linux-kernel - Re: [PATCH 0/6] usbip fixes to crashes found by syzbot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <41d21338-19f4-ac4f-2aef-e26180f4c573@linuxfoundation.org>
Date:   Thu, 18 Mar 2021 07:13:37 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>, shuah@...nel.org
Cc:     valentina.manea.m@...il.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 0/6] usbip fixes to crashes found by syzbot

On 3/17/21 9:06 AM, Shuah Khan wrote:
> 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.
>>
> 

Please don't review code that isn't sent upstream. This repo you are
looking at is a private branch created just to verify fixes on syzbot.

I understand the race window you are talking about. I have my way of
working to resolve it.

thanks,
-- Shuah