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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 10 Feb 2020 16:04:47 +0100
Message-ID: <CACT4Y+bDNjj_RGLtvRCaV3k9+QX4eENyKyWWAbsHcbwR7CDrWQ@mail.gmail.com>
Subject: Re: INFO: task hung in wdm_flush
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Oliver Neukum <oneukum@suse.de>,
        syzbot <syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Jia-Ju Bai <baijiaju1990@gmail.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Colin King <colin.king@canonical.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>,
        yuehaibing@huawei.com, =?UTF-8?Q?Bj=C3=B8rn_Mork?= <bjorn@mork.no>
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On Mon, Feb 10, 2020 at 1:46 PM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> On 2020/02/10 19:09, Dmitry Vyukov wrote:
> > You may also try on the exact commit the bug was reported, because
> > usb-fuzzer is tracking branch, things may change there.
>
> OK. I explicitly tried
>
>   #syz test: https://github.com/google/kasan.git e5cd56e94edde38ca4dafae5a450c5a16b8a5f23
>
> but syzbot still cannot reproduce this bug using the reproducer...
>
> On 2020/02/10 21:02, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Note: testing is done by a robot and is best-effort only.
> >
>
> Anyway, I'm just suspecting that we are forgetting to wake up all waiters
> after clearing WDM_IN_USE bit because sometimes multiple threads are reported
> as hung.
>
> On 2020/02/10 15:27, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=117c3ae9e00000
> >
> > Note: testing is done by a robot and is best-effort only.
> >
>
> On 2020/02/10 15:55, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=13b3f6e9e00000
> >
> > Note: testing is done by a robot and is best-effort only.
> >
>
> On 2020/02/10 16:21, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=115026b5e00000
> >
> > Note: testing is done by a robot and is best-effort only.
> >
>
> On 2020/02/10 16:44, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=17285431e00000
> >
> > Note: testing is done by a robot and is best-effort only.
> >
>
> On 2020/02/10 17:05, syzbot wrote:
> > Hello,
> >
> > syzbot has tested the proposed patch and the reproducer did not trigger crash:
> >
> > Reported-and-tested-by: syzbot+854768b99f19e89d7f81@syzkaller.appspotmail.com
> >
> > Tested on:
> >
> > commit:         e5cd56e9 usb: gadget: add raw-gadget interface
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=c372cdb7140fc162
> > dashboard link: https://syzkaller.appspot.com/bug?extid=854768b99f19e89d7f81
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Note: testing is done by a robot and is best-effort only.


On Mon, Feb 10, 2020 at 4:03 PM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> On 2020/02/10 21:46, Tetsuo Handa wrote:
> > On 2020/02/10 19:09, Dmitry Vyukov wrote:
> >> You may also try on the exact commit the bug was reported, because
> >> usb-fuzzer is tracking branch, things may change there.
> >
> > OK. I explicitly tried
> >
> >   #syz test: https://github.com/google/kasan.git e5cd56e94edde38ca4dafae5a450c5a16b8a5f23
> >
> > but syzbot still cannot reproduce this bug using the reproducer...
>
> It seems that there is non-trivial difference between kernel config in dashboard
> and kernel config in "syz test:" mails. Maybe that's the cause...