Linux Virtualization - Dec 2013 - [PATCH V2] virtio-scsi: Fix hotcpu_notifier use-after-free with virtscsi_freeze

From: Asias He <asias.hejun at gmail.com>

vqs are freed in virtscsi_freeze but the hotcpu_notifier is not
unregistered. We will have a use-after-free usage when the notifier
callback is called after virtscsi_freeze.

Fixes: 285e71ea6f3583a85e27cb2b9a7d8c35d4c0d558
("virtio-scsi: reset virtqueue affinity when doing cpu hotplug")

Cc: stable at vger.kernel.org
Signed-off-by: Asias He <asias.hejun at gmail.com>
Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
Changes from V1:
- Add "Fixes" line
- CC stable
---
 drivers/scsi/virtio_scsi.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index c3173dc..16bfd50 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -956,6 +956,10 @@ static void virtscsi_remove(struct virtio_device *vdev)
 #ifdef CONFIG_PM_SLEEP
 static int virtscsi_freeze(struct virtio_device *vdev)
 {
+	struct Scsi_Host *sh = virtio_scsi_host(vdev);
+	struct virtio_scsi *vscsi = shost_priv(sh);
+
+	unregister_hotcpu_notifier(&vscsi->nb);
 	virtscsi_remove_vqs(vdev);
 	return 0;
 }
@@ -964,8 +968,17 @@ static int virtscsi_restore(struct virtio_device *vdev)
 {
 	struct Scsi_Host *sh = virtio_scsi_host(vdev);
 	struct virtio_scsi *vscsi = shost_priv(sh);
+	int err;
+
+	err = virtscsi_init(vdev, vscsi);
+	if (err)
+		return err;
+
+	err = register_hotcpu_notifier(&vscsi->nb);
+	if (err)
+		vdev->config->del_vqs(vdev);
 
-	return virtscsi_init(vdev, vscsi);
+	return err;
 }
 #endif
 
-- 
1.8.3.2

Jason Wang <jasowang at redhat.com> writes:
> From: Asias He <asias.hejun at gmail.com>
>
> vqs are freed in virtscsi_freeze but the hotcpu_notifier is not
> unregistered. We will have a use-after-free usage when the notifier
> callback is called after virtscsi_freeze.
>
> Fixes: 285e71ea6f3583a85e27cb2b9a7d8c35d4c0d558
> ("virtio-scsi: reset virtqueue affinity when doing cpu hotplug")
Sorry, I missed this in my earlier sweep (I was only skimming emails
during the break).

Applied,
Rusty.
> Cc: stable at vger.kernel.org
> Signed-off-by: Asias He <asias.hejun at gmail.com>
> Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
> Changes from V1:
> - Add "Fixes" line
> - CC stable
> ---
>  drivers/scsi/virtio_scsi.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index c3173dc..16bfd50 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -956,6 +956,10 @@ static void virtscsi_remove(struct virtio_device
*vdev)
>  #ifdef CONFIG_PM_SLEEP
>  static int virtscsi_freeze(struct virtio_device *vdev)
>  {
> +	struct Scsi_Host *sh = virtio_scsi_host(vdev);
> +	struct virtio_scsi *vscsi = shost_priv(sh);
> +
> +	unregister_hotcpu_notifier(&vscsi->nb);
>  	virtscsi_remove_vqs(vdev);
>  	return 0;
>  }
> @@ -964,8 +968,17 @@ static int virtscsi_restore(struct virtio_device
*vdev)
>  {
>  	struct Scsi_Host *sh = virtio_scsi_host(vdev);
>  	struct virtio_scsi *vscsi = shost_priv(sh);
> +	int err;
> +
> +	err = virtscsi_init(vdev, vscsi);
> +	if (err)
> +		return err;
> +
> +	err = register_hotcpu_notifier(&vscsi->nb);
> +	if (err)
> +		vdev->config->del_vqs(vdev);
>  
> -	return virtscsi_init(vdev, vscsi);
> +	return err;
>  }
>  #endif
>  
> -- 
> 1.8.3.2