On Tue, Aug 10, 2021 at 05:25:51PM -0600, Shuah Khan wrote: > On 8/6/21 12:13 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. Since the code is almost the > > same, extract it into a new function and call it for both unlink_rx and > > unlink_tx lists. > > > > Let's not do the refactor - let's first fix the problem and then the refactor. Sure, I will make it a two patch series where the first one fixes the problem and the second one does the refactor. > > > [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> > > --- > > > > Changes in v2: > > Use WARN_ON() instead of BUG() when unlink_list is neither unlink_tx nor > > unlink_rx. > > > > v1: https://lore.kernel.org/lkml/20210806164015.25263-1-mail@xxxxxxxxxxxxx/ > > > > --- > > drivers/usb/usbip/vhci_hcd.c | 45 +++++++++++++++++++++++++----------- > > 1 file changed, 32 insertions(+), 13 deletions(-) > > > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c > > index 4ba6bcdaa8e9..67e638f4c455 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 +954,23 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > > struct vhci_unlink *unlink, *tmp; > > unsigned long flags; > > + if (WARN(unlink_list != &vdev->unlink_tx > > + && unlink_list != &vdev->unlink_rx, > > + "Invalid list passed to __vhci_cleanup_unlink_list\n")) > > + return; > > + > > With this change, this will be only place unlink_rx is used without > vdev->priv_lock hold? Please explain why this is safe. Well, this doesn't read or modify the contents of unlink_rx and unlink_tx. So, it looks safe to me. Let me know if I'm missing something here. > > > spin_lock_irqsave(&vhci->lock, flags); > > spin_lock(&vdev->priv_lock); > > - list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) { > > - pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum); > > - list_del(&unlink->list); > > - kfree(unlink); > > - } > > - > > - while (!list_empty(&vdev->unlink_rx)) { > > + list_for_each_entry_safe(unlink, tmp, unlink_list, list) { > > struct urb *urb; > > - unlink = list_first_entry(&vdev->unlink_rx, struct vhci_unlink, > > - list); > > - > > - /* give back URB of unanswered unlink request */ > > - pr_info("unlink cleanup rx %lu\n", unlink->unlink_seqnum); > > + if (unlink_list == &vdev->unlink_tx) > > + pr_info("unlink cleanup tx %lu\n", > > + unlink->unlink_seqnum); > > + else > > + pr_info("unlink cleanup rx %lu\n", > > + unlink->unlink_seqnum); > > urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum); > > if (!urb) { > > @@ -1001,6 +1002,24 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev) > > spin_unlock_irqrestore(&vhci->lock, flags); > > } > > +static inline void vhci_cleanup_unlink_tx(struct vhci_device *vdev) > > +{ > > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_tx); > > With this change, this will be only place unlink_rx is used without > vdev->priv_lock hold? Please explain why this is safe. > > > +} > > + > > Is there a need for this layer? > > > +static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev) > > +{ > > + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx); > > With this change, this will be only place unlink_rx is used without > vdev->priv_lock hold? Please explain why this is safe. > > > +} > > + > Is there a need for this layer? I added these wrappers purely for convenience. There is no other purpose. Would you prefer this patch without the wrappers? Thanks for the review! - Anirudh.
