[PATCH 4.17 07/42] vhost: reset metadata cache when initializing new IOTLB

[Greg Kroah-Hartman]

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

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

From: Jason Wang <jasow...@redhat.com>

[ 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+c51e6736a1bf614b3...@syzkaller.appspotmail.com
Fixes: f88949138058 ("vhost: introduce O(1) vq metadata cache")
Signed-off-by: Jason Wang <jasow...@redhat.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/vhost/vhost.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1556,9 +1556,12 @@ 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);