Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <00000000000026d72f058fb33242@google.com> <Pine.LNX.4.44L0.1908091531590.1630-100000@iolanthe.rowland.org>
In-Reply-To: <Pine.LNX.4.44L0.1908091531590.1630-100000@iolanthe.rowland.org>
From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Mon, 12 Aug 2019 14:11:54 +0200
Message-ID: <CAAeHK+wh=oQo4rorPuKR6dKGbwx4pNL8Of8mDUqbpV-G0kt6_w@mail.gmail.com>
Subject: Re: possible deadlock in usb_deregister_dev
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     syzbot <syzbot+a64a382964bf6c71a9c0@syzkaller.appspotmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>, oneukum@suse.de,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Content-Type: multipart/mixed; boundary="000000000000bd1494058fea6eae"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

--000000000000bd1494058fea6eae
Content-Type: text/plain; charset="UTF-8"

On Fri, Aug 9, 2019 at 9:32 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Fri, 9 Aug 2019, syzbot wrote:
>
> > syzbot has found a reproducer for the following crash on:
> >
> > HEAD commit:    e96407b4 usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15bf780e600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=cfa2c18fb6a8068e
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a64a382964bf6c71a9c0
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16787574600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=136cc4d2600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+a64a382964bf6c71a9c0@syzkaller.appspotmail.com
> >
> > usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> > usb 1-1: config 0 descriptor??
> > iowarrior 1-1:0.236: IOWarrior product=0x1501, serial= interface=236 now
> > attached to iowarrior0
> > usb 1-1: USB disconnect, device number 2
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 5.3.0-rc2+ #25 Not tainted
> > ------------------------------------------------------
> > kworker/0:1/12 is trying to acquire lock:
> > 00000000cd63e8f1 (minor_rwsem){++++}, at: usb_deregister_dev
> > drivers/usb/core/file.c:238 [inline]
> > 00000000cd63e8f1 (minor_rwsem){++++}, at: usb_deregister_dev+0x61/0x270
> > drivers/usb/core/file.c:230
> >
> > but task is already holding lock:
> > 000000001d1989ef (iowarrior_open_disc_lock){+.+.}, at:
> > iowarrior_disconnect+0x45/0x2c0 drivers/usb/misc/iowarrior.c:867
> >
> > which lock already depends on the new lock.
>
> https://syzkaller.appspot.com/bug?extid=ca52394faa436d8131df is
> undoubtedly a duplicate of this.

I've marked it as one, thanks!

Now that we have a reproducer, let's retry Oliver's fix:

#syz test: https://github.com/google/kasan.git e96407b4

--000000000000bd1494058fea6eae
Content-Type: text/x-patch; charset="US-ASCII"; name="iowarrior.patch"
Content-Disposition: attachment; filename="iowarrior.patch"
Content-Transfer-Encoding: base64
Content-ID: <f_jz8cwrb50>
X-Attachment-Id: f_jz8cwrb50
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--000000000000bd1494058fea6eae--