Messages in this thread | | | Subject | Re: [PATCH 0/6] usbip fixes to crashes found by syzbot | From | Shuah Khan <> | Date | Wed, 17 Mar 2021 09:06:47 -0600 |
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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
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