net: diag: slightly refactor the inet_diag_bc_audit error checks.

This simplifies the code a bit and also allows inet_diag_bc_audit
to send to userspace an error that isn't EINVAL.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Acked-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/inet_diag.c

@@ -706,10 +706,16 @@ static bool valid_port_comparison(const struct inet_diag_bc_op *op,
 	return true;
 }
 
-static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
+static int inet_diag_bc_audit(const struct nlattr *attr)
 {
-	const void *bc = bytecode;
+	const void *bytecode, *bc;
-	int  len = bytecode_len;
+	int bytecode_len, len;
+
+	if (!attr || nla_len(attr) < sizeof(struct inet_diag_bc_op))
+		return -EINVAL;
+
+	bytecode = bc = nla_data(attr);
+	len = bytecode_len = nla_len(attr);
 
 	while (len > 0) {
 		int min_len = sizeof(struct inet_diag_bc_op);
@@ -1020,13 +1026,13 @@ static int inet_diag_rcv_msg_compat(struct sk_buff *skb, struct nlmsghdr *nlh)
 	if (nlh->nlmsg_flags & NLM_F_DUMP) {
 		if (nlmsg_attrlen(nlh, hdrlen)) {
 			struct nlattr *attr;
+			int err;
 
 			attr = nlmsg_find_attr(nlh, hdrlen,
 					       INET_DIAG_REQ_BYTECODE);
-			if (!attr ||
+			err = inet_diag_bc_audit(attr);
-			    nla_len(attr) < sizeof(struct inet_diag_bc_op) ||
+			if (err)
-			    inet_diag_bc_audit(nla_data(attr), nla_len(attr)))
+				return err;
-				return -EINVAL;
 		}
 		{
 			struct netlink_dump_control c = {
@@ -1051,13 +1057,13 @@ static int inet_diag_handler_cmd(struct sk_buff *skb, struct nlmsghdr *h)
 	    h->nlmsg_flags & NLM_F_DUMP) {
 		if (nlmsg_attrlen(h, hdrlen)) {
 			struct nlattr *attr;
+			int err;
 
 			attr = nlmsg_find_attr(h, hdrlen,
 					       INET_DIAG_REQ_BYTECODE);
-			if (!attr ||
+			err = inet_diag_bc_audit(attr);
-			    nla_len(attr) < sizeof(struct inet_diag_bc_op) ||
+			if (err)
-			    inet_diag_bc_audit(nla_data(attr), nla_len(attr)))
+				return err;
-				return -EINVAL;
 		}
 		{
 			struct netlink_dump_control c = {