staging: r8192U: Fix check pointer after usage problem

In routine rtl8192_tx_isr(), pointer skb is dereferenced before it is
checked for NULL. This patch has only been compile-tested, as I do not
have the hardware. This problem was reported at
https://bugzilla.kernel.org/show_bug.cgi?id=109951.

Fixes: bugzilla.kernel.org: #109951
Reported-by: Yong Shi <brave_shi@163.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Yong Shi <brave_shi@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/rtl8192u/r8192U_core.c b/drivers/staging/rtl8192u/r8192U_core.c
index 07f4e7a5469aeb85b818fd45786fd0e8fcb6b591..3c589636139a8e7016754b6db6e4a7f3bf98e2f1 100644 (file)
--- a/drivers/staging/rtl8192u/r8192U_core.c
+++ b/drivers/staging/rtl8192u/r8192U_core.c
@@ -1092,10 +1092,17 @@ static int rtl8192_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
 static void rtl8192_tx_isr(struct urb *tx_urb)
 {
        struct sk_buff *skb = (struct sk_buff *)tx_urb->context;
-       struct net_device *dev = (struct net_device *)(skb->cb);
+       struct net_device *dev;
        struct r8192_priv *priv = NULL;
-       cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
-       u8  queue_index = tcb_desc->queue_index;
+       cb_desc *tcb_desc;
+       u8  queue_index;
+
+       if (!skb)
+               return;
+
+       dev = (struct net_device *)(skb->cb);
+       tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
+       queue_index = tcb_desc->queue_index;
 
        priv = ieee80211_priv(dev);
 
@@ -1113,11 +1120,9 @@ static void rtl8192_tx_isr(struct urb *tx_urb)
        }
 
        /* free skb and tx_urb */
-       if (skb != NULL) {
-               dev_kfree_skb_any(skb);
-               usb_free_urb(tx_urb);
-               atomic_dec(&priv->tx_pending[queue_index]);
-       }
+       dev_kfree_skb_any(skb);
+       usb_free_urb(tx_urb);
+       atomic_dec(&priv->tx_pending[queue_index]);
 
        /*
         * Handle HW Beacon: