Re: [S390] cio: kernel stack overflow.

From: Martin Schwidefsky
Date: Thu Aug 31 2006 - 05:03:18 EST


On Wed, 2006-08-30 at 21:19 +0200, Heiko Carstens wrote:
> > >- cdev->id = (struct ccw_device_id) {
> > >- .cu_type = cdev->private->senseid.cu_type,
> > >- .cu_model = cdev->private->senseid.cu_model,
> > >- .dev_type = cdev->private->senseid.dev_type,
> > >- .dev_model = cdev->private->senseid.dev_model,
> > >- };
> > >+ cdev->id.cu_type = cdev->private->senseid.cu_type;
> > >+ cdev->id.cu_model = cdev->private->senseid.cu_model;
> > >+ cdev->id.dev_type = cdev->private->senseid.dev_type;
> > >+ cdev->id.dev_model = cdev->private->senseid.dev_model;
> >
> > I don't see any obvious place that zeroes out cdev->id.
> > In particular, it looks like cdev->id.match_flags and .driver_info
> > are never cleared (i.e., they retain whatever old garbage they had
> > before). More importantly, if anyone ever adds any more fields to
> > struct ccw_device_id, then they will also be retain old garbage values,
> > which is a maintenance pitfall. Is this right, or did I miss something
> > again?
>
> You're right. Thanks for pointing this out! I will take care of it.

The ccw_device_id structure contains two more fields in addition to the
field that are set up in ccw_device_recog_done, namely match_flags and
driver_info. driver_info is set later in ccw_bus_match, so that is fine.
match_flags of the device is never used, only the match_flags of the
drivers version of the ccw_device_id is used. So the code is correct
even without the memset. But your point about the maintenance pitfall is
valid, we will add a memset after 2.6.18. I don't want to push yet
another patch.

--
blue skies,
Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.


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