netdev - [PATCH net-next v2 2/3] netdev: let netlink core handle -EMSGSIZE errors

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Date: Sat,  2 Mar 2024 21:24:07 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	jiri@...nulli.us,
	idosch@...sch.org,
	johannes@...solutions.net,
	fw@...len.de,
	pablo@...filter.org,
	Jakub Kicinski <kuba@...nel.org>,
	amritha.nambiar@...el.com,
	sridhar.samudrala@...el.com,
	hawk@...nel.org
Subject: [PATCH net-next v2 2/3] netdev: let netlink core handle -EMSGSIZE errors

Previous change added -EMSGSIZE handling to af_netlink, we don't
have to hide these errors any longer.

Theoretically the error handling changes from:
 if (err == -EMSGSIZE)
to
 if (err == -EMSGSIZE && skb->len)

everywhere, but in practice it doesn't matter.
All messages fit into NLMSG_GOODSIZE, so overflow of an empty
skb cannot happen.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: amritha.nambiar@...el.com
CC: sridhar.samudrala@...el.com
CC: hawk@...nel.org
---
 net/core/netdev-genl.c    | 15 +++------------
 net/core/page_pool_user.c |  2 --
 2 files changed, 3 insertions(+), 14 deletions(-)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index fd98936da3ae..918b109e0cf4 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -152,10 +152,7 @@ int netdev_nl_dev_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 	}
 	rtnl_unlock();
 
-	if (err != -EMSGSIZE)
-		return err;
-
-	return skb->len;
+	return err;
 }
 
 static int
@@ -287,10 +284,7 @@ int netdev_nl_napi_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 	}
 	rtnl_unlock();
 
-	if (err != -EMSGSIZE)
-		return err;
-
-	return skb->len;
+	return err;
 }
 
 static int
@@ -463,10 +457,7 @@ int netdev_nl_queue_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 	}
 	rtnl_unlock();
 
-	if (err != -EMSGSIZE)
-		return err;
-
-	return skb->len;
+	return err;
 }
 
 static int netdev_genl_netdevice_event(struct notifier_block *nb,
diff --git a/net/core/page_pool_user.c b/net/core/page_pool_user.c
index 278294aca66a..3a3277ba167b 100644
--- a/net/core/page_pool_user.c
+++ b/net/core/page_pool_user.c
@@ -103,8 +103,6 @@ netdev_nl_page_pool_get_dump(struct sk_buff *skb, struct netlink_callback *cb,
 	mutex_unlock(&page_pools_lock);
 	rtnl_unlock();
 
-	if (skb->len && err == -EMSGSIZE)
-		return skb->len;
 	return err;
 }
 
-- 
2.44.0