[PATCH 5.16 0011/1017] virtio_console: break out of buf poll on remove

Greg Kroah-Hartman
2022-04-05T08:55:55Z

From: Michael S. Tsirkin <mst@redhat.com>

[ Upstream commit 0e7174b9d5877130fec41fb4a16e0c2ee4958d44 ]

A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
modprobe virtio_console
modprobe -r virtio_console
in a loop.

Fix this up by calling virtio_break_device + flush before reset.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1786239
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/char/virtio_console.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 660c5c388c29..f864b17be7e3 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1957,6 +1957,13 @@ static void virtcons_remove(struct virtio_device *vdev)
list_del(&portdev->list);
spin_unlock_irq(&pdrvdata_lock);

+ /* Device is going away, exit any polling for buffers */
+ virtio_break_device(vdev);
+ if (use_multiport(portdev))
+ flush_work(&portdev->control_work);
+ else
+ flush_work(&portdev->config_work);
+
/* Disable interrupts for vqs */
vdev->config->reset(vdev);
/* Finish up work that's lined up */
--
2.34.1