[PATCH 5.8 013/124] vhost: Dont call access_ok() when using IOTLB

[Greg Kroah-Hartman]

From: Greg Kurz <groug@xxxxxxxx>

commit 0210a8db2aeca393fb3067e234967877e3146266 upstream.

When the IOTLB device is enabled, the vring addresses we get
from userspace are GIOVAs. It is thus wrong to pass them down
to access_ok() which only takes HVAs.

Access validation is done at prefetch time with IOTLB. Teach
vq_access_ok() about that by moving the (vq->iotlb) check
from vhost_vq_access_ok() to vq_access_ok(). This prevents
vhost_vring_set_addr() to fail when verifying the accesses.
No behavior change for vhost_vq_access_ok().

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1883084
Fixes: 6b1e6cc7855b ("vhost: new device IOTLB API")
Cc: jasowang@xxxxxxxxxx
CC: stable@xxxxxxxxxxxxxxx # 4.14+
Signed-off-by: Greg Kurz <groug@xxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Link: https://lore.kernel.org/r/160171931213.284610.2052489816407219136.stgit@xxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/vhost/vhost.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1283,6 +1283,11 @@ static bool vq_access_ok(struct vhost_vi
 			 vring_used_t __user *used)
 
 {
+	/* If an IOTLB device is present, the vring addresses are
+	 * GIOVAs. Access validation occurs at prefetch time. */
+	if (vq->iotlb)
+		return true;
+
 	return access_ok(desc, vhost_get_desc_size(vq, num)) &&
 	       access_ok(avail, vhost_get_avail_size(vq, num)) &&
 	       access_ok(used, vhost_get_used_size(vq, num));
@@ -1376,10 +1381,6 @@ bool vhost_vq_access_ok(struct vhost_vir
 	if (!vq_log_access_ok(vq, vq->log_base))
 		return false;
 
-	/* Access validation occurs at prefetch time with IOTLB */
-	if (vq->iotlb)
-		return true;
-
 	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);