[PATCH 3.19 19/75] virtio_balloon: set DRIVER_OK before using device

From: Greg Kroah-Hartman
Date: Fri Apr 10 2015 - 09:24:12 EST

3.19-stable review patch. If anyone has any objections, please let me know.


From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/virtio/virtio_balloon.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -494,6 +494,8 @@ static int virtballoon_probe(struct virt
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);

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