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

Leon Romanovsky
2026-01-21T15:46:25Z

On Wed, Jan 21, 2026 at 11:41:37AM -0400, Jason Gunthorpe wrote:
> On Wed, Jan 21, 2026 at 04:47:01PM +0200, Leon Romanovsky wrote:
> > > 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.
> >
> > I don't see any urgency here. In the current kernel, the RDMA importer
> > prints a warning to indicate it was attached to the wrong exporter.
> > VFIO also invokes dma_buf_move_notify().
>
> The design of vfio was always that it must not work with RDMA because
> we cannot tolerate the errors that happen due to ignoring the
> move_notify.
>
> The entire purpose of this series could be stated as continuing to
> block RDMA while opening up other pining users.
>
> So it must be addressed urgently before someone builds an application
> relying on this connection.

Done, https://lore.kernel.org/all/20260121-vfio-add-pin-v1-1-4e04916b17f1@nvidia.com/T/#u

Thanks

>
> Jason