media: dm1105: Fix use after free bug in dm1105_remove due to race condition

In dm1105_probe, it called dm1105_ir_init and bound
&dm1105->ir.work with dm1105_emit_key.
When it handles IRQ request with dm1105_irq,
it may call schedule_work to start the work.

When we call dm1105_remove to remove the driver, there
may be a sequence as follows:

Fix it by finishing the work before cleanup in dm1105_remove

CPU0                  CPU1

                    |dm1105_emit_key
dm1105_remove      |
  dm1105_ir_exit       |
    rc_unregister_device |
    rc_free_device  |
    rc_dev_release  |
    kfree(dev);     |
                    |
                    | rc_keydown
                    |   //use

Fixes: 34d2f9bf18 ("V4L/DVB: dm1105: use dm1105_dev & dev instead of dm1105dvb")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/pci/dm1105/dm1105.c

@@ -1176,6 +1176,7 @@ static void dm1105_remove(struct pci_dev *pdev)
 	struct dvb_demux *dvbdemux = &dev->demux;
 	struct dmx_demux *dmx = &dvbdemux->dmx;
 
+	cancel_work_sync(&dev->ir.work);
 	dm1105_ir_exit(dev);
 	dmx->close(dmx);
 	dvb_net_release(&dev->dvbnet);