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

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Date:   Thu, 4 Jun 2020 16:15:29 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Denis Efremov <efremov@...ux.com>
cc:     cocci@...teme.lip6.fr, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coccinelle: api: add kzfree script



On Thu, 4 Jun 2020, Denis Efremov wrote:

> Check for memset() with 0 followed by kfree().
>
> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---
> Patches:
> 1. kzfree in drivers/w1 https://lkml.org/lkml/2020/6/4/438
> 2. kzfree in drivers/iommu/ https://lkml.org/lkml/2020/6/4/421
> 3. kzfree in drivers/scsi/ https://lkml.org/lkml/2020/6/4/442
>
>  scripts/coccinelle/api/kzfree.cocci | 53 +++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 scripts/coccinelle/api/kzfree.cocci
>
> diff --git a/scripts/coccinelle/api/kzfree.cocci b/scripts/coccinelle/api/kzfree.cocci
> new file mode 100644
> index 000000000000..c6b8f7676af4
> --- /dev/null
> +++ b/scripts/coccinelle/api/kzfree.cocci
> @@ -0,0 +1,53 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +///
> +/// Use kzfree rather than memset with 0 followed by kfree
> +///
> +// Confidence: High
> +// Copyright: (C) 2020 Denis Efremov ISPRAS
> +// Options: --no-includes --include-headers
> +//
> +// Keywords: kzfree
> +//
> +
> +virtual context
> +virtual org
> +virtual report
> +virtual patch
> +
> +// Ignore kzfree definition
> +// Ignore kasan test
> +@r depends on !patch && !(file in "lib/test_kasan.c") && !(file in "mm/slab_common.c")@
> +expression E;
> +position p;
> +@@
> +
> +(
> +* memset(E, 0, ...);
> +|
> +* memset(E, '\0', ...);
> +)

You shouldn't need both cases.  0 should be enough.

Did you try ... here but find that some subexpressions of E could be
modified in between?

julia

> +* kfree(E)@p;
> +
> +@r1 depends on patch && !(file in "lib/test_kasan.c") && !(file in "mm/slab_common.c")@
> +expression E;
> +@@
> +
> +(
> +- memset(E, 0, ...);
> +|
> +- memset(E, '\0', ...);
> +)
> +- kfree(E);
> ++ kzfree(E);
> +
> +@...ipt:python depends on report@
> +p << r.p;
> +@@
> +
> +coccilib.report.print_report(p[0], "WARNING opportunity for kzfree")
> +
> +@...ipt:python depends on org@
> +p << r.p;
> +@@
> +
> +coccilib.org.print_todo(p[0], "WARNING opportunity for kzfree")
> --
> 2.26.2
>
>