linux-kernel - Re: [PATCH] Sanitize possible_parent_show to Handle Return Value of of_clk_get_parent

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Message-ID: <CAPp5cGTshQJ3aLeLqv=CbaVeg9GnK_k9nsoaWrBKs1dcXzNZow@mail.gmail.com>
Date:   Thu, 7 Sep 2023 16:15:36 +0200
From:   Alessandro Carminati <alessandro.carminati@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Philip Daly <pdaly@...hat.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Sanitize possible_parent_show to Handle Return Value of of_clk_get_parent_name

this is a gentle ping

thank you
Alessandro Carminati

Il giorno mar 22 ago 2023 alle ore 15:49 Alessandro Carminati
<alessandro.carminati@...il.com> ha scritto:
>
> 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.
>
> Reported-by: Philip Daly <pdaly@...hat.com>
> Signed-off-by: Alessandro Carminati (Red Hat) <alessandro.carminati@...il.com>
> ---
>  drivers/clk/clk.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index c249f9791ae8..ab999644e185 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 *tmp;
>
>         /*
>          * Go through the following options to fetch a parent's name.
> @@ -3436,12 +3437,12 @@ static void possible_parent_show(struct seq_file *s, struct clk_core *core,
>                 seq_puts(s, core->parents[i].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
> +       else if (core->parents[i].index >= 0) {
> +               tmp = of_clk_get_parent_name(core->of_node, core->parents[i].index);
> +               seq_puts(s, tmp ? tmp : "(none)");
> +       } else {
>                 seq_puts(s, "(missing)");
> +       }
>
>         seq_putc(s, terminator);
>  }
> --
> 2.34.1
>