staging/dgnc: fix info leak in ioctl

commit 4b618433 upstream.

The dgnc_mgmt_ioctl() code fails to initialize the 16 _reserved bytes of
struct digi_dinfo after the ->dinfo_nboards member. Add an explicit
memset(0) before filling the structure to avoid the info leak.
Signed-off-by: Salva Peiró <speirofr@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reference: CVE-2015-7885
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/staging/dgnc/dgnc_mgmt.c

@@ -133,6 +133,7 @@ long dgnc_mgmt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 		spin_lock_irqsave(&dgnc_global_lock, flags);
 
+		memset(&ddi, 0, sizeof(ddi));
 		ddi.dinfo_nboards = dgnc_NumBoards;
 		sprintf(ddi.dinfo_version, "%s", DG_PART);