xfrm_user: fix info leak in copy_to_user_policy()

The memory reserved to dump the xfrm policy includes multiple padding
bytes added by the compiler for alignment (padding bytes in struct
xfrm_selector and struct xfrm_userpolicy_info). Add an explicit
memset(0) before filling the buffer to avoid the heap info leak.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_user.c

@@ -1320,6 +1320,7 @@ static void copy_from_user_policy(struct xfrm_policy *xp, struct xfrm_userpolicy
 
 static void copy_to_user_policy(struct xfrm_policy *xp, struct xfrm_userpolicy_info *p, int dir)
 {
+	memset(p, 0, sizeof(*p));
 	memcpy(&p->sel, &xp->selector, sizeof(p->sel));
 	memcpy(&p->lft, &xp->lft, sizeof(p->lft));
 	memcpy(&p->curlft, &xp->curlft, sizeof(p->curlft));