This is a note to let you know that I've just added the patch titled
netpoll: Use rcu_access_pointer() in netpoll_poll_lock
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netpoll-use-rcu_access_pointer-in-netpoll_poll_lock.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 3e24b456c574212d2cdb03fd75503692487702fc
Author: Breno Leitao <leitao@xxxxxxxxxx>
Date: Mon Nov 18 03:15:18 2024 -0800
netpoll: Use rcu_access_pointer() in netpoll_poll_lock
[ 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>
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index e6a2d72e0dc7a..533f8a5323a3b 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -70,7 +70,7 @@ 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)
