linux-kernel - [PATCH] USB: gadget: udc: Fix use after free bug in udc_plat

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Date:   Fri, 10 Mar 2023 15:00:39 +0800
From:   Zheng Wang <zyytlz.wz@....com>
To:     gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        hackerzheng666@...il.com, 1395428693sheep@...il.com,
        alex000young@...il.com, Zheng Wang <zyytlz.wz@....com>
Subject: [PATCH] USB: gadget: udc: Fix use after free bug in udc_plat_remove due to race condition

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@....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