usb: gadget: avoid exposing kernel stack

commit ffeee83a upstream.

Function in_rq_cur copies random bytes from the stack.
Zero the memory instead.

Fixes: 132fcb46 ("usb: gadget: Add Audio Class 2.0 Driver")
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/gadget/f_uac2.c

@@ -1153,6 +1153,7 @@ in_rq_cur(struct usb_function *fn, const struct usb_ctrlrequest *cr)
 
 	if (control_selector == UAC2_CS_CONTROL_SAM_FREQ) {
 		struct cntrl_cur_lay3 c;
+		memset(&c, 0, sizeof(struct cntrl_cur_lay3));
 
 		if (entity_id == USB_IN_CLK_ID)
 			c.dCUR = p_srate;