On Fri, 27 Oct 2017 21:50:43 +0000 "Wang, Liang-min" <liang-min.wang@xxxxxxxxx> wrote: > > -----Original Message----- > > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > > Sent: Tuesday, October 24, 2017 6:07 PM > > To: Wang, Liang-min <liang-min.wang@xxxxxxxxx> > > Cc: Kirsher, Jeffrey T <jeffrey.t.kirsher@xxxxxxxxx>; kvm@xxxxxxxxxxxxxxx; > > linux-pci@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > > bhelgaas@xxxxxxxxxx; Duyck, Alexander H <alexander.h.duyck@xxxxxxxxx> > > 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@xxxxxxxxx> 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 > > Firstly, the concern is on user-space PF driver based upon vfio-pci, this patch doesn't > change PF behavior so with/without this patch, the concern remains the same. This patch enables SR-IOV to be enabled via the host on a user-owned PF, how is this not a change in behavior? > Secondly, the security concern (including denial of service) in general is to ensure trust > entity to be trust-worthy. No matter the PF driver is in kernel-space or in user- space, > necessary mechanism needs to be enforced on the device driver to ensure it's > trusted worthy. For example, ixgbe kernel driver introduces a Tx hang detection > to avoid driver stays in a bad state. Therefore, it's the responsibility of user-space > driver function, which based upon vfio-pci, to enforce necessary mechanism to ensure > its trust-ness. That's a given. Userspace is not trustworthy, therefore the host kernel cannot place responsibility on a userspace driver for anything, including the behavior of VFs. I'm sorry, but it's a NAK unless you intend to follow-up with some proposal to quarantine the VFs enabled by the userspace PF driver. Thanks, Alex
