On device shutdown, make vfio_pci_core_close_device() call
vfio_pci_dma_buf_cleanup() before the function is disabled via
vfio_pci_core_disable().  This ensures that all access via DMABUFs is
revoked before the function's BARs become inaccessible.

This fixes an issue where, if the function is disabled first, a tiny
window exists in which the function's MSE is cleared and yet BARs
could still be accessed via the DMABUF.  The resources would also be
freed and up for grabs by a different driver.

Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO regions")
Signed-off-by: Matt Evans <mattev@meta.com>
---
 drivers/vfio/pci/vfio_pci_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index d43745fe4c84..f9ed3374d268 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -734,10 +734,10 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev)
 #if IS_ENABLED(CONFIG_EEH)
 	eeh_dev_release(vdev->pdev);
 #endif
-	vfio_pci_core_disable(vdev);
-
 	vfio_pci_dma_buf_cleanup(vdev);
 
+	vfio_pci_core_disable(vdev);
+
 	mutex_lock(&vdev->igate);
 	vfio_pci_eventfd_replace_locked(vdev, &vdev->err_trigger, NULL);
 	vfio_pci_eventfd_replace_locked(vdev, &vdev->req_trigger, NULL);
-- 
2.47.3

On Thu, Mar 12, 2026 at 11:46:00AM -0700, Matt Evans wrote:
> On device shutdown, make vfio_pci_core_close_device() call
> vfio_pci_dma_buf_cleanup() before the function is disabled via
> vfio_pci_core_disable().  This ensures that all access via DMABUFs is
> revoked before the function's BARs become inaccessible.
> 
> This fixes an issue where, if the function is disabled first, a tiny
> window exists in which the function's MSE is cleared and yet BARs
> could still be accessed via the DMABUF.  The resources would also be
> freed and up for grabs by a different driver.
> 
> Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO regions")
> Signed-off-by: Matt Evans <mattev@meta.com>
> ---
>  drivers/vfio/pci/vfio_pci_core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

This seems like it should not be RFC and it should go to stable?

The normal mmaps are cleaned because they hold the file open while
they exist, dmabuf upends that and it does need zapping early.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason