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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Fri, 10 Jan 2020 17:46:06 +0100
Message-ID: <CAAeHK+x5psxWYNvgfxBiLoQt-o3n+-t_ZhLxueRJ8bHsv=Pmbg@mail.gmail.com>
Subject: Re: WARNING in usbhid_raw_request/usb_submit_urb (2)
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     syzbot <syzbot+10e5f68920f13587ab12@syzkaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        ingrassia@epigenesys.com, LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Thu, Jan 9, 2020 at 5:46 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Wed, 8 Jan 2020, syzbot wrote:
>
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger
> > crash:
> >
> > Reported-and-tested-by:
> > syzbot+10e5f68920f13587ab12@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         ecdf2214 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=b06a019075333661
> > dashboard link: https://syzkaller.appspot.com/bug?extid=10e5f68920f13587ab12
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=1583963ee00000
> >
> > Note: testing is done by a robot and is best-effort only.
>
> I'm at a loss for a way to track this down any farther.  The difference
> between this patch and the previous was very small and almost entirely
> confined to actions that take place _after_ the bug condition has been
> detected.
>
> If this is indeed caused by a race, it would be nice to know that the
> two racing threads are doing.  One of them we can see in the log output
> (it's calling usb_control_msg) but the other is a mystery.

I've tried to reproduce this manually, but failed :( I don't think
there's anything else we can do with this. Let's close this bug,
there's a chance syzbot comes up with a better reproducer.

#syz invalid