4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Breno Leitao <leitao@xxxxxxxxxx>
[ Upstream commit a57d5a72f8dec7db8a79d0016fb0a3bdecc82b56 ]
The ndev->npinfo pointer in netpoll_poll_lock() 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.
Fixes: bea3348eef27 ("[NET]: Make NAPI polling independent of struct net_device objects.")
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
Reviewed-by: Michal Kubiak <michal.kubiak@xxxxxxxxx>
Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-2-a1888dcb4a02@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/netpoll.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 3ef82d3a78db5..c47f74e6bd2cb 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -80,7 +80,7 @@ static inline void *netpoll_poll_lock(struct napi_struct *napi)
{
struct net_device *dev = napi->dev;
- if (dev && dev->npinfo) {
+ if (dev && rcu_access_pointer(dev->npinfo)) {
int owner = smp_processor_id();
while (cmpxchg(&napi->poll_owner, -1, owner) != -1)
--
2.43.0
