Re: [Qemu-devel] [PATCH] vhost: fix invalid downcast

[Jia He]

On 7/14/2018 12:15 AM, Michael S. Tsirkin Wrote:
> On Fri, Jul 13, 2018 at 05:04:05PM +0300, Yury Kotov wrote:
>> virtio_queue_get_desc_addr returns 64-bit hwaddr while int is usually 32-bit.
>> If returned hwaddr is not equal to 0 but least-significant 32 bits are
>> equal to 0 then this code will not actually stop running queue.
>>
>> Signed-off-by: Yury Kotov <address@hidden>
> 
> So IIUC
> 
> Fixes: fb20fbb764aa1 ("vhost: avoid to start/stop virtqueue which is not 
> ready")

> And 
> Cc: address@hidden
> 
>> ---
>>  hw/virtio/vhost.c | 4 +---
>>  1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
>> index b129cb9..7edeee7 100644
>> --- a/hw/virtio/vhost.c
>> +++ b/hw/virtio/vhost.c
>> @@ -1071,10 +1071,8 @@ static void vhost_virtqueue_stop(struct vhost_dev 
>> *dev,
>>          .index = vhost_vq_index,
>>      };
>>      int r;
>> -    int a;
>>  
>> -    a = virtio_queue_get_desc_addr(vdev, idx);
>> -    if (a == 0) {
>> +    if (virtio_queue_get_desc_addr(vdev, idx) == 0) {
>>          /* Don't stop the virtqueue which might have not been started */
>>          return;
>>      }
>> -- 
>> 2.7.4
> 
yes, it is a bug introduced by fb20fbb764aa1
Acked-by: Jia He <address@hidden>
-- 
Cheers,
Jia