[PATCH RFC net-next 5/5] net/ipv6: Update inet6_dump_addr to support NLM_F_DUMP_PROPER_HDR

[dsahern@kernel.org]

From: David Ahern <dsahern@gmail.com>

Update inet6_dump_addr 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 ifaddrmsg struct as the header potentially followed by one or more
attributes. Any data passed in the header or as an attribute is taken as
a request to influence the data returned. Only values suppored by the
dump handler are allowed to be non-0 or set in the request. At the moment
only the IFA_TARGET_NETNSID attribute is supported. Follow on patches
will support for other fields (e.g., honor ifa_index and only return data
for the given device index).

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 net/ipv6/addrconf.c | 50 ++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 375ea9d9869b..888e5a4b8dd2 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5001,6 +5001,8 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 			   enum addr_type_t type)
 {
+	struct netlink_ext_ack *extack = cb->extack;
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct inet6_fill_args fillargs = {
 		.portid = NETLINK_CB(cb->skb).portid,
 		.seq = cb->nlh->nlmsg_seq,
@@ -5009,7 +5011,6 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 		.type = type,
 	};
 	struct net *net = sock_net(skb->sk);
-	struct nlattr *tb[IFA_MAX+1];
 	struct net *tgt_net = net;
 	int h, s_h;
 	int idx, ip_idx;
@@ -5022,17 +5023,46 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	s_idx = idx = cb->args[1];
 	s_ip_idx = ip_idx = cb->args[2];
 
-	if (nlmsg_parse(cb->nlh, sizeof(struct ifaddrmsg), tb, IFA_MAX,
-			ifa_ipv6_policy, NULL) >= 0) {
-		if (tb[IFA_TARGET_NETNSID]) {
-			fillargs.netnsid = nla_get_s32(tb[IFA_TARGET_NETNSID]);
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		struct nlattr *tb[IFA_MAX+1];
+		struct ifaddrmsg *ifm;
+		int err, i;
+
+		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ifm))) {
+			NL_SET_ERR_MSG(extack, "Invalid header");
+			return -EINVAL;
+		}
 
-			tgt_net = rtnl_get_net_ns_capable(skb->sk,
-							  fillargs.netnsid);
-			if (IS_ERR(tgt_net))
-				return PTR_ERR(tgt_net);
+		ifm = (struct ifaddrmsg *)nlmsg_data(cb->nlh);
+		if (ifm->ifa_prefixlen || ifm->ifa_flags || ifm->ifa_scope) {
+			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
+			return -EINVAL;
+		}
+		if (ifm->ifa_index) {
+			NL_SET_ERR_MSG(extack, "Filter by device index not supported");
+			return -EINVAL;
+		}
 
-			fillargs.flags |= NLM_F_DUMP_FILTERED;
+		err = nlmsg_parse(cb->nlh, sizeof(struct ifaddrmsg), tb, IFA_MAX,
+				  ifa_ipv6_policy, NULL);
+		if (err < 0)
+			return err;
+
+		for (i = 0; i < IFA_MAX; ++i) {
+			if (i == IFA_TARGET_NETNSID) {
+				fillargs.netnsid = nla_get_s32(tb[i]);
+
+				tgt_net = rtnl_get_net_ns_capable(skb->sk,
+								  fillargs.netnsid);
+				if (IS_ERR(tgt_net))
+					return PTR_ERR(tgt_net);
+
+				fillargs.flags |= NLM_F_DUMP_FILTERED;
+			}
+			if (tb[i]) {
+				NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
+				return -EINVAL;
+			}
 		}
 	}
 
-- 
2.11.0