linux-kernel - Re: [PATCH v2 02/17] virtio: pci-legacy: Validate queue pfn

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Message-ID: <20180327170823-mutt-send-email-mst@kernel.org>
Date:   Tue, 27 Mar 2018 17:11:04 +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 02/17] virtio: pci-legacy: Validate queue pfn

On Tue, Mar 27, 2018 at 02:15:12PM +0100, Suzuki K Poulose wrote:
> Legacy PCI over virtio 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>
> ---
>  drivers/virtio/virtio_pci_legacy.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index 2780886..4b84a75 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -122,6 +122,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  	struct virtqueue *vq;
>  	u16 num;
>  	int err;
> +	u64 q_pfn;
>  
>  	/* Select the queue we're interested in */
>  	iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
> @@ -141,9 +142,15 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  	if (!vq)
>  		return ERR_PTR(-ENOMEM);
>  
> +	q_pfn = virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT;
> +	if (q_pfn >> 32) {
> +		dev_err(&vp_dev->pci_dev->dev, "virtio-pci queue PFN too large\n");
> +		err = -ENOMEM;

ENOMEM seems wrong here. E2BIG?

> +		goto out_del_vq;
> +	}
> +
>  	/* activate the queue */
> -	iowrite32(virtqueue_get_desc_addr(vq) >> VIRTIO_PCI_QUEUE_ADDR_SHIFT,
> -		  vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
> +	iowrite32((u32)q_pfn, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);

Is the cast really necessary here?

>  
>  	vq->priv = (void __force *)vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NOTIFY;
>  
> @@ -160,6 +167,7 @@ static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
>  
>  out_deactivate:
>  	iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
> +out_del_vq:
>  	vring_del_virtqueue(vq);
>  	return ERR_PTR(err);
>  }
> -- 
> 2.7.4