[PATCH 4.9 192/199] vfio/pci: call irq_bypass_unregister_producer() before freeing irq

[Greg Kroah-Hartman]

From: Jiang Yi <giangyi@xxxxxxxxxx>

commit d567fb8819162099035e546b11a736e29c2af0ea upstream.

Since irq_bypass_register_producer() is called after request_irq(), we
should do tear-down in reverse order: irq_bypass_unregister_producer()
then free_irq().

Specifically free_irq() may release resources required by the
irqbypass del_producer() callback.  Notably an example provided by
Marc Zyngier on arm64 with GICv4 that he indicates has the potential
to wedge the hardware:

 free_irq(irq)
   __free_irq(irq)
     irq_domain_deactivate_irq(irq)
       its_irq_domain_deactivate()
         [unmap the VLPI from the ITS]

 kvm_arch_irq_bypass_del_producer(cons, prod)
   kvm_vgic_v4_unset_forwarding(kvm, irq, ...)
     its_unmap_vlpi(irq)
       [Unmap the VLPI from the ITS (again), remap the original LPI]

Signed-off-by: Jiang Yi <giangyi@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.4+
Fixes: 6d7425f109d26 ("vfio: Register/unregister irq_bypass_producer")
Link: https://lore.kernel.org/kvm/20191127164910.15888-1-giangyi@xxxxxxxxxx
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
[aw: commit log]
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/vfio/pci/vfio_pci_intrs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -297,8 +297,8 @@ static int vfio_msi_set_vector_signal(st
 	irq = pci_irq_vector(pdev, vector);
 
 	if (vdev->ctx[vector].trigger) {
-		free_irq(irq, vdev->ctx[vector].trigger);
 		irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
+		free_irq(irq, vdev->ctx[vector].trigger);
 		kfree(vdev->ctx[vector].name);
 		eventfd_ctx_put(vdev->ctx[vector].trigger);
 		vdev->ctx[vector].trigger = NULL;