Re: [PATCH v3 1/2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan <skhan@linuxfoundation.org>]

On 8/19/21 12:09 PM, Anirudh Rayabharam wrote:
> On Wed, Aug 18, 2021 at 12:36:11PM -0600, Shuah Khan wrote:
>> On 8/17/21 11:39 PM, Greg KH wrote:
>>> On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:
>>>> On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:
>>>>> In vhci_device_unlink_cleanup(), the URBs for unsent unlink requests are
>>>>> not given back. This sometimes causes usb_kill_urb to wait indefinitely
>>>>> for that urb to be given back. syzbot has reported a hung task issue [1]
>>>>> for this.
>>>>>
>>>>> To fix this, give back the urbs corresponding to unsent unlink requests
>>>>> (unlink_tx list) similar to how urbs corresponding to unanswered unlink
>>>>> requests (unlink_rx list) are given back.
>>>>>
>>>>> [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
>>>>>
>>>>> Reported-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>>>> Tested-by: syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com
>>>>> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
>>>>> ---
>>>>>     drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
>>>>>     1 file changed, 26 insertions(+)
>>>>>
>>>>> diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
>>>>> index 4ba6bcdaa8e9..6f3f374d4bbc 100644
>>>>> --- a/drivers/usb/usbip/vhci_hcd.c
>>>>> +++ b/drivers/usb/usbip/vhci_hcd.c
>>>>> @@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
>>>>>     	spin_lock(&vdev->priv_lock);
>>>>>     	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
>>>>> +		struct urb *urb;
>>>>> +
>>>>> +		/* give back URB of unsent unlink request */
>>>>>     		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);
>>>>
>>>> I know this is an exiting one.
>>>> Let's make this pr_debug or remove it all together.
>>>>
>>>>> +
>>>>> +		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
>>>>> +		if (!urb) {
>>>>> +			pr_info("the urb (seqnum %lu) was already given back\n",
>>>>> +				unlink->unlink_seqnum);
>>>>
>>>> Let's make this pr_debug or remove it all together.
>>>
>>> As you have a struct device for all of these, please use dev_dbg() and
>>> friends, not pr_*(), for all of these.
>>>
>>
>> Yes. Makes perfect sense.
> 
> Perhaps we should use usbip_dbg_vhci_hc() instead of dev_dbg()? It is
> one of the custom macros defined by the usbip driver for printing debug
> logs.
> 

Yes that macro could be used. However, let's just get rid of the messages.
I don't see much use for them.

thanks,
-- Shuah
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