linux-kernel - RE: [PATCH] Enable SR-IOV instantiation through /sys file

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Date:   Tue, 24 Oct 2017 22:29:00 +0000
From:   "Wang, Liang-min" <liang-min.wang@...el.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>
Subject: RE: [PATCH] Enable SR-IOV instantiation through /sys file



> -----Original Message-----
> From: Alex Williamson [mailto:alex.williamson@...hat.com]
> Sent: Tuesday, October 24, 2017 6:07 PM
> To: Wang, Liang-min <liang-min.wang@...el.com>
> Cc: Kirsher, Jeffrey T <jeffrey.t.kirsher@...el.com>; kvm@...r.kernel.org;
> linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org;
> bhelgaas@...gle.com; Duyck, Alexander H <alexander.h.duyck@...el.com>
> Subject: Re: [PATCH] Enable SR-IOV instantiation through /sys file
> 
> On Tue, 24 Oct 2017 21:49:15 +0000
> "Wang, Liang-min" <liang-min.wang@...el.com> wrote:
> 
> > Just like any PCIe devices that supports SR-IOV. There are restrictions set for
> VF. Also, there is a concept of trust VF now available for PF to manage certain
> features that only selected VF could exercise. Are you saying all the devices
> supporting SR-IOV all have security issue?
> 
> Here's a simple example, most SR-IOV capable NICs, including those from
> Intel, require the PF interface to be up in order to route traffic from
> the VF.  If the user controls the PF interface and VFs are used
> elsewhere in the host, the PF driver in userspace can induce a denial
> of service on the VFs.  That doesn't even take into account that VFs
> might be in separate IOMMU groups from the PF and therefore not
> isolated from the host like the PF and that the PF driver can
> potentially manipulate the VF, possibly performing DMA on behalf of the
> PF.  VFs are only considered secure today because the PF is managed by
> a driver in the host kernel.  Allowing simple enablement of VFs for a
> user owned PF seems inherently insecure to me.  Thanks,
> 
> Alex

So, I assume over PF+SR-IOV usage model, you would agree that PF is trusted, and not VF. So, the "potential" insecure issue occurs on both native device kernel driver and vfio-pci. The interface that is used to create SR-IOV is also considered trusted, either it's a script run by a network manager or manually done by network manager. So, it's up to the trusted network manager to give privileges to each individual VF according to respective policy. BTW, there is a separate effort on a similar support (https://lkml.org/lkml/2017/9/27/348). Do you have the same concern for uio_pci_generic?

Liang-Min