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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 13 Apr 2021 19:11:11 +0200
Message-ID: <CACT4Y+aX-cMJxMYmWms3MG-4=Rb9eG_N+pOjorRHoV1MGQXtkA@mail.gmail.com>
Subject: Re: [syzbot] general protection fault in gadget_setup
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     syzbot <syzbot+eb4674092e6cc8d9e0bd@syzkaller.appspotmail.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Felipe Balbi <balbi@kernel.org>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        syzkaller <syzkaller@googlegroups.com>
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On Tue, Apr 13, 2021 at 6:57 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Tue, Apr 13, 2021 at 06:47:47PM +0200, Dmitry Vyukov wrote:
> > On Tue, Apr 13, 2021 at 6:13 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> > > Hopefully this patch will make the race a lot more likely to occur.  Is
> > > there any way to tell syzkaller to test it, despite the fact that
> > > syzkaller doesn't think it has a reproducer for this issue?
> >
> > If there is no reproducer the only way syzbot can test it is if it's
> > in linux-next under CONFIG_DEBUG_AID_FOR_SYZBOT:
> > http://bit.do/syzbot#no-custom-patches
>
> There _is_ a theoretical reproducer: the test that provoked syzkaller's
> original bug report.  But syzkaller doesn't realize that it is (or may
> be) a reproducer.
>
> It ought to be possible to ask syzkaller to run a particular test that
> it has done before, with a patch applied -- and without having to add
> anything to linux-next.

Yes, this is possible:
http://bit.do/syzbot#syzkaller-reproducers

The log of tests executed before the crash is available under the
"console output" link:
console output: https://syzkaller.appspot.com/x/log.txt?x=124adbf6d00000
And this log can be replayed using syz-execprog utility.