wusb: replace memset by memzero_explicit

Memset on a local variable may be removed when it is called just before the
variable goes out of scope.  Using memzero_explicit defeats this
optimization.  A simplified version of the semantic patch that makes this
change is as follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier x;
type T;
@@

{
... when any
T x[...];
... when any
    when exists
- memset
+ memzero_explicit
  (x,
-0,
  ...)
... when != x
    when strict
}
// </smpl>

This change was suggested by Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/wusbcore/dev-sysfs.c

@@ -101,7 +101,7 @@ static ssize_t wusb_ck_store(struct device *dev,
 	if (wusbhc == NULL)
 		return -ENODEV;
 	result = wusb_dev_4way_handshake(wusbhc, usb_dev->wusb_dev, &ck);
-	memset(&ck, 0, sizeof(ck));
+	memzero_explicit(&ck, sizeof(ck));
 	wusbhc_put(wusbhc);
 	return result < 0 ? result : size;
 }

drivers/usb/wusbcore/security.c

@@ -522,10 +522,10 @@ int wusb_dev_4way_handshake(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev,
 error_hs2:
 error_hs1:
 	memset(hs, 0, 3*sizeof(hs[0]));
-	memset(&keydvt_out, 0, sizeof(keydvt_out));
-	memset(&keydvt_in, 0, sizeof(keydvt_in));
-	memset(&ccm_n, 0, sizeof(ccm_n));
-	memset(mic, 0, sizeof(mic));
+	memzero_explicit(&keydvt_out, sizeof(keydvt_out));
+	memzero_explicit(&keydvt_in, sizeof(keydvt_in));
+	memzero_explicit(&ccm_n, sizeof(ccm_n));
+	memzero_explicit(mic, sizeof(mic));
 	if (result < 0)
 		wusb_dev_set_encryption(usb_dev, 0);
 error_dev_set_encryption: