Subject: [PATCH RFC v2 net-next 17/25] net/ipv6: Update ip6addrlbl_dump to support NLM_F_DUMP_PROPER_HDR

From: David Ahern <[email-masked]>
Date: Mon, 1 Oct 2018 17:28:43 -0700

From: David Ahern <[email-masked]>

Update ip6addrlbl_dump to check for NLM_F_DUMP_PROPER_HDR in the netlink
message header. If the flag is set, the dump request is expected to have
an ifaddrlblmsg struct as the header. All elements of the struct are
expected to be 0 and no attributes can be appended.

Signed-off-by: David Ahern <[email-masked]>
---
 net/ipv6/addrlabel.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
index 1d6ced37ad71..89e15ed78c60 100644
--- a/net/ipv6/addrlabel.c
+++ b/net/ipv6/addrlabel.c
@@ -460,18 +460,41 @@ static int ip6addrlbl_fill(struct sk_buff *skb,
 
 static int ip6addrlbl_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	struct ip6addrlbl_entry *p;
 	int idx = 0, s_idx = cb->args[0];
 	int err;
 
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		struct netlink_ext_ack *extack = cb->extack;
+		struct ifaddrlblmsg *ifal;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ifal))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
+
+		ifal = nlmsg_data(nlh);
+		if (ifal->__ifal_reserved || ifal->ifal_prefixlen ||
+		    ifal->ifal_flags || ifal->ifal_index || ifal->ifal_seq) {
+			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
+			return -EINVAL;
+		}
+
+		if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*ifal))) {
+			NL_SET_ERR_MSG(extack, "Invalid data after header");
+			return -EINVAL;
+		}
+	}
+
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(p, &net->ipv6.ip6addrlbl_table.head, list) {
 		if (idx >= s_idx) {
 			err = ip6addrlbl_fill(skb, p,
 					      net->ipv6.ip6addrlbl_table.seq,
 					      NETLINK_CB(cb->skb).portid,
-					      cb->nlh->nlmsg_seq,
+					      nlh->nlmsg_seq,
 					      RTM_NEWADDRLABEL,
 					      NLM_F_MULTI);
 			if (err < 0)
-- 
2.11.0