linux-kernel - Re: [v5] coccinelle: semantic code search for missingput

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Date:   Sat, 16 Feb 2019 09:36:48 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     wen.yang99@....com.cn
cc:     Markus.Elfring@....de, julia.lawall@...6.fr, Gilles.Muller@...6.fr,
        nicolas.palix@...g.fr, michal.lkml@...kovi.net,
        wang.yi59@....com.cn, yamada.masahiro@...ionext.com,
        yellowriver2010@...mail.com, cheng.shengyu@....com.cn,
        cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [v5] coccinelle: semantic code search for missingput_device()



On Sat, 16 Feb 2019, wen.yang99@....com.cn wrote:

> > > Thanks, We will change it to something like this:
> > > In a function, for a local variable obtained by of_find_device_by_node()
> >
> > How do you think about another wording approach?
> >
> > 1. Precondition:
> > It will be checked where the return value is stored from
> > a call of the function “of_find_device_by_node”.
> >
> > 2. The source code search will be continued with …
>
> Thanks.
> This is more rigorous, we will follow your advice
>
> > > Thank you, but a local variable is necessary.
> >
> > Would you like to take additional storage possibilities for a safer
> > analysis approach into account?
> >
> > Is the restriction “local” really sufficient when such a pointer
> > could be copied to other variables?
>
> We may be able to handle this situation:
> +id = of_find_device_by_node@p1(x)
> ...
> +    when != e1 = (T)id
> +    when != e1 = &id->dev
> +    when != e1 = get_device(&id->dev)

This looks good.  To be double sure, you can put (T)(&id->dev) in the
second case.

When you have a chance please send the revised version.  As long as I
don't see that it is giving many false positives, I will accept it.  We
don't need perfection.  We need more to eliminate the memory leaks.

julia

>
> > > But it's over 80 characters.
> >
> > Long string literals can be accepted because of error message search concerns
> > around a tool like “grep”.
>
> Thanks.
> We will follow your advice
>
> >> Will any more advanced error diagnostics be eventually developed?
> > >
> > > Hello, we are just doing the practical work in this field.
> >
> > Are you aware of additional software design options from computer science
> > and existing analysis tools?
>
> We also use the commercial software klockwork, which will also find errors in the code,
> but a lot of false positives.
>
> Regards,
> Wen