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Date:   Tue, 13 Nov 2018 15:37:59 -0500 (EST)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     syzbot <syzbot+7634edaea4d0b341c625@syzkaller.appspotmail.com>
cc:     Thinh.Nguyen@synopsys.com, <felipe.balbi@linux.intel.com>,
        <gregkh@linuxfoundation.org>, <linux-kernel@vger.kernel.org>,
        <linux-usb@vger.kernel.org>, <shuah@kernel.org>,
        <syzkaller-bugs@googlegroups.com>
Subject: Re: WARNING in usb_submit_urb (4)
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Message-ID: <Pine.LNX.4.44L0.1811131532270.1503-100000@iolanthe.rowland.org>
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On Mon, 12 Nov 2018, syzbot wrote:

> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    e12e00e388de Merge tag 'kbuild-fixes-v4.20' of git://git.k..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=100e4ef5400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8f215f21f041a0d7
> dashboard link: https://syzkaller.appspot.com/bug?extid=7634edaea4d0b341c625
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11ce6fbd400000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7634edaea4d0b341c625@syzkaller.appspotmail.com

I tried reproducing this bug on my own system, following the 
instructions at

https://github.com/google/syzkaller/blob/master/docs/executing_syzkaller_programs.md

The reproducer failed to run properly.  It produced the following 
output:


$ ./syz-execprog -cover=0 -threaded=1 -repeat=1 -procs=4 /tmp/repro.syz 
2018/11/13 15:29:32 parsed 1 programs
2018/11/13 15:29:32 executed programs: 0
2018/11/13 15:29:32 result: failed=false hanged=false err=executor 3: failed: tun: ioctl(TUNSETIFF) failed (errno 1)
loop failed (errno 0)


tun: ioctl(TUNSETIFF) failed (errno 1)
loop failed (errno 0)


The system is Fedora 28 running the 4.18.16-200.fc28.x86_64 kernel.  
What should I do to investigate further?

Alan Stern