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From:   Alessandro Carminati <alessandro.carminati@gmail.com>
Date:   Wed, 4 Oct 2023 10:38:39 +0200
Message-ID: <CAPp5cGRSGQGq-4DckxrXTuG=BqwLm9cLHgjY8+MMe8Qgcon4Cw@mail.gmail.com>
Subject: Re: [PATCH v2] clk: Sanitize possible_parent_show to Handle Return
 Value of of_clk_get_parent_name
To:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>
Cc:     linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
        Philip Daly <pdaly@redhat.com>
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gentle ping

In the original email, I acknowledge that I misplaced the maintainers mail
addresse from the "to" field.

Il giorno gio 21 set 2023 alle ore 09:33 Alessandro Carminati (Red
Hat) <alessandro.carminati@gmail.com> ha scritto:
>
> From: Alessandro Carminati <alessandro.carminati@gmail.com>
>
> In the possible_parent_show function, ensure proper handling of the return
> value from of_clk_get_parent_name to prevent potential issues arising from
> a NULL return.
> The current implementation invokes seq_puts directly on the result of
> of_clk_get_parent_name without verifying the return value, which can lead
> to kernel panic if the function returns NULL.
>
> This patch addresses the concern by introducing a check on the return
> value of of_clk_get_parent_name. If the return value is not NULL, the
> function proceeds to call seq_puts, providing the returned value as
> argument.
> However, if of_clk_get_parent_name returns NULL, the function provides a
> static string as argument, avoiding the panic.
>
> Fixes: 1ccc0ddf046a ("clk: Use seq_puts() in possible_parent_show()")
> Reported-by: Philip Daly <pdaly@redhat.com>
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@gmail.com>
> ---
>  drivers/clk/clk.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index c249f9791ae8..473563bc7496 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -3416,6 +3416,7 @@ static void possible_parent_show(struct seq_file *s, struct clk_core *core,
>                                  unsigned int i, char terminator)
>  {
>         struct clk_core *parent;
> +       const char *name = NULL;
>
>         /*
>          * Go through the following options to fetch a parent's name.
> @@ -3430,18 +3431,20 @@ static void possible_parent_show(struct seq_file *s, struct clk_core *core,
>          * registered (yet).
>          */
>         parent = clk_core_get_parent_by_index(core, i);
> -       if (parent)
> +       if (parent) {
>                 seq_puts(s, parent->name);
> -       else if (core->parents[i].name)
> +       } else if (core->parents[i].name) {
>                 seq_puts(s, core->parents[i].name);
> -       else if (core->parents[i].fw_name)
> +       } else if (core->parents[i].fw_name) {
>                 seq_printf(s, "<%s>(fw)", core->parents[i].fw_name);
> -       else if (core->parents[i].index >= 0)
> -               seq_puts(s,
> -                        of_clk_get_parent_name(core->of_node,
> -                                               core->parents[i].index));
> -       else
> -               seq_puts(s, "(missing)");
> +       } else {
> +               if (core->parents[i].index >= 0)
> +                       name = of_clk_get_parent_name(core->of_node, core->parents[i].index);
> +               if (!name)
> +                       name = "(missing)";
> +
> +               seq_puts(s, name);
> +       }
>
>         seq_putc(s, terminator);
>  }
> --
> 2.34.1
>