genetlink: extend info user-storage to match NL cb ctx

This allows a more uniform implementation of non-dump and dump
operations, and will be used later in the series to avoid some
per-operation allocation.

Additionally rename the NL_ASSERT_DUMP_CTX_FITS macro, to
fit a more extended usage.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Link: https://patch.msgid.link/1130cc2896626b84587a2a5f96a5c6829638f4da.1728460186.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

9 files changed, 17 insertions, 12 deletions

diff --git a/drivers/net/vxlan/vxlan_mdb.c b/drivers/net/vxlan/vxlan_mdb.c
index 60eb95a06d55..ebed05a2804c 100644
--- a/drivers/net/vxlan/vxlan_mdb.c
+++ b/drivers/net/vxlan/vxlan_mdb.c
@@ -284,7 +284,7 @@ int vxlan_mdb_dump(struct net_device *dev, struct sk_buff *skb,
 
 	ASSERT_RTNL();
 
-	NL_ASSERT_DUMP_CTX_FITS(struct vxlan_mdb_dump_ctx);
+	NL_ASSERT_CTX_FITS(struct vxlan_mdb_dump_ctx);
 
 	nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid,
 			cb->nlh->nlmsg_seq, RTM_NEWMDB, sizeof(*bpm),
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index b332c2048c75..a3ca198a3a9e 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -34,6 +34,7 @@ struct netlink_skb_parms {
 
 #define NETLINK_CB(skb)		(*(struct netlink_skb_parms*)&((skb)->cb))
 #define NETLINK_CREDS(skb)	(&NETLINK_CB((skb)).creds)
+#define NETLINK_CTX_SIZE	48
 
 
 void netlink_table_grab(void);
@@ -293,7 +294,7 @@ struct netlink_callback {
 	int			flags;
 	bool			strict_check;
 	union {
-		u8		ctx[48];
+		u8		ctx[NETLINK_CTX_SIZE];
 
 		/* args is deprecated. Cast a struct over ctx instead
 		 * for proper type safety.
@@ -302,7 +303,7 @@ struct netlink_callback {
 	};
 };
 
-#define NL_ASSERT_DUMP_CTX_FITS(type_name)				\
+#define NL_ASSERT_CTX_FITS(type_name)					\
 	BUILD_BUG_ON(sizeof(type_name) >				\
 		     sizeof_field(struct netlink_callback, ctx))
 
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 9ab49bfeae78..9d3726e8f90e 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -124,7 +124,8 @@ struct genl_family {
  * @genlhdr: generic netlink message header
  * @attrs: netlink attributes
  * @_net: network namespace
- * @user_ptr: user pointers
+ * @ctx: storage space for the use by the family
+ * @user_ptr: user pointers (deprecated, use ctx instead)
  * @extack: extended ACK report struct
  */
 struct genl_info {
@@ -135,7 +136,10 @@ struct genl_info {
 	struct genlmsghdr *	genlhdr;
 	struct nlattr **	attrs;
 	possible_net_t		_net;
-	void *			user_ptr[2];
+	union {
+		u8		ctx[NETLINK_CTX_SIZE];
+		void *		user_ptr[2];
+	};
 	struct netlink_ext_ack *extack;
 };
 
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index 1cb954f2d39e..358cba248796 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -24,7 +24,7 @@ struct netdev_nl_dump_ctx {
 
 static struct netdev_nl_dump_ctx *netdev_dump_ctx(struct netlink_callback *cb)
 {
-	NL_ASSERT_DUMP_CTX_FITS(struct netdev_nl_dump_ctx);
+	NL_ASSERT_CTX_FITS(struct netdev_nl_dump_ctx);
 
 	return (struct netdev_nl_dump_ctx *)cb->ctx;
 }
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 6d68247aea70..a9b81b7d9746 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -6243,7 +6243,7 @@ static int rtnl_mdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 	int idx, s_idx;
 	int err;
 
-	NL_ASSERT_DUMP_CTX_FITS(struct rtnl_mdb_dump_ctx);
+	NL_ASSERT_CTX_FITS(struct rtnl_mdb_dump_ctx);
 
 	if (cb->strict_check) {
 		err = rtnl_mdb_valid_dump_req(cb->nlh, cb->extack);
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index c7a8e13f917c..a9f064ab9ed9 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h
@@ -166,7 +166,7 @@ int devlink_nl_dumpit(struct sk_buff *msg, struct netlink_callback *cb,
 static inline struct devlink_nl_dump_state *
 devlink_dump_state(struct netlink_callback *cb)
 {
-	NL_ASSERT_DUMP_CTX_FITS(struct devlink_nl_dump_state);
+	NL_ASSERT_CTX_FITS(struct devlink_nl_dump_state);
 
 	return (struct devlink_nl_dump_state *)cb->ctx;
 }
diff --git a/net/ethtool/rss.c b/net/ethtool/rss.c
index e07386275e14..7cb106b590ab 100644
--- a/net/ethtool/rss.c
+++ b/net/ethtool/rss.c
@@ -224,7 +224,7 @@ struct rss_nl_dump_ctx {
 
 static struct rss_nl_dump_ctx *rss_dump_ctx(struct netlink_callback *cb)
 {
-	NL_ASSERT_DUMP_CTX_FITS(struct rss_nl_dump_ctx);
+	NL_ASSERT_CTX_FITS(struct rss_nl_dump_ctx);
 
 	return (struct rss_nl_dump_ctx *)cb->ctx;
 }
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 6a1239433830..36168f8b6efa 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -3870,7 +3870,7 @@ static int __init ctnetlink_init(void)
 {
 	int ret;
 
-	NL_ASSERT_DUMP_CTX_FITS(struct ctnetlink_list_dump_ctx);
+	NL_ASSERT_CTX_FITS(struct ctnetlink_list_dump_ctx);
 
 	ret = nfnetlink_subsys_register(&ctnl_subsys);
 	if (ret < 0) {
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index feb54c63a116..29387b605f3e 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -997,7 +997,7 @@ static int genl_start(struct netlink_callback *cb)
 	info->info.attrs	= attrs;
 	genl_info_net_set(&info->info, sock_net(cb->skb->sk));
 	info->info.extack	= cb->extack;
-	memset(&info->info.user_ptr, 0, sizeof(info->info.user_ptr));
+	memset(&info->info.ctx, 0, sizeof(info->info.ctx));
 
 	cb->data = info;
 	if (ops->start) {
@@ -1104,7 +1104,7 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	info.attrs = attrbuf;
 	info.extack = extack;
 	genl_info_net_set(&info, net);
-	memset(&info.user_ptr, 0, sizeof(info.user_ptr));
+	memset(&info.ctx, 0, sizeof(info.ctx));
 
 	if (ops->pre_doit) {
 		err = ops->pre_doit(ops, skb, &info);