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(); + return; + } + 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 +1004,24 @@ 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); +} + +static inline void vhci_cleanup_unlink_rx(struct vhci_device *vdev) +{ + __vhci_cleanup_unlink_list(vdev, &vdev->unlink_rx); +} + +static void vhci_device_unlink_cleanup(struct vhci_device *vdev) +{ + /* give back URBs of unsent unlink requests */ + vhci_cleanup_unlink_tx(vdev); + /* give back URBs of unanswered unlink requests */ + vhci_cleanup_unlink_rx(vdev); +} + /* * The important thing is that only one context begins cleanup. * This is why error handling and cleanup become simple. -- 2.26.2
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. thanks, greg k-h
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`. 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.
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