netdev-genl: Hold rcu_read_lock in napi_get

Hold rcu_read_lock in netdev_nl_napi_get_doit, which calls napi_by_id
and is required to be called under rcu_read_lock.

Cc: stable@vger.kernel.org
Fixes: 27f91aa ("netdev-genl: Add netlink framework functions for napi")
Signed-off-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20241114175157.16604-1-jdamato@fastly.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: jdamato-fsly

net/core/netdev-genl.c

@@ -215,6 +215,7 @@ int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info)
 		return -ENOMEM;
 
 	rtnl_lock();
+	rcu_read_lock();
 
 	napi = napi_by_id(napi_id);
 	if (napi) {
@@ -224,6 +225,7 @@ int netdev_nl_napi_get_doit(struct sk_buff *skb, struct genl_info *info)
 		err = -ENOENT;
 	}
 
+	rcu_read_unlock();
 	rtnl_unlock();
 
 	if (err)