linux-kernel - Re: [PATCH] acpi/processor_idle.c: Fix kernel pointer leak

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Date:   Wed, 29 Sep 2021 14:07:51 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Guo Zhi <qtxuning1999@...u.edu.cn>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] acpi/processor_idle.c: Fix kernel pointer leak

On Wed, Sep 29, 2021 at 12:56 PM Guo Zhi <qtxuning1999@...u.edu.cn> wrote:
>
> Pointers should be printed with %p or %px rather than
> cast to 'long' and pinted with %ld.
> Change %ld to %p to print the secured pointer.

In this particular case, id->driver_data represents a proper integer,
not an address, although technically it is a pointer data type.  It
shouldn't be printed with %p and the patch is incorrect.

>
> Signed-off-by: Guo Zhi <qtxuning1999@...u.edu.cn>
> ---
>  drivers/acpi/processor_idle.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index f37fba9e5ba0..a9f4ab072583 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -73,9 +73,9 @@ static int set_max_cstate(const struct dmi_system_id *id)
>         if (max_cstate > ACPI_PROCESSOR_MAX_POWER)
>                 return 0;
>
> -       pr_notice("%s detected - limiting to C%ld max_cstate."
> +       pr_notice("%s detected - limiting to C%p max_cstate."
>                   " Override with \"processor.max_cstate=%d\"\n", id->ident,
> -                 (long)id->driver_data, ACPI_PROCESSOR_MAX_POWER + 1);
> +               id->driver_data, ACPI_PROCESSOR_MAX_POWER + 1);
>
>         max_cstate = (long)id->driver_data;
>
> --
> 2.33.0
>