media: venus: fix use after free bug in venus_remove due to race condition

media: venus: fix use after free bug in venus_remove due to race condition

in venus_probe, core->work is bound with venus_sys_error_handler, which is
used to handle error. The code use core->sys_err_done to make sync work.
The core->work is started in venus_event_notify.

If we call venus_remove, there might be an unfished work. The possible
sequence is as follows:

CPU0                  CPU1

                     |venus_sys_error_handler
venus_remove         |
hfi_destroy	 		 |
venus_hfi_destroy	 |
kfree(hdev);	     |
                     |hfi_reinit
					 |venus_hfi_queues_reinit
                     |//use hdev

Fix it by canceling the work in venus_remove.

Cc: stable@vger.kernel.org
Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Signed-off-by: Stanimir Varbanov <stanimir.k.varbanov@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>