Re: WARNING in yurex_write/usb_submit_urb

From: Johan Hovold <johan@kernel.org>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Johan Hovold <johan@kernel.org>,
	syzbot <syzbot+e87ebe0f7913f71f2ea5@syzkaller.appspotmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	USB list <linux-usb@vger.kernel.org>,
	stable <stable@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: WARNING in yurex_write/usb_submit_urb
Date: Mon, 14 Dec 2020 16:16:53 +0100	[thread overview]
Message-ID: <X9eB5ZZMq6q5j4eW@localhost> (raw)
In-Reply-To: <CAAeHK+xLiLjGMJLuWpyPHMO=zD6k33s5VYSBDMMbTkAEauF3dA@mail.gmail.com>

On Mon, Dec 14, 2020 at 04:06:49PM +0100, Andrey Konovalov wrote:
> On Mon, Dec 14, 2020 at 4:02 PM Johan Hovold <johan@kernel.org> wrote:
> >
> > On Mon, Dec 14, 2020 at 06:48:03AM -0800, syzbot wrote:
> > > Hello,
> > >
> > > syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> > > WARNING in yurex_write/usb_submit_urb
> >
> > It appears syzbot never tested the patch from the thread. Probably using
> > it's mail interface incorrectly, I don't know and I don't have time to
> > investigate. The patch itself is correct.
> 
> Hi Johan,
> 
> I wasn't CCed on the testing request, so I can't say what exactly was wrong.

Here's the patch and the "syz test" command in a reply:

	https://lore.kernel.org/r/20201214104444.28386-1-johan@kernel.org

Probably needs to go in the same mail, right?

How about including the command needed to test a patch in the syzbot
report mail to assist the casual user of its interfaces? I had to browse
the web page you link to and still got it wrong apparently.

> Could you send me the patch you were trying to test?

Does this work better:

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing

Johan


From 3bb77b2ac604d70b06f45a850e326dda9c99c9cd Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Mon, 14 Dec 2020 11:30:53 +0100
Subject: [PATCH] USB: yurex: fix control-URB timeout handling

Make sure to always cancel the control URB in write() so that it can be
reused after a timeout or spurious CMD_ACK.

Currently any further write requests after a timeout would fail after
triggering a WARN() in usb_submit_urb() when attempting to submit the
already active URB.

Reported-by: syzbot+e87ebe0f7913f71f2ea5@syzkaller.appspotmail.com
Fixes: 6bc235a2e24a ("USB: add driver for Meywa-Denki & Kayac YUREX")
Cc: stable <stable@vger.kernel.org>     # 2.6.37
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/misc/yurex.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 73ebfa6e9715..c640f98d20c5 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -496,6 +496,9 @@ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
 		timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
 	finish_wait(&dev->waitq, &wait);
 
+	/* make sure URB is idle after timeout or (spurious) CMD_ACK */
+	usb_kill_urb(dev->cntl_urb);
+
 	mutex_unlock(&dev->io_mutex);
 
 	if (retval < 0) {
-- 
2.26.2


