[NETFILTER]: nfnetlink_queue: don't unregister handler of other subsystem

The queue handlers registered by ip[6]_queue.ko at initialization should
not be unregistered according to requests from userland program
using nfnetlink_queue. If we allow that, there is no way to register
the handlers of built-in ip[6]_queue again.
Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter.h

@@ -275,7 +275,8 @@ struct nf_queue_handler {
 };
 extern int nf_register_queue_handler(int pf, 
                                      struct nf_queue_handler *qh);
-extern int nf_unregister_queue_handler(int pf);
+extern int nf_unregister_queue_handler(int pf,
+				       struct nf_queue_handler *qh);
 extern void nf_unregister_queue_handlers(struct nf_queue_handler *qh);
 extern void nf_reinject(struct sk_buff *skb,
 			struct nf_info *info,

net/netfilter/nf_queue.c

@@ -44,12 +44,17 @@ int nf_register_queue_handler(int pf, struct nf_queue_handler *qh)
 EXPORT_SYMBOL(nf_register_queue_handler);
 
 /* The caller must flush their queue before this */
-int nf_unregister_queue_handler(int pf)
+int nf_unregister_queue_handler(int pf, struct nf_queue_handler *qh)
 {
 	if (pf >= NPROTO)
 		return -EINVAL;
 
 	write_lock_bh(&queue_handler_lock);
+	if (queue_handler[pf] != qh) {
+		write_unlock_bh(&queue_handler_lock);
+		return -EINVAL;
+	}
+
 	queue_handler[pf] = NULL;
 	write_unlock_bh(&queue_handler_lock);
 

net/netfilter/nfnetlink_queue.c

@@ -913,9 +913,7 @@ nfqnl_recv_config(struct sock *ctnl, struct sk_buff *skb,
 		case NFQNL_CFG_CMD_PF_UNBIND:
 			QDEBUG("unregistering queue handler for pf=%u\n",
 				ntohs(cmd->pf));
-			/* This is a bug and a feature.  We can unregister
-			 * other handlers(!) */
-			ret = nf_unregister_queue_handler(ntohs(cmd->pf));
+			ret = nf_unregister_queue_handler(ntohs(cmd->pf), &nfqh);
 			break;
 		default:
 			ret = -EINVAL;