qemu: avoid memory leak while remove disk

Memset vhost_dev to zero in the vhost_dev_cleanup function.
This causes dev.vqs to be NULL, so that
vqs does not free up space when calling the g_free function.
This will result in a memory leak. But you can't release vqs
directly in the vhost_dev_cleanup function, because vhost_net
will also call this function, and vhost_net's vqs is assigned by array.
In order to solve this problem, we first save the pointer of vqs,
and release the space of vqs after vhost_dev_cleanup is called.

Signed-off-by: Jian Wang <wangjian161@huawei.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/block/vhost-user-blk.c

@@ -250,6 +250,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
     VhostUserState *user;
+    struct vhost_virtqueue *vqs = NULL;
     int i, ret;
 
     if (!s->chardev.chr) {
@@ -288,6 +289,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
     s->dev.vqs = g_new(struct vhost_virtqueue, s->dev.nvqs);
     s->dev.vq_index = 0;
     s->dev.backend_features = 0;
+    vqs = s->dev.vqs;
 
     vhost_dev_set_config_notifier(&s->dev, &blk_ops);
 
@@ -314,7 +316,7 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
 vhost_err:
     vhost_dev_cleanup(&s->dev);
 virtio_err:
-    g_free(s->dev.vqs);
+    g_free(vqs);
     virtio_cleanup(vdev);
 
     vhost_user_cleanup(user);
@@ -326,10 +328,11 @@ static void vhost_user_blk_device_unrealize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostUserBlk *s = VHOST_USER_BLK(dev);
+    struct vhost_virtqueue *vqs = s->dev.vqs;
 
     vhost_user_blk_set_status(vdev, 0);
     vhost_dev_cleanup(&s->dev);
-    g_free(s->dev.vqs);
+    g_free(vqs);
     virtio_cleanup(vdev);
 
     if (s->vhost_user) {

hw/scsi/vhost-scsi.c

@@ -215,6 +215,7 @@ static void vhost_scsi_unrealize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostSCSICommon *vsc = VHOST_SCSI_COMMON(dev);
+    struct vhost_virtqueue *vqs = vsc->dev.vqs;
 
     migrate_del_blocker(vsc->migration_blocker);
     error_free(vsc->migration_blocker);
@@ -223,7 +224,7 @@ static void vhost_scsi_unrealize(DeviceState *dev, Error **errp)
     vhost_scsi_set_status(vdev, 0);
 
     vhost_dev_cleanup(&vsc->dev);
-    g_free(vsc->dev.vqs);
+    g_free(vqs);
 
     virtio_scsi_common_unrealize(dev, errp);
 }

hw/scsi/vhost-user-scsi.c

@@ -121,12 +121,13 @@ static void vhost_user_scsi_unrealize(DeviceState *dev, Error **errp)
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostUserSCSI *s = VHOST_USER_SCSI(dev);
     VHostSCSICommon *vsc = VHOST_SCSI_COMMON(s);
+    struct vhost_virtqueue *vqs = vsc->dev.vqs;
 
     /* This will stop the vhost backend. */
     vhost_user_scsi_set_status(vdev, 0);
 
     vhost_dev_cleanup(&vsc->dev);
-    g_free(vsc->dev.vqs);
+    g_free(vqs);
 
     virtio_scsi_common_unrealize(dev, errp);