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

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Date:   Wed, 18 Aug 2021 07:39:37 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Anirudh Rayabharam <mail@...rudhrb.com>,
        valentina.manea.m@...il.com, shuah@...nel.org,
        syzbot+74d6ef051d3d2eacf428@...kaller.appspotmail.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] usbip: give back URBs for unsent unlink requests
 during cleanup

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@...kaller.appspotmail.com
> > Tested-by: syzbot+74d6ef051d3d2eacf428@...kaller.appspotmail.com
> > Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.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.

thanks,

greg k-h