linux-kernel - Re: [PATCH] drivers: bus: Fix resource leaks in for_each_available_child_of

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Message-ID: <CAMuHMdWG01LNa2Umgzcv6knAtbPnRSQYs71bwh3yL9W9XN=CFw@mail.gmail.com>
Date:   Thu, 6 Jul 2023 09:53:05 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Lu Hongfei <luhongfei@...o.com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Rob Herring <robh@...nel.org>, Mark Brown <broonie@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Minghao Chi <chi.minghao@....com.cn>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        opensource.kernel@...o.com
Subject: Re: [PATCH] drivers: bus: Fix resource leaks in for_each_available_child_of_node
 loop

On Thu, Jul 6, 2023 at 9:43 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Thu, Jul 6, 2023 at 9:13 AM Lu Hongfei <luhongfei@...o.com> wrote:
> > Ensure child node references are decremented properly in
> > the error path.
>
> Which error path?
>
> >
> > Signed-off-by: Lu Hongfei <luhongfei@...o.com>
> > ---
> >  drivers/bus/imx-weim.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
> > index 52a5d0447390..d05472f7c20f 100644
> > --- a/drivers/bus/imx-weim.c
> > +++ b/drivers/bus/imx-weim.c
> > @@ -251,6 +251,7 @@ static int weim_parse_dt(struct platform_device *pdev)
> >                 else
> >                         have_child = 1;
> >         }
> > +       of_node_put(child);
>
> This is not an error path.
>
> for_each_available_child_of_node() walks a list, getting a reference
> to each child, and releasing the reference afterwards.

FTR, calling of_node_put() manually is only needed when breaking
out of for_each_available_child_of_node().

>
> Have you tested this patch?
> I expect the of_node_put() to trigger a refcount underflow error
> message on the console.
>
> >
> >         if (have_child)
> >                 ret = of_platform_default_populate(pdev->dev.of_node,

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds