genetlink: start to validate reserved header bytes

We had historically not checked that genlmsghdr.reserved
is 0 on input which prevents us from using those precious
bytes in the future.

One use case would be to extend the cmd field, which is
currently just 8 bits wide and 256 is not a lot of commands
for some core families.

To make sure that new families do the right thing by default
put the onus of opting out of validation on existing families.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com> (NetLabel)
Signed-off-by: David S. Miller <davem@davemloft.net>

31 files changed, 38 insertions, 2 deletions

diff --git a/net/batman-adv/netlink.c b/net/batman-adv/netlink.c
index 00875e1d8c44..a5e4a4e976cf 100644
--- a/net/batman-adv/netlink.c
+++ b/net/batman-adv/netlink.c
@@ -1493,6 +1493,7 @@ struct genl_family batadv_netlink_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = batadv_netlink_ops,
 	.n_small_ops = ARRAY_SIZE(batadv_netlink_ops),
+	.resv_start_op = BATADV_CMD_SET_VLAN + 1,
 	.mcgrps = batadv_netlink_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(batadv_netlink_mcgrps),
 };
diff --git a/net/core/devlink.c b/net/core/devlink.c
index 2afbeb6eca67..3396fdf802b6 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -9610,6 +9610,7 @@ static struct genl_family devlink_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= devlink_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(devlink_nl_ops),
+	.resv_start_op	= DEVLINK_CMD_SELFTESTS_RUN + 1,
 	.mcgrps		= devlink_nl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(devlink_nl_mcgrps),
 };
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 876664fc605e..f084a4a6b7ab 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -1645,6 +1645,7 @@ static struct genl_family net_drop_monitor_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= dropmon_ops,
 	.n_small_ops	= ARRAY_SIZE(dropmon_ops),
+	.resv_start_op	= NET_DM_CMD_STATS_GET + 1,
 	.mcgrps		= dropmon_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(dropmon_mcgrps),
 };
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index e26079e11835..d5e77f1cbbfa 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -1033,6 +1033,7 @@ static struct genl_family ethtool_genl_family __ro_after_init = {
 	.parallel_ops	= true,
 	.ops		= ethtool_genl_ops,
 	.n_ops		= ARRAY_SIZE(ethtool_genl_ops),
+	.resv_start_op	= ETHTOOL_MSG_MODULE_GET + 1,
 	.mcgrps		= ethtool_nl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(ethtool_nl_mcgrps),
 };
diff --git a/net/hsr/hsr_netlink.c b/net/hsr/hsr_netlink.c
index 1405c037cf7a..7174a9092900 100644
--- a/net/hsr/hsr_netlink.c
+++ b/net/hsr/hsr_netlink.c
@@ -522,6 +522,7 @@ static struct genl_family hsr_genl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = hsr_ops,
 	.n_small_ops = ARRAY_SIZE(hsr_ops),
+	.resv_start_op = HSR_C_SET_NODE_LIST + 1,
 	.mcgrps = hsr_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(hsr_mcgrps),
 };
diff --git a/net/ieee802154/netlink.c b/net/ieee802154/netlink.c
index b07abc38b4b3..7d2de4ee6992 100644
--- a/net/ieee802154/netlink.c
+++ b/net/ieee802154/netlink.c
@@ -132,6 +132,7 @@ struct genl_family nl802154_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= ieee802154_ops,
 	.n_small_ops	= ARRAY_SIZE(ieee802154_ops),
+	.resv_start_op	= IEEE802154_LLSEC_DEL_SECLEVEL + 1,
 	.mcgrps		= ieee802154_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(ieee802154_mcgrps),
 };
diff --git a/net/ieee802154/nl802154.c b/net/ieee802154/nl802154.c
index e0b072aecf0f..38c4f3cb010e 100644
--- a/net/ieee802154/nl802154.c
+++ b/net/ieee802154/nl802154.c
@@ -2500,6 +2500,7 @@ static struct genl_family nl802154_fam __ro_after_init = {
 	.module = THIS_MODULE,
 	.ops = nl802154_ops,
 	.n_ops = ARRAY_SIZE(nl802154_ops),
+	.resv_start_op = NL802154_CMD_DEL_SEC_LEVEL + 1,
 	.mcgrps = nl802154_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(nl802154_mcgrps),
 };
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index cb5bfb77944c..0c3c6d0cee29 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -928,6 +928,7 @@ static struct genl_family fou_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= fou_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(fou_nl_ops),
+	.resv_start_op	= FOU_CMD_GET + 1,
 };
 
 size_t fou_encap_hlen(struct ip_tunnel_encap *e)
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index d58e672be31c..82f4575f9cd9 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -969,6 +969,7 @@ static struct genl_family tcp_metrics_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= tcp_metrics_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(tcp_metrics_nl_ops),
+	.resv_start_op	= TCP_METRICS_CMD_DEL + 1,
 };
 
 static unsigned int tcpmhash_entries;
diff --git a/net/ipv6/ila/ila_main.c b/net/ipv6/ila/ila_main.c
index 36c58aa257e8..3faf62530d6a 100644
--- a/net/ipv6/ila/ila_main.c
+++ b/net/ipv6/ila/ila_main.c
@@ -55,6 +55,7 @@ struct genl_family ila_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.ops		= ila_nl_ops,
 	.n_ops		= ARRAY_SIZE(ila_nl_ops),
+	.resv_start_op	= ILA_CMD_FLUSH + 1,
 };
 
 static __net_init int ila_init_net(struct net *net)
diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
index 1098131ed90c..571f0e4d9cf3 100644
--- a/net/ipv6/ioam6.c
+++ b/net/ipv6/ioam6.c
@@ -619,6 +619,7 @@ static struct genl_family ioam6_genl_family __ro_after_init = {
 	.parallel_ops	= true,
 	.ops		= ioam6_genl_ops,
 	.n_ops		= ARRAY_SIZE(ioam6_genl_ops),
+	.resv_start_op	= IOAM6_CMD_NS_SET_SCHEMA + 1,
 	.module		= THIS_MODULE,
 };
 
diff --git a/net/ipv6/seg6.c b/net/ipv6/seg6.c
index 73aaabf0e966..5421cc7c935f 100644
--- a/net/ipv6/seg6.c
+++ b/net/ipv6/seg6.c
@@ -499,6 +499,7 @@ static struct genl_family seg6_genl_family __ro_after_init = {
 	.parallel_ops	= true,
 	.ops		= seg6_genl_ops,
 	.n_ops		= ARRAY_SIZE(seg6_genl_ops),
+	.resv_start_op	= SEG6_CMD_GET_TUNSRC + 1,
 	.module		= THIS_MODULE,
 };
 
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 96eb91be9238..a901fd14fe3b 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -989,6 +989,7 @@ static struct genl_family l2tp_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= l2tp_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(l2tp_nl_ops),
+	.resv_start_op	= L2TP_CMD_SESSION_GET + 1,
 	.mcgrps		= l2tp_multicast_group,
 	.n_mcgrps	= ARRAY_SIZE(l2tp_multicast_group),
 };
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index 291b5da42fdb..a3e4ee7af0ee 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -2280,6 +2280,7 @@ static struct genl_family mptcp_genl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= mptcp_pm_ops,
 	.n_small_ops	= ARRAY_SIZE(mptcp_pm_ops),
+	.resv_start_op	= MPTCP_PM_CMD_SUBFLOW_DESTROY + 1,
 	.mcgrps		= mptcp_pm_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(mptcp_pm_mcgrps),
 };
diff --git a/net/ncsi/ncsi-netlink.c b/net/ncsi/ncsi-netlink.c
index c189b4c8a182..d27f4eccce6d 100644
--- a/net/ncsi/ncsi-netlink.c
+++ b/net/ncsi/ncsi-netlink.c
@@ -768,6 +768,7 @@ static struct genl_family ncsi_genl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = ncsi_ops,
 	.n_small_ops = ARRAY_SIZE(ncsi_ops),
+	.resv_start_op = NCSI_CMD_SET_CHANNEL_MASK + 1,
 };
 
 static int __init ncsi_init_netlink(void)
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index efab2b06d373..818b0b058b10 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -4005,6 +4005,7 @@ static struct genl_family ip_vs_genl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= ip_vs_genl_ops,
 	.n_small_ops	= ARRAY_SIZE(ip_vs_genl_ops),
+	.resv_start_op	= IPVS_CMD_FLUSH + 1,
 };
 
 static int __init ip_vs_genl_register(void)
diff --git a/net/netlabel/netlabel_calipso.c b/net/netlabel/netlabel_calipso.c
index 91a19c3ea1a3..f1d5b8465217 100644
--- a/net/netlabel/netlabel_calipso.c
+++ b/net/netlabel/netlabel_calipso.c
@@ -344,6 +344,7 @@ static struct genl_family netlbl_calipso_gnl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = netlbl_calipso_ops,
 	.n_small_ops = ARRAY_SIZE(netlbl_calipso_ops),
+	.resv_start_op = NLBL_CALIPSO_C_LISTALL + 1,
 };
 
