On Wed, Aug 18, 2021 at 12:36:11PM -0600, Shuah Khan wrote:

On 8/17/21 11:39 PM, Greg KH wrote:

quoted

On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:

quoted

On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:

quoted

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.

[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 <redacted>
---
   drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
   1 file changed, 26 insertions(+)

diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
index 4ba6bcdaa8e9..6f3f374d4bbc 100644
--- a/drivers/usb/usbip/vhci_hcd.c
+++ b/drivers/usb/usbip/vhci_hcd.c

@@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
   	spin_lock(&vdev->priv_lock);
   	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
+		struct urb *urb;
+
+		/* give back URB of unsent unlink request */
   		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);

I know this is an exiting one.
Let's make this pr_debug or remove it all together.

quoted

+
+		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
+		if (!urb) {
+			pr_info("the urb (seqnum %lu) was already given back\n",
+				unlink->unlink_seqnum);

Let's make this pr_debug or remove it all together.

As you have a struct device for all of these, please use dev_dbg() and
friends, not pr_*(), for all of these.

Yes. Makes perfect sense.

Perhaps we should use usbip_dbg_vhci_hc() instead of dev_dbg()? It is
one of the custom macros defined by the usbip driver for printing debug
logs.

Thanks,

	Anirudh