On 3/17/21 12:21 AM, Tetsuo Handa wrote:
Shuah, this driver is getting more and more cryptic and buggy.
Please explain the strategy for serialization before you write patches.
- Fix attach_store() to check usbip_event_happened() before
waking up threads.
No, this helps nothing.
diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
index c4b4256e5dad3..f0a770adebd97 100644
--- a/drivers/usb/usbip/vhci_sysfs.c
+++ b/drivers/usb/usbip/vhci_sysfs.c
@@ -418,6 +418,15 @@ static ssize_t attach_store(struct device *dev, struct device_attribute *attr,
spin_unlock_irqrestore(&vhci->lock, flags);
/* end the lock */
+ if (usbip_event_happened(&vdev->ud)) {
+ /*
+ * something went wrong - event handler shutting
+ * the connection and doing reset - bail out
+ */
+ dev_err(dev, "Event happended - handler is active\n");
+ return -EAGAIN;
+ }
+
detach_store() can queue shutdown event as soon as reaching "/* end the lock */" line
but attach_store() might be preempted immediately after verifying that
usbip_event_happened() was false (i.e. at this location) in order to wait for
shutdown event posted by detach_store() to be processed.
Yes. I haven't sent the patch for that reason. I am trying to test a
solution. I haven't come up with a solution yet.
Holding event_lock isn't the right solution. I am not going to accept
that. This is a window that gets triggered by syzbot injecting errors
in a sequence. Fixing this should be done taking other moving parts of
the driver into account.
thanks,
-- Shuah
