[PATCH RESEND net] vhost: fix vhost_vq_access_ok() log check

From: Michael S. Tsirkin
Date: Mon Apr 09 2018 - 15:40:08 EST


From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>

Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
when IOTLB is enabled") introduced a regression. The logic was
originally:

if (vq->iotlb)
return 1;
return A && B;

After the patch the short-circuit logic for A was inverted:

if (A || vq->iotlb)
return A;
return B;

The correct logic is:

if (!A || vq->iotlb)
return A;
return B;

Reported-by: syzbot+65a84dde0214b0387ccd@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

---
drivers/vhost/vhost.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5320039671b7..f6af4210679a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1246,7 +1246,7 @@ int vhost_vq_access_ok(struct vhost_virtqueue *vq)
{
int ret = vq_log_access_ok(vq, vq->log_base);

- if (ret || vq->iotlb)
+ if (!ret || vq->iotlb)
return ret;

return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
--
2.14.3