| Message ID | 20241118-netpoll_rcu-v1-1-a1888dcb4a02@debian.org (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | netpoll: Use RCU primitives for npinfo pointer access | expand |
On Mon, Nov 18, 2024 at 03:15:17AM -0800, Breno Leitao wrote: > 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. > > Signed-off-by: Breno Leitao <leitao@debian.org> > Fixes: 8fdd95ec162a ("netpoll: Allow netpoll_setup/cleanup recursion") nitpick: Shouldn't the "Signed-off-by" tag go as the last one? Thanks, Reviewed-by: Michal Kubiak <michal.kubiak@intel.com> > --- > net/core/netpoll.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/core/netpoll.c b/net/core/netpoll.c > index aa49b92e9194babab17b2e039daf092a524c5b88..45fb60bc4803958eb07d4038028269fc0c19622e 100644 > --- a/net/core/netpoll.c > +++ b/net/core/netpoll.c > @@ -626,7 +626,7 @@ 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; > > -- > 2.43.5 > >
diff --git a/net/core/netpoll.c b/net/core/netpoll.c index aa49b92e9194babab17b2e039daf092a524c5b88..45fb60bc4803958eb07d4038028269fc0c19622e 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -626,7 +626,7 @@ 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;
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. Signed-off-by: Breno Leitao <leitao@debian.org> Fixes: 8fdd95ec162a ("netpoll: Allow netpoll_setup/cleanup recursion") --- net/core/netpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)