 /* NetLabel Generic NETLINK Protocol Functions
diff --git a/net/netlabel/netlabel_cipso_v4.c b/net/netlabel/netlabel_cipso_v4.c
index 894e6b8f1a86..fa08ee75ac06 100644
--- a/net/netlabel/netlabel_cipso_v4.c
+++ b/net/netlabel/netlabel_cipso_v4.c
@@ -767,6 +767,7 @@ static struct genl_family netlbl_cipsov4_gnl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = netlbl_cipsov4_ops,
 	.n_small_ops = ARRAY_SIZE(netlbl_cipsov4_ops),
+	.resv_start_op = NLBL_CIPSOV4_C_LISTALL + 1,
 };
 
 /*
diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
index 032b7d7b32c7..689eaa2afbec 100644
--- a/net/netlabel/netlabel_mgmt.c
+++ b/net/netlabel/netlabel_mgmt.c
@@ -826,6 +826,7 @@ static struct genl_family netlbl_mgmt_gnl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = netlbl_mgmt_genl_ops,
 	.n_small_ops = ARRAY_SIZE(netlbl_mgmt_genl_ops),
+	.resv_start_op = NLBL_MGMT_C_VERSION + 1,
 };
 
 /*
diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
index 0555dffd80e0..9996883bf2b7 100644
--- a/net/netlabel/netlabel_unlabeled.c
+++ b/net/netlabel/netlabel_unlabeled.c
@@ -1374,6 +1374,7 @@ static struct genl_family netlbl_unlabel_gnl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = netlbl_unlabel_genl_ops,
 	.n_small_ops = ARRAY_SIZE(netlbl_unlabel_genl_ops),
+	.resv_start_op = NLBL_UNLABEL_C_STATICLISTDEF + 1,
 };
 
 /*
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 76aed0571e3a..7c136de117eb 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -757,6 +757,9 @@ static int genl_family_rcv_msg(const struct genl_family *family,
 	if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 		return -EINVAL;
 
+	if (hdr->cmd >= family->resv_start_op && hdr->reserved)
+		return -EINVAL;
+
 	if (genl_get_cmd(hdr->cmd, family, &op))
 		return -EOPNOTSUPP;
 
@@ -1348,6 +1351,7 @@ static struct genl_family genl_ctrl __ro_after_init = {
 	.module = THIS_MODULE,
 	.ops = genl_ctrl_ops,
 	.n_ops = ARRAY_SIZE(genl_ctrl_ops),
+	.resv_start_op = CTRL_CMD_GETPOLICY + 1,
 	.mcgrps = genl_ctrl_groups,
 	.n_mcgrps = ARRAY_SIZE(genl_ctrl_groups),
 	.id = GENL_ID_CTRL,
diff --git a/net/nfc/netlink.c b/net/nfc/netlink.c
index 7c62417ccfd7..9d91087b9399 100644
--- a/net/nfc/netlink.c
+++ b/net/nfc/netlink.c
@@ -1783,6 +1783,7 @@ static struct genl_family nfc_genl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.ops = nfc_genl_ops,
 	.n_ops = ARRAY_SIZE(nfc_genl_ops),
+	.resv_start_op = NFC_CMD_DEACTIVATE_TARGET + 1,
 	.mcgrps = nfc_genl_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(nfc_genl_mcgrps),
 };
diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 4e70df91d0f2..48e8f5c29b67 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -2283,6 +2283,7 @@ struct genl_family dp_ct_limit_genl_family __ro_after_init = {
 	.parallel_ops = true,
 	.small_ops = ct_limit_genl_ops,
 	.n_small_ops = ARRAY_SIZE(ct_limit_genl_ops),
+	.resv_start_op = OVS_CT_LIMIT_CMD_GET + 1,
 	.mcgrps = &ovs_ct_limit_multicast_group,
 	.n_mcgrps = 1,
 	.module = THIS_MODULE,
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index e4667700336b..8f49e2359a1b 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -692,6 +692,7 @@ static struct genl_family dp_packet_genl_family __ro_after_init = {
 	.parallel_ops = true,
 	.small_ops = dp_packet_genl_ops,
 	.n_small_ops = ARRAY_SIZE(dp_packet_genl_ops),
+	.resv_start_op = OVS_PACKET_CMD_EXECUTE + 1,
 	.module = THIS_MODULE,
 };
 
