Re: [PATCH v4 8/8] vfio: Validate dma-buf revocation semantics

[Jason Gunthorpe]

On Wed, Jan 21, 2026 at 02:59:16PM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@xxxxxxxxxx>
> 
> Use the new dma_buf_attach_revocable() helper to restrict attachments to
> importers that support mapping invalidation.
> 
> Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> ---
>  drivers/vfio/pci/vfio_pci_dmabuf.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
> index 5fceefc40e27..85056a5a3faf 100644
> --- a/drivers/vfio/pci/vfio_pci_dmabuf.c
> +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
> @@ -31,6 +31,9 @@ static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
>  	if (priv->revoked)
>  		return -ENODEV;
>  
> +	if (!dma_buf_attach_revocable(attachment))
> +		return -EOPNOTSUPP;
> +
>  	return 0;
>  }

We need to push an urgent -rc fix to implement a pin function here
that always fails. That was missed and it means things like rdma can
import vfio when the intention was to block that. It would be bad for
that uAPI mistake to reach a released kernel.

It's tricky that NULL pin ops means "I support pin" :|

Jason