[PATCH v2] media: venus: fix use after free bug in venus_remove due to race condition

[Zheng Wang]

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.

Fixes: af2c3834c8ca ("[media] media: venus: adding core part and helper functions")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
---
v2:
- add more details to clarify the bug
---
 drivers/media/platform/qcom/venus/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/platform/qcom/venus/core.c b/drivers/media/platform/qcom/venus/core.c
index 990a1519f968..54ace8bf45e7 100644
--- a/drivers/media/platform/qcom/venus/core.c
+++ b/drivers/media/platform/qcom/venus/core.c
@@ -423,6 +423,7 @@ static int venus_remove(struct platform_device *pdev)
 	struct device *dev = core->dev;
 	int ret;
 
+	cancel_delayed_work(&core->work);
 	ret = pm_runtime_get_sync(dev);
 	WARN_ON(ret < 0);
 
-- 
2.25.1