From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEF85C352A4 for ; Mon, 10 Feb 2020 21:11:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B38CA2070A for ; Mon, 10 Feb 2020 21:11:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727347AbgBJVLM (ORCPT ); Mon, 10 Feb 2020 16:11:12 -0500 Received: from netrider.rowland.org ([192.131.102.5]:34095 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1727254AbgBJVLL (ORCPT ); Mon, 10 Feb 2020 16:11:11 -0500 Received: (qmail 15433 invoked by uid 500); 10 Feb 2020 16:11:10 -0500 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 10 Feb 2020 16:11:10 -0500 Date: Mon, 10 Feb 2020 16:11:10 -0500 (EST) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Greg KH cc: Dan Carpenter , syzbot , , , , , Subject: Re: [PATCH] usb: core: urb: change a dev_WARN() to dev_err() for syzbot In-Reply-To: <20200210190419.GC1058087@kroah.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org 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 > > --- > > > > 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