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

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Message-ID: <20260121154621.GH13201@unreal>
Date: Wed, 21 Jan 2026 17:46:21 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Jason Gunthorpe <jgg@...pe.ca>, Alex Williamson <alex@...zbot.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Alex Deucher <alexander.deucher@....com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Dmitry Osipenko <dmitry.osipenko@...labora.com>,
	Gurchetan Singh <gurchetansingh@...omium.org>,
	Chia-I Wu <olvaffe@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Felix Kuehling <Felix.Kuehling@....com>,
	Ankit Agrawal <ankita@...dia.com>,
	Vivek Kasireddy <vivek.kasireddy@...el.com>,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
	amd-gfx@...ts.freedesktop.org, virtualization@...ts.linux.dev,
	intel-xe@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
	iommu@...ts.linux.dev, kvm@...r.kernel.org
Subject: Re: [PATCH v4 8/8] vfio: Validate dma-buf revocation semantics

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