5.4-stable review patch. If anyone has any objections, please let me know.
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From: Breno Leitao leitao@debian.org
[ 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@debian.org Reviewed-by: Michal Kubiak michal.kubiak@intel.com Link: https://patch.msgid.link/20241118-netpoll_rcu-v1-2-a1888dcb4a02@debian.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 676f1ff161a98..3ff0303672842 100644 --- a/include/linux/netpoll.h +++ b/include/linux/netpoll.h @@ -78,7 +78,7 @@ 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)