linux-kernel - Re: net: xfrm: Deletion of an unnecessary check before the function call "ipcomp_free

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Date:	Wed, 19 Nov 2014 10:58:01 +0100 (CET)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org
Subject: Re: net: xfrm: Deletion of an unnecessary check before the function
 call "ipcomp_free_tfms"



On Wed, 19 Nov 2014, SF Markus Elfring wrote:

> >> The ipcomp_free_tfms() function tests whether its argument is NULL and then
> >> returns immediately. Thus the test around the call is not needed.
> >
> > It doesn't though...
>
> You are right that this function implementation does a bit more before
> returning because of a detected null pointer.
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/net/xfrm/xfrm_ipcomp.c?id=394efd19d5fcae936261bd48e5b33b21897aacf8#n247
>
> Can you agree that input parameter validation is also performed there?
> Do you want that I resend my patch with a corrected commit message?

This is completely crazy.  The function performs a side effect on a data
structure.  If the call site doesn't want that done in a certain case,
then it should not be done.

julia
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