diff mbox series

[v8] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3_remove due to race condition

Message ID 20230316181623.1603914-1-zyytlz.wz@163.com
State New
Headers
Series [v8] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3_remove due to race condition |

Commit Message

Zheng Wang March 16, 2023, 6:16 p.m. UTC 
  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@163.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
---
v8:
- replace | with spaces to make line up suggested by Greg KH
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(+)

Comments

Greg KH March 16, 2023, 7:07 p.m. UTC | #1 
On Fri, Mar 17, 2023 at 02:16:23AM +0800, Zheng Wang wrote:
> 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

No line at all?
Zheng Hacker March 17, 2023, 4:09 a.m. UTC | #2 
Greg KH <gregkh@linuxfoundation.org> 于2023年3月17日周五 03:07写道：
>
> On Fri, Mar 17, 2023 at 02:16:23AM +0800, Zheng Wang wrote:
> > 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
>
> No line at all?
>

Sorry, I'll remove the empty line. And I think there are other ways to
trigger device's remove like directly unpluging the USB device if
accessible. I think we nee to append this msg in the next version.

Best regards,
Zheng
diff mbox series

Patch

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);