Commit 505ead7a authored by Breno Leitao's avatar Breno Leitao Committed by Jakub Kicinski
Browse files

netpoll: hold rcu read lock in __netpoll_send_skb() 



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: 2899656b ("netpoll: take rcu_read_lock_bh() in netpoll_send_skb_on_dev()")
Signed-off-by: default avatarBreno Leitao <leitao@debian.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250306-netpoll_rcu_v2-v2-1-bc4f5c51742a@debian.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent e6360f0d

net/core/netpoll.c

+7 −2
Original line number Diff line number Diff line
@@ -319,6 +319,7 @@ static int netpoll_owner_active(struct net_device *dev) 
static netdev_tx_t __netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)

{

	netdev_tx_t status = NETDEV_TX_BUSY;

	netdev_tx_t ret = NET_XMIT_DROP;

	struct net_device *dev;

	unsigned long tries;

	/* It is up to the caller to keep npinfo alive. */
@@ -327,11 +328,12 @@ static netdev_tx_t __netpoll_send_skb(struct netpoll *np, struct sk_buff *skb) 
	lockdep_assert_irqs_disabled();



	dev = np->dev;

	rcu_read_lock();

	npinfo = rcu_dereference_bh(dev->npinfo);



	if (!npinfo || !netif_running(dev) || !netif_device_present(dev)) {

		dev_kfree_skb_irq(skb);

		return NET_XMIT_DROP;

		goto out;

	}



	/* don't get messages out of order, and no recursion */
@@ -370,7 +372,10 @@ static netdev_tx_t __netpoll_send_skb(struct netpoll *np, struct sk_buff *skb) 
		skb_queue_tail(&npinfo->txq, skb);

		schedule_delayed_work(&npinfo->tx_work,0);

	}

	return NETDEV_TX_OK;

	ret = NETDEV_TX_OK;

out:

	rcu_read_unlock();

	return ret;

}



netdev_tx_t netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)