From: David Ahern <redacted>

Update br_mdb_dump for strict data checking. 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 <redacted>
---
 net/bridge/br_mdb.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/net/bridge/br_mdb.c b/net/bridge/br_mdb.c
index a4a848bf827b..7beeee658d6c 100644
--- a/net/bridge/br_mdb.c
+++ b/net/bridge/br_mdb.c

@@ -162,6 +162,28 @@ static int br_mdb_fill_info(struct sk_buff *skb, struct netlink_callback *cb,
 	return err;
 }
 
+static int br_mdb_valid_dump_req(const struct nlmsghdr *nlh,
+				 struct netlink_ext_ack *extack)
+{
+	struct br_port_msg *bpm;
+
+	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;
+	}
+
+	return 0;
+}
+
 static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	struct net_device *dev;

@@ -169,6 +191,13 @@ static int br_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	struct nlmsghdr *nlh = NULL;
 	int idx = 0, s_idx;
 
+	if (cb->strict_check) {
+		int err = br_mdb_valid_dump_req(cb->nlh, cb->extack);
+
+		if (err)
+			return err;