[1/2] virtio: check VirtQueue Vring object is set

Commit Message

Prasad Pandit Nov. 23, 2017, 7:01 p.m. UTC

From: Prasad J Pandit <[e-mail]>

An user could attempt to use an uninitialised VirtQueue object
or unset Vring.align leading to a arithmetic exception. Add check
to avoid it.

Reported-by: Zhangboxian <[e-mail]>
Signed-off-by: Prasad J Pandit <[e-mail]>
---
 hw/virtio/virtio.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Comments

Paolo Bonzini Nov. 23, 2017, 11:39 p.m. UTC | #1

On 23/11/2017 20:01, P J P wrote:
> @@ -182,7 +182,7 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n)
>  {
>      VRing *vring = &vdev->vq[n].vring;
>  
> -    if (!vring->desc) {
> +    if (!vring->desc || !vring->align) {
>          /* not yet setup -> nothing to do */
>          return;
>      }
> @@ -1414,6 +1414,9 @@ void virtio_config_modern_writel(VirtIODevice *vdev,
>  
>  void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
>  {
> +    if (!vdev->vq[n].vring.num) {
> +        return;
> +    }

Why not check vring->num in virtio_queue_update_rings too?

Thanks,

Paolo

>      vdev->vq[n].vring.desc = addr;
>      virtio_queue_update_rings(vdev, n);
>  }

Prasad Pandit Nov. 24, 2017, 7:59 a.m. UTC | #2

+-- On Fri, 24 Nov 2017, Paolo Bonzini wrote --+
| Why not check vring->num in virtio_queue_update_rings too?

Yes, sent a revised patch v1. These checks seem to repeat through sequence of 
functions. I guess it'll help to do them in one place.

Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F

Patch

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 5884ce3480..d961780384 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -182,7 +182,7 @@  void virtio_queue_update_rings(VirtIODevice *vdev, int n)
 {
     VRing *vring = &vdev->vq[n].vring;
 
-    if (!vring->desc) {
+    if (!vring->desc || !vring->align) {
         /* not yet setup -> nothing to do */
         return;
     }
@@ -1414,6 +1414,9 @@  void virtio_config_modern_writel(VirtIODevice *vdev,
 
 void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
 {
+    if (!vdev->vq[n].vring.num) {
+        return;
+    }
     vdev->vq[n].vring.desc = addr;
     virtio_queue_update_rings(vdev, n);
 }
@@ -1494,8 +1497,10 @@  void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
      */
     assert(k->has_variable_vring_alignment);
 
-    vdev->vq[n].vring.align = align;
-    virtio_queue_update_rings(vdev, n);
+    if (align) {
+        vdev->vq[n].vring.align = align;
+        virtio_queue_update_rings(vdev, n);
+    }
 }
 
 static bool virtio_queue_notify_aio_vq(VirtQueue *vq)