linux-kernel - Re: [PATCH v6] coccinelle: api: add kvfree script

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Date:   Sun, 2 Aug 2020 09:09:04 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Markus Elfring <Markus.Elfring@....de>
cc:     Denis Efremov <efremov@...ux.com>,
        Coccinelle <cocci@...teme.lip6.fr>,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v6] coccinelle: api: add kvfree script



On Sun, 2 Aug 2020, Markus Elfring wrote:

> …
> > +++ b/scripts/coccinelle/api/kvfree.cocci
> …
> > +@...ice@
> > +expression E, E1;
> > +position kok, vok;
> > +@@
> > +
> > +(
> …
> > +|
> > +  E = \(kmalloc\|kzalloc\|krealloc\|kcalloc\|kmalloc_node\|kzalloc_node\|
> > +        kmalloc_array\|kmalloc_array_node\|kcalloc_node\)(...)@kok
> > +  ... when != E = E1
> > +      when any
> > +  if (\(!E\|E == NULL\)) {
> …
>
> Can the SmPL code exclusion specification be incomplete here?
>
> How do you think about to check also if the memory is passed to any function
> (or macro) calls before the shown detection of a null pointer?

It seems both extremely unlikely and not relevant to the question at hand.
Passing E to another function will not change the value of E itself.
Passing &E to another function could change E, but it would be very
unusual to do that, and doesn't seem worth checking for.

julia