linux-kernel - Re: [PATCH 32/58] isdn/gigaset: Convert timers to use timer

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Date:   Fri, 20 Oct 2017 00:28:39 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Paul Bolle <pebolle@...cali.nl>
cc:     Kees Cook <keescook@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Karsten Keil <isdn@...ux-pingi.de>,
        Johan Hovold <johan@...nel.org>,
        gigaset307x-common@...ts.sourceforge.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 32/58] isdn/gigaset: Convert timers to use
 timer_setup()

On Thu, 19 Oct 2017, Paul Bolle wrote:

> On Thu, 2017-10-19 at 23:31 +0200, Thomas Gleixner wrote:
> > bas_gigaset_exit()
> > {
> >         for (i = 0; i < driver->minors; i++) {
> >                 if (gigaset_shutdown(driver->cs + i) < 0)
> > 
> > gigaset_shutdown(cs)
> > {
> > 	mutex_lock(&cs->mutex); <-------- Explodes here
> > 
> > So driver->cs + i is invalid. No idea how that might be related to that
> > timer conversion patch, but ....
> 
> Thanks for peeking into this!
> 
> Please note that driver->minors is one of the more embarrassing warts of the
> gigaset code. It's basically hardcoded to 1 for all three drivers (including
> bas_gigaset). So driver->cs itself is invalid here.
> 
> And since the patch uses
>     struct cardstate *cs = urb->context;
> 
> in a few places my guess is that it's really the patch that triggers this.

Well, that does not explain why

      drivers->cs + i

would be corrupted. That would require that this cs -> urb link points at
driver magically and then wreckages that driver data structure. Might be
the case, but if so then there are dragons burried somehwere

Thanks,

	tglx