[PATCH AUTOSEL 5.4 28/28] netpoll: Use rcu_access_pointer() in __netpoll_setup

[Sasha Levin]

From: Breno Leitao <leitao@xxxxxxxxxx>

[ Upstream commit c69c5e10adb903ae2438d4f9c16eccf43d1fcbc1 ]

The ndev->npinfo pointer in __netpoll_setup() is RCU-protected but is being
accessed directly for a NULL check. While no RCU read lock is held in this
context, we should still use proper RCU primitives for consistency and
correctness.

Replace the direct NULL check with rcu_access_pointer(), which is the
appropriate primitive when only checking for NULL without dereferencing
the pointer. This function provides the necessary ordering guarantees
without requiring RCU read-side protection.

Reviewed-by: Michal Kubiak <michal.kubiak@xxxxxxxxx>
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-1-a1888dcb4a02@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/core/netpoll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9b263a5c0f36f..9a67aa989d606 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -615,7 +615,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 		goto out;
 	}
 
-	if (!ndev->npinfo) {
+	if (!rcu_access_pointer(ndev->npinfo)) {
 		npinfo = kmalloc(sizeof(*npinfo), GFP_KERNEL);
 		if (!npinfo) {
 			err = -ENOMEM;
-- 
2.43.0