[PATCH RFC v2 net-next 19/25] net/bridge: Update br_mdb_dump to support NLM_F_DUMP_PROPER_HDR

[David Ahern <dsahern@kernel.org>]

From: David Ahern <dsahern@gmail.com>

Update br_mdb_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
a br_port_msg 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 <dsahern@gmail.com>
---
 net/bridge/br_mdb.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index a4a848bf827b..57c43c1b1e71 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c
@@ -167,8 +167,26 @@ static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	struct net_device *dev;
 	struct net *net = sock_net(skb->sk);
 	struct nlmsghdr *nlh = NULL;
+	struct br_port_msg *bpm;
 	int idx = 0, s_idx;
 
+	if (cb->nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		struct netlink_ext_ack *extack = cb->extack;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*bpm))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
+		if (bpm->ifindex) {
+			NL_SET_ERR_MSG(extack, "Filtering by device index is not supported");
+			return -EINVAL;
+		}
+		if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*bpm))) {
+			NL_SET_ERR_MSG(extack, "Invalid data after header");
+			return -EINVAL;
+		}
+	}
+
 	s_idx = cb->args[0];
 
 	rcu_read_lock();
@@ -178,8 +196,6 @@ static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 
 	for_each_netdev_rcu(net, dev) {
 		if (dev->priv_flags & IFF_EBRIDGE) {
-			struct br_port_msg *bpm;
-
 			if (idx < s_idx)
 				goto skip;
 
-- 
2.11.0