[PATCH 4.4 03/30] iwlwifi: pcie: fix to correct null check

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>

The fixes made in commit: 4ae5798004d8 ("iwlwifi: pcie: add a NULL check in
iwl_pcie_txq_unmap") is not enough in 4.4.y tree.. This still have problems
with null references. This provides the correct fix.
Also, this is a problem only in 4.4.y. This patch has been applied to other
LTS trees, but with the correct fixes.

Fixes: 4ae5798004d8 ("iwlwifi: pcie: add a NULL check in iwl_pcie_txq_unmap")
Cc: stable@vger.kernel.org
Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Cc: Luca Coelho <luciano.coelho@intel.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/net/wireless/iwlwifi/pcie/tx.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
@@ -583,13 +583,15 @@ static void iwl_pcie_txq_unmap(struct iw
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	struct iwl_txq *txq = &trans_pcie->txq[txq_id];
-	struct iwl_queue *q = &txq->q;
+	struct iwl_queue *q;
 
 	if (!txq) {
 		IWL_ERR(trans, "Trying to free a queue that wasn't allocated?\n");
 		return;
 	}
 
+	q = &txq->q;
+
 	spin_lock_bh(&txq->lock);
 	while (q->write_ptr != q->read_ptr) {
 		IWL_DEBUG_TX_REPLY(trans, "Q %d Free %d\n",