xfrm_user: fix info leak in copy_to_user_state()

The memory reserved to dump the xfrm state includes the padding bytes of
struct xfrm_usersa_info added by the compiler for alignment (7 for
amd64, 3 for i386). Add an explicit memset(0) before filling the buffer
to avoid the info leak.

Signed-off-by: Mathias Krause <[email protected]>
Acked-by: Steffen Klassert <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

net/xfrm/xfrm_user.c

@@ -689,6 +689,7 @@ static int xfrm_del_sa(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 static void copy_to_user_state(struct xfrm_state *x, struct xfrm_usersa_info *p)
 {
+	memset(p, 0, sizeof(*p));
 	memcpy(&p->id, &x->id, sizeof(p->id));
 	memcpy(&p->sel, &x->sel, sizeof(p->sel));
 	memcpy(&p->lft, &x->lft, sizeof(p->lft));