From: Alan Stern <stern@rowland.harvard.edu>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>,
syzbot <syzbot+1bc2c2afd44f820a669f@syzkaller.appspotmail.com>,
<andreyknvl@google.com>, <ingrassia@epigenesys.com>,
<linux-kernel@vger.kernel.org>, <linux-usb@vger.kernel.org>,
<syzkaller-bugs@googlegroups.com>
Subject: Re: [PATCH] usb: core: urb: change a dev_WARN() to dev_err() for syzbot
Date: Mon, 10 Feb 2020 16:11:10 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.44L0.2002101609090.13988-100000@netrider.rowland.org> (raw)
In-Reply-To: <20200210190419.GC1058087@kroah.com>
On Mon, 10 Feb 2020, Greg KH wrote:
> On Fri, Jan 31, 2020 at 08:06:52AM +0300, Dan Carpenter wrote:
> > We changed this from dev_err() to dev_WARN() in commit 0cb54a3e47cb
> > ("USB: debugging code shouldn't alter control flow").
> >
> > The difference between dev_WARN() and dev_err() is that dev_WARN()
> > prints a stack trace and if you have panic on OOPS enabled then it leads
> > to a panic. The dev_err() function just prints the error message.
> >
> > Back in the day we didn't have usb emulators fuzz testing the kernel
> > so dev_WARN() didn't cause a problem for anyone, but these days the
> > dev_WARN() interferes with syzbot so let's change this to a dev_err().
> >
> > Reported-by: syzbot+1bc2c2afd44f820a669f@syzkaller.appspotmail.com
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >
> > drivers/usb/core/urb.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
> > index da923ec17612..0980c1d2253d 100644
> > --- a/drivers/usb/core/urb.c
> > +++ b/drivers/usb/core/urb.c
> > @@ -475,7 +475,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
> >
> > /* Check that the pipe's type matches the endpoint's type */
> > if (usb_urb_ep_type_check(urb))
> > - dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
> > + dev_err(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
> > usb_pipetype(urb->pipe), pipetypes[xfertype]);
>
> Like others said, we should have the stack trace here. So can you
> change this to dev_warn() and a stacktrace?
In fact we want both a stack trace and a syzbot notification, because
this particular error indicates a bug in a kernel driver. Therefore
dev_WARN is appropriate.
Alan Stern
> thanks,
>
> greg k-h
next prev parent reply other threads:[~2020-02-10 21:11 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-29 12:27 WARNING in ar5523_cmd/usb_submit_urb syzbot
2020-01-31 5:06 ` [PATCH] usb: core: urb: change a dev_WARN() to dev_err() for syzbot Dan Carpenter
2020-01-31 13:30 ` Johan Hovold
2020-01-31 13:39 ` Dan Carpenter
2020-02-10 19:04 ` Greg KH
2020-02-10 21:11 ` Alan Stern [this message]
2020-02-10 21:50 ` Greg KH
2020-02-11 6:03 ` Dan Carpenter
[not found] ` <20200131090510.7112-1-hdanton@sina.com>
2020-01-31 10:16 ` Dan Carpenter
2020-01-31 11:19 ` Dmitry Vyukov
2020-01-31 13:37 ` Johan Hovold
2020-01-31 14:25 ` Steven Rostedt
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