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

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Message-ID: <0e475b0c-5c38-ef37-3c87-486f418c609e@arm.com>
Date:   Fri, 13 Jul 2018 09:54:56 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     "Michael S. Tsirkin" <mst@...hat.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 13/07/18 01:36, Michael S. Tsirkin wrote:
> On Tue, Mar 27, 2018 at 05:11:04PM +0300, Michael S. Tsirkin wrote:
>> 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

Michael,

> 
> Ping are you going to address and repost, or should I drop this?

This was addressed and reposted as v3, which needs a minor update to the
error message as mentioned here [0]. I will post the fixed version today.

[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2018-July/588398.html

Thanks
Suzuki