netpoll: Use rcu_access_pointer() in __netpoll_setup

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@intel.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-1-a1888dcb4a02@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index aa49b92..45fb60b 100644 (file)
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -626,7 +626,7 @@ 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;