genetlink: remove userhdr from struct genl_info

Only three families use info->userhdr today and going forward
we discourage using fixed headers in new families.
So having the pointer to user header in struct genl_info
is an overkill. Compute the header pointer at runtime.

Reviewed-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://lore.kernel.org/r/20230814214723.2924989-4-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/block/drbd/drbd_nl.c

@@ -159,7 +159,7 @@ static int drbd_msg_sprintf_info(struct sk_buff *skb, const char *fmt, ...)
 static int drbd_adm_prepare(struct drbd_config_context *adm_ctx,
 	struct sk_buff *skb, struct genl_info *info, unsigned flags)
 {
-	struct drbd_genlmsghdr *d_in = info->userhdr;
+	struct drbd_genlmsghdr *d_in = genl_info_userhdr(info);
 	const u8 cmd = info->genlhdr->cmd;
 	int err;
 
@@ -1396,8 +1396,9 @@ static void drbd_suspend_al(struct drbd_device *device)
 
 static bool should_set_defaults(struct genl_info *info)
 {
-	unsigned flags = ((struct drbd_genlmsghdr*)info->userhdr)->flags;
-	return 0 != (flags & DRBD_GENL_F_SET_DEFAULTS);
+	struct drbd_genlmsghdr *dh = genl_info_userhdr(info);
+
+	return 0 != (dh->flags & DRBD_GENL_F_SET_DEFAULTS);
 }
 
 static unsigned int drbd_al_extents_max(struct drbd_backing_dev *bdev)
@@ -4276,7 +4277,7 @@ static void device_to_info(struct device_info *info,
 int drbd_adm_new_minor(struct sk_buff *skb, struct genl_info *info)
 {
 	struct drbd_config_context adm_ctx;
-	struct drbd_genlmsghdr *dh = info->userhdr;
+	struct drbd_genlmsghdr *dh = genl_info_userhdr(info);
 	enum drbd_ret_code retcode;
 
 	retcode = drbd_adm_prepare(&adm_ctx, skb, info, DRBD_ADM_NEED_RESOURCE);

include/net/genetlink.h

@@ -95,7 +95,6 @@ struct genl_family {
  * @snd_portid: netlink portid of sender
  * @nlhdr: netlink message header
  * @genlhdr: generic netlink message header
- * @userhdr: user specific header
  * @attrs: netlink attributes
  * @_net: network namespace
  * @user_ptr: user pointers
@@ -106,7 +105,6 @@ struct genl_info {
 	u32			snd_portid;
 	const struct nlmsghdr *	nlhdr;
 	struct genlmsghdr *	genlhdr;
-	void *			userhdr;
 	struct nlattr **	attrs;
 	possible_net_t		_net;
 	void *			user_ptr[2];
@@ -123,6 +121,11 @@ static inline void genl_info_net_set(struct genl_info *info, struct net *net)
 	write_pnet(&info->_net, net);
 }
 
+static inline void *genl_info_userhdr(const struct genl_info *info)
+{
+	return (u8 *)info->genlhdr + GENL_HDRLEN;
+}
+
 #define GENL_SET_ERR_MSG(info, msg) NL_SET_ERR_MSG((info)->extack, msg)
 
 #define GENL_SET_ERR_MSG_FMT(info, msg, args...) \

net/netlink/genetlink.c

@@ -943,7 +943,6 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	info.snd_portid = NETLINK_CB(skb).portid;
 	info.nlhdr = nlh;
 	info.genlhdr = nlmsg_data(nlh);
-	info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
 	info.attrs = attrbuf;
 	info.extack = extack;
 	genl_info_net_set(&info, net);

net/openvswitch/conntrack.c

@@ -1605,7 +1605,7 @@ static struct sk_buff *
 ovs_ct_limit_cmd_reply_start(struct genl_info *info, u8 cmd,
 			     struct ovs_header **ovs_reply_header)
 {
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct sk_buff *skb;
 
 	skb = genlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);

net/openvswitch/datapath.c

@@ -590,7 +590,7 @@ out:
 
 static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 {
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct net *net = sock_net(skb->sk);
 	struct nlattr **a = info->attrs;
 	struct sw_flow_actions *acts;
@@ -967,7 +967,7 @@ static int ovs_flow_cmd_new(struct sk_buff *skb, struct genl_info *info)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct sw_flow *flow = NULL, *new_flow;
 	struct sw_flow_mask mask;
 	struct sk_buff *reply;
@@ -1214,7 +1214,7 @@ static int ovs_flow_cmd_set(struct sk_buff *skb, struct genl_info *info)
 {
 	struct net *net = sock_net(skb->sk);
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct sw_flow_key key;
 	struct sw_flow *flow;
 	struct sk_buff *reply = NULL;
@@ -1315,7 +1315,7 @@ error:
 static int ovs_flow_cmd_get(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct net *net = sock_net(skb->sk);
 	struct sw_flow_key key;
 	struct sk_buff *reply;
@@ -1374,7 +1374,7 @@ unlock:
 static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct net *net = sock_net(skb->sk);
 	struct sw_flow_key key;
 	struct sk_buff *reply;
@@ -1642,7 +1642,7 @@ static void ovs_dp_reset_user_features(struct sk_buff *skb,
 {
 	struct datapath *dp;
 
