This is a note to let you know that I've just added the patch titled
netpoll: Use rcu_access_pointer() in __netpoll_setup
to the 5.4-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_setup.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 48b9cbbc42f77bed8e9f1ecc364c8711e92d22ef
Author: Breno Leitao <leitao@xxxxxxxxxx>
Date: Mon Nov 18 03:15:17 2024 -0800
netpoll: Use rcu_access_pointer() in __netpoll_setup
[ 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>
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;
