linux-kernel - [PATCH v7] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Message-Id: <20230316180850.1600867-1-zyytlz.wz@163.com>
Date:   Fri, 17 Mar 2023 02:08:50 +0800
From:   Zheng Wang <zyytlz.wz@....com>
To:     gregkh@...uxfoundation.org
Cc:     skhan@...uxfoundation.org, p.zabel@...gutronix.de,
        biju.das.jz@...renesas.com, phil.edworthy@...esas.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        hackerzheng666@...il.com, 1395428693sheep@...il.com,
        alex000young@...il.com, yoshihiro.shimoda.uh@...esas.com,
        Zheng Wang <zyytlz.wz@....com>
Subject: [PATCH v7] usb: gadget: udc: renesas_usb3: Fix use after free bug in  renesas_usb3_remove due to race condition

In renesas_usb3_probe, role_work is bound with renesas_usb3_role_work.
renesas_usb3_start will be called to start the work.

If we remove the driver which will call usbhs_remove, there may be
an unfinished work. The possible sequence is as follows:

Fix it by canceling the work before cleanup in the renesas_usb3_remove.

Note that removing a driver is a root-only operation, and should never
happen.

CPU0                  			CPU1

                    			| renesas_usb3_role_work
renesas_usb3_remove 			|
usb_role_switch_unregister|
device_unregister   			|
kfree(sw)  	     					|
free usb3->role_sw  			|
                    			| usb_role_switch_set_role
                    			| //use usb3->role_sw

This bug was found by static analysis.

Fixes: 39facfa01c9f ("usb: gadget: udc: renesas_usb3: Add register of usb role switch")
Signed-off-by: Zheng Wang <zyytlz.wz@....com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
---
v7:
- add more details about how the bug was found suggested by Shuah
v6:
- beautify the format and add note suggested by Greg KH
v5:
- fix typo
v4:
- add Reviewed-by label and resubmit v4 suggested by Greg KH
v3:
- modify the commit message to make it clearer suggested by Yoshihiro Shimoda
v2:
- fix typo, use clearer commit message and only cancel the UAF-related work suggested by Yoshihiro Shimoda
---
 drivers/usb/gadget/udc/renesas_usb3.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/udc/renesas_usb3.c b/drivers/usb/gadget/udc/renesas_usb3.c
index bee6bceafc4f..a301af66bd91 100644
--- a/drivers/usb/gadget/udc/renesas_usb3.c
+++ b/drivers/usb/gadget/udc/renesas_usb3.c
@@ -2661,6 +2661,7 @@ static int renesas_usb3_remove(struct platform_device *pdev)
 	debugfs_remove_recursive(usb3->dentry);
 	device_remove_file(&pdev->dev, &dev_attr_role);
 
+	cancel_work_sync(&usb3->role_work);
 	usb_role_switch_unregister(usb3->role_sw);
 
 	usb_del_gadget_udc(&usb3->gadget);
-- 
2.25.1