linux-kernel - Re: [PATCH v3 01/20] virtio: mmio-v1: Validate queue PFN

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Date:   Wed, 4 Jul 2018 08:37:42 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        james.morse@....com, marc.zyngier@....com, cdall@...nel.org,
        eric.auger@...hat.com, julien.grall@....com, will.deacon@....com,
        catalin.marinas@....com, punit.agrawal@....com,
        qemu-devel@...gnu.org, Jason Wang <jasowang@...hat.com>,
        Peter Maydel <peter.maydell@...aro.org>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>
Subject: Re: [PATCH v3 01/20] virtio: mmio-v1: Validate queue PFN

On Tue, Jul 03, 2018 at 09:04:01AM +0100, Suzuki K Poulose wrote:
> Hi Michael,
> 
> On 06/29/2018 06:42 PM, Michael S. Tsirkin wrote:
> > On Fri, Jun 29, 2018 at 12:15:21PM +0100, Suzuki K Poulose wrote:
> > > virtio-mmio with virtio-v1 uses a 32bit PFN for the queue.
> > > If the queue pfn is too large to fit in 32bits, which
> > > we could hit on arm64 systems with 52bit physical addresses
> > > (even with 64K page size), we simply miss out a proper link
> > > to the other side of the queue.
> > > 
> > > Add a check to validate the PFN, rather than silently breaking
> > > the devices.
> > > 
> > > Cc: "Michael S. Tsirkin" <mst@...hat.com>
> > > Cc: Jason Wang <jasowang@...hat.com>
> > > Cc: Marc Zyngier <marc.zyngier@....com>
> > > Cc: Christoffer Dall <cdall@...nel.org>
> > > Cc: Peter Maydel <peter.maydell@...aro.org>
> > > Cc: Jean-Philippe Brucker <jean-philippe.brucker@....com>
> > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> > > ---
> > > Changes since v2:
> > >   - Change errno to -E2BIG
> > > ---
> > >   drivers/virtio/virtio_mmio.c | 18 ++++++++++++++++--
> > >   1 file changed, 16 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> > > index 67763d3..82cedc8 100644
> > > --- a/drivers/virtio/virtio_mmio.c
> > > +++ b/drivers/virtio/virtio_mmio.c
> > > @@ -397,9 +397,21 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
> > >   	/* Activate the queue */
> > >   	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
> > >   	if (vm_dev->version == 1) {
> > > +		u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
> > > +
> > > +		/*
> > > +		 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
> > > +		 * that doesn't fit in 32bit, fail the setup rather than
> > > +		 * pretending to be successful.
> > > +		 */
> > > +		if (q_pfn >> 32) {
> > > +			dev_err(&vdev->dev, "virtio-mmio: queue address too large\n");
> > 
> > How about:
> > 	"hypervisor bug: legacy virtio-mmio must not be used with more than 0x%llx Gigabytes of memory",
> > 	0x1ULL << (32 - 30) << PAGE_SHIFT
> 
> nit : Do we need change "hypervisor" => "platform" ? Virtio is used by other
> tools (e.g, emulators) and not just virtual machines.
> 
> Suzuki

OK.