linux-kernel - Re: kernel oops

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Message-ID: <20080818163906.GA11619@suse.de>
Date:	Mon, 18 Aug 2008 09:39:06 -0700
From:	Greg KH <gregkh@...e.de>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	Andrei Popa <andrei.popa@...eo.ro>,
	Oliver Neukum <oneukum@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel oops

On Mon, Aug 18, 2008 at 06:33:42PM +0200, Vegard Nossum wrote:
> On Wed, Jul 23, 2008 at 7:11 PM, Vegard Nossum <vegard.nossum@...il.com> wrote:
> > On Wed, Jul 23, 2008 at 2:52 PM, Andrei Popa <andrei.popa@...eo.ro> wrote:
> >>
> >> I installed gnokii-0.6.22-r2 and gave the command "gnokii --identify"
> >> and the kernel oopsed:
> >>
> >> BUG: unable to handle kernel NULL pointer dereference at 00000458
> >> IP: [<c0444b52>] mutex_unlock+0x0/0xb
> >> *pde = 00000000
> >> Oops: 0002 [#1] PREEMPT SMP
> >>
> >> Pid: 19043, comm: gnokii Not tainted (2.6.26-ineo7 #2)
> >> EIP: 0060:[<c0444b52>] EFLAGS: 00010246 CPU: 0
> >> EIP is at mutex_unlock+0x0/0xb
> > ...
> >>  [<c03830ae>] acm_tty_open+0x4c/0x214
> >
> > This shouldn't be too hard; the code is trying to unlock the mutex
> > &acm->mutex even when "acm" is NULL. It seems that the label "err_out"
> > is otherwise unused, so it makes sense to move this one step further
> > down, so that it doesn't try to unlock the non-existent mutex.
> >
> > If the problem is reproducible, you could try the patch below!
> >
> >
> > Vegard
> >
> > PS: I actually think the code has some other problems too. Shouldn't
> > &acm->mutex be locked before we even inspect acm->dev?
> >
> >
> > Reported-by: Andrei Popa <andrei.popa@...eo.ro>
> > Signed-off-by: Vegard Nossum <vegard.nossum@...il.com>
> >
> > diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
> > index 63c3404..74d03a7 100644
> > --- a/drivers/usb/class/cdc-acm.c
> > +++ b/drivers/usb/class/cdc-acm.c
> > @@ -525,8 +525,8 @@ static int acm_tty_open(struct tty_struct *tty, struct file *filp)
> >        tasklet_schedule(&acm->urb_task);
> >
> >  done:
> > -err_out:
> >        mutex_unlock(&acm->mutex);
> > +err_out:
> >        mutex_unlock(&open_mutex);
> >        return rv;
> >
> >
> 
> Hi,
> 
> Latest -git seems to have the same problem, and this was about three
> weeks ago, so.. Ping?

Hm, I thought I took a patch to fix this a few weeks ago.

Oliver, have I missed anything recently?

thanks,

greg k-h
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