netfilter: nfnetlink_queue: fix secctx memory leak

We must call security_release_secctx to free the memory returned by
security_secid_to_secctx, otherwise memory may be leaked forever.

Fixes: ef493bd930 ("netfilter: nfnetlink_queue: add security context information")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_queue.c

@@ -443,7 +443,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	skb = alloc_skb(size, GFP_ATOMIC);
 	if (!skb) {
 		skb_tx_error(entskb);
-		return NULL;
+		goto nlmsg_failure;
 	}
 
 	nlh = nlmsg_put(skb, 0, 0,
@@ -452,7 +452,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	if (!nlh) {
 		skb_tx_error(entskb);
 		kfree_skb(skb);
-		return NULL;
+		goto nlmsg_failure;
 	}
 	nfmsg = nlmsg_data(nlh);
 	nfmsg->nfgen_family = entry->state.pf;
@@ -598,12 +598,17 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	}
 
 	nlh->nlmsg_len = skb->len;
+	if (seclen)
+		security_release_secctx(secdata, seclen);
 	return skb;
 
 nla_put_failure:
 	skb_tx_error(entskb);
 	kfree_skb(skb);
 	net_err_ratelimited("nf_queue: error creating packet message\n");
+nlmsg_failure:
+	if (seclen)
+		security_release_secctx(secdata, seclen);
 	return NULL;
 }