Re: [Qemu-devel] [PATCH 2/3] virtio: Strictly check queue_size when adding virtqueue

Re: [Qemu-devel] [PATCH 2/3] virtio: Strictly check queue_size when adding virtqueue

[Amos Kong]

On Wed, Jun 15, 2011 at 11:36:02PM +0300, Michael S. Tsirkin wrote:
> On Wed, Jun 15, 2011 at 10:25:33PM +0800, Amos Kong wrote:
> > Qemu should abort when 'queue_size' is less than or equals to zero.
> > 
> > Signed-off-by: Amos Kong <akong@redhat.com>
> 
> BTW, these patches apply upstream so should be sent to qemu-devel.
> 
> > ---
> >  hw/virtio.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/hw/virtio.c b/hw/virtio.c
> > index a3d0eee..855fe54 100644
> > --- a/hw/virtio.c
> > +++ b/hw/virtio.c
> > @@ -612,7 +612,8 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
> >              break;
> >      }
> >  
> > -    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE)
> > +    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE ||
> > +        queue_size <= 0)
> >          abort();
> >  
> >      vdev->vq[i].vring.num = queue_size;
> 
> These checks are just a debugging aid - there's no way
> for the guest or user to trigger this.
> I guess it does no harm, but what are we guarding against?
> Why would anyone pass in a negative value?

It seems all exist usage of this function are all right, guest/user could not trigger this right now.
So we don't need to fix this kind of problem?

Re: [Qemu-devel] [PATCH 2/3] virtio: Strictly check queue_size when adding virtqueue

[Anthony Liguori]

On 06/15/2011 05:53 PM, Amos Kong wrote:
> On Wed, Jun 15, 2011 at 11:36:02PM +0300, Michael S. Tsirkin wrote:
>> On Wed, Jun 15, 2011 at 10:25:33PM +0800, Amos Kong wrote:
>>> Qemu should abort when 'queue_size' is less than or equals to zero.
>>>
>>> Signed-off-by: Amos Kong<akong@redhat.com>
>>
>> BTW, these patches apply upstream so should be sent to qemu-devel.
>>
>>> ---
>>>   hw/virtio.c |    3 ++-
>>>   1 files changed, 2 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/hw/virtio.c b/hw/virtio.c
>>> index a3d0eee..855fe54 100644
>>> --- a/hw/virtio.c
>>> +++ b/hw/virtio.c
>>> @@ -612,7 +612,8 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
>>>               break;
>>>       }
>>>
>>> -    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size>  VIRTQUEUE_MAX_SIZE)
>>> +    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size>  VIRTQUEUE_MAX_SIZE ||
>>> +        queue_size<= 0)
>>>           abort();
>>>
>>>       vdev->vq[i].vring.num = queue_size;
>>
>> These checks are just a debugging aid - there's no way
>> for the guest or user to trigger this.
>> I guess it does no harm, but what are we guarding against?
>> Why would anyone pass in a negative value?
>
> It seems all exist usage of this function are all right, guest/user could not trigger this right now.
> So we don't need to fix this kind of problem?

If it's not valid for queue_size to be negative, then the type ought to 
be unsigned.

Regards,

Anthony Liguori

>

[Qemu-devel] [PATCH v2] virtio: Define queue_size to unsigned

[Amos Kong]

It's not valid for queue_size to be negative, then the type ought
to be unsigned.

Changes from V1:
- drop the check and just define it to unsigned.

Signed-off-by: Amos Kong <akong@redhat.com>
---
 hw/virtio.c |    2 +-
 hw/virtio.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/virtio.c b/hw/virtio.c
index 6e8814c..4c1e334 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -602,7 +602,7 @@ void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector)
         vdev->vq[n].vector = vector;
 }
 
-VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
+VirtQueue *virtio_add_queue(VirtIODevice *vdev, unsigned int queue_size,
                             void (*handle_output)(VirtIODevice *, VirtQueue *))
 {
     int i;
diff --git a/hw/virtio.h b/hw/virtio.h
index bc72289..ff0c9b5 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -138,7 +138,7 @@ static inline void virtio_set_status(VirtIODevice *vdev, uint8_t val)
     vdev->status = val;
 }
 
-VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
+VirtQueue *virtio_add_queue(VirtIODevice *vdev, unsigned int queue_size,
                             void (*handle_output)(VirtIODevice *,
                                                   VirtQueue *));