linux-kernel - Re: [PATCH] appletalk: prevent unregister_sysctl

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Message-ID: <Pine.LNX.4.64N.0610241313310.8933@attu4.cs.washington.edu>
Date:	Tue, 24 Oct 2006 13:18:04 -0700 (PDT)
From:	David Rientjes <rientjes@...washington.edu>
To:	Akinobu Mita <akinobu.mita@...il.com>
cc:	linux-kernel@...r.kernel.org, akpm@...l.org,
	Arnaldo Carvalho de Melo <acme@...ectiva.com.br>
Subject: Re: [PATCH] appletalk: prevent unregister_sysctl_table() with a NULL
 argument

On Tue, 24 Oct 2006, Akinobu Mita wrote:

> On Tue, Oct 24, 2006 at 02:38:24AM -0700, David Rientjes wrote:
> 
> > The only way this would happen at atalk_unregister_sysctl is if the 
> > kmalloc failed on register_sysctl_table during init.  In that case there 
> > is no need to unregister atalk in the first place since it never came up, 
> 
> Yes. this patch doesn't cause failure if sysctl registration failed.
> It aims to avoid that minor possible NULL pointer dereference.
> 

That dereference should never be possible.  If sysctl registration fails, 
it should not be left partially initialized so that it would ever need to 
be cleaned up later; it should just fail to register.  So the fix, if 
indeed one is required in this instance that you have witnessed, should be 
an immediate response to an -ENOMEM on register_sysctl_table.  Adding this 
to atalk_unregister_sysctl is incorrect because that function should only 
be entered given the condition that the register was successful, which in 
this case it was not.

		David
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