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: [email protected]
Tested-by: [email protected]
Signed-off-by: Anirudh Rayabharam <[email protected]>
---
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: [email protected]
> Tested-by: [email protected]
> Signed-off-by: Anirudh Rayabharam <[email protected]>
> ---
> 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: [email protected]
> > Tested-by: [email protected]
> > Signed-off-by: Anirudh Rayabharam <[email protected]>
> > ---
> > 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: [email protected]
> > > Tested-by: [email protected]
> > > Signed-off-by: Anirudh Rayabharam <[email protected]>
> > > ---
> > > 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