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

[sicong <congei42@163.com>]

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)

regards,

Sicong Huang