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Subject[PATCH] USB: gadget: udc: Fix use after free bug in udc_plat_remove due to race condition
Date
In udc_plat_probe, &udc->drd_work is bound with
udc_drd_work. udc_drd_work may be called by
usbd_connect_notify to start the work.

Besides, there is a invoking chain:
udc_plat_probe
->udc_probe
->usb_add_gadget_udc_release
->usb_add_gadget

It will add a new gadget to the udc class driver
list. In usb_add_gadget, it uses usb_udc_release
as its release function, which will kfree(udc)
to when destroying the gadget.

If we remove the module which will call udc_plat_remove
to make cleanup, there may be a unfinished work.
The possible sequence is as follows:

Fix it by finishing the work before cleanup in the udc_plat_remove

Fixes: 1b9f35adb0ff ("usb: gadget: udc: Add Synopsys UDC Platform driver")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
---
drivers/usb/gadget/udc/snps_udc_plat.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/udc/snps_udc_plat.c b/drivers/usb/gadget/udc/snps_udc_plat.c
index 8bbb89c80348..6228e178cc0a 100644
--- a/drivers/usb/gadget/udc/snps_udc_plat.c
+++ b/drivers/usb/gadget/udc/snps_udc_plat.c
@@ -230,6 +230,7 @@ static int udc_plat_remove(struct platform_device *pdev)
struct udc *dev;

dev = platform_get_drvdata(pdev);
+ cancel_delayed_work_sync(&dev->drd_work);

usb_del_gadget_udc(&dev->gadget);
/* gadget driver must not be registered */
--
2.25.1
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