isdn: hfc_usb: Fix read buffer overflow

Check whether index is within bounds before testing the element.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/isdn/hisax/hfc_usb.c b/drivers/isdn/hisax/hfc_usb.c
index 9de54202c90c..a420b64472e3 100644
--- a/drivers/isdn/hisax/hfc_usb.c
+++ b/drivers/isdn/hisax/hfc_usb.c
@@ -817,8 +817,8 @@ collect_rx_frame(usb_fifo * fifo, __u8 * data, int len, int finish)
         }
         /* we have a complete hdlc packet */
         if (finish) {
-                if ((!fifo->skbuff->data[fifo->skbuff->len - 1])
-                    && (fifo->skbuff->len > 3)) {
+                if (fifo->skbuff->len > 3 &&
+                                !fifo->skbuff->data[fifo->skbuff->len - 1]) {
 
                         if (fifon == HFCUSB_D_RX) {
                                 DBG(HFCUSB_DBG_DCHANNEL,