usbatm: fix potential NULL pointer dereference

The dereference to 'instance' in the debug code should be moved
below the NULL test.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/atm/usbatm.c

@@ -672,9 +672,6 @@ static int usbatm_atm_send(struct atm_vcc *vcc, struct sk_buff *skb)
 	struct usbatm_control *ctrl = UDSL_SKB(skb);
 	int err;
 
-	vdbg(&instance->usb_intf->dev, "%s called (skb 0x%p, len %u)", __func__,
-	     skb, skb->len);
-
 	/* racy disconnection check - fine */
 	if (!instance || instance->disconnected) {
 #ifdef DEBUG
@@ -684,6 +681,9 @@ static int usbatm_atm_send(struct atm_vcc *vcc, struct sk_buff *skb)
 		goto fail;
 	}
 
+	vdbg(&instance->usb_intf->dev, "%s called (skb 0x%p, len %u)", __func__,
+	     skb, skb->len);
+
 	if (vcc->qos.aal != ATM_AAL5) {
 		atm_rldbg(instance, "%s: unsupported ATM type %d!\n", __func__, vcc->qos.aal);
 		err = -EINVAL;