linux-kernel - Re: [PATCH V3] scripts/coccinelle/free: add NULL test before freeing functions

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Date:	Sat, 28 Jun 2014 19:55:33 +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 V3] scripts/coccinelle/free: add NULL test before freeing
 functions

On Sat, 28 Jun 2014, Fabian Frederick wrote:

> Warns or generates patch for 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>

Acked-by: Julia Lawall <Julia.Lawall@...6.fr>

> ---
>
> V3:
>    -Update print_main message.
>    -Add patch mode (suggested by Julia Lawall)
>
> 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 | 53 ++++++++++++++++++++++++++++++++
>  1 file changed, 53 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..c826d98
> --- /dev/null
> +++ b/scripts/coccinelle/free/ifnullfree.cocci
> @@ -0,0 +1,53 @@
> +/// 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 patch
> +virtual org
> +virtual report
> +virtual context
> +
> +@r2 depends on patch@
> +expression E;
> +@@
> +- if (E)
> +(
> +-	kfree(E);
> ++ kfree(E);
> +|
> +-	debugfs_remove(E);
> ++ debugfs_remove(E);
> +|
> +-	debugfs_remove_recursive(E);
> ++ debugfs_remove_recursive(E);
> +|
> +-	usb_free_urb(E);
> ++ usb_free_urb(E);
> +)
> +
> +@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("NULL check before that freeing function is not needed", 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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