From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julia Lawall <julia.lawall@lip6.fr>
Subject: Re: net-PA Semi: Deletion of unnecessary checks before the function
 call "pci_dev_put"
Date: Mon, 1 Dec 2014 21:34:45 +0100 (CET)
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Cc: SF Markus Elfring <elfring@users.sourceforge.net>,
	Lino Sanfilippo <LinoSanfilippo@gmx.de>,
	Olof Johansson <olof@lixom.net>, netdev@vger.kernel.org,
	backports@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	kernel-janitors@vger.kernel.org,
	"Luis R. Rodriguez" <mcgrof@suse.com>
To: Johannes Berg <johannes@sipsolutions.net>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1417465745.28610.0.camel@sipsolutions.net>
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On Mon, 1 Dec 2014, Johannes Berg wrote:

> On Mon, 2014-12-01 at 02:34 +0100, SF Markus Elfring wrote:
> 
> > > Some of those NULL pointer checks on input parameters may have been
> > > added subsequently to functions. So there may be older kernel versions
> > > out there in which those checks dont exists in some cases. If some of
> > > the now "cleaned up" code is backported to such a kernel chances are
> > > good that those missing checks are overseen. And then neither caller nor
> > > callee is doing the NULL pointer check.
> 
> > I assume that a few backporters can tell you more about their corresponding
> > software development experiences.
> > http://www.do-not-panic.com/2014/04/automatic-linux-kernel-backporting-with-coccinelle.html
> 
> In such cases we just provide an appropriate wrapper and replace callers
> of the original function by callers of the wrapper, typically with a
> #define.
> 
> So this kind of evolution is no problem for the (automated) backports
> using the backports project - although it can be difficult to detect
> such a thing is needed.

That is exactly the problem...

julia