From: Breno Leitao Date: Mon, 18 Nov 2024 11:15:18 +0000 (-0800) Subject: netpoll: Use rcu_access_pointer() in netpoll_poll_lock X-Git-Tag: v4.19.325~81 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3cc7dfd720b94ccb8464ef28957363621c9e959c;p=thirdparty%2Fkernel%2Fstable.git 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 Reviewed-by: Michal Kubiak Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-2-a1888dcb4a02@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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)