linux-kernel - Re: [PATCH v4] irqchip/renesas-rzg2l: Fix missing put

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Message-ID: <CAMuHMdUrg+gqJsg2LaBkzaLPzh4nZefqVdqH2rLhCEGQDya88g@mail.gmail.com>
Date: Tue, 11 Feb 2025 16:11:57 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Fabrizio Castro <fabrizio.castro.jz@...esas.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Markus Elfring <elfring@...rs.sourceforge.net>, 
	Markus Elfring <Markus.Elfring@....de>, Marc Zyngier <maz@...nel.org>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, linux-kernel@...r.kernel.org, 
	Chris Paterson <Chris.Paterson2@...esas.com>, Biju Das <biju.das.jz@...renesas.com>, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v4] irqchip/renesas-rzg2l: Fix missing put_device

Hi Fabrizio,

On Fri, 11 Oct 2024 at 19:20, Fabrizio Castro
<fabrizio.castro.jz@...esas.com> wrote:
> rzg2l_irqc_common_init calls of_find_device_by_node, but the
> corresponding put_device call is missing.
> This also gets reported by make coccicheck.
>
> Make use of the cleanup interfaces from cleanup.h to call into
> __free_put_device (which in turn calls into put_device) when
> leaving function rzg2l_irqc_common_init and variable "dev" goes
> out of scope.
>
> Mind that we don't want to "put" "dev" when rzg2l_irqc_common_init
> completes successfully, therefore assign NULL to "dev" to prevent
> __free_put_device from calling into put_device within the successful
> path.
>
> "make coccicheck" will still complain about missing put_device calls,
> but those are false positives now.
>
> Fixes: 3fed09559cd8 ("irqchip: Add RZ/G2L IA55 Interrupt Controller driver")
> Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@...esas.com>

Revisiting commit d038109ac1c6bf61 ("irqchip/renesas-rzg2l: Fix missing
put_device")...

> --- a/drivers/irqchip/irq-renesas-rzg2l.c
> +++ b/drivers/irqchip/irq-renesas-rzg2l.c
> @@ -8,6 +8,7 @@
>   */
>
>  #include <linux/bitfield.h>
> +#include <linux/cleanup.h>
>  #include <linux/clk.h>
>  #include <linux/err.h>
>  #include <linux/io.h>
> @@ -530,12 +531,12 @@ static int rzg2l_irqc_parse_interrupts(struct rzg2l_irqc_priv *priv,
>  static int rzg2l_irqc_common_init(struct device_node *node, struct device_node *parent,
>                                   const struct irq_chip *irq_chip)
>  {
> +       struct platform_device *pdev = of_find_device_by_node(node);
> +       struct device *dev __free(put_device) = pdev ? &pdev->dev : NULL;

Now there is a variable holding "&pdev->dev", all below references
to the latter can be replaced by "dev"...

>         struct irq_domain *irq_domain, *parent_domain;
> -       struct platform_device *pdev;
>         struct reset_control *resetn;
>         int ret;
>
> -       pdev = of_find_device_by_node(node);
>         if (!pdev)
>                 return -ENODEV;
>
> @@ -591,6 +592,17 @@ static int rzg2l_irqc_common_init(struct device_node *node, struct device_node *
>
>         register_syscore_ops(&rzg2l_irqc_syscore_ops);
>
> +       /*
> +        * Prevent the cleanup function from invoking put_device by assigning
> +        * NULL to dev.
> +        *
> +        * make coccicheck will complain about missing put_device calls, but
> +        * those are false positives, as dev will be automatically "put" via
> +        * __free_put_device on the failing path.
> +        * On the successful path we don't actually want to "put" dev.
> +        */
> +       dev = NULL;
> +
>         return 0;

Can't the above be replaced by

    no_free_ptr(dev);

? Or would Coccinelle still complain?

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