[PATCH net] netpoll: guard __netpoll_send_skb() with RCU read lock

[Breno Leitao <leitao@debian.org>]

The function __netpoll_send_skb() is being invoked without holding the
RCU read lock. This oversight triggers a warning message when
CONFIG_PROVE_RCU_LIST is enabled:

	net/core/netpoll.c:330 suspicious rcu_dereference_check() usage!

	 netpoll_send_skb
	 netpoll_send_udp
	 write_ext_msg
	 console_flush_all
	 console_unlock
	 vprintk_emit

To prevent npinfo from disappearing unexpectedly, ensure that
__netpoll_send_skb() is protected with the RCU read lock.

Fixes: 2899656b494dcd1 ("netpoll: take rcu_read_lock_bh() in netpoll_send_skb_on_dev()")
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 net/core/netpoll.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 62b4041aae1ae..cac389105e2d1 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -326,6 +326,7 @@ static netdev_tx_t __netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 
 	lockdep_assert_irqs_disabled();
 
+	guard(rcu)();
 	dev = np->dev;
 	npinfo = rcu_dereference_bh(dev->npinfo);
 

---
base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6
change-id: 20250303-netpoll_rcu_v2-fed72eb0cb83

Best regards,
-- 
Breno Leitao <leitao@debian.org>