From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julia Lawall <julia.lawall@lip6.fr>
Date: Sun, 17 Feb 2019 11:37:18 +0000
Subject: Re: [PATCH v6] coccinelle: semantic code search for missing put_device()
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To: Markus Elfring <Markus.Elfring@web.de>
Cc: kernel-janitors@vger.kernel.org, Michal Marek <michal.lkml@markovi.net>, Wen Yang <yellowriver2010@hotmail.com>, Nicolas Palix <nicolas.palix@imag.fr>, LKML <linux-kernel@vger.kernel.org>, Coccinelle <cocci@systeme.lip6.fr>, Cheng Shengyu <cheng.shengyu@zte.com.cn>, Wen Yang <wen.yang99@zte.com.cn>



On Sun, 17 Feb 2019, Markus Elfring wrote:

> > +@search exists@
> > +local idexpression id;
> > +expression x,e,e1;
> > +position p1,p2;
> > +type T,T1,T2;
> > +@@
> > +
> > +id = of_find_device_by_node@p1(x)
> > +... when != e = id
>
> I suggest to increase your software development attention also for
> another implementation detail.
> Source code analysis triggers challenges for safe data flow handling.
> the semantic patch language supports search specifications for
> the exclusion of specific assignments.
>
> Does this SmPL code contain a questionable order for the source
> and target metavariables?
> Can the following variant be more appropriate?
>
> + ... when != id = e

This is possible, but I think unlikely.

>
>
> > +if (id = NULL || ...) { ... return ...; }
> > +... when != put_device(&id->dev)
> > +    when != platform_device_put(id)
> > +    when != of_dev_put(id)
> > +    when != if (id) { ... put_device(&id->dev) ... }
> > +    when != e1 = (T)id
>
> Would you like to avoid that the return value from the shown function call
> gets overwritten in the variable before it was used once at least
> (when a bit of extra C code is tolerated before a null pointer check)?

Indeed there should be a put then too, but again, it seems unlikely.

julia


>
> Regards,
> Markus
>