[PATCH 4.4 105/342] rtlwifi: rtl_pci: Fix kernel panic

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Larry Finger <Larry.Finger@xxxxxxxxxxxx>

commit f99551a2d39dc26ea03dc6761be11ac913eb2d57 upstream.

In commit 38506ecefab9 (rtlwifi: rtl_pci: Start modification for new
drivers), a bug was introduced that causes a NULL pointer dereference.
As this bug only affects the infrequently used RTL8192EE and only under
low-memory conditions, it has taken a long time for the bug to show up.

The bug was reported on the linux-wireless mailing list and also at
https://bugs.launchpad.net/ubuntu/+source/ubuntu-release-upgrader/ as
bug #1527603 (kernel crashes due to rtl8192ee driver on ubuntu 15.10).

Fixes: 38506ecefab9 ("rtlwifi: rtl_pci: Start modification for new drivers")
Signed-off-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/wireless/realtek/rtlwifi/pci.c |   11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

--- a/drivers/net/wireless/realtek/rtlwifi/pci.c
+++ b/drivers/net/wireless/realtek/rtlwifi/pci.c
@@ -801,7 +801,9 @@ static void _rtl_pci_rx_interrupt(struct
 								      hw_queue);
 			if (rx_remained_cnt == 0)
 				return;
-
+			buffer_desc = &rtlpci->rx_ring[rxring_idx].buffer_desc[
+				rtlpci->rx_ring[rxring_idx].idx];
+			pdesc = (struct rtl_rx_desc *)skb->data;
 		} else {	/* rx descriptor */
 			pdesc = &rtlpci->rx_ring[rxring_idx].desc[
 				rtlpci->rx_ring[rxring_idx].idx];
@@ -824,13 +826,6 @@ static void _rtl_pci_rx_interrupt(struct
 		new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
 		if (unlikely(!new_skb))
 			goto no_new;
-		if (rtlpriv->use_new_trx_flow) {
-			buffer_desc =
-			  &rtlpci->rx_ring[rxring_idx].buffer_desc
-				[rtlpci->rx_ring[rxring_idx].idx];
-			/*means rx wifi info*/
-			pdesc = (struct rtl_rx_desc *)skb->data;
-		}
 		memset(&rx_status , 0 , sizeof(rx_status));
 		rtlpriv->cfg->ops->query_rx_desc(hw, &stats,
 						 &rx_status, (u8 *)pdesc, skb);