Re: [PATCH v5 9/9] vfio/pci: Add dma-buf export support for MMIO regions

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Oct 17, 2025 at 08:40:07AM +0300, Leon Romanovsky wrote:
> > > +static void vfio_pci_dma_buf_detach(struct dma_buf *dmabuf,
> > > +				    struct dma_buf_attachment *attachment)
> > > +{
> > > +	kfree(attachment->priv);
> > > +}
> > 
> > If the caller fails to call map then it leaks the iova.
> 
> I'm relying on dmabuf code and documentation:
> 
>    926 /**
>    927  * dma_buf_dynamic_attach - Add the device to dma_buf's attachments list
> ...   
>    932  *
>    933  * Returns struct dma_buf_attachment pointer for this attachment. Attachments
>    934  * must be cleaned up by calling dma_buf_detach().
> 
> Successful call to vfio_pci_dma_buf_attach() MUST be accompanied by call
> to vfio_pci_dma_buf_detach(), so as far as dmabuf implementation follows
> it, there is no leak.

It leaks the ivoa because there is no dma_iova_destroy() unless you
call unmap. detach is not unmap and unmap is not mandatory to call.

Jason