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

[Christian König]

On 1/21/26 14:47, Jason Gunthorpe wrote:
> 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" :|

Well it means: "I have no memory management and my buffers are always pinned.".

Christian.

> 
> Jason