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openvswitch: vport: fix self-deadlock on release of tunnel ports

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vports are used concurrently and protected by RCU, so netdev_put()
must happen after the RCU grace period.  So, either in an RCU call or
after the synchronize_net().  The rtnl_delete_link() must happen under
RTNL and so can't be executed in RCU context.  Calling synchronize_net()
while holding RTNL is not a good idea for performance and system
stability under load in general, so calling netdev_put() in RCU call
is the right solution here.

However,
when the device is deleted, rtnl_unlock() will call netdev_run_todo()
and block until all the references are gone.  In the current code this
means that we never reach the call_rcu() and the vport is never freed
and the reference is never released, causing a self-deadlock on device
removal.

Fix that by moving the rcu_call() before the rtnl_unlock(), so the
scheduled RCU callback will be executed when synchronize_net() is
called from the rtnl_unlock()->netdev_run_todo() while the RTNL itself
is already released.

Fixes: 6931d21f87 ("openvswitch: defer tunnel netdev_put to RCU release")
Cc: stable@vger.kernel.org
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260430233848.440994-2-i.maximets@ovn.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Ilya Maximets 2026-05-01 01:38:37 +02:00 committed by Paolo Abeni
parent 83861c48ba
commit aa69918bd4
1 changed files with 5 additions and 1 deletions
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6
net/openvswitch/vport-netdev.c
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@ -208,9 +208,13 @@ void ovs_netdev_tunnel_destroy(struct vport *vport)
*/
if (vport->dev->reg_state == NETREG_REGISTERED)
rtnl_delete_link(vport->dev, 0, NULL);
rtnl_unlock();
/* We can't put the device reference yet, since it can still be in
* use, but rtnl_unlock()->netdev_run_todo() will block until all
* the references are released, so the RCU call must be before it.
*/
call_rcu(&vport->rcu, vport_netdev_free);
rtnl_unlock();
}
EXPORT_SYMBOL_GPL(ovs_netdev_tunnel_destroy);