[PATCH] misc: hisi_hikey_usb: Fix use after free bug in hisi_hikey_usb_remove due to race condition

[Zheng Wang]

In hisi_hikey_usb_probe, it called hisi_hikey_usb_of_role_switch
and bound &hisi_hikey_usb->work with relay_set_role_switch.
When it calls hub_usb_role_switch_set, it will finally call
schedule_work to start the work.

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

Fix it by finishing the work before cleanup in hisi_hikey_usb_remove.

CPU0                  CPU1

                    |relay_set_role_switch
hisi_hikey_usb_remove|
  usb_role_switch_put|
    usb_role_switch_release  |
     kfree(sw)     |
                    | usb_role_switch_set_role
                    |   //use

Fixes: 7a6ff4c4cbc3 ("misc: hisi_hikey_usb: Driver to support onboard USB gpio hub on Hikey960")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
---
 drivers/misc/hisi_hikey_usb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/misc/hisi_hikey_usb.c b/drivers/misc/hisi_hikey_usb.c
index 2165ec35a343..26fc895c4418 100644
--- a/drivers/misc/hisi_hikey_usb.c
+++ b/drivers/misc/hisi_hikey_usb.c
@@ -242,6 +242,7 @@ static int hisi_hikey_usb_probe(struct platform_device *pdev)
 static int  hisi_hikey_usb_remove(struct platform_device *pdev)
 {
 	struct hisi_hikey_usb *hisi_hikey_usb = platform_get_drvdata(pdev);
+	cancel_work_sync(&hisi_hikey_usb->work);
 
 	if (hisi_hikey_usb->hub_role_sw) {
 		usb_role_switch_unregister(hisi_hikey_usb->hub_role_sw);
-- 
2.25.1