mwifiex: don't leak DMA command skbuffs

The current mwifiex pcie driver assumed that it would get
its cmdrsp_complete() callback called before another command
was sent to unmap the command's skbuff. However, that is not
true. The mwifiex_check_ps_cond() will send a sleep command
to the card without having adapter->curr_cmd set. Within the
workqueue's state machine the adapter's state would be set
to allow commands (curr_cmd = NULL && cmd_sent = false) after
having receieved the response from the sleep command. The
card->cmd_buf would then be overridden with the new command
but the first command's skbuff was not unmapped. This leaks
mapped skbuffs when a bounce buffer is employed.

To rectify this unmap the card->cmd_buf when the response is
received from the card instead of waiting for the
cmdrsp_complete() callback.

Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Reviewed-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/mwifiex/pcie.c

@@ -1513,6 +1513,13 @@ static int mwifiex_pcie_process_cmd_complete(struct mwifiex_adapter *adapter)
 
 	mwifiex_unmap_pci_memory(adapter, skb, PCI_DMA_FROMDEVICE);
 
+	/* Unmap the command as a response has been received. */
+	if (card->cmd_buf) {
+		mwifiex_unmap_pci_memory(adapter, card->cmd_buf,
+					 PCI_DMA_TODEVICE);
+		card->cmd_buf = NULL;
+	}
+
 	pkt_len = *((__le16 *)skb->data);
 	rx_len = le16_to_cpu(pkt_len);
 	skb_trim(skb, rx_len);
@@ -1569,7 +1576,6 @@ static int mwifiex_pcie_cmdrsp_complete(struct mwifiex_adapter *adapter,
 					struct sk_buff *skb)
 {
 	struct pcie_service_card *card = adapter->card;
-	struct sk_buff *skb_tmp;
 
 	if (skb) {
 		card->cmdrsp_buf = skb;
@@ -1579,12 +1585,6 @@ static int mwifiex_pcie_cmdrsp_complete(struct mwifiex_adapter *adapter,
 			return -1;
 	}
 
-	skb_tmp = card->cmd_buf;
-	if (skb_tmp) {
-		mwifiex_unmap_pci_memory(adapter, skb_tmp, PCI_DMA_FROMDEVICE);
-		card->cmd_buf = NULL;
-	}
-
 	return 0;
 }