Subject: [PATCH RFC v2 net-next 16/25] net/fib_rules: Update fib_nl_dumprule to support NLM_F_DUMP_PROPER_HDR

From: David Ahern <[email-masked]>
Date: Mon, 1 Oct 2018 17:28:42 -0700

From: David Ahern <[email-masked]>

Update fib_nl_dumprule 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
fib_rule_hdr 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/core/fib_rules.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 0ff3953f64aa..e9f9dc501b2e 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -1065,11 +1065,34 @@ static int dump_rules(struct sk_buff *skb, struct netlink_callback *cb,
 
 static int fib_nl_dumprule(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	struct fib_rules_ops *ops;
 	int idx = 0, family;
 
-	family = rtnl_msg_family(cb->nlh);
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		struct netlink_ext_ack *extack = cb->extack;
+		struct fib_rule_hdr *frh;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*frh))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
+
+		frh = nlmsg_data(nlh);
+		if (frh->dst_len || frh->src_len || frh->tos || frh->table ||
+		    frh->res1 || frh->res2 || frh->action || frh->flags) {
+			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
+			return -EINVAL;
+		}
+
+		if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*frh))) {
+			NL_SET_ERR_MSG(extack, "Invalid data after header");
+			return -EINVAL;
+		}
+	}
+
+	family = rtnl_msg_family(nlh);
 	if (family != AF_UNSPEC) {
 		/* Protocol specific dump request */
 		ops = lookup_rules_ops(net, family);
-- 
2.11.0