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Subject: Re: PROBLEM: Kernel Oops on cat /proc/ioports
From: Berend De Schouwer <bds@jhb.ucs.co.za>
To: Andrew Morton <akpm@zip.com.au>
Cc: linux-kernel@vger.kernel.org
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Date: 12 Dec 2001 12:30:19 +0200
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On Wed, 2001-12-12 at 03:06, Andrew Morton wrote:
> Berend De Schouwer wrote:
> > 
> > [1.] One line summary of the problem:
> > 
> > Running "cat /proc/ioports" causes a segfault and kernel oops.
> > 
> > ...
> > [7.3.] Module information (from /proc/modules):
> > 
> > cyclades              147616  16 (autoclean)
> 
> cyclades does request_region(), but forgets to do release_region().
> This will leave the region allocated in kernel data structures,
> but its "name" field resides in module memory.
> 
> So if you load cyclades.o, then rmmod it, then cat /proc/ioports,
> you'll touch unmapped memory and go boom.

I have confirmed this.  rmmod cyclades && cat /proc/ioports causes the
oops (but not necessarily a system crash).  I have a applied your patch,
and repeatedly ran insmod cyclades && rmmod cyclades && cat
/proc/ioports without causing the kernel oops.
> 
> Some brave soul needs to teach cyclades about release_region().
> Shame the Nobel prizes are all gone this year.

Thanks very much for the patch.

PS.  I needed to change the offsets to apply your patch to 2.4.14, but
no logic was changed.

> -
-- 
Berend De Schouwer

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