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@xxxxxxxxxxxxxxxxxxxxxxxxx > > Tested-by: syzbot+74d6ef051d3d2eacf428@xxxxxxxxxxxxxxxxxxxxxxxxx > > Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx> > > --- > > 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`. So, BUG() here crashes the kernel and draws attention to this fact. Is WARN() a better option here? There is no way to recover from this and continue with the rest of the function. Either we WARN()/BUG() or we return silently. Thanks! - Anirudh.
