From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Anirudh Rayabharam <mail@anirudhrb.com>
Cc: Valentina Manea <valentina.manea.m@gmail.com>,
Shuah Khan <shuah@kernel.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
syzbot+74d6ef051d3d2eacf428@syzkaller.appspotmail.com,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usbip: give back URBs for unsent unlink requests during cleanup
Date: Fri, 13 Aug 2021 08:55:25 +0200 [thread overview]
Message-ID: <YRYXXbFyI1k9JBgR@kroah.com> (raw)
In-Reply-To: <YQ1uYSQ2T5kMrwfI@anirudhrb.com>
On Fri, Aug 06, 2021 at 10:46:17PM +0530, Anirudh Rayabharam wrote:
> On Fri, Aug 06, 2021 at 06:47:54PM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Aug 06, 2021 at 10:10:14PM +0530, 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. Since the code is almost the
> > > same, extract it into a new function and call it for both unlink_rx and
> > > unlink_tx lists.
> > >
> > > [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 | 47 ++++++++++++++++++++++++++----------
> > > 1 file changed, 34 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> > > index 4ba6bcdaa8e9..45f98aa12895 100644
> > > --- a/drivers/usb/usbip/vhci_hcd.c
> > > +++ b/drivers/usb/usbip/vhci_hcd.c
> > > @@ -945,7 +945,8 @@ static int vhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status)
> > > return 0;
> > > }
> > >
> > > -static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
> > > +static void __vhci_cleanup_unlink_list(struct vhci_device *vdev,
> > > + struct list_head *unlink_list)
> > > {
> > > struct vhci_hcd *vhci_hcd = vdev_to_vhci_hcd(vdev);
> > > struct usb_hcd *hcd = vhci_hcd_to_hcd(vhci_hcd);
> > > @@ -953,23 +954,25 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
> > > struct vhci_unlink *unlink, *tmp;
> > > unsigned long flags;
> > >
> > > + if (unlink_list != &vdev->unlink_tx
> > > + && unlink_list != &vdev->unlink_rx) {
> > > + pr_err("Invalid list passed to __vhci_cleanup_unlink_list\n");
> > > + BUG();
> >
> > Do not allow the system to crash, that is not ok.
> >
> > > + return;
> >
> > This call makes no sense as you just rebooted the machine :(
> >
> > Handle errors properly and recover from them and move on. A single tiny
> > driver should not take down the whole system.
>
> The execution can reach only if there is a developer error and they passed
> some random list in `unlink_list`.
Why would a developer do that? As that is not the case in the kernel
tree, no need to check for it.
thanks,
greg k-h
prev parent reply other threads:[~2021-08-13 6:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-06 16:40 [PATCH] usbip: give back URBs for unsent unlink requests during cleanup Anirudh Rayabharam
2021-08-06 16:47 ` Greg Kroah-Hartman
2021-08-06 17:16 ` Anirudh Rayabharam
2021-08-13 6:55 ` Greg Kroah-Hartman [this message]
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