vhost: allow batching hint without size

Commit e2ae38cf3d91 ("vhost: fix hung thread due to erroneous iotlb
entries") tries to reject the IOTLB message whose size is zero. But
the size is not necessarily meaningful, one example is the batching
hint, so the commit breaks that.

Fixing this be reject zero size message only if the message is used to
update/invalidate the IOTLB.

Fixes: e2ae38cf3d91 ("vhost: fix hung thread due to erroneous iotlb entries")
Reported-by: Eli Cohen <elic@nvidia.com>
Cc: Anirudh Rayabharam <mail@anirudhrb.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20220310075211.4801-1-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Eli Cohen <elic@nvidia.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 082380c03a3e51ae60ca7830b1ae8b8db8f590af..1768362115c6bb4f81e8faaca2ee713f21c67711 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1170,7 +1170,9 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
                goto done;
        }
 
-       if (msg.size == 0) {
+       if ((msg.type == VHOST_IOTLB_UPDATE ||
+            msg.type == VHOST_IOTLB_INVALIDATE) &&
+            msg.size == 0) {
                ret = -EINVAL;
                goto done;
        }