ar9170usb: fix panic triggered by undersized rxstream buffer

While ar9170's USB transport packet size is currently set to 8KiB,
the PHY is capable of receiving AMPDUs with up to 64KiB.
Such a large frame will be split over several rx URBs and
exceed the previously allocated space for rx stream reconstruction.

This patch increases the buffer size to 64KiB which is
in fact the phy & rx stream designed size limit.

Cc: stable@kernel.org
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=15591
Reported-by: Christian Mehlis <mehlis@inf.fu-berlin.de>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ar9170/hw.h

@@ -425,5 +425,6 @@ enum ar9170_txq {
 
 #define AR9170_TXQ_DEPTH	32
 #define AR9170_TX_MAX_PENDING	128
+#define AR9170_RX_STREAM_MAX_SIZE 65535
 
 #endif /* __AR9170_HW_H */

drivers/net/wireless/ath/ar9170/main.c

@@ -2515,7 +2515,7 @@ void *ar9170_alloc(size_t priv_size)
 	 * tends to split the streams into seperate rx descriptors.
 	 */
 
-	skb = __dev_alloc_skb(AR9170_MAX_RX_BUFFER_SIZE, GFP_KERNEL);
+	skb = __dev_alloc_skb(AR9170_RX_STREAM_MAX_SIZE, GFP_KERNEL);
 	if (!skb)
 		goto err_nomem;