5.4-stable review patch. If anyone has any objections, please let me know.
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From: Breno Leitao leitao@debian.org
[ Upstream commit 505ead7ab77f289f12d8a68ac83da068e4d4408b ]
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 Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20250306-netpoll_rcu_v2-v2-1-bc4f5c51742a@debian.or... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/netpoll.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 408fc07007900..940d371f5f3b5 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -326,6 +326,7 @@ 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. */ @@ -334,11 +335,12 @@ 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 */ @@ -377,7 +379,10 @@ 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)