Re: [Qemu-devel] [PATCH] qemu: avoid memory leak while remove disk

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Dec 07, 2018 at 09:53:06AM +0800, wangjian wrote:
> 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>

Thanks!
This will be needed upstream and in the stable branch I think.

> ---
>  hw/block/vhost-user-blk.c | 7 +++++--
>  hw/scsi/vhost-scsi.c      | 3 ++-
>  hw/scsi/vhost-user-scsi.c | 3 ++-
>  3 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 1451940..c3af28f 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/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) {
> diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
> index 7f21b4f..61e2e57 100644
> --- a/hw/scsi/vhost-scsi.c
> +++ b/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);
>  }
> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
> index 2e1ba4a..6728878 100644
> --- a/hw/scsi/vhost-user-scsi.c
> +++ b/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);
> 
> --
> 1.8.3.1
>