linux-kernel - Re: [PATCH V2] scripts/coccinelle/free: add NULL test before freeing functions

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Date:	Fri, 27 Jun 2014 22:13:32 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Fabian Frederick <fabf@...net.be>
cc:	linux-kernel@...r.kernel.org, Julia Lawall <Julia.Lawall@...6.fr>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Joe Perches <joe@...ches.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH V2] scripts/coccinelle/free: add NULL test before freeing
 functions

Why not make a patch case that removes the test?  Since the expression is 
duplicated in the test and in the argument to kfree it does not seem 
likely that it will have a side effect.

julia

On Fri, 27 Jun 2014, Fabian Frederick wrote:

> Warns on NULL check before the following functions:
> 
> kfree
> usb_free_urb
> debugfs_remove
> debugfs_remove_recursive
> 
> Cc: Julia Lawall <Julia.Lawall@...6.fr>
> Cc: Gilles Muller <Gilles.Muller@...6.fr>
> Cc: Joe Perches <joe@...ches.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Fabian Frederick <fabf@...net.be>
> ---
> V2:
>    -Add 3 more functions to kfree (suggested by Joe Perches)
>    -Update warning message to involve code analysis (suggested by Julia Lawall)
> 
>  scripts/coccinelle/free/ifnullfree.cocci | 34 ++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
>  create mode 100644 scripts/coccinelle/free/ifnullfree.cocci
> 
> diff --git a/scripts/coccinelle/free/ifnullfree.cocci b/scripts/coccinelle/free/ifnullfree.cocci
> new file mode 100644
> index 0000000..626309c
> --- /dev/null
> +++ b/scripts/coccinelle/free/ifnullfree.cocci
> @@ -0,0 +1,34 @@
> +/// NULL check before some freeing functions is not needed.
> +///
> +/// Based on checkpatch warning
> +/// "kfree(NULL) is safe this check is probably not required"
> +/// and kfreeaddr.cocci by Julia Lawall.
> +///
> +/// Comments: -
> +/// Options: --no-includes --include-headers
> +
> +virtual org
> +virtual report
> +virtual context
> +
> +@r depends on context || report || org @
> +expression E;
> +position p;
> +@@
> +
> +* if (E)
> +*	\(kfree@p\|debugfs_remove@p\|debugfs_remove_recursive@p\|usb_free_urb\)(E);
> +
> +@...ipt:python depends on org@
> +p << r.p;
> +@@
> +
> +cocci.print_main("freeing", p)
> +
> +@...ipt:python depends on report@
> +p << r.p;
> +@@
> +
> +msg = "WARNING: NULL check before freeing functions like kfree, debugfs_remove, debugfs_remove_recursive or usb_free_urb is not needed. Maybe consider reorganizing relevant code to avoid passing NULL values."
> +coccilib.report.print_report(p[0], msg)
> +
> -- 
> 1.8.4.5
> 
> 
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