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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aXDhJ89Yru577jeY@google.com>
Date: Wed, 21 Jan 2026 14:22:31 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: Leon Romanovsky <leon@...nel.org>,
	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>,
	Alex Williamson <alex@...zbot.org>,
	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 09:47:12AM -0400, Jason Gunthorpe wrote:
> On Wed, Jan 21, 2026 at 02:59:16PM +0200, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@...dia.com>
> > 
> > Use the new dma_buf_attach_revocable() helper to restrict attachments to
> > importers that support mapping invalidation.
> > 
> > Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> > ---
> >  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" :|
> 

I've been wondering about this for a while now, I've been sitting on the
following:

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index a4d8f2ff94e4..962bce959366 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1133,6 +1133,8 @@ int dma_buf_pin(struct dma_buf_attachment *attach)

        if (dmabuf->ops->pin)
                ret = dmabuf->ops->pin(attach);
+       else
+               ret = -EOPNOTSUPP;

        return ret;
 }

But didn't get a chance to dive in the history yet. I thought there's a
good reason we didn't have it? Would it break exisitng dmabuf users?

Praan