linux-kernel - Re: [PATCH v2 01/17] virtio: mmio-v1: Validate queue PFN

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Date:   Tue, 27 Mar 2018 17:07:27 +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,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        cdall@...nel.org, marc.zyngier@....com, punit.agrawal@....com,
        will.deacon@....com, catalin.marinas@....com, pbonzini@...hat.com,
        rkrcmar@...hat.com, ard.biesheuvel@...aro.org,
        peter.maydell@...aro.org, kristina.martsenko@....com,
        mark.rutland@....com, Jason Wang <jasowang@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>
Subject: Re: [PATCH v2 01/17] virtio: mmio-v1: Validate queue PFN

On Tue, Mar 27, 2018 at 02:15:11PM +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>

OK - seems harmless so I will queue this.
But I really think effort should be spent on
adding v1.0 support in QEMU.

> ---
>  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..b2f9b5c 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");
> +			err = -ENOMEM;
> +			goto error_bad_pfn;
> +		}
> +
>  		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
> -		writel(virtqueue_get_desc_addr(vq) >> PAGE_SHIFT,
> -				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> +		writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
>  	} else {
>  		u64 addr;
>  
> @@ -430,6 +442,8 @@ static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
>  
>  	return vq;
>  
> +error_bad_pfn:
> +	vring_del_virtqueue(vq);
>  error_new_virtqueue:
>  	if (vm_dev->version == 1) {
>  		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
> -- 
> 2.7.4