virtio: update MemoryRegionCaches when guest set bad features

Current the 'virtio_set_features' only update the 'MemorRegionCaches'
when the 'virtio_set_features_nocheck' return '0' which means it is
not bad features. However the guest can still trigger the access of the
used vring after set bad features. In this situation it will cause assert
failure in 'ADDRESS_SPACE_ST_CACHED'.

Buglink: https://bugs.launchpad.net/qemu/+bug/1890333
Fixes: db812c4073c7 ("virtio: update MemoryRegionCaches when guest negotiates features")
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Signed-off-by: Li Qiang <liq3ea@163.com>
Message-Id: <20200919082706.6703-1-liq3ea@163.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index a2edb4f386909326417364e35bf35f9a5aa6e46b..6f8f865aff77ae311c59a2563e05954f274fdb32 100644 (file)
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2963,17 +2963,16 @@ int virtio_set_features(VirtIODevice *vdev, uint64_t val)
         return -EINVAL;
     }
     ret = virtio_set_features_nocheck(vdev, val);
-    if (!ret) {
-        if (virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
-            /* VIRTIO_RING_F_EVENT_IDX changes the size of the caches.  */
-            int i;
-            for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
-                if (vdev->vq[i].vring.num != 0) {
-                    virtio_init_region_cache(vdev, i);
-                }
+    if (virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
+        /* VIRTIO_RING_F_EVENT_IDX changes the size of the caches.  */
+        int i;
+        for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
+            if (vdev->vq[i].vring.num != 0) {
+                virtio_init_region_cache(vdev, i);
             }
         }
-
+    }
+    if (!ret) {
         if (!virtio_device_started(vdev, vdev->status) &&
             !virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
             vdev->start_on_kick = true;