virtio_balloon: set DRIVER_OK before using device

commit 88660f7fb94cda1f8f63ee92bfcd0db39a6361e2 upstream.

virtio spec requires that all drivers set DRIVER_OK
before using devices. While balloon isn't yet
included in the virtio 1 spec, previous spec versions
also required this.

virtio balloon might violate this rule: probe calls
kthread_run before setting DRIVER_OK, which might run
immediately and cause balloon to inflate/deflate.

To fix, call virtio_device_ready before running the kthread.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 50c5f42d7a9f3010c5f12275b7fd540161900392..8a969320ad423f1bf073d67c06f10dc3e0d2a9a7 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -494,6 +494,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
        if (err < 0)
                goto out_oom_notify;
 
+       virtio_device_ready(vdev);
+
        vb->thread = kthread_run(balloon, vb, "vballoon");
        if (IS_ERR(vb->thread)) {
                err = PTR_ERR(vb->thread);