dccp qpolicy: Parameter checking of cmsg qpolicy parameters

Ensure that cmsg->cmsg_type value is valid for qpolicy 
that is currently in use.
Signed-off-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>

net/dccp/dccp.h

@@ -242,6 +242,7 @@ extern bool		dccp_qpolicy_full(struct sock *sk);
 extern void		dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb);
 extern struct sk_buff	*dccp_qpolicy_top(struct sock *sk);
 extern struct sk_buff	*dccp_qpolicy_pop(struct sock *sk);
+extern bool		dccp_qpolicy_param_ok(struct sock *sk, __be32 param);
 
 /*
  * TX Packet Output and TX Timers

net/dccp/proto.c

@@ -735,6 +735,10 @@ static int dccp_msghdr_parse(struct msghdr *msg, struct sk_buff *skb)
 		if (cmsg->cmsg_level != SOL_DCCP)
 			continue;
 
+		if (cmsg->cmsg_type <= DCCP_SCM_QPOLICY_MAX &&
+		    !dccp_qpolicy_param_ok(skb->sk, cmsg->cmsg_type))
+			return -EINVAL;
+
 		switch (cmsg->cmsg_type) {
 		case DCCP_SCM_PRIORITY:
 			if (cmsg->cmsg_len != CMSG_LEN(sizeof(__u32)))

net/dccp/qpolicy.c

@@ -73,17 +73,20 @@ static struct dccp_qpolicy_operations {
 	void		(*push)	(struct sock *sk, struct sk_buff *skb);
 	bool		(*full) (struct sock *sk);
 	struct sk_buff*	(*top)  (struct sock *sk);
+	__be32		params;
 
 } qpol_table[DCCPQ_POLICY_MAX] = {
 	[DCCPQ_POLICY_SIMPLE] = {
-		.push = qpolicy_simple_push,
-		.full = qpolicy_simple_full,
-		.top  = qpolicy_simple_top,
+		.push   = qpolicy_simple_push,
+		.full   = qpolicy_simple_full,
+		.top    = qpolicy_simple_top,
+		.params = 0,
 	},
 	[DCCPQ_POLICY_PRIO] = {
-		.push = qpolicy_simple_push,
-		.full = qpolicy_prio_full,
-		.top  = qpolicy_prio_best_skb,
+		.push   = qpolicy_simple_push,
+		.full   = qpolicy_prio_full,
+		.top    = qpolicy_prio_best_skb,
+		.params = DCCP_SCM_PRIORITY,
 	},
 };
 
@@ -124,3 +127,11 @@ struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
 		skb_unlink(skb, &sk->sk_write_queue);
 	return skb;
 }
+
+bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
+{
+	/* check if exactly one bit is set */
+	if (!param || (param & (param - 1)))
+		return false;
+	return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
+}