans *trans, int queue)
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
-	struct iwl_rxq *rxq = &trans_pcie->rxq[queue];
+	struct iwl_rxq *rxq;
 	u32 r, i, count = 0;
 	bool emergency = false;
 
+	if (WARN_ON_ONCE(!trans_pcie->rxq || !trans_pcie->rxq[queue].bd))
+		return;
+
+	rxq = &trans_pcie->rxq[queue];
+
 restart:
 	spin_lock(&rxq->lock);
 	/* uCode's read index (stored in shared DRAM) indicates the last Rx