linux-kernel - Re: [PATCH v1 3/7] powercap/dtpm: Fixup kfree for virtual node

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Message-ID: <CAPDyKFqV++g63Asax8TNSEgujxJ=uM9XG2_Advu34JidYBCGtg@mail.gmail.com>
Date:   Wed, 16 Feb 2022 17:22:59 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     rjw@...ysocki.net, heiko@...ech.de, lukasz.luba@....com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Daniel Lezcano <daniel.lezcano@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH v1 3/7] powercap/dtpm: Fixup kfree for virtual node

On Sun, 30 Jan 2022 at 22:02, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>
> When the node is virtual there is no release function associated which
> can free the memory.
>
> Free the memory when no 'ops' exists.
>
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  drivers/powercap/dtpm.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/powercap/dtpm.c b/drivers/powercap/dtpm.c
> index 0b0121c37a1b..7bddd25a6767 100644
> --- a/drivers/powercap/dtpm.c
> +++ b/drivers/powercap/dtpm.c
> @@ -181,12 +181,12 @@ int dtpm_release_zone(struct powercap_zone *pcz)
>
>         if (dtpm->ops)
>                 dtpm->ops->release(dtpm);
> +       else
> +               kfree(dtpm);
>

This doesn't look correct. Below you check dtpm against "root", which
may be after its memory has been freed.

If the ->release() function should be responsible for freeing the
dtpm, it needs to be called after the check below.

>         if (root == dtpm)
>                 root = NULL;
>
> -       kfree(dtpm);
> -
>         return 0;
>  }
>

Kind regards
Uffe