@@ -1509,6 +1510,7 @@ static struct genl_family dp_flow_genl_family __ro_after_init = {
 	.parallel_ops = true,
 	.small_ops = dp_flow_genl_ops,
 	.n_small_ops = ARRAY_SIZE(dp_flow_genl_ops),
+	.resv_start_op = OVS_FLOW_CMD_SET + 1,
 	.mcgrps = &ovs_dp_flow_multicast_group,
 	.n_mcgrps = 1,
 	.module = THIS_MODULE,
@@ -2051,6 +2053,7 @@ static struct genl_family dp_datapath_genl_family __ro_after_init = {
 	.parallel_ops = true,
 	.small_ops = dp_datapath_genl_ops,
 	.n_small_ops = ARRAY_SIZE(dp_datapath_genl_ops),
+	.resv_start_op = OVS_DP_CMD_SET + 1,
 	.mcgrps = &ovs_dp_datapath_multicast_group,
 	.n_mcgrps = 1,
 	.module = THIS_MODULE,
diff --git a/net/openvswitch/meter.c b/net/openvswitch/meter.c
index 04a060ac7fdf..51111a9009bd 100644
--- a/net/openvswitch/meter.c
+++ b/net/openvswitch/meter.c
@@ -720,6 +720,7 @@ struct genl_family dp_meter_genl_family __ro_after_init = {
 	.parallel_ops = true,
 	.small_ops = dp_meter_genl_ops,
 	.n_small_ops = ARRAY_SIZE(dp_meter_genl_ops),
+	.resv_start_op = OVS_METER_CMD_GET + 1,
 	.mcgrps = &ovs_meter_multicast_group,
 	.n_mcgrps = 1,
 	.module = THIS_MODULE,
diff --git a/net/psample/psample.c b/net/psample/psample.c
index 118d5d2a81a0..81a794e36f53 100644
--- a/net/psample/psample.c
+++ b/net/psample/psample.c
@@ -115,6 +115,7 @@ static struct genl_family psample_nl_family __ro_after_init = {
 	.mcgrps		= psample_nl_mcgrps,
 	.small_ops	= psample_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(psample_nl_ops),
+	.resv_start_op	= PSAMPLE_CMD_GET_GROUP + 1,
 	.n_mcgrps	= ARRAY_SIZE(psample_nl_mcgrps),
 };
 
diff --git a/net/smc/smc_netlink.c b/net/smc/smc_netlink.c
index c5a62f6f52ba..621c46c70073 100644
--- a/net/smc/smc_netlink.c
+++ b/net/smc/smc_netlink.c
@@ -142,7 +142,8 @@ struct genl_family smc_gen_nl_family __ro_after_init = {
 	.netnsok =	true,
 	.module =	THIS_MODULE,
 	.ops =		smc_gen_nl_ops,
-	.n_ops =	ARRAY_SIZE(smc_gen_nl_ops)
+	.n_ops =	ARRAY_SIZE(smc_gen_nl_ops),
+	.resv_start_op = SMC_NETLINK_DISABLE_HS_LIMITATION + 1,
 };
 
 int __init smc_nl_init(void)
diff --git a/net/smc/smc_pnet.c b/net/smc/smc_pnet.c
index 4c3bf6db7038..25fb2fd186e2 100644
--- a/net/smc/smc_pnet.c
+++ b/net/smc/smc_pnet.c
@@ -715,7 +715,8 @@ static struct genl_family smc_pnet_nl_family __ro_after_init = {
 	.netnsok = true,
 	.module = THIS_MODULE,
 	.ops = smc_pnet_ops,
-	.n_ops =  ARRAY_SIZE(smc_pnet_ops)
+	.n_ops =  ARRAY_SIZE(smc_pnet_ops),
+	.resv_start_op = SMC_PNETID_FLUSH + 1,
 };
 
 bool smc_pnet_is_ndev_pnetid(struct net *net, u8 *pnetid)
diff --git a/net/tipc/netlink.c b/net/tipc/netlink.c
index c447cb5f879e..e8fd257c0e68 100644
--- a/net/tipc/netlink.c
+++ b/net/tipc/netlink.c
@@ -294,6 +294,7 @@ struct genl_family tipc_genl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.ops		= tipc_genl_v2_ops,
 	.n_ops		= ARRAY_SIZE(tipc_genl_v2_ops),
+	.resv_start_op	= TIPC_NL_ADDR_LEGACY_GET + 1,
 };
 
 int __init tipc_netlink_start(void)
diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index 0749df80454d..fc68733673ba 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -1357,6 +1357,7 @@ static struct genl_family tipc_genl_compat_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= tipc_genl_compat_ops,
 	.n_small_ops	= ARRAY_SIZE(tipc_genl_compat_ops),
+	.resv_start_op	= TIPC_GENL_CMD + 1,
 };
 
 int __init tipc_netlink_compat_start(void)
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index dad88d231d56..e0087176796c 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -17237,6 +17237,7 @@ static struct genl_family nl80211_fam __ro_after_init = {
 	.n_ops = ARRAY_SIZE(nl80211_ops),
 	.small_ops = nl80211_small_ops,
 	.n_small_ops = ARRAY_SIZE(nl80211_small_ops),
+	.resv_start_op = NL80211_CMD_REMOVE_LINK_STA + 1,
 	.mcgrps = nl80211_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(nl80211_mcgrps),
 	.parallel_ops = true,