netdev - [PATCH net] netdev-genl: avoid empty messages in napi get

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Message-ID: <20241218024305.823683-1-kuba@kernel.org>
Date: Tue, 17 Dec 2024 18:43:05 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	Jakub Kicinski <kuba@...nel.org>,
	jdamato@...tly.com,
	almasrymina@...gle.com,
	sridhar.samudrala@...el.com,
	amritha.nambiar@...el.com
Subject: [PATCH net] netdev-genl: avoid empty messages in napi get

Empty netlink responses from do() are not correct (as opposed to
dump() where not dumping anything is perfectly fine).
We should return an error if the target object does not exist,
in this case if the netdev is down we "hide" the NAPI instances.

Fixes: 27f91aaf49b3 ("netdev-genl: Add netlink framework functions for napi")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: jdamato@...tly.com
CC: almasrymina@...gle.com
CC: sridhar.samudrala@...el.com
CC: amritha.nambiar@...el.com
---
 net/core/netdev-genl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b4becd4065d9..dfb2430a0fe3 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -238,6 +238,10 @@ int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info)
 	napi = napi_by_id(napi_id);
 	if (napi) {
 		err = netdev_nl_napi_fill_one(rsp, napi, info);
+		if (!rsp->len) {
+			err = -ENOENT;
+			goto err_free_msg;
+		}
 	} else {
 		NL_SET_BAD_ATTR(info->extack, info->attrs[NETDEV_A_NAPI_ID]);
 		err = -ENOENT;
-- 
2.47.1