xfrm_user: return error pointer instead of NULL #2

commit c2546372 upstream.

When dump_one_policy() returns an error, e.g. because of a too small
buffer to dump the whole xfrm policy, xfrm_policy_netlink() returns
NULL instead of an error pointer. But its caller expects an error
pointer and therefore continues to operate on a NULL skbuff.
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>
Signed-off-by: Willy Tarreau <w@1wt.eu>

net/xfrm/xfrm_user.c

@@ -1306,6 +1306,7 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb,
 {
 	struct xfrm_dump_info info;
 	struct sk_buff *skb;
+	int err;
 
 	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
 	if (!skb)
@@ -1316,9 +1317,10 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb,
 	info.nlmsg_seq = seq;
 	info.nlmsg_flags = 0;
 
-	if (dump_one_policy(xp, dir, 0, &info) < 0) {
+	err = dump_one_policy(xp, dir, 0, &info);
+	if (err) {
 		kfree_skb(skb);
-		return NULL;
+		return ERR_PTR(err);
 	}
 
 	return skb;