[PATCH 5.4 256/309] virtio-balloon: Fix memory leak when unloading while hinting is in progress

[Greg Kroah-Hartman]

From: David Hildenbrand <david@xxxxxxxxxx>

commit 6c22dc61c76b7e7d355f1697ba0ecf26d1334ba6 upstream.

When unloading the driver while hinting is in progress, we will not
release the free page blocks back to MM, resulting in a memory leak.

Fixes: 86a559787e6f ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Liang Li <liang.z.li@xxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200205163402.42627-2-david@xxxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/virtio/virtio_balloon.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -967,6 +967,10 @@ static void remove_common(struct virtio_
 		leak_balloon(vb, vb->num_pages);
 	update_balloon_size(vb);
 
+	/* There might be free pages that are being reported: release them. */
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		return_free_pages_to_mm(vb, ULONG_MAX);
+
 	/* Now we reset the device so we can clean up the queues. */
 	vb->vdev->config->reset(vb->vdev);