[PATCH 4.14 07/29] vhost: reset metadata cache when initializing new IOTLB

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Wang <jasowang@xxxxxxxxxx>

[ Upstream commit b13f9c6364373a1b9f71e9846dc4fb199296f926 ]

We need to reset metadata cache during new IOTLB initialization,
otherwise the stale pointers to previous IOTLB may be still accessed
which will lead a use after free.

Reported-by: syzbot+c51e6736a1bf614b3272@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: f88949138058 ("vhost: introduce O(1) vq metadata cache")
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vhost/vhost.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1578,9 +1578,12 @@ int vhost_init_device_iotlb(struct vhost
 	d->iotlb = niotlb;
 
 	for (i = 0; i < d->nvqs; ++i) {
-		mutex_lock(&d->vqs[i]->mutex);
-		d->vqs[i]->iotlb = niotlb;
-		mutex_unlock(&d->vqs[i]->mutex);
+		struct vhost_virtqueue *vq = d->vqs[i];
+
+		mutex_lock(&vq->mutex);
+		vq->iotlb = niotlb;
+		__vhost_vq_meta_reset(vq);
+		mutex_unlock(&vq->mutex);
 	}
 
 	vhost_umem_clean(oiotlb);