Subject: [PATCH RFC v2 net-next 14/25] net/neighbor: Update neightbl_dump_info to support NLM_F_DUMP_PROPER_HDR

From: David Ahern <[email-masked]>
Date: Mon, 1 Oct 2018 17:28:40 -0700

From: David Ahern <[email-masked]>

Update neightbl_dump_info 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 ndtmsg 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/neighbour.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index aaf2526e5da4..8488f2e2c865 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2166,13 +2166,35 @@ static int neightbl_set(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	int family, tidx, nidx = 0;
 	int tbl_skip = cb->args[0];
 	int neigh_skip = cb->args[1];
 	struct neigh_table *tbl;
 
-	family = ((struct rtgenmsg *) nlmsg_data(cb->nlh))->rtgen_family;
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		struct netlink_ext_ack *extack = cb->extack;
+		struct ndtmsg *ndtm;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ndtm))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
+
+		ndtm = nlmsg_data(nlh);
+		if (ndtm->ndtm_pad1  || ndtm->ndtm_pad2) {
+			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
+			return -EINVAL;
+		}
+
+		if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*ndtm))) {
+			NL_SET_ERR_MSG(extack, "Invalid data after header");
+			return -EINVAL;
+		}
+	}
+
+	family = ((struct rtgenmsg *)nlmsg_data(nlh))->rtgen_family;
 
 	for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
 		struct neigh_parms *p;
@@ -2185,7 +2207,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 			continue;
 
 		if (neightbl_fill_info(skb, tbl, NETLINK_CB(cb->skb).portid,
-				       cb->nlh->nlmsg_seq, RTM_NEWNEIGHTBL,
+				       nlh->nlmsg_seq, RTM_NEWNEIGHTBL,
 				       NLM_F_MULTI) < 0)
 			break;
 
@@ -2200,7 +2222,7 @@ static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
 
 			if (neightbl_fill_param_info(skb, tbl, p,
 						     NETLINK_CB(cb->skb).portid,
-						     cb->nlh->nlmsg_seq,
+						     nlh->nlmsg_seq,
 						     RTM_NEWNEIGHTBL,
 						     NLM_F_MULTI) < 0)
 				goto out;
-- 
2.11.0