-	dp = lookup_datapath(sock_net(skb->sk), info->userhdr,
+	dp = lookup_datapath(sock_net(skb->sk), genl_info_userhdr(info),
 			     info->attrs);
 	if (IS_ERR(dp))
 		return;
@@ -1935,7 +1935,8 @@ static int ovs_dp_cmd_del(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	ovs_lock();
-	dp = lookup_datapath(sock_net(skb->sk), info->userhdr, info->attrs);
+	dp = lookup_datapath(sock_net(skb->sk), genl_info_userhdr(info),
+			     info->attrs);
 	err = PTR_ERR(dp);
 	if (IS_ERR(dp))
 		goto err_unlock_free;
@@ -1968,7 +1969,8 @@ static int ovs_dp_cmd_set(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	ovs_lock();
-	dp = lookup_datapath(sock_net(skb->sk), info->userhdr, info->attrs);
+	dp = lookup_datapath(sock_net(skb->sk), genl_info_userhdr(info),
+			     info->attrs);
 	err = PTR_ERR(dp);
 	if (IS_ERR(dp))
 		goto err_unlock_free;
@@ -2003,7 +2005,8 @@ static int ovs_dp_cmd_get(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	ovs_lock();
-	dp = lookup_datapath(sock_net(skb->sk), info->userhdr, info->attrs);
+	dp = lookup_datapath(sock_net(skb->sk), genl_info_userhdr(info),
+			     info->attrs);
 	if (IS_ERR(dp)) {
 		err = PTR_ERR(dp);
 		goto err_unlock_free;
@@ -2246,7 +2249,7 @@ static void ovs_update_headroom(struct datapath *dp, unsigned int new_headroom)
 static int ovs_vport_cmd_new(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct vport_parms parms;
 	struct sk_buff *reply;
 	struct vport *vport;
@@ -2348,7 +2351,7 @@ static int ovs_vport_cmd_set(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	ovs_lock();
-	vport = lookup_vport(sock_net(skb->sk), info->userhdr, a);
+	vport = lookup_vport(sock_net(skb->sk), genl_info_userhdr(info), a);
 	err = PTR_ERR(vport);
 	if (IS_ERR(vport))
 		goto exit_unlock_free;
@@ -2404,7 +2407,7 @@ static int ovs_vport_cmd_del(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	ovs_lock();
-	vport = lookup_vport(sock_net(skb->sk), info->userhdr, a);
+	vport = lookup_vport(sock_net(skb->sk), genl_info_userhdr(info), a);
 	err = PTR_ERR(vport);
 	if (IS_ERR(vport))
 		goto exit_unlock_free;
@@ -2447,7 +2450,7 @@ exit_unlock_free:
 static int ovs_vport_cmd_get(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct sk_buff *reply;
 	struct vport *vport;
 	int err;

net/openvswitch/meter.c

@@ -211,7 +211,7 @@ ovs_meter_cmd_reply_start(struct genl_info *info, u8 cmd,
 			  struct ovs_header **ovs_reply_header)
 {
 	struct sk_buff *skb;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 
 	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
 	if (!skb)
@@ -272,7 +272,7 @@ error:
 
 static int ovs_meter_cmd_features(struct sk_buff *skb, struct genl_info *info)
 {
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct ovs_header *ovs_reply_header;
 	struct nlattr *nla, *band_nla;
 	struct sk_buff *reply;
@@ -409,7 +409,7 @@ static int ovs_meter_cmd_set(struct sk_buff *skb, struct genl_info *info)
 	struct dp_meter *meter, *old_meter;
 	struct sk_buff *reply;
 	struct ovs_header *ovs_reply_header;
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct dp_meter_table *meter_tbl;
 	struct datapath *dp;
 	int err;
@@ -482,7 +482,7 @@ exit_free_meter:
 
 static int ovs_meter_cmd_get(struct sk_buff *skb, struct genl_info *info)
 {
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct ovs_header *ovs_reply_header;
 	struct nlattr **a = info->attrs;
 	struct dp_meter *meter;
@@ -535,7 +535,7 @@ exit_unlock:
 
 static int ovs_meter_cmd_del(struct sk_buff *skb, struct genl_info *info)
 {
-	struct ovs_header *ovs_header = info->userhdr;
+	struct ovs_header *ovs_header = genl_info_userhdr(info);
 	struct ovs_header *ovs_reply_header;
 	struct nlattr **a = info->attrs;
 	struct dp_meter *old_meter;

net/tipc/netlink_compat.c

@@ -1294,7 +1294,7 @@ static int tipc_nl_compat_recv(struct sk_buff *skb, struct genl_info *info)
 	struct tipc_nl_compat_msg msg;
 	struct nlmsghdr *req_nlh;
 	struct nlmsghdr *rep_nlh;
-	struct tipc_genlmsghdr *req_userhdr = info->userhdr;
+	struct tipc_genlmsghdr *req_userhdr = genl_info_userhdr(info);
 
 	memset(&msg, 0, sizeof(msg));