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

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Message-ID: <20171025000654.7621b84e@t450s.home>
Date:   Wed, 25 Oct 2017 00:06:54 +0200
From:   Alex Williamson <alex.williamson@...hat.com>
To:     "Wang, Liang-min" <liang-min.wang@...el.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

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