[PATCH RFC v2 net-next 11/25] rtnetlink: Update fib dumps to support NLM_F_DUMP_PROPER_HDR

[David Ahern <dsahern@kernel.org>]

From: David Ahern <dsahern@gmail.com>

Add helper to check netlink message for route dumps. The dump request
is expected to have an rtmsg struct as the header. All elements of the
struct are expected to be 0 with the exception of rtm_flags (which is
used by both ipv4 and ipv6 dumps) and with no attributes can be appended.

Update inet_dump_fib, inet6_dump_fib, mpls_dump_routes, ipmr_rtm_dumproute,
and ip6mr_rtm_dumproute to call this helper if NLM_F_DUMP_PROPER_HDR is
set in the netlink message header.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/net/ip_fib.h    |  2 ++
 net/ipv4/fib_frontend.c | 43 +++++++++++++++++++++++++++++++++++++++++--
 net/ipv4/ipmr.c         |  9 +++++++++
 net/ipv6/ip6_fib.c      |  8 ++++++++
 net/ipv6/ip6mr.c        |  9 +++++++++
 net/mpls/af_mpls.c      |  8 ++++++++
 6 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index f7c109e37298..9846b79c9ee1 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -452,4 +452,6 @@ static inline void fib_proc_exit(struct net *net)
 
 u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr);
 
+int ip_valid_fib_dump_req(const struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack);
 #endif  /* _NET_FIB_H */
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 30e2bcc3ef2a..c608b393ae49 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -802,8 +802,41 @@ static int inet_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
+int ip_valid_fib_dump_req(const struct nlmsghdr *nlh,
+			  struct netlink_ext_ack *extack)
+{
+	struct rtmsg *rtm;
+
+	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
+		NL_SET_ERR_MSG(extack, "Invalid header");
+		return -EINVAL;
+	}
+
+	rtm = nlmsg_data(nlh);
+	if (rtm->rtm_dst_len || rtm->rtm_src_len  || rtm->rtm_tos   ||
+	    rtm->rtm_table   || rtm->rtm_protocol || rtm->rtm_scope ||
+	    rtm->rtm_type) {
+		NL_SET_ERR_MSG(extack,
+			       "Invalid values in header for dump request");
+		return -EINVAL;
+	}
+
+	if (rtm->rtm_flags & ~(RTM_F_CLONED | RTM_F_PREFIX)) {
+		NL_SET_ERR_MSG(extack, "Invalid flags for dump request");
+		return -EINVAL;
+	}
+	if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*rtm))) {
+		NL_SET_ERR_MSG(extack, "Invalid data after header");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ip_valid_fib_dump_req);
+
 static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	unsigned int h, s_h;
 	unsigned int e = 0, s_e;
@@ -811,8 +844,14 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 	struct hlist_head *head;
 	int dumped = 0, err;
 
-	if (nlmsg_len(cb->nlh) >= sizeof(struct rtmsg) &&
-	    ((struct rtmsg *) nlmsg_data(cb->nlh))->rtm_flags & RTM_F_CLONED)
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		err = ip_valid_fib_dump_req(nlh, cb->extack);
+		if (err)
+			return err;
+	}
+
+	if (nlmsg_len(nlh) >= sizeof(struct rtmsg) &&
+	    ((struct rtmsg *)nlmsg_data(nlh))->rtm_flags & RTM_F_CLONED)
 		return skb->len;
 
 	s_h = cb->args[0];
diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index a706e9269e8c..91b5991ed536 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -2527,6 +2527,15 @@ static int ipmr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
 
 static int ipmr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
+
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		int err = ip_valid_fib_dump_req(nlh, cb->extack);
+
+		if (err)
+			return err;
+	}
+
 	return mr_rtm_dumproute(skb, cb, ipmr_mr_table_iter,
 				_ipmr_fill_mroute, &mfc_unres_lock);
 }
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 5516f55e214b..fc14733fbad8 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -568,6 +568,7 @@ static int fib6_dump_table(struct fib6_table *table, struct sk_buff *skb,
 
 static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	unsigned int h, s_h;
 	unsigned int e = 0, s_e;
@@ -577,6 +578,13 @@ static int inet6_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 	struct hlist_head *head;
 	int res = 0;
 
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		int err = ip_valid_fib_dump_req(nlh, cb->extack);
+
+		if (err)
+			return err;
+	}
+
 	s_h = cb->args[0];
 	s_e = cb->args[1];
 
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index d0b7e0249c13..aa668214edc2 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -2433,6 +2433,15 @@ static void mrt6msg_netlink_event(struct mr_table *mrt, struct sk_buff *pkt)
 
 static int ip6mr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
+
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		int err = ip_valid_fib_dump_req(nlh, cb->extack);
+
+		if (err)
+			return err;
+	}
+
 	return mr_rtm_dumproute(skb, cb, ip6mr_mr_table_iter,
 				_ip6mr_fill_mroute, &mfc_unres_lock);
 }
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 8fbe6cdbe255..812100a5a906 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -2017,6 +2017,7 @@ static int mpls_dump_route(struct sk_buff *skb, u32 portid, u32 seq, int event,
 
 static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	struct mpls_route __rcu **platform_label;
 	size_t platform_labels;
@@ -2024,6 +2025,13 @@ static int mpls_dump_routes(struct sk_buff *skb, struct netlink_callback *cb)
 
 	ASSERT_RTNL();
 
+	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
+		int err = ip_valid_fib_dump_req(nlh, cb->extack);
+
+		if (err)
+			return err;
+	}
+
 	index = cb->args[0];
 	if (index < MPLS_LABEL_FIRST_UNRESERVED)
 		index = MPLS_LABEL_FIRST_UNRESERVED;
-- 
2.11.0