> -----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. 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.
