Re: Re: [PATCH v1] usb: cdns3: cdns3-gadget: fix use-after-free bug in cdns3_gadget_exit due to race

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Jun 05, 2024 at 10:36:30AM +0800, sicong wrote:
> 
> 
> At 2024-06-04 21:11:57, "Greg KH" <gregkh@linuxfoundation.org> wrote:
> >On Mon, May 13, 2024 at 10:19:48AM +0800, Sicong Huang wrote:
> >> This bug exists in drivers/usb/cdns3/cdns3-gadget.c. Function
> >> __cdns3_gadget_init will call cdns3_gadget_start to do futher jobs
> >> during the initialization proccess of cdns3 gadget. In cdns3_gadget_start,
> >> &priv_dev->pending_status_wq is bound with cdns3_pending_setup_status_handler.
> >> Then this work will be added to system_freezable_wq in cdns3_gadget_ep0_queue.
> >> Here is the code.
> >> queue_work(system_freezable_wq, &priv_dev->pending_status_wq);
> >> 
> >> If we call cdns3_gadget_exit to remove the device and make cleanup,
> >> there are some unfinished works. This function will call cdns3_free_all_eps to
> >> free all the endpoints. However, if cdns3_pending_setup_status_handler is
> >> scheduled to run after the free job, it will cause use-after-free error as
> >> cdns3_pending_setup_status_handler will use the endpoint in the following code.
> >> request->complete(&priv_dev->eps[0]->endpoint, request);
> >> 
> >> The possible execution flow that may lead to this issue is as follows:
> >> CPU0                    CPU1
> >>                       | __cdns3_gadget_init
> >>                       | cdns3_gadget_start
> >> cdns3_gadget_exit     |
> >> cdns3_free_all_eps    |
> >> devm_kfree (free)     |
> >>                       | cdns3_pending_setup_status_handler
> >>                       | &priv_dev->eps[0]->endpoint (use)
> >> 
> >> Fix it by cleaning the work in cdns3_gadget_exit.
> >> 
> >> Signed-off-by: Sicong Huang <congei42@163.com>
> >> ---
> >>  drivers/usb/cdns3/cdns3-gadget.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >> 
> >> diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
> >> index fd1beb10bba7..0f2e143bd17a 100644
> >> --- a/drivers/usb/cdns3/cdns3-gadget.c
> >> +++ b/drivers/usb/cdns3/cdns3-gadget.c
> >> @@ -3252,6 +3252,9 @@ static void cdns3_gadget_exit(struct cdns *cdns)
> >>  	pm_runtime_mark_last_busy(cdns->dev);
> >>  	pm_runtime_put_autosuspend(cdns->dev);
> >>  
> >> +	cancel_work_sync(&priv_dev->pending_status_wq);
> >> +	cancel_work_sync(&priv_dev->aligned_buf_wq);
> >> +
> >>  	usb_del_gadget(&priv_dev->gadget);
> >>  	devm_free_irq(cdns->dev, cdns->dev_irq, priv_dev);
> >>  
> >> -- 
> >> 2.34.1
> >
> >What commit id does this fix?
> >
> >thanks,
> >
> 
> >greg k-h
> 
> 
> I made the changes based on the following commit information.
> commit 51474ab44abf907023a8a875e799b07de461e466 (origin/usb-testing, origin/usb-next)

That is not what I meant, sorry.

I mean, "this is a bugfix, so what commit caused the problem that this
is fixing?"

thanks,

greg k-h