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 <[email protected]>
Acked-by: Paul Moore <[email protected]> (NetLabel)
Signed-off-by: David S. Miller <[email protected]>

Author: kuba-moo

drivers/block/nbd.c

@@ -2322,6 +2322,7 @@ static struct genl_family nbd_genl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= nbd_connect_genl_ops,
 	.n_small_ops	= ARRAY_SIZE(nbd_connect_genl_ops),
+	.resv_start_op	= NBD_CMD_STATUS + 1,
 	.maxattr	= NBD_ATTR_MAX,
 	.policy = nbd_attr_policy,
 	.mcgrps		= nbd_mcast_grps,

drivers/net/gtp.c

@@ -1859,6 +1859,7 @@ static struct genl_family gtp_genl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= gtp_genl_ops,
 	.n_small_ops	= ARRAY_SIZE(gtp_genl_ops),
+	.resv_start_op	= GTP_CMD_ECHOREQ + 1,
 	.mcgrps		= gtp_genl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(gtp_genl_mcgrps),
 };

drivers/net/ieee802154/mac802154_hwsim.c

@@ -630,6 +630,7 @@ static struct genl_family hwsim_genl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = hwsim_nl_ops,
 	.n_small_ops = ARRAY_SIZE(hwsim_nl_ops),
+	.resv_start_op = MAC802154_HWSIM_CMD_NEW_EDGE + 1,
 	.mcgrps = hwsim_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(hwsim_mcgrps),
 };

drivers/net/macsec.c

@@ -3404,6 +3404,7 @@ static struct genl_family macsec_fam __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= macsec_genl_ops,
 	.n_small_ops	= ARRAY_SIZE(macsec_genl_ops),
+	.resv_start_op	= MACSEC_CMD_UPD_OFFLOAD + 1,
 };
 
 static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,

drivers/net/team/team.c

@@ -2840,6 +2840,7 @@ static struct genl_family team_nl_family __ro_after_init = {
 	.module		= THIS_MODULE,
 	.small_ops	= team_nl_ops,
 	.n_small_ops	= ARRAY_SIZE(team_nl_ops),
+	.resv_start_op	= TEAM_CMD_PORT_LIST_GET + 1,
 	.mcgrps		= team_nl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(team_nl_mcgrps),
 };

drivers/net/wireguard/netlink.c

@@ -621,6 +621,7 @@ static const struct genl_ops genl_ops[] = {
 static struct genl_family genl_family __ro_after_init = {
 	.ops = genl_ops,
 	.n_ops = ARRAY_SIZE(genl_ops),
+	.resv_start_op = WG_CMD_SET_DEVICE + 1,
 	.name = WG_GENL_NAME,
 	.version = WG_GENL_VERSION,
 	.maxattr = WGDEVICE_A_MAX,

drivers/net/wireless/mac80211_hwsim.c

@@ -5288,6 +5288,7 @@ static struct genl_family hwsim_genl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.small_ops = hwsim_ops,
 	.n_small_ops = ARRAY_SIZE(hwsim_ops),
+	.resv_start_op = HWSIM_CMD_DEL_MAC_ADDR + 1,
 	.mcgrps = hwsim_mcgrps,
 	.n_mcgrps = ARRAY_SIZE(hwsim_mcgrps),
 };

drivers/target/target_core_user.c

@@ -486,6 +486,7 @@ static struct genl_family tcmu_genl_family __ro_after_init = {
 	.netnsok = true,
 	.small_ops = tcmu_genl_ops,
 	.n_small_ops = ARRAY_SIZE(tcmu_genl_ops),
+	.resv_start_op = TCMU_CMD_SET_FEATURES + 1,
 };
 
 #define tcmu_cmd_set_dbi_cur(cmd, index) ((cmd)->dbi_cur = (index))

drivers/thermal/thermal_netlink.c

@@ -693,6 +693,7 @@ static struct genl_family thermal_gnl_family __ro_after_init = {
 	.policy		= thermal_genl_policy,
 	.small_ops	= thermal_genl_ops,
 	.n_small_ops	= ARRAY_SIZE(thermal_genl_ops),
+	.resv_start_op	= THERMAL_GENL_CMD_CDEV_GET + 1,
 	.mcgrps		= thermal_genl_mcgrps,
 	.n_mcgrps	= ARRAY_SIZE(thermal_genl_mcgrps),
 };

drivers/vdpa/vdpa.c

@@ -1183,6 +1183,7 @@ static struct genl_family vdpa_nl_family __ro_after_init = {
 	.module = THIS_MODULE,
 	.ops = vdpa_nl_ops,
 	.n_ops = ARRAY_SIZE(vdpa_nl_ops),
+	.resv_start_op = VDPA_CMD_DEV_VSTATS_GET + 1,
 };
 
 static int vdpa_init(void)