linux-kernel - Re: [PATCH] usb-serial regression fix

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Message-ID: <20070313004142.GA4835@blackbean.org>
Date:	Mon, 12 Mar 2007 17:41:42 -0700
From:	Jim Radford <radford@...ckbean.org>
To:	Greg KH <greg@...ah.com>
Cc:	Mark Lord <lkml@....ca>, linux-usb-devel@...ts.sourceforge.net,
	Oliver Neukum <oneukum@...e.de>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb-serial regression fix

On Mon, Mar 12, 2007 at 05:18:19PM -0700, Greg KH wrote:
> On Mon, Mar 12, 2007 at 03:59:22PM -0700, Jim Radford wrote:
> > On Mon, Mar 12, 2007 at 03:42:35PM -0700, Jim Radford wrote:
> > > On Mon, Mar 12, 2007 at 01:33:31PM -0700, Greg KH wrote:
> > > > On Mon, Mar 12, 2007 at 04:22:22PM -0400, Mark Lord wrote:
> > > > > Oliver Neukum wrote:
> > > > > > >Mark Lord wrote:
> > > > > > > >Okay, from that part (above), the problem is obvious:
> > > > > > > >in that the "MCT U232 converter now disconnected"
> > > > > > > >appears, and then we continue to try and call the
> > > > > > > >driver's method.. Oops!

> > > > > >IMHO shutdown() is using serial->port[] and bombs.
> > > > > >Could you reverse the order here?

> > Do not NULL serial->port[i] since it is used in ->shutdown().
> > This wasn't an issue until the order or ->shutdown() and
> > device_unregister was corrected.

> >         for (i = 0; i < serial->num_ports; ++i)
> >                 if (serial->port[i]->dev.parent != NULL) {
> >                         device_unregister(&serial->port[i]->dev);
> > -                       serial->port[i] = NULL;
> >                 }

> But shouldn't you null it out somewhere?  It will be an "empty"
> pointer at some point in time...

Not as far as I can see. The serial structure that ->port[i] is in
gets kfree()ed soon after, in the same function, and nothing in
between, other than ->shutdown(), uses ->port[].  I assume it was
someone being overly cautious.

-Jim
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