vhost: validate log when IOTLB is enabled

Vq log_base is the userspace address of bitmap which has nothing to do
with IOTLB. So it needs to be validated unconditionally otherwise we
may try use 0 as log_base which may lead to pin pages that will lead
unexpected result (e.g trigger BUG_ON() in set_bit_to_user()).

Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
Reported-by: syzbot+6304bf97ef436580fede@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 8 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 5d5a9d9e66d3..5320039671b7 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1244,14 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
 /* Caller should have vq mutex and device mutex */
 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 {
-        if (vq->iotlb) {
-                /* When device IOTLB was used, the access validation
-                 * will be validated during prefetching.
-                 */
-                return 1;
-        }
-        return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
-                vq_log_access_ok(vq, vq->log_base);
+        int ret = vq_log_access_ok(vq, vq->log_base);
+
+        if (ret || vq->iotlb)
+                return ret;
+
+        